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Fukushima nuclear accident: Saturday 19 March summary

Last Saturday the the crisis level at the Fukushima Daiichi nuclear power station was rapidly on the rise. Hydrogen explosions, cracks in the wetwell torus and fires in a shutdown unit’s building — it seemed the sequence of new problems would never end. A week later, the situation remains troubling, but, over the last few days, it has not got any worse. Indeed, one could make a reasonable argument that it’s actually got better.

Yes, the IAEA has now formally listed the overall accident at an INES level 5 (see here for a description of the scales), up from the original estimate of 4. This is right and proper — but it doesn’t mean the situation has escalated further, as some have inferred. Here is a summary of the main site activities for today, followed by the latest JAIF and FEPC reports. You also might be interested in the following site map:

Another large cohort of 100 Tokyo fire fighters joined the spraying operation to cool down the reactors and keep the water in the spent fuel ponds. The ‘Hyper Rescue’ team have set up a special vehicle for firing a water cannon from 22 m high (in combination with a super pump truck), and today have been targeting the SNF pond in unit 3. About 60 tons of sea water successfully penetrated the building in the vicinity of the pool, at a flow rate of 3,000 litres per minute. Spraying with standard unmanned vehicles was also undertaken for 7 hours into other parts of the the unit 3 building (delivering more than 1,200 tons), to keep the general containment area cool. The temperature around the fuel rods is now reported by TEPCO (via NHK news) to be below 100C.

Conditions in unit 3 are stabilising but will need attention for many days to come. Promisingly, TEPCO has now connected AC cables to the unit 1 and 2 reactor buildings, with hopes that powered systems can be restored to these building by as early as tomorrow (including, it is hoped, the AC core cooling systems), once various safety and equipment condition checks are made.

Holes were made in the secondary containment buildings of Units 5 and 6 as a precautionary measure, to vent any hydrogen that might accumulate and so prevent explosions in these otherwise undamaged structures.  The residual heat removal system for these units has now been brought back on line and these pools maintain a tolerable steady temperature of 60C. More here. These buildings were operating on a single emergency diesel generator, but now have a second electricity supply via the external AC power cable.

Why are they concentrating on these activities? Let’s revisit a bit of the history of last week. The spent fuel pool still has decay heat (probably of the order of few MW in each pool) that requires active cooling. When power went out on Friday, the cooling stopped and the pool temperature has been rising slowly over the weekend, and probably started boiling off (and a large volume may have also been lost due to ‘sloshing’ during the seismic event). The pool is located on the 4th floor above the reactor vessel level. It remains unclear why they could not arrange fire trucks to deliver the sea water before the fuel rods got damaged and started releasing radioactivity. Now the effort is hampered by the high radiation level (primarily penetrating gamma rays). This is the inventory of those spent fuel ponds that have been causing so many headaches:


In order to remove the decay heat after the reactor shutdown, the cooling system should be operating. Following the loss of offsite power, the on-site diesel generators came on but the tsunami arrived an hour or so later and wiped out the diesel generators. Then the battery provided the power for 8 hours or so, during which time they brought in portable generators. However, the connectors were incompatible. As the steam pressure built up inside the pressure vessel, the relief valve was open and dumped the steam to the pressure suppression chamber, which in turn was filtered out to the confinement building and the hydrogen explosion took out the slabs.

The sea water was then pumped in by fire trucks and the reactor pressure vessels are now cooled down to near atmospheric pressure but the fuel assemblies are uncovered at the top quarter or third (the FEPC updates give the actual pressure and water levels). It appears that the pressure vessels and the reactor containment structures are intact, except the Unit 2, where the hydrogen explosion took place inside the containment and hence damaging the lower wetwell torus structure (but almost certainly not the reactor vessel, although the exact status is unclear). It appears that the radioactivity releases are mostly coming from the spent fuel storages than the reactor cores.

World Nuclear News has a really excellent extended article here entitled “Insight to Fukushima engineering challenges“. Read it! Further, you must watch this 8 minute reconstruction of the timeline of the accident done by NHK — brilliant, and really highlights the enormous stresses this poor station faced against a record-breaking force of nature. As I’d noted earlier, just about everything that could have went wrong, did. But valuable lessons must also be learned.

The IAEA and Japanese government has reported the potential contamination of food products from the local Fukushima area via radioactive iodine (mostly vented as part of the pressure relief operations of units 1 to 3). This is a short-term risk due to the 8-day half-life of radioactive iodine (and a small risk, given the trace amounts recorded), but precautions are warranted, as discussed here. What does this mean?

In the case of the milk samples, even if consumed for one year, the radiation dose would be equivalent to that a person would receive in a single CT scan. The levels found in the spinach were much lower, equivalent to one-fifth of a single CT scan.

… and to further put this in context:

The UK government’s chief independent scientific advisor has told the British Embassy in Tokyo that radiation fears from the stricken Fukushima nuclear power plant are a “sideshow” compared with the general devastation caused by the massive earthquake and tsunami that struck on 11 March. Speaking from London in a teleconference on 15 March to the embassy, chief scientific officer John Beddington said that the only people likely to receive doses of radiation that could damage their health are the on-site workers at the Fukushima Daiichi plant. He said that the general population outside of the 20 kilometre evacuation zone should not be concerned about contamination.

As to the possibility of a zirconium fire in the SNF ponds, this seems unlikely. Zr has a very high combustion point, as illustrated in video produced by UC Berkeley nuclear engineers. They applied a blowtorch to a zirconium rod and it did not catch on fire. The demonstration is shown about 50 seconds into this video. The temperature was said to reach 2000C [incidentally, I visited that lab last year!].

The the Japan Atomic Industrial Forum has provided their 12th reactor-by-reactor status update (16:00 March 19).

Here is the latest FEPC status report:

———————-

  • Radiation Levels
    • At 7:30PM on March 18, radiation level outside main office building (approximately 1,640 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 3,699 micro Sv/h.
    • Measurement results of ambient dose rate around Fukushima Nuclear Power Station at 4:00PM and 7:00PM on March 18 are shown in the attached two PDF files respectively.
    • At 1:00PM on March 18, MEXT decided to carry out thorough radiation monitoring nationwide.
    • For comparison, a human receives 2,400 micro Sv per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6,900 micro Sv per scan.
  • Fukushima Daiichi Unit 1 reactor
    • Since 10:30AM on March 14, the pressure within the primary containment vessel cannot be measured.
    • At 4:00PM on March 18, pressure inside the reactor core: 0.191MPa.
    • At 4:00PM on March 18, water level inside the reactor core: 1.7 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
    • Activities for connecting the commercial electricity grid are underway.
  • Fukushima Daiichi Unit 2 reactor
    • At 4:00PM on March 18, pressure inside the primary containment vessel: 0.139MPaabs.
    • At 4:00PM on March 18, pressure inside the reactor core: -0.002MPa.
    • At 4:00PM on March 18, water level inside the reactor core: 1.4 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
    • Activities for connecting the commercial electricity grid are underway.
  • Fukushima Daiichi Unit 3 reactor
    • At 2:00PM on March 18, six Self Defense emergency fire vehicles began to shoot water aimed at the spent fuel pool, until 2:38PM (39 tones of water in total).
    • At 2:42PM on March 18, TEPCO began to shoot water aimed at the spent fuel pool, until 2:45PM, by one US Army high pressure water cannon.
    • At 3:55PM on March 18, pressure inside the primary containment vessel: 0.160MPaabs.
    • At 3:55PM on March 18, pressure inside the reactor core: -0.016MPa.
    • At 3:55PM on March 18, water level inside the reactor core: 2.0 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
  • Fukushima Daiichi Unit 4 reactor
    • No official updates to the information in our March 18 update have been provided.
  • Fukushima Daiichi Unit 5 reactor
    • At 4:00PM on March 18, the temperature of the spent fuel pool was measured at 152.4 degrees Fahrenheit.
  • Fukushima Daiichi Unit 6 reactor
    • At 4:00PM on March 18, the temperature of the spent fuel pool was measured at 148.1 degrees Fahrenheit.
  • Fukushima Daiichi Common Spent Fuel Pool
    • At 10:00AM on March 18, it was confirmed that water level in the pool was secured.
  • Fukushima Daiichi Dry Cask Storage Building
    • At 10:00AM on March 18, it was confirmed that there was no damage by visual checking of external appearance.

At 5:50PM on March 18, Japanese Safety Authority (NISA: Nuclear and Industrial Safety Agency) announced provisional INES (International Nuclear and Radiological Event Scale) rating to the incidents due to the earthquake.

Fukushima Daiichi Unit 1, 2 and 3 Unit = 5 (Accident with wider consequences)

Fukushima Daiichi Unit 4 = 3 (Serious incident)

Fukushima Daini Unit 1, 2 and 4 Unit = 3 (Serious incident)

(No official provisional rating for Fukushima Daini Unit 3 has been provided.)

———————-

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

344 replies on “Fukushima nuclear accident: Saturday 19 March summary”

Leo Hansen, on 20 March 2011 at 1:18 PM — Do not #3 & #4 share a common wall? If so, the #3 explosion could have impacted some of #4 without the effect being visible.

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@Eagles Eyes 1:42 Thank you for photo, it confirms JAIF reports that R4 bdlg was not damaged by R3 bdlg explosion on Mar 14.

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Is it posible that the blast in U3 propagated through the interconecting structure causing a breach into U4? I do not know the geometry in there but blast/shock waves can do some pretty strange things with all of the phase transitions in those buildings (Multiple water pools, widely varing concrete densities, possible via with high pressure piping between/joining buildings etc.

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bchtd1parrot, on 20 March 2011 at 1:47 PM — I only raise the possibility of some lateral blast making its way into #4 without any outward sign of damage to #4. I have no means of assessing a probability.

Hydrogen from #4 SFP would, one would suppose, be largely confined to the top story and damage would be to the sheet metal sides and the roof, as in #3. That concrete, much further down and on two sides was removed suggests that the hydrogen was down there, making the top of #4 SFP an unlikely source.

It is quite difficult to reach a high enough temperature to oxidize zirconium using air or steam. This makes the spent fuel as a source unlikely, especially given the radiation readings for #3 versus #4.

I’m not suggesting impossibility, but rather trying to obtain possible sources and routes for the hydrogen gas to create the explosion results in the aerial photograph. IMHO hydrogen from #3, by some route, remains a possible source.

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> response from the wind farm operators

I’d guess that would be “defer shutting down for any routine maintenance, take a chance on running longer, do the maintenance during the middle of the lowest wind period even if it’s off-shift hours, and run closer to the redline if they have high winds before shutting down to protect the hardware” — what would you do, if you knew there was a need to wring out everything you could?

The hydro plant operators, assuming there are some, could run their reservoirs down, trading off a risk of low water later for power now.

I have no expertise in wind energy, but there are options, always, to wring more performance at more cost or more risk.

And always, there’s conservation — besides the roling blackouts.

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Joshua, on 20 March 2011 at 1:52 PM — Yes, that is a possibility, but one cannot say how likely or how much damage that would do to #4.

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Hank, that white linear thing, that would be the vent pipe right? They both bend into the direction of the stack, but what is that thing sticking the other way? A valve? A fan? And then look at the pipe at the top of the stack. Thats just one pipe. To my carpenters eye test too narrow to contain the two down on the ground. And its not a concrete or brick structure, its one pipe in an open steel stack. If the blast at U3 rips the inventory out of that connection into the stacks direction, there’ s your connection between 3 and 4.

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We have heard this all before – 40 years ago…..

* * * * *

Interview with Greg Minor,
Former Senior Nuclear Engineer with General Electric

In 1976 Minor with two other senior engineers from General Electric resigned because they had come to believe that nuclear energy represented a “profound threat to man”. Together the three experts had 54 years experience in the nuclear industry. Greg Minor is interviewed by Mike Rann.

Rann: What prompted your decision to resign from General Electric.

Minor: Well, it was a series of events that happened over several years, but some of the primary reasons include the
fact that I began to see the link between the nuclear reactor programme we are using for commercial power and the
weapons problem which is being proliferated around the world. There were also a series of accidents and problems occurring, such as the Browns Ferry incident in Alabama. This was a plant I had worked on and it came dangerously close to the accident we are all trying to prevent.

Rann: What actually happened at Browns Ferry?

Minor: Browns Ferry was a plant where we had done very careful and improved design to try to prevent a single event from wiping out all the emergency systems that are used to protect the reactor and protect the public from an accident. But what had basically happened was that a single event, a fire caused by a lighted candle being used by an electrician checking airflow in the cable spreading room – wiped out 1,600 cables which connect the control room with the reactor. In doing so, the fire – which burned for seven hours – wiped out all the safety functions of the emergency core cooling systems that are normally called on in an emergency condition to save the reactor from a dangerous situation. Fortunately it didn’t quite come to the condition where it needed those emergency core cooling systems. If it had, they would not have been available. (Two of Browns Ferry reactors, supplying 15% of the total electricity demand for the huge Tennessee Valley Authority, had to be “scrammed” when erratic readings began to appear on the controls. Browns Ferry was out of action for many months and repairs cost tens of millions of dollars. Until the Three Mile Island/Harrisburg incident in April 1979, the Browns Ferry incident was regarded by nuclear critics and advocates alike as potentially the most serious incident in the history of the nuclear industry.)

Rann: The Browns Ferry incident was really the culmination of a number of very silly mistakes, particularly human
error. If the safety and control systems could be made more foolproof, would this remove most of your doubts about
nuclear power?

Minor: Well, I think the thing we learnt from the Browns Ferry plant was that you cannot make them more foolproof.
The thing that happens is that human element. Human error in either design oversight or the problems we didn’t
foresee in designing the plant, or in the manufacturing where a manufacturer didn’t follow the quality procedures or
the installation procedures, or maintenance problems. It was a maintenance problems that happened to catch Browns Ferry. But it could be any of those that would produce the accident in some other plant, regardless
of how carefully you think you have designed it.

Rann: Supporters of nuclear power say it is cleaner than other forms of power generation. They say it is less
wasteful, less environmentally disruptive. When you look at the track record of nuclear power generation over
the years, isn’t the Browns Ferry incident really the exception that proves the rule: the rule being that nuclear
power is efficient and pretty well safe?

Minor: Well, you have to be very careful in making that statement about cleanliness. A nuclear reactor is only
clean if it operates exactly as it is designed and these incidents around the United States and around the world
where reactors have released radio-activity into the environment, which they are not designed to release, and which ·
really overrides the rule of cleanliness they all like to speak about. The Browns Ferry incident was, as far as proving the rule that reactors are safe and clean, I would say, quite the opposite. It proves that they are vulnerable and they were very lucky that this reactor accident didn’t go all the way.

Rann: What about the potential benefits? Most proponents of nuclear energy would concede that the risk can
never be zeroed, but don’t the benefits from nuclear power more than compensate for what the proponents
describe as a very slight risk?

Minor: In my opinion they do not. The risks are so large that it is hard to put it on a scale that we normally think of in
any mechanical or technical disaster. The risks of a nuclear accident can be so devastating and so widespread and last such enormously long periods of time. We are talking about thousands and thousands of years of contamination of an area which may make it uninhabitable forever. These are dangers of a scale we do not normally think of.

Rann: What sort of catastrophe, then, could have resulted from the Browns Ferry incident?

Minor: The danger at Browns Ferry was that during the process of trying to get this reactor under control, when it experienced this devastating fire which was burning up the control cables, the operators had to relieve the pressure
inside the reactor and in doing so they had to manually open some valves which normally they would not open. But in manually opening those valves they released the pressure but they also lost a large part of the cooling water that
normally covers the reactor core, and that’s the concern. Because it you lose the cooling water and it gets below the
surface of the core, then you begin to have core melting and the danger would be that this core melting would
release radioactive material which was contained in there. If it went on further to melt out of the pressure vessel and out of the containing building, in a “China Syndrome” situation, then you would have that radio-activity released to the
public and the environment. And that would be a very, very serious accident.

[Mr. Minor is a anti-nuclear activist and was a consultant for the film “China Syndrome”.]

Source: Adelaide Independent
Adelaide, South Australia
Volume 1 Number 1
pages 6 – 7

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@ David B Benson 12:59

The R4 picture

clearly shows the R4side wall blown out is at and above the green machinery at the top of the SFP. Also see that concrete & rebar blown out not in, indicating an internal blast.

Also blasts propagate thru open space and the presence of damage to walls only meant that the blast wave could propagate to there, not that H2 & O2 were present there.

That said, I’m not sure why the R4 roof was not blowen off. Maybe we dont have that picture.

Re R3 blast being ducted into R4 would only make sense if duct is stronger than R4 walls.

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A couple of people have mentioned their concern about the refinery fire in Chiba. Lack of information on this has been bothering me too. Usually this kind of event would merit ongoing attention.

Anyway, this is the most recent article I could find:
http://bit.ly/g6Cb0i (in Japanese).

The following is a paraphrasing of the article, not strictly a translation, but pretty close fact-wise (if anyone has additional newer info, please post):

As of March 16, 13:30 the fire is still burning. To extinguish the fire all the remaining LPG in the tank needs to burn itself out, which is expected to take a few more days. Water is being sprayed and other measures are being taken to prevent any spread of the fire. As well, efforts to extinguish the fire itself are continuing, but at this point the fire is still burning.

The gas is the same type of gas used by people in their homes, so this fire is not expected to pose any health threat. There are some rumors circulating on the Internet about exposure risk especially in the case of rain, but “there is not truth to this” (Note: the article shows this as quote, but not attributed to anyone in particular).

All operations are currently suspended at the facility.

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Dear Bazza

To paraphrase Kipling:

“You are a man my son”

We have always been proud of you and your achievements but never more proud than we are now.

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More good news re ratiuation levels

TEPCOSAYS RADIATION LEVELS CONTINUE TO DECLINE

Tokyo Electric Power Company says radiation levels around the compound at its Fukushima Daiichi nuclear plant are on the decline since water-spraying began in earnest on Saturday afternoon.

The company told reporters that the radiation level at the plant’s headquarters building, located some 500 meters northeast of the No. 3 reactor, dropped to 2,625 microsieverts per hour at 8:30 on Sunday morning.

The reading shows a drop of more than 800 microsieverts from 18 hours ago–about the time the water-spraying at the No.3 reactor began.

Sunday, March 20, 2011 11:49 +0900 (JST)

http://www3.nhk.or.jp/daily/english/20_15.html

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Leo Hansen, on 20 March 2011 at 2:19 PM — The #3 explosiions were clearly different events than the subsequent #4 explosion. The (presumed) hydrogen came from somewhere, possibly #3 or reactions in the #4 SFP.

But the #4 explosion didn’t take off the roof and did take off concrete walls quite far down. One might suspect eartquake damage, but measurements at #3 were just over 500 gals and the units were designed to take 600 gals; quite unlikely that #4 concrete sustained any significnt damage.

So I entertain the possibility of a route for hydrogen so that an actual explosion could destroy reinforced concrete and still leave the roof intact.

Just trying to avoid leaving any credible alternatives out, thus not jumping to conclusions.

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neilvw, on 20 March 2011 at 2:29 PM — Try the Mobile, Alabama, newpaper. Sister city to Ichihara City and sending aid.

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David
Thank you.

Were those buildings designed for an internal blast? I remember seeing a hole on the side of one of the units that looked very regular, like a blow out pannel. I would guess that being a containment building it was designed contain what it could then fail. Would the design criteria be to hold the maximum overpressure and fail catastrophically or take a lesser load anf fail gracefully?

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bchtd1parrot:

The difference in average power between 50 hz and 60 hz is 20%. So running a 60 hz pump on 50 hz power will probably just provide less pumping power. Running a 50hz on 60 hz might burn it out – you would probably be eating up all of the safety margin (typically 20%).

Mike

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Joshua, on 20 March 2011 at 2:55 PM — I don’t know. From my inexpert interpretation of the aerial photo of the blast damage to #4, I suspect that the exterior walls were in precast sections; the walls appear to have failed along the connections between those precast panels.

That said, that form of construction wasn’t so common that long ago, but I otherwise have no way the explain, even to myself, that photgraph.

Take it with a big grain of salt, please.

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Sounds like things keep progressing towards a safe situation – hope so.

“The operator of Japan’s crippled nuclear plant is hopeful of connecting all six reactor cooling systems to external power by late tomorrow, a major step in bringing the nation’s nuclear emergency under control.
Cables were connected to the No. 1 and No. 2 reactors yesterday and technicians were testing this morning before activating them today.”
“Emergency services at the Fukushima plant were hopeful technicians could re-occupy the central control room this afternoon, making it easier to check various functions before external power was returned to the cooling systems.”

http://www.theaustralian.com.au/nuclear-plant-to-supply-power-to-cooling-systems-at-two-fukushima-reactors/story-fn84naht-1226024926342

Temperatures in the spent fuel rod pools at Fukushima Daiichi’s No. 5 and No.6 reactor buildings had been brought back to normal levels today and the firemen doused the No.4 reactor – the condition of which caused a panic in Washington on Thursday.

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This might be an interesting read:

Idaho National Engineering and Environmental Laboratory
INEEL/EXT-99-01318 December 1999
Ventilation Systems Operating Experience Review for Fusion Applications

http://www.inl.gov/technicalpublications/Documents/3318120.pdf

“This report is a collection and review of system operation and failure experiences for air ventilation systems in nuclear facilities. These experiences are applicable for magnetic and inertial fusion facilities since air ventilation systems are support systems that can be considered generic to nuclear facilities. The report contains descriptions of ventilation system components, operating experiences with these systems, component failure rates, and component repair times. Since ventilation systems have a role in mitigating accident releases in nuclear facilities, these data are useful in safety analysis and risk assessment of public safety. An effort has also been given to identifying any safety issues with personnel operating or maintaining ventilation systems….”

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uh, yeah … sounds like the ventilation, as well as the cooling systems, needed power all the time.

“…Fans showed many problems in the occurrence reports, followed by modest numbers of filter problems, the circuit breakers, motors, controllers and instruments, dampers, electrical connections, relays, ducts, gaskets, and switches…. Moeller (1975) cataloged other nuclear industry experiences. These experiences showed that fires and explosions have occurred in ventilation systems, particularly in power plant off-gas systems that handle hydrogen gas…. Moeller (1979) then cataloged other, later experiences with these systems…. An important event from 1976 was also mentioned there, ice buildup in the upper portion of an exhaust stack at a boiling water reactor. Exhaust air backed up into the off-gas building. The air was rich in hydrogen, and the hydrogen deflagrated. The off-gas building was demolished (Bertini, 1980)….”

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To Chris Warren at 2:15

So? Any conflict of interest there? I am not making any accusation but your motive for posting that piece was not at all clear to me. What exactly are you trying to assert? I’m just curious.

I’ll say right up front that in my opinion, that piece is just an example of the early format of anti-nuclear propaganda leading up to the golden opportunity of TMI where people could actually extol the horrors of a “meltdown” and the “China syndrome”. Except for the fact that nothing really happened.

So please clarify your reason for posting.

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Cosmo Oil to Boost Processing at Yokkaichi, Sakaide Plants

How do the fossil fuel industries get away with this? A 40 year old nuclear power plant goes down, the whole nuclear industry world wide is shaken by it. An oil refinery goes up in flames, and they just say “That’s okay, we’ll just boost supply from elsewhere. Don’t worry about the impacts!“. No one batters an eyelid.

Can anyone confirm if there have been any fatalities from the Chiba refinery fire?

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K. Nyankoye, on 20 March 2011 at 3:45 PM said:

I think anyone reasonably sensitive to the needs of the global community would see the points being made. I don’t want to appear didactic but:

1) Greg Minor was a Senior Nuclear Engineer with General Electric

He indicates that:

1) Browns Ferry was a plant designed knowing the dangers if all the emergency systems were knocked out – but a nuke accident still erupted.

This has been the case repeatedly for 40 years.

2) We get the leading suggestion from Mike Rann (a Australian politician, who is now known as Mr “U-Rann-ium”)

If the safety and control systems could be made more foolproof, would this remove most of your doubts about nuclear power?

This suggestion has been floated regularly for over 40 years, now – with the results we now see.

3) 40 years ago, nuclear engineers concluded: the thing we learnt from the Browns Ferry plant was that you cannot make them more foolproof. BP’s oil rig represents similar phenonema. Although it is more likely that commercial cots cutting is a greater source of risk in nuclear power. In every new technology – unforseen risks create catastrophe – eg NASA’s two space shuttles.

Only slow learners need more than 40 years to lean the lessons. Browns Ferry, TMI, Chernobyl, Fukushima giver us one nuke disaster every 10 years (actually less than 40 years – the rate is one every 8.5 years. Improving safety does not reduce the risk if you increase the quantity.

4) Next ancient (now refuted?) proposition by Mike Rann,

isn’t the Browns Ferry incident really the exception that proves the rule: the rule being that nuclear power is efficient and pretty well safe?

The best exposure of this nuclear “rationality” is simply to publish it.

Nothing refutes the processes that has led to the modern nuclear nightmare better than the actual earlier words of nuclear pundits – eg Mike Rann. The real subtext is in Mike Rann, not the poor GE engineer being played by Rann.

5) The next fabulation from Rann was his attempted suggestion that:

don’t the benefits from nuclear power more than compensate for what the proponents
describe as a very slight risk?

I wonder what his answer is now?

Imagine the risk in the future if Westinghouse or Chinese capitalists sell nuclear plants to Libya, Yemen, and Bahrain, and they are attacked in future political Middle Eastern volcanoes.

In short there is no:

conflict of interest there

there is no:

anti-nuclear propaganda

and pefull most will see the inherent denial in suggestions that:

TMI … nothing really happened.

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Things are going well. Yes, cooling of the U3/4 SFP is not restored yet, but water is refilled. Potentially power can be restored to U3/4 after U1/2 and hopefully cooling of SFPs of U1-4 soon.

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@bchtd1parrot, thanks

when I watched the vid, after I posted, I also noticed that, :oops:

In here http://www.wickedmike.com/main-facts-about-the-japanese-tsunami-2011/ it states that the mg sets were in the basement. If that’s true then even if the tanks hadn’t been knocked over they presumably would have lost the MG sets due to flooding.

As a former electrician I would be wary of running 50Hz pumps on 60Hz power, especially in a mission critical situation. Also there may be other kit to which they want to get power that’s more sensitive to power frequency. But if that was the problem then TEPCo should not have made that mistake, but maybe they didn’t actually supply it..

@Tom – That statement has been there for several days, I guess it’ll stay like that as long as the real cooling system isn’t working.

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What if hey pumps are so damaged that they will not work once the turn on the power?
Is it possible to fix them?
If not will they have to continue what they are doing now for months or even years?
Surely that is the biggest problem. If they cant get control within the next few weeks then what?

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‘Defense in depth’ backup systems to keep nuclear reactors and fuel storage pools cool all seem to depend on electric systems.

Safety depends entirely on electric motors driving cooling pumps. These motors are to be powered as follows; by electricity from the station’s turbines, by electricity from the grid, by diesel generators or by batteries.

Electric supply lines, motors, control systems and generators are all easily damaged by seawater. Diesels on the other hand are not, as long as air intakes, exhaust and fuel supplies are placed high enough.

If just one backup used pumps driven directly by diesel engines, by shaft, chain or belt, wouldn’t this add considerably to the overall safety?

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@ neilvw, thanks a lot for the information, the oil refinery fire is bothering me a lot, for several reasons
– it is far closer to big populated areas than the Fukushima plant
– it looks that the toxic fuel is spilling into the environment, spent or aflame, while the Fukushima fuel is still all contained inside aiproof containers
– I don’t know enough about refineries, but I cannot understand how is possible that a gas tank coulb BURN for many days a if it was a gas pipe connected to a large underground reservoir, instead of simply blast away
– I read nothing about the health risks caused by free flame combustion in open air of oil derivates, and the consequent breathing of different oxydes plus the environmental pollution of rain washed heavy black smoke
– we know the measurement of a Fukushima fart in µSv even 50 km away and two days after the fart happened, but I saw NO measurement data of any damage caused or inflicted to oil and oil related industry

if somebody has more accurate news, please let me know more on the subject.
thanks

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Hello Professor,
I’ve been following your updates the last couple of days and they’re great! My daily nwespaper is the FAZ, to which you gave an interview yesterday; it was refreshing to read opinions so contrary to the German media trend. And I agree with you that it is cynical to allow so much news space for potential dangers and consequences in a far-away country (Germany), when the misery of the people of Japan is real and tangible.
Kind regards

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@BerGonella
The burning tank you refer contains liquid petroleum gas. It has to evaporate to become combustible. It needs heat for that. The top of the tank is burning like a torch whilst the bottom is covered in ice. The greatest risk actually is the ice on the bottem. If it tears up the tanks lower level, the lpg floats out burning. Having the experience of standing face to face with about 120 kilos of lpg after opening the trunk of a car once i know it has to cook first. After a truck accident in a village south of Amsterdam some years ago 15 tons of lpg were vented smack in the middle of a village. What i do not understand about the burning tank is why they dont simply pump it empty.

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Here’s one i need to drop now for this here as i believe it is in the better interst of the post.

The argument against deleting PARTS of text out of a comment is that it leaves the remaining text out of context and thus changes the message. I have noticed on this post that partialy deleted messages read totally beyond the intend of the initial message some times. Since the comments are not anonymus i suggest to consider full delete if any delete is needed or consideration of consequences for comment message when in need for partial delete. Being someone who sometimes depends on moderator intervention i would welcome this. Thank you.
MODERATOR
Point taken.

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Since there are obviously many very knowledgeable people here, I decided to ask if someone has any insight about how the situation at the 2nd reactor’s damaged wetwell torus should ultimately be managed?

The water there is certainly heavily contaminated with fission products and it would seem that it would be a very good idea to try to keep it out of the environment. What can be done about this, after the more pressing issues have been dealt with? Is it already too late to do anything?

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I don’t know what is going on with the explosion at the spent fuel points, but all I know is this: if the bottom of the ponds are still covered in water at near ambient pressures (<200 kPa), I cannot for the life of me get temperatures over 800 degrees Celcius at the top of the spent fuel rods in my thermo model. And this is a pretty simple heat transfer situation, even with very poor ventilation it does not happen if there is still water at the bottom of the pond.

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I expect that the answer to this question is “No one really knows”, but I’ll ask it anyway.

Let’s acknowledge that the GE/Toshiba/Hitachi Mark 1 reactors have done a remarkable job in containment. Despite being 40 years old, they have withstood an earthquake 7 times as severe as they were designed to do. Then they were hit with a major tsunami. Then there were these hydrogen venting explosions, various fires, and intermittent high pressures, temperatures, and likely partial melting from within the reactors. Along the way there have been hundreds of afterquakes, some as high in intensity as normal earthquakes. And perhaps another big earthquake is still to come.

How does one intelligently evaluate the risk of a reactor rupture at this point? Should the thinking be: ‘Well, the reactors have taken this much punishment already. They’re probably also likely to withstand whatever else Mother Nature can dish out from here on in’? Or should the thinking be: ‘We’ve already pushed these reactors too far and gotten lucky. Any other event could well be the straw that breaks the camel’s back and cause a rupture’?

In other words, as we focus on reducing the risk of meltdown rupture, we also still have to contend with the current risk of quake rupture, which could negate all of our meltdown prevention efforts thus far. What do we know about the current general structural integrity of the reactors (other than “containment has not yet been breached”), how great is the risk of quake rupture, how bad would it be if it happened, and how great an evacuation perimeter should there be, given this risk, balanced against the risks posed by an evacuation itself?

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@bchtd1parrot,
thanks a lot for the explanation, I really did not know quite anything about LPG, knowing that it is really strange they do not try and pump it away, maybe it’s not possible to get close enough to the plant, because of fire.

anyhow, this it is not a reassuring situation, indeed.
I mean, now (if still aflame) the tanks are acting as big torches, but the risk of explosion of the “ice” is still clear and present?
what if it happens, do we know anything about evacuation plans?
and what about, of course, the pollution and the rise in cancer probability for the population in a 20 km range?

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David and Hank,
David is likely correct that the tall structures are the offgas vent stacks which primarily vent the non – condensible gases from the units condenser. During normal operations this gas would be processed by the hydrogen recombiners prior to release. Without power, the recombiners do not function. I thought about this too after signing off last night.

There are accident strategies though that use that path as a vent path from the reactor vessel (via main steam to the condenser).

No ability to make a conclusion if it’s related to the explosion on unit 4 still for now.

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I guess no one has posted this yet: As of 19th 16:20, the LPG fire at the Cosmo Oil facility in Chiba has been put “under control without risk of spreading”. They’d put out a total of 6 statements over 9 days on the status since the fire started, all accessible directly from the main page of their website.

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Another thought that came to mind and I have been unable to confirm this except for links stating a fire had occurred early on in Unit 4.

Most large generators are cooled with hydrogen. In fire situations depending on the location this hydrogen is vented through the turbine building roof. Since unit 4 initially only had a fire it is plausable that a generator hydrogen venting evolution may have contributed.

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@ BerGonella, what’s on fire is a huge tank of condensate (Butane, Propane), which burns fairly cleanly. It will have to burn itself out because it can’t be extinguished. It is doubtful any feeds to it are still delivering more HCs

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I don’t know if anyone has reported this here, but the latest JAIF reactor status report mentions that they are injecting seawater into the SFP of unit 2. This along with spray water to the SFPs of unit 3 and 4. This means they still have access to the normal ways of putting water into SFP 2, but maybe don’t have pumping to maintain cooling, but that is speculative. Still saying no outside AC power yet for 1 and 2. Does not mention if they will be injecting seawater into the SFP of unit 1

Click to access ENGNEWS01_1300624909P.pdf

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My mental picture of these processes is incomplete (Showing I have a firm grasp of the blindingly obvious.)
Can someone please comment on what is happening to the seawater after it is pumped into the plant?

I’ve been attributing the low reactor pressures (<0.02MPa in units 2 & 3) to some sort of containment rupture which prevents pressurization above atmospheric and allows leakage of the injected seawater. So where is it going? Is it carrying fission products?

Only part of the firetruck streams are hitting/staying in the SFPs. Again, are there fission products being carried away by the overflow?

Early on, there was concern about salt precipitation from the evaporation seawater. Is this no longer a concern?

Thanks for the level headed information. In contrast, a couple days ago one of our national news outlets referred to the "near certain death" faced by the plant workers. I think we all face that given enough time.

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We’re starting to see the effect on food supply — I thought relevant here at bravenewclimate as it has to do with contamination spread and geography.

Samples of milk and spinach near the plant were found to be tainted. In the case of spinach, up to 54,100 Bq/kg of Iodine and 1,931 Bq/kg of Cesium. With these numbers, wouldn’t even the shorter-lived varieties of I and Cs require several months to reduce to international limits?

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sorry Ctch, but where have you found those figures? t
the reading I found for the Tokyo water was very different (about 2.85 for iodine and 0.21 for cesium, as found HERE), can you confirm the figures, the unit and the source? it looks to me completely out of scale, given that is Bq/kg.

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With the caveat that I haven’t seen either the spinach or reports other than massmedia about it, it seems most likely that the reading is from particles _on top of_ the leaves, not inside them.
So a good washing might be all that is needed to bring it down to safe levels.
Though, except in cases of severe food shortages, I’d guess that it’s just easier to junk it.

WRT now growing, not yet harvested spinach, it is hard to tell whether just a few heavy (clean) rain showers will be enough. It all depends on so many factors (particulate spread even over a field or in spots here and there, drainage, how it would be diluted etc).
Best case scenario would be hose the field down with clean water, problem goes away.
Worst case scenario would be unusable crop from this field for this growing season.

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BerGonella – I think Ctch is talking about the reports of tainted milk and spinach from farms/fields 30-50 km from the NPP.
I too would love to see some more exact figures and sources for this.

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> Aspsusa, on 21 March 2011 at 12:44 AM said:
> With the caveat that I haven’t seen
> either the spinach or reports …
> it seems most likely

Speculation, unless you have some professional experience, is just baseless opinion. Why bother?

You can look this stuff up.

Assuming you’re a professional with access to an academic library, you can read the research on this; just for example:

http://www.springerlink.com/content/h5642u252l131l64/

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Why so nasty, Hank? :-)
Do we have any good, exact, sources for the figures Ctch posted?
I think I asked this yesterday (not in regards to the figures Ctch posted, haven’t seen those before, but the general reports about spinach and milk) but that might have been on some other site.

What would you say the likelyhood of contamination ON spinach as opposed to INSIDE spinach would be?

This type of data (measured contamination in produce) would be very interesting if we had exact locations and dates for it.

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> If just one backup used pumps driven directly by
> diesel engines ….

Have you seen the pictures of the diesel engines used at the plant? They are the size of locomotives, huge multi-story things. Starting a diesel requires turning the engine over with a starter motor. Yes, they could have designed in a huge tank of compressed air, or a huge windup spring, or something else as standby starting power, if the electricity failed, but nobody planned for this.

Nor did they have a harbor to bring in a large ship to supply power, apparently. A deepwater port and dock, if one had survived, might have solved many problems.

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Thanks for the link, btw. But it is about an experiment started _one year after_ Chernobyl. Shouldn’t say much about where stuff lands within a week of a leak.

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Cyril, it appears no one here can help you with your model, since you haven’t published it. You could get a blog? Looking in Scholar, near as I can tell, everything published is consistent, and much of the work on the subject is not published for the amateur reader. It appears that if you have a professional or academic institutional connection, you can download the models and computer code used for the cooling pool papers.

Example:
http://www.ingentaconnect.com/content/routledg/gsgs/2003/00000011/00000001/art00002

“… open-rack storage for the remaining more recently discharged fuel. If accompanied by the installation of large emergency doors or blowers to provide large-scale airflow through the buildings housing the pools, natural convection air cooling of this spent fuel should be possible if airflow has not been blocked by collapse of the building or other cause. Other possible risk-reduction measures are also discussed.

Our purpose in writing this article is to make this problem accessible to a broader audience than has been considering it, with the goal of encouraging further public discussion and analysis. More detailed technical discussions of scenarios that could result in loss-of-coolant from spent-fuel pools and of the likelihood of spent-fuel fires resulting are available in published reports prepared for the NRC over the past two decades. Although it may be necessary to keep some specific vulnerabilities confidential ….”

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Eagles Eyes, on 21 March 2011 at 12:14 AM said:
Now a confirmation in the last JAIF report for U4 SFP: “Hydrogen from the pool exploded.”

Actually they have been reporting that for several days now. I was doing other things/sleeping when this discussion got going or I would have pointed that out. Maybe we should accept that as the explaination, until proven otherwise. It seems to be the offical explaination as of right now.

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Aspsusa, the search term to use is “translocation” and you can look this up.

There’s a reason people look first, and specifically, in milk for iodine and in spinach for cesium, after a radioactive leak. Why do you think that is? These are ‘sentiel’ sources. Spinach has a very high rate of translocation, moves water from the ground and from rain on leaves into the plant’s leaves and stems fast (wilts if not watered very regularly!).

That’s what I’m encouraging you to do rather than speculate — read, it’s available. You can help people by making the effort to read and filter what’s there, or rely on people who do have time. Pure speculation without research wastes your time and the reader’s time to no benefit. Just sayin’. This is meant to be a science blog, not a chatroom, and citing sources is highly encouraged (and has been for years). The moderators have to sleep, the ordinary readers like us are asked to hold to a higher standard than at chatrooms. I’m not being nasty, I ‘m urging you to do your best to be helpful. I get the same, um, helpful advice (grin) and try to hold up my side.

Try here, just as examples of finding a place to start:
http://www.ingentaconnect.com/content/klu/wate/1998/00000101/F0040001/00122821
http://www.springerlink.com/content/u862t5266l15710k/

Look at p.111 here — an experimental comparison to determine whether putting plastic sheet over top of the growing plants changes the amount of fallout-derived cesium in spinach, among other plants and other elements:
http://books.google.com/books?hl=en&lr=&id=rdPMjXAOfmoC&oi=fnd&pg=PA96&dq=spinach+fallout+rate+translocation&ots=6V4qihhlgs&sig=VrBkZ_9TC1gHdeGMMMZLP_kUGw4#v=onepage&q&f=false

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For example (wow):
http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6168063

“This study describes the predicted response of Unit One at the Browns Ferry Nuclear Plant to a postulated loss of decay heat removal (DHR) capability following scram from full power with the power conversion system unavailable. In accident sequences without DHR capability, the residual heat removal (RHR) system functions of pressure suppression pool cooling and reactor vessel shutdown cooling are unavailable. Consequently, all decay heat energy is stored in the pressure suppression pool with a concomitant increase in pool temperature and primary containment pressure. With the assumption that DHR capability is not regained during the lengthy course of this accident sequence, the containment ultimately fails by overpressurization. Although unlikely, this catastrophic failure might lead to loss of the ability to inject cooling water into the reactor vessel, causing subsequent core uncovery and meltdown. The timing of these events and the effective mitigating actions that might be taken by the operator are discussed in this report.”

Pages: 176
Availability http://www.ntis.gov/search/index.aspx?frm_qry_Search=DE83012314
PC A09/MF A01; 1.

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Luke Weston

Looking at the top of the reactor vessel and then the cap sitting below in that image, made me think “Hey they screwed it on.” A few seconds of contemplation and those groves in the reactor vessel must be for the O-rings. Gives you an idea how large these reactors are.

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Thanks Hank! (I really mean that – having “translocation” as a word meant that my searches wrt milk suddenly turned up interesting stuff)

Still, what _data_ do we have about this (where does Ctch’s figures come from)?

With all the weirdly wrong and slanted stuff in the normal media, it is not that far fetched to question stuff like this (especially when not sourced).
Within one week of a release of stuff, I still think the first place to look for the source of high activity would be _on_, not _in_. In a few weeks, totally different story.

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what I think about data is that maybe the ones displayed by Ctch were originally in micro- (or nano-) becquerel, and that the prefix got lost somewhere.
just a guess, useless until someone founds the source

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Yes, seems absolutely out of scale, doesn’t it? Here’s the link for spinach — it’s a .go.jp site, Japanese equivalent of .gov.

Click to access 2r98520000015mig.pdf

The upper number for each item is “Radioactive Iodine”, the lower “Radioactive Cesium”. Doesn’t specify which variety (ex. Cs-134/136/137).

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For amateur readers like us, our best hope is to ask smart enough questions in public (showing what we’ve tried to do to learn) — and maybe attract the attention and help from someone who actually knows the field.

Pardon the pun, unintentional.

But seriously, logic isn’t reliable here. If we assume that fallout will be on but not in the leafy green plants in the first day or two, logic says wash them and then test the wash-water instead of looking in the plant.

My old doctor used to remind people that ‘theory and practice are, in theory, the same, but in practice, not’ or words to that effect.

Some plants are really good at taking in both water and nutrients (think airborne dust) from the leaves — “foliar feeding” — so to find out what’s happening takes experiments like those described.

http://scholar.google.com/scholar?q=spinach+translocation+cesium

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BerGonella, on 21 March 2011 at 2:22 AM said:
“what I think about data is that maybe the ones displayed by Ctch were originally in micro- (or nano-) becquerel, and that the prefix got lost somewhere.
just a guess, useless until someone founds the source”

No, I think you are confusing becquerels and sieverts. Becquerels are counts per second. Sieverts is energy deposited in one kg of a human tissue after multiplier effects of different types of radiation. Thery are related but not directly. Becquerels from different sources have different effects since the energy of the source is not considered. That is one of the reasons they have different limits for different radioisotopes. Here is the link where the numbers come from.

http://e.nikkei.com/e/fr/tnks/Nni20110320D20JF510.htm

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There are some vague, dodgy media reports of potential criticality in the Unit 4 used fuel pool.

However, I’m skeptical until I see better reporting on it.

Used fuel pool water is usually loaded with boron to keep it subcritical. Furthermore, if there is some kind of fuel-pool LOCA, you will have even less reactivity in the system because you’ve taken away the moderator, just like in a light water reactor.

To me, criticality seems quite unlikely, especially if the water is lost.

To get a criticality you would need to lose the pool water, then re-fill the water without adding more boron (plausible in an emergency LOCA situation?) and then disrupt the geometry, putting all the fuel too close together.

If you actually get criticality in the pool, you would immediately strongly light up the gamma dose rate and neutron dose rate monitors (and nothing else around the plant could possibly be emitting neutrons) across the plant, so we would certainly know about it if it actually happened.

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One advantage of using becquerels is that you do not have to calculate anything. You get it directly from the detector, asuming they have measured in a way that is standard for that detector. Geometry makes a difference and can cause errors, but I doubt enough to make much difference as these levels are well above the standards.

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Can someone pls. create a rule-of-conduct-on-this-post listing link for this exeptional situation? It can then be rapidly referred to. It saves space, nerves and can filter out sensations of personal judgement. (engage the slip-up, not the person).
We have thousands on non academix looking in here.

I have no means to do it myself ( one hand on the ladder).

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@ William Fairholm 3:13 AM

The “criticality” thing emanates, as far as I know, from a BBC information thread published on Wednesday http://www.bbc.co.uk/news/science-environment-12762608 in the form of the sentence :

“More remarkably, the Tokyo Electric Power Company (Tepco), which owns the power station, has warned: “The possibility of re-criticality is not zero”.”

Just googling now, I have not found a document containing this sentence directly on Tepco website.

This has scared me totally (I am a layman), and, 4 days later, I still don’t understand.

Hypothesis 1 : this is a mistake from a BBC journalist, but as this is not a smallish blunder, and as BBC is a serious institution, Tepco would have taken contact with BBC and some denial would have been published. Nope.

Hypothesis 2 : this really comes from Tepco, this is quite founded, and I cannot understand _why_, even if they believe it, they would have transmitted such a scary information. Even if true, this is pointless and can only add to anguish.

Hypothesis 3 : this really comes from Tepco, but this is unfounded, and this would be a gigantic blunder of their communication team. But no denial four days later ???

I have no qualification to judge it from the scientific viewpoint, but from the communication viewpoint this is also a deep enigma, and I shall appreciate to read other views of what that may mean.

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Question on the dousing of the pools.

Rather then dump water on it 24×7 they seem to be doing it in stages. Is this to give the fuel rods to come down to normal temperature smoothy rather then too fast?

Thanks,

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@ew-3
There must be a plan behing it for sure. 24/7 dousing being an option. Another possible expl. comes from the fact that the seawater in evaporating leaves deposits that may obstruct later ‘clean’ cooling. Cooling with seawater is an option now, but not indefinitely.

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The chances of criticality are never zero. They limit to zero at best, like the odds of winning the lotto every week or a bird singing the complete works of Beethoven by chance. As a result the remark: “…is not zero..” in abdolute terms doesnt mean a thing. As for those fearing global disaster in this context: read Ted Rockwell’s contribution. It may be coming from the one side and be a bit heavy, but the man does know what he’s talking about.

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Jean-Luc

Yes, I remember this from some days ago. I think I then read some old reports that discussed various scenarios for this. Can’t remember much of it or where I found it. The miscommunication/not correcting by TEPCO may be just that they are overwelmed.

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> Luke Weston
> Used fuel pool water is usually loaded
> with boron to keep it subcritical.

Mr. Weston, once again, please, _please_ cite your sources for what you believe, and give us some idea why you consider them credible for the claims you make. When I try to check your facts, I often find different information. You could do this yourself.

Pasting your sentence above into Scholar finds in the first page of hits:

Click to access 20104883541.pdf

“… BWR pools are filled with demineralized water while PWR pools are filled with borated water. The reason for this difference is that PWRs use borated water in the primary system for reactivity control, which mixes with the pool water during the refuelling operation. BWRs use the demineralized water for coolant….”

If you have another source on this particular reactor, please post it.

I appreciate your eagerness to present what you know, but it will always help if you would cite sources for what you believe.

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As far as I have experts at hand, a question which does not scare me but puzzles me, and whose answer must be obvious for the knowledgeable.

This document http://www.meti.go.jp/press/20110317008/20110317008-4.pdf (in Japanese, but with little text, this is mainly a table) is on the Meti website – I know its existence from Wikipedia talk page. On this page, somebody translated its legend by “The first column is the total storage capacity, the second column is the spent fuel, the final column is the unused fuel”.

The figures on the first and second column can be found elsewhere, and I understand them. The figures in the third column I have never met somewhere else (OK I am not reading everything written on this topic). What can they mean ?

(Example : line “3” of the table. First column : 1220 ; second column : 514 ; third column : 52).

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Hank, please make the link i asked for. You know the demands better than most. By the way:
@Hank Roberts, on 21 March 2011 at 1:09 AM
I know for a fact that AGA in Holland has compressed air powered emergency equipment available. Anything from pumps over submergable generators to lights. Its not that this stuff doesnt exist. The general rule at emergency equipment is to keep it as reliable as possible, or k.i.s.s. as they call it.

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@dhill001, on 21 March 2011 at 12:11 AM

The seawater is used as a coolant that is ‘consumed’ by the process. Either in the way of evaporating of seeping away. Both carry some radio activity likely, but content of fission product would render this method highly risky. It is to my opinion safe to assume this possibility is being monitored on site continuously. Radiation effects released due to the currently used method would disappate/decay in acceptable time relatively locally. In a non scientific way, try think of radiation as light. In that idea such a steamcloud would be a flash light, but stop flashing relatively fast. (Someone correct me if this is an incorrect illustration).

As for the ‘certain death’ thing: We all face certain death, life’s a killer. Radiation is a funny customer. You may stand somewhere getting a full blast while someone standing a few feet away gets not one tenth as much. Add to that the fact that differt peoples different health condition and precondition respond differently to different kinds of radioactive influence and you will understand that there are both chances and risks for these men. Considering both in any way these men qualify as huahh courageous. They are there.

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This is beginning to sound like a lawyer thing. Assume its for real and do the homework on how bad bad is or drop the subject. Tepco doesnt own the truth and this is the look-for-answers post. No offense.

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“– Reactor No. 4 (Under maintenance when quake struck)

Renewed nuclear chain reaction feared at spent-fuel storage pool, fire at building housing containment of reactor Tuesday and Wednesday, only frame remains of reactor building roof, temperature in the pool reached 84 C on March 14, water sprayed at pool on Sunday.”

http://english.kyodonews.jp/news/2011/03/79849.html

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