Time for a new Open Thread on the Fukushima Daiichi nuclear crisis. Please use this post to put any new comments about the situation (including technical information, situation updates, analysis, questions, reflections, etc.). Note that the Open Threads on BraveNewClimate.com are a general discussion forum; please follow the commenting rules, although the ‘stay on topic’ rule obviously does not apply as strictly here.
For context, below is a brief list of recent events since the previous FD post. (For day-by-day detailed updates, I suggest you follow the ANS Nuclear Cafe news and updates (includes links to official reports like JAIF and TEPCO and news feeds from NHK, NY Times, etc.), see also NEI updates, and other links provided in previous posts.)
1) Fuel melt: Recent analysis suggests that the fuel assemblies in unit 1 were almost completely melted in the days following the March 11 earthquake and tsunami. The ‘corium’ (melted actinide fuel, contained fission products, clad etc.) then dropped to the bottom of the reactor pressure vessel (RPV). It is now suspected that during the initial accident, the fuel rods of Reactor No. 1 could have been fully exposed for up to 17 hours, and the earthquake may have caused some structural damage that led to pipe leakage and other problems, in addition to the severe troubles caused by the extended station blackout following the tsunami (which remains the principal cause of the problems).
The temperature of the RPV is now in the range of 100℃ – 120℃, and so the core (or what remains of it) and RPV are stably cooled. That is, this new information is part of a post mortem analysis of events and timeline of the accident, rather than a trigger for a new urgent crisis.
Despite this, this announcement inevitably led to a whole new wave of speculation (and hype), including rumours alleging “1) “melt down in unit 1 has burned a hole through the bottom of the containment vessel” and 2) “that there was a detonation of the fuel rods & pieces of fuel rods were found two miles from the reactors”.
What is the reality? A close nuclear engineer friend of mine says the following:
There is no evidence that the molten fuel has melted through the bottom of the reactor pressure vessel. The latest TEPCO analyses suggest the molten fuel is submerged in water at the bottom of the pressure vessel. Some TEPCO reports mention about “holes” in the containment vessel. What they mean by “holes” is that the seals on pipe penetrations, etc. may not be leak-tight, and hence steam and/or water leaks out of the vessel.
The second claim is absolutely not true. The site is highly contaminated. The radiation mapping of the site, which has taken more than a dozen surveys (because you can do just a few at a time) indicates the contamination is concentrated in the rubble. The steam vented to the reactor building would have carried along volatilized I and Cs, some of which were condensed onto the walls and surfaces, which then blew up in hydrogen explosion.
The soil sample around the site indicated detection of minute quantities of plutonium (some samples included both Pu-238 and Pu-239, and others just Pu-239). The magnitude was within normal fallout contamination ranges. It is not clear whether these Pu detections indicate they are old contaminations or fresh from Fukushima Daiichi.
2) Restoration roadmap timelines revised: Obviously, the more extensive fuel damage at unit 1 will hamper restoration efforts and set back the site management plans. Workers entering unit 1 to install a new cooling system encountered high radiation levels, although because of of protective gear the workers were only exposed to very little radiation (about 2 mSv). However, the company still expects the damaged units to be stabilized by the end of the year. To quote WNN:
Work has already started on constructing a cover over the damaged reactor building of unit 1 to prevent the spread of radioactive materials. Similar covers for the reactor buildings of units 3 and 4 are now being designed. Unit 2 will not require a cover as the reactor building remains intact.
The current status (17 May) of the roadmap can be read in these 8 diagrams (PDF file).
3) New theory for Unit 4 hydrogen explosion: An apparent contradiction at the unit 4 spent fuel pond was the lack of visual damage of the fuel assessmblies and the difficulty in explaining how radiolysis alone could have evolved so much hydrogen — especially if the fuel was never exposed to air. There is now a new explanation for the source of the fire. TEPCO stated:
The SGTS line of Unit 4 merges into Unit 3 exhaust pipe and it might be a case where hydrogen gas came from Unit 3 flew into Unit 4 reactor building. But this estimation remains presumptive and we have not reached to conclude that the vent operation at Unit 3 caused the explosion at Unit 4. And it is not clear the open/close status of valves in SGTS and when and what amount of hydrogen was generated/ flew in the Unit 4 as of this moment.
Some further details here. This is also a plausible explanation of why the unit 4 storage pool had a low level of radioactivity, and why the two fires extinguished themselves without intervention.
4) Worker death: A sub-contractor at the site has died — he had been working on the drainage system of the centralised radioactive waste store. Tests showed that the worker had not been contaminated with radiation (he was exposed to 0.17 mSv), and he appears to have unfortunately died of a heart attack (he was in his 60s). To underscore: sad as this is, ut is not a radiation-sickness-induced death.
5) Hamaoka Nuclear power plant shutdown: Run by Chubu Electric, Hamaoka may be closed, based on political edict. The site includes four ‘Generation II’ boiling water reactors opened between 1976 and 1993, and a new Advanced BWR (1,200 MWe) opened in 2005 (unit 5). As it turns out, units 1 — 3 may not ever be restarted, and further site reinforcement will be required before units 4 and 5 can resume operating.
But what if Japan decided to retreat from their plans to expand nuclear power to meet 50% of their energy needs by 2030? What would it cost them, in terms of (a) increased emissions of greenhouse gases, and (2) financial alternatives. In a superb analysis, The Breakthrough Institute looked at the possible alternative scenarios in their piece: The Costs of Canceling Japan’s Plans for Nuclear Power.
The bottom line is this: (i) if coal and/or gas is used, emissions will rise 15 to 26% and the cost will be $90 — 150 billion in capital costs and a $17 — 27 billion annual hit in terms of increased imported fuel (coal or LNG); (ii) if attempted with renewables, the cost would range from $330 billion (wind, no storage) to $690 billion (solar, with some generous assumptions, representing a 190-fold increase in installed capacity). I’m reminded of what George Monbiot said recently, “The Lost World“:
The case against abandoning nuclear power, for example, is a simple one: it will be replaced either by fossil fuels or by renewables which would otherwise have replaced fossil fuels. In either circumstance, greenhouse gases, other forms of destruction and human deaths and injuries all rise.
Which do you want, folks? If you care about climate change mitigation and clean, reliable and cost-effective power, then it’s time to get real about nuclear energy.
290 replies on “Fukushima Daiichi Open and Update Thread #6”
(Comment deleted as previous comment, to which you refer, has also been deleted.)
@shamus, the limited uranium resources claim is an incredibly old and tired claim that misrepresents the known uranium deposits as all there is – not true of any mineral, let alone one as little explored for as uranium – and ignores other options, like the potential use of already-mined U-238 in advanced reactors or uranium extraction from seawater.
http://world-nuclear.org/info/inf75.html for more…
The unsubstantiated comment by Shamus was deleted for not providing references to support his claim – thank you for providing refs to support your.
In fact, shamus, you could do a lot worse than look up practically any vague negative claim you come across on http://world-nuclear.org/info/info.html – there is a lot there.
By systemic failure I mean a system which has failed.
You claim Fukushima was a “unique event” and ascribe it to “a plant operator not having the necessary backups in place”.
We need to ask *why* the necessary backups were not in place; *why* the regulators failed to spot it; *why* the operator chose to ignore warnings.
My answer is that the *system* of nuclear regulation failed. Any even in your terms there is a systemic failure of us to provide long term storage for high level waste.
Your analogy with chemical plants is good, and the Seveso II EU regulations show how specific learning from one incident can be well applied to correct systemic failure. Flixborough in the UK likewise brought about systemic change in the control of modifications.
Cyril R – by adjacent I meant immediately adjacent in the same building – I completely agree with your comments and you also highlight the systemic failures now evident.
Brian, on 2 June 2011 at 9:00 PM said:
We need to ask *why* the necessary backups were not in place; *why* the regulators failed to spot it; *why* the operator chose to ignore warnings.
Predicting Tsunami run-up heights is not a simplistic exercise nor is it an exact science.
Here is a table of Modeled vs Actual Tsunami runup heights for the US for March 11.
For Adak,AK the model forecast 52cm, the actual was 110cm. The Tsunami height in Adak, Alaska was double what the best experts in the world predicted.
How does one prepare for a Tsunami created by an earthquake of unknown characteristics when even when we know the characteristics we can’t model the Tsunami height with any degree of accuracy?
Should we take the most pessimistic prediction made by anybody and assume that? The consensus? The worst case to have happened anywhere in the world ever?
The highest Tsunami runup ever recorded was 524 meters.
Brain, I’m just not sure how useful it is to talk about ‘systemic failure’. I guess you can argue that external safety, in which I am involved on a professional level, is event-driven and only partially pro-active. You could argue that this type of external safety ‘attitude’ is a systemic failure. But how useful is this?
Much more useful is to make a list of things that went wrong in an accident, whether its a chemical plant or nuclear plant, and then use that to make a list of upgrades/technical changes required to prevent
What I find interesting at the Fukushima Daiichi events is that the upgrades required are obvious, simple, and low cost. So we can solve the issue of future nuclear safety during prolonged outages, large radiological releases, and flooding very easily.
I do agree about the systemic failure, but would stress that this is generic to the world of public (external) safety in general, and I argue that its much more useful to take a pragmatic, measures-based approach, rather than getting into philosophical debates of systemic versus technical failures. I talk to a lot of so called ‘environmentalists’ which get into these type of philosophical debates all the time, and its just not useful or productive.
“Should we take the most pessimistic prediction made by anybody and assume that? The consensus? The worst case to have happened anywhere in the world ever?”
Perhaps the criterion could be: the design must be robust enough that it requires a disaster such that a BDB failure of the design is a minor problem compared to the disaster itself.
This is the case for some 28K Japanese casualties, and 1000 orphans. But the psychology of nuclear is such that this criterion is not high enough for too many other people.
Moderator: Here are some sources to the comment above that you removed. I fear now you have removed that comment, this comment is now going to be against the guidelines… but its an open thread… let’s see what happens.
If all the existing on Earth uranium beds are set in motion they can enable running of 440 nuclear power plants for 45-80 years. Uranium stocks will run out and all the plants and their infrastructure will turn out to be absolutely useless. Moreover, because of residual nuclear radiation these plants can’t be restructured for different functions.
Perhaps the most worrying problem is the misconception that uranium is plentiful. The world’s nuclear plants today eat through some 65,000 tons of uranium each year. Of this, the mining industry supplies about 40,000 tons. The rest comes from secondary sources such as civilian and military stockpiles, reprocessed fuel and re-enriched uranium. “But without access to the military stocks, the civilian western uranium stocks will be exhausted by 2013, concludes Dittmar.
Brian and V*2XL have differing views of the meaning of the term “systemic failure”.
Simply, DV82XL is correct, in that his interpretation corresponds with normal english usage.
See: Dictionary.com or Wikipedia, for instance.
Systemic refers to something that is spread throughout, system-wide, affecting a group or system such as a body, economy, market or society as a whole.
Brian may have drawn attention to failures at Fukishima, but he has not demonstrated that they are systemic by nature, beyond vague affirmations in his subsequent post.
No, Brian… Fukushima’s problems are plant-specific unless and until industry-wide spread is demonstrated.
We must use our best endeavours to ensure that our language is not debased by cliches and loose usage. After all, this is a web site, where 100% of our communication is via the written word. There are no facial expressions, no verbal inflections, no body signals. There are only words, which should be respected and treated with care.
@shamus, Apparently nether you or your sources understand how markets work. Uranium mines in known deposits are not being created BECAUSE cheaper uranium is available from military stockpiles. The reason is that this surplus has depressed the price, making it uneconomical to exploit other sources.
All other statements about a general shortage of uranium is wrong, and this has been established here on several other occasions.
Please supply a reference for your statement “Uranium mines in known deposits are not being created BECAUSE cheaper uranium is available from military stockpiles” otherwise it will be deleted.
“Should we take the most pessimistic prediction made by anybody and assume that? The consensus? The worst case to have happened anywhere in the world ever?”
it would be pretty easy to build new nuclear power plants high enough. simply place them 50+ Meters above the highest flood that pessimistic scenarios expect. (and do not build it below an overhanging cliff, to avoid the extreme scenario described in your “worst tsunami”-link)
the problem are the existing plants. their flood protection is often lousy, as described in the German report done after Fukushima.
Click to access sicherheitsueberpruefung_stellungnahme_rsk.pdf
the 10000 year flood would be 0.5 meters below the doors of reactors. it would turn several plants into islands. (not good for access during an emergency)
the IAEA report on Fukushima is drawing serious critisism in Germany. even the conservative “handelsblatt” (“trading paper”) has written a sharp response:
it calls the conclusions “strange” and “abstruse”.
the IAEA doesn t even mention damages done by the quake and calling the reaction “exemplary” is beyond bizarre.
after the accidents the plant was lacking such obvious needed goods as dosimeters or flash lights. they failed in bringing in back up diesels, water pumps or robots early enough. the workers had to go without beds, showers or fresh food until the start of this month. and even now there is danger of water leaking out, because they can not bring in water tanks in time.
so i am with Brian on this one: there is a systematic failure, basically the worst case was never considered. the plant was not prepared for response to a melt down and leaking radioactivity.
this is strange, because as Cyril said above, it would cost very little money.
Swiss is storing exactly this kind of emergency equipment now, so it is a systematic failure, that happened in several countries.
i also think that reports like the IAEA one are a systematic failure. the nuclear industry and society reacts in a defensive way, trying to downplay serious problems. in the long run, honesty and realistic assessments would be the better approach.
DV82XL : Hey if you say so. Don’t trouble yourself with citing any sources: if your unsupported contradiction is good enough for the moderator, that’s good enough for me. If you say the military sells uranium, it must be so. (snide remark deleted)
As DV82XL states:
“All other statements about a general shortage of uranium is wrong, and this has been established here on several other occasions.”
Facts that have been established on previous BNC posts cannot be expected to be continually raised and referenced for each new commenter. It is incumbent on you to research this site yourself. DV8 has been asked for the missing reference re the military.See also Moderator comment above. Note Shamus that DV8 has provided the ref above at 9:13 PM
shamus 3 June 10:51 AM “Here are the sources”
No, they are not sources for anything other than the text that you have pasted in. We need the links to discover something we didnt know from sources we can respect. However, the source you quoted ( http://www.theurbn.com/2011/06/50-arguments-against-nuclear-power-engineering-2/ ) doesnt connect to facts either.
The Megatons to Megawatts Program, the name given to the program that implemented the 1993 United States-Russia nonproliferation agreement to convert high-enriched uranium (HEU) taken from dismantled Russian nuclear weapons into low-enriched-uranium (LEU) for nuclear fuel has had a well known and classically predictable effect on the uranium market.
Among many others.
Thank you DV8. Shamus please note!
@Sod – No one was ever arguing that this plant wasn’t unprepared for this event. I am arguing that this does not imply that ALL nuclear plants are unprepared, or in fact need to be prepared for this particular type of event as most are in seismically quiet zones, and/or far enough inland to be out of reach by a tsunami
sod, on 3 June 2011 at 4:59 PM said:
the IAEA doesn t even mention damages done by the quake and calling the reaction “exemplary” is beyond bizarre. </i
The unparsed sentence –
Japan’s response to the nuclear accident has been exemplary, particularly illustrated by the dedicated, determined and expert staff working under exceptional circumstances;
Here is a progress report on setting up the waste water purification system that is ‘almost’ complete.
The article notes the waste water purification system for the TMI accident took 18 months to install.
People with experience in the Nuclear Industry familiar with normal time frames for completing X,Y or Z task may have a different opinion as to ‘progress’ then a member of the public.
The MIT faculty report was just released here: Technical Lessons Learned from the Fukushima-Daichii Accident and Possible Corrective Actions for the Nuclear Industry : An Initial Evaluation [PDF] (19 Pages). This seems to me to be the reasoned assessment we should expect from a team of engineers accustomed to risk analysis. Unfortunately, the German government did not take the time for a similar lessons-learned assessment. The report begins with this paragraph:
@ Steve Darden, on 4 June 2011 at 6:34 PM:
The document is short and easily read.
My initial response is that, in parts, the language used appears to be somewhat of an apologia for NPP’s. This is unfortunate, because the underlying messages were about the need for calm and ongoing preparedness and the risks and costs of panic.
MIT are to be commended for their willingness to publish on this subject only a couple of months after the incident, while many matters are still incompletely investigated.
I think plant operator reactions were ok, with the important exception of waiting too long with the seawater injection.
I would blame GE for the design flaws of positioning the diesel generators and flood-vulnerable critical electronical infrastructure failing that is impossible to repair, spent fuel pools high up, not having a small electrical generator attached to the emergency steam turbine cooling system, not having high quality filter systems on the emergency steam venting lines, and letting the venting lines terminate to the upper portion of the building in stead of a hardened external chimney higher up.
TEPCO migh be blamed of being the most terrible communicator of the century. But it might be a bit early in the century for that ; )
I don’t blame the Japanese for not going with the frenzy that the US regulators had on their plants after three mile island. Yes some good improvements were made, but it was hugely excessive in most cases, and therefore needlessly expensive. If we look at the above design flaws it could probably be fixed for a couple million per reactor at most in new (mostly passively safe – no moving parts) equipment.
Cyril R., on 4 June 2011 at 8:16 PM said:
I would blame GE for the design flaws of positioning the diesel generators and flood-vulnerable critical electronical infrastructure failing that is impossible to repair
Not all the GE BWR’s have the electrical equipment in the basement.
I think that problem lays at the feet of Japanese regulators.
Venting inside provides time for the short lived radioactive material half lives to end.
In hindsight a foolish idea…the thought process at the time was probably to keep any radiation levels the public is exposed to as a result of any venting as close to zero as possible. “Penny wise, pound foolish” seems to apply.
It would have been less foolish if there were lots of passive hydrogen recombiners.
Personally I’d prefer just lots of carbon and HEPA filters in the vent lines. Remove 99.99% or so. And maybe even terminate the vent into an artificial lake next to the reactor so that any residual activity would be scrubbed and the steam would be quenched.
Cyril R., on 5 June 2011 at 1:12 AM — Or just bubble down into the nearby ocean.
Sure you can also terminate the vent pipes into the sea, several meters below the surface, with sparger nozzles attached for maximum scrubbing efficiency. At least there wouldn’t be much air emissions to worry about (and the seawater emissions self-dilute to safe levels very quickly, contrary to some worried environmentalists). A seperate lake body would be even better though, as people can’t cry about the poor fish and all that.
I just read this reference which goes into the features of CANDU reactors in a Fukushima scenario. Various design features cause a favorable performance in such an event:
“CANDU plants are designed to withstand standard earthquakes multiplied by a comfortable safety factor. They are, essentially pressurized heavy water reactors (PHWR’s) with vastly different heat sinks and cooling systems than available to BWRs (boiling water reactors) in Japan. A CANDU reactor has primary and secondary heat removal systems that do not connect but interface through steam generator tubes. One could start listing even more differences between a modern CANDU and Daiichi plant such as: the CANDU has two independent, horizontally oriented cooling loops composed of pressure tubes, not a pressure vessel; there are four standby generators for backup power, of which only one is required to supply power for long term core cooling. As a ‘backup to backup’ there are redundant, seismically qualified, emergency power generators out of which only one must operate to supply long term power needs. There are the post-accident hydrogen igniters that would burn any hydrogen before it reached explosive concentrations in the reactor vault. CANDU reactors have multiple safety systems addressing one type of accident and all critical equipment is environmentally qualified to perform its mission in a most adverse, post-accident environment.
CANDU reactors are designed to protect against or mitigate the effects of credible common mode failures such as a seismic event. A common mode failure, the tsunami initiated wetting of all emergency power supplies disabled emergency core cooling systems and caused multiple nuclear accidents at Fukushima.
High fields around reactors at Fukushima impeded access to their cooling ponds located in the reactor buildings. CANDU spent fuel bays are located outside of the reactor buildings.
CANDU nuclear power plants have huge spent fuel bays designed to hold all fuel removed from the reactor for ten years under a ten metre layer of water. Even with a prolonged interruption of bay water cooling and make-up, the water level would not be rapidly dropping due to evaporation as was the case at the Fukushima unit 4 cooling pond.
This is because of a difference in fuelling systems. In BWRs fuel from the entire core is replaced at once during fuelling outage (15 tons of spent fuel at one time). On the other hand, only a small quantity of spent fuel is removed from a CANDU reactor on a daily basis (about 0.27 % of the core inventory at a 935 MWe CANDU unit , approximately 320 kg or 16 fuel bundles). The difference in fuelling strategy in conjunction with the type of fuel used, results in the amount of residual heat being much lower in CANDU spent fuel bays than the amount of heat in the cooling ponds at Fukushima.
In terms of potential spread of radioactive contamination from damaged spent fuel, the cooling ponds at Fukushima are located at high elevation above ground. In contrast, CANDU reactors have their spent fuel stored under a 10 metre layer of water and the fuel resides below the ground level which impedes the spread of contamination to the environment.
Storing CANDU irradiated fuel in spent fuel bays is 100% safe and cannot cause out-of-core criticality. There is no physical possibility of CANDU spent fuel to ever go critical while submerged in demineralised water. CANDU fuel requires heavy water moderator in a special lattice to sustain a chain reaction.”
Cyril R., on 5 June 2011 at 9:35 PM said:
the water level would not be rapidly dropping due to evaporation as was the case at the Fukushima unit 4 cooling pond
I can’t find the link but… IIRC unit #4 was undergoing a ‘shroud replacement’ which is why a full core offload was in the spent fuel pool.
Hmm, well, even with a normal refuelling outage, about 1/3 of the fuel would be in the spent fuel pool.
Candu’s don’t have core shrouds, but they do have pressure tube replacement once every couple decades. But even then, the bigger spent fuel pool combined with below grade siting, and no possibility of recriticality in light water (need heavy water) gives it an inherent advantage during prolonged blackouts etc. Heck, you can walk up to it, plunk in a firehose and that’s it.
Newer BWRs also have spent fuel pools below grade.
Did anybody see hungry beast on the ABC last night? On their ‘stuff said’ segment they quoted financialgreenwatch.org putting the cost to decommission fukushima at $90,000,000,000 and the cost to rebuild “fukushima power plant” – Dai-ichi I presume – at $600,000,000,000. I realise this segment is often used to quote silly very things people say, but it was presented in a very matter of fact manner, to a likely audience of anti’s. A quick browse through the FGW site showed it to be exactly what I expected. A quick google suggested the whole march earthquake rebuild cost could be up to $600b, so if that amount of money were just spent on reactors, I imagine Japan would put a pretty serious dent in their FF emissions.
I wonder if it’ll get a mention on mediawatch… I’d write to them, but I think I’d have more luck getting a church choir to belt out some tunes by slayer.
I caught the following article on ABC website yesterday… surprised to see nothing about it here? Is it fair dinkum?
Japan raises spectre of Fukushima ‘melt-through’
An official report, which Japan will submit to the UN’s nuclear watchdog, says nuclear fuel in three reactors at Fukushima has possibly melted through the pressure vessels and accumulated in outer containment vessels.
Japan’s Yomiuri Shimbun newspaper says this “melt-through” is far worse than a core meltdown, and is the worst possibility in a nuclear accident.
Poor, poor form HUNGRY BEAST!
RE: NinetySix – the worse thing is – you are incorrect as it was not on their ‘STUFF SAID’ segment which simply quotes random people, it was on their ‘factual and news’ segment called “FOLLOW THE MONEY” – which is presented as FACT and NEWS to viewers.
They stated as fact: “$600 billion to rebuild the Fukushima power plant”
Wrong! That is the estimated cost (up to) to rebuild the entire country from the earthquake and tsunami!
Hungry Beasts MAJOR factual error can be seen here @28:00 mins: http://hungrybeast.abc.net.au/episodes/episode-32
maybe post a comment under the video? but i don’t think anybody reads them.
Sorry my bad, it was actually part of hungrybeast’s “follow the money” segment. This lends far more credibility to the suggestion that replacing 4 reactors will cost $0.6 trillion.
Further to MattB’s comment about the ABC report of a melt-through, today the reports are of PU and Sr 90 found in Fukushima township. Does anyone have any further information on this or is it just a journalist that’s gone off half cocked?
I understand that Sr 90 has a half life of 29 years so could it be from nuclear bombing 65 years ago?
There’s some fascinating discussion here – great thread. I’m a nuke with 13 years of experience (PWRs, so I’m not terribly familiar with BWR designs), and perhaps the major question for me is in regards to hydrogen control at the plant. In the advanced reactor design I was working on, passive hydrogen recombiners are used to avoid hydrogen buildup and explosions like those that occurred at Fukushima.
What hydrogen control mechanism was used at Fukushima, if anything? Did they have igniters that were lost with the LOOP? Is there no requirement in Japan for having hydrogen control devices?
There are quite a few things that really piss me off about this accident, including things that cannot be interpreted as anything but serious design flaws:
>> Putting emergency-critical electrical switch gear in a basement not hardened against floods is sheer stupidity. Anybody who has a basement knows they get flooded. Particularly if you live near water.
>> Putting in a SFP high in a building where it is coupled to the reactor in accidents is mind-boggling. If anything, locate it down low so it *does* get flooded.
>> Allowed hydrogen to vent into your reactor building rather than out a hardened stack or vent, and losing all hydrogen mitigation equipment concurrent with a LOOP.
>> Having no diversity in your emergency diesels (so that a single event takes out all 13) is anathema to what we are taught about reactor safety.
>> Not being able to simply airlift in batteries or diesels/diesel fuel and plug them in (to extend the coping period)
>> Siting a reactor on a beach in a tsunami prone area, then only planning for a 5 meter wave. Particularly when you have 500 year old tsunami stones on cliffs far above the beach:
I understand the catastrophic and extraordinarily rare initiating event for this accident, but it could have and should have been handled much better. It has done severe damage to our industry and our reputations.
TPL, they do have hydrogen recombiners, or there would be trouble in normal operation due to radiolysis gas buildup. But they are actively powered, need electricity for fans and such. That wasn’t there, so no or very little hydrogen recombination. I’m not sure if the active recombiners were spark igniters or fan powered flow over catalysts.
It’s sad, since passive hydrogen recombiners, that need no electricity, have been available on the market for some time now. And even the active igniters need very little electricity so can just have their own lithium batteries and keep working for months.
Definately agree that some funny stuff is going on here – in the negative sense. Putting the diesel generators high up, having redundant transformers and other electrical equipment in a seperate AC system, would have prevented the entire core damage sequence, and is so obvious it should have been detected by the regulators as a common mode failure risk. Venting hydrogen rich gas to the top of a building where the ventilation systems depend on external electricity supply, gee is that a good idea. Putting the spent fuel pool in that same explosion prone area a hundred feet up in the air, oh yes a very good design choice.
A simple firehose standpipe on all sides of the building with hardened spray nozzles above the spent fuel pool would have made refilling with water very easy.
Why was there no generator attached to the decay heat steam turbine cooling system? No power for the valves, not enough battery capacity. Amateur hour!
GE made serious and egregiously obvious design flaws in their oldest BWRs and the Japan regulators allowed it. I remain flabbergasted by this. Most of the technical improvements required cost very little.
I’m also disappointed in the political response to the events around the world. Germany’s response is absurd. They’re not going to close down their oil refineries despite serious problems with the oil refineries in Japan (burning for days, throwing out carginogenic half burned hydrocarbons).
People are talking about removing spent fuel from pools into dry casks, but that serves no point. Its the fresh fuel that’s the problem, and this cannot be put in dry casks yet. Plus only the high up fuel pools of older BWRs are vulnerable – at Daiichi there is also a central below grade storage pool and that’s fine. No chance of water sloshing or catastrophically breaking out, easy to refill and repair. Nothing wrong with below grade spent fuel pools. Add the hardened spray and standpipe connections is about the only technical measure one might improve on with these pools.
Its clear that nuclear power is entirely political and that most people don’t know a thing about the technology. Its not any different than thirty years ago. So sad.
Martin Nicholson, yes Japan has high background levels due to atmospheric bomb tests:
This is enough to explain the measured amounts, more or less; please see discussion here, debate with a nuclear engineer from Canada (Jaro) and with calculations from a nuclear chemist (Luke)
@MattB, on 9 June 2011 at 11:14 AM said:
An official report, which Japan will submit to the UN’s nuclear watchdog, says nuclear fuel in three reactors at Fukushima has possibly melted through the pressure vessels and accumulated in outer containment vessels.
The control rods on this type of reactor are inserted thru the bottom of the reactor. A high probability of leakage via the control rod seals has been assumed for some time.
“Putting in a SFP high in a building where it is coupled to the reactor in accidents is mind-boggling. If anything, locate it down low so it *does* get flooded.”:
I believe the current GE ABWR design still has the SFP upstairs… most likely due to ease of handling fuel in and out of the reactor…
The do have the generator high up in the building…
BWR reactor designers have always argued that the many control rod housing tubes are a benefit in an accident because of the heat-bridge effect (enhanced cooling) that the extra surface area gives. It also makes it more likely that molten fuel will cool and solidify between the housing tubes. The part that does not will drop onto the containment floor. In unit 1 at least that part of the containment has been flooded with water. So that’s effectively cooled. Flooding that lower part of the drywell (containment) is used in most BWRs as in-vessel melt retention & arrest. This is better than letting the molten fuel escape the vessel because it doesn’t challenge the concrete containment below. Should any chunks of fuel penetrate the vessel anyway, they are effectively cooled by dropping into the deluge water there.
I still don’t get that they didn’t filter the steam overpressure relief operations early in the accident. They’ve got filters for the seawater injection boil off steam, removing the radioactive particles before the steam is released through a big vent in the building wall. There’s just way too much iodine released for it to be a filtered vent path.
NinetySix, on 9 June 2011 at 7:38 AM said:
On their ‘stuff said’ segment they quoted financialgreenwatch.org putting the cost to decommission fukushima at $90,000,000,000
Tepco is estimating 426 billion yen to achieve cold shutdown and 207 billion yen for decommisioning as of May 31st.
Click to access 110526-e.pdf
Re. the “melt-through”.
Despite the dramatic headline, if you read through to the end of the article you find nuclear scientist Yoshiaki Oka is quoted “… we now know that this happened at the very beginning of the accident, so I see no particular additional affects on human health”.
Does anyone know the basis of the “$250 billion” cost estimate claim in the article? (i.e. which “studies”?)
Tom Keen, on 10 June 2011 at 12:47 AM said:
Does anyone know the basis of the “$250 billion” cost estimate claim in the article?
Some University professer.
The costs broke out as $8 billion for short term compensation(IMHO an accurate estimate).
$54 billion to buy all the real estate within a 20 km radius. The radiation levels within a 20km radius vary by a factor of 100..so how much will be declared safe, how much will be mitigated and how much will have to end up being a long term exclusion zone is at this point unknown.
Radiation readings within 20km zone –
Click to access 1305391_0606.pdf
I can’t imagine that it would be cheaper to buy someones house then send out a backhoe and dump truck and scrape up the top 6″ of top soil and cart it off and replace it with fresh top soil. On the other hand it would probably be cheaper to buy a forest then attempt to mitigate but then I don’t know if Japan has a radiation safety standard for forest products.
Then the remainder was a WAG as to decommissioning costs…between $9 billion and $188 billion.
Looking at the real-time video of the plant, there seems to be quite a bit of steam coming out of one of the buildings. Any thoughts?
is that REALLY an accurate assessment to have to buy out that entire area? hydrogen blasts spread that much long term radiation or is this just some quack thinking this is like chernobyl?
Thanks for the link Harry. I cannot find the article claiming $600b for daiichi replacement, but the $90b decommissioning claim is here: http://financegreenwatch.org/?p=495
Well worth the read to see how they came up with the $90b figure… I guess if you wish for something hard enough, it just might come true.
That telegraph article reminds me of several media outlets interpretation of the WHO’s recent bit about mobile phones and brain tumors … insisting your children will die while quietly mentioning that the data is highly unscientific and no conclusions can yet be drawn. So nothing has changed, worry if you want to etc, etc…
schla, on 10 June 2011 at 8:08 AM said:
is that REALLY an accurate assessment to have to buy out that entire area?
Half the circle is the ocean. So 1/2 * 3.14 *20,000m * 20,000m = 628 million sq meters. At $100/sq meter that would be $62 billion.
Here’s a nice brochure from the Fukushima Development folks…Industrial land is available at 12,200 yen/m2.
A quick look via google earth shows a lot of uninhabited mountainous forest land in the exclusion zone. Land without nearby roads doesn’t tend to have much value.
NinetySix, on 10 June 2011 at 9:27 AM — I think that estimate is complete nonsense. First of all, only three units have suffered actual recator damage, roughly comperable to Three Mile Island (TMI). Decommsioning that unit cast almost a US$ one billion. Factoring in inflation and addional difficultiers, say US$ 4 billion for each of the four damaged units. That’s US$ 16 billion plus the normal decommising costs for the relatviely undamged readots.
Eric Moore, I believe the steam eminating from the higher portion of the building is from the boil off from the freshwater injection cooling. The water is boiled off from the decay heat, turns into steam that passes through the reactor vessel through a filter system that removes radionuclides, and then vents the cleaned up steam up into the air through a large vent in the side of the building.
There are confusing reports as to how this is done specifically. But the water they inject through the fire extinguishing line has to be vented – which is why they must inject fresh water constantly. I think this also causes recirculated waste streams (condensate, brine etc.) which contributes to the large volumes of radioactive water at the plant that must be cleaned up through the water treatment plant TEPCO is setting up right now. If they clean the water of both radionuclides and salt they can re-inject the cleaned water back into the coolant injection line for more cooling. This would minimise the amount of low radioactive water and would leave a much smaller volume of radioactive brines eventually. I think this final brine gunk can be boiled leaving a concentrate dry waste product in the filters and concentrate residues, that can be stored in dry casks (as one would store spent fuel normally) or in medium level waste storage facilities.
Thanks cyril. I guess something would have cropped up in the media if was a major problem.
(comment deleted for violation of the citation policy.)
I see the media is reporting high levels of strontium in ground water and seawater around Fukushima, is this likely to be coming from the cooling water, or is it an indication of deeper problems?
Does this find give more ammunition to the anti-nuclear argument?
Please supply the links/refs to the articles as per BNC Comments Policy. Please read the Citation Policy on the About page. We need more in-put from you demonstarting you have read and understood the literature.
the links are easy to find: 6 additional workers have received dosis above the limit of 250 mS
“TEPCO said on Monday that provisional readings suggest 6 male employees, in their 20s to 50s, received exposure of up to 497 millisieverts.”
and strontium in groundwater:
“TEPCO announced that strontium-90 was also detected for the first time in ground water near the reactors’ buildings.”
there are also radioactive readings above the limit in a town call Date:
“Date is about 60 kilometers from the troubled Fukushima Daiichi nuclear plant. The central government announced earlier this month that the accumulated radiation levels at 3 locations in the city’s Ryozen area are estimated to exceed 20 millisieverts for the year that ends next March. People living in areas receiving this amount of radiation are urged to evacuate within a month.”
this is problematic, as the town has over 40000 inhabitants.
Strontium is found everywhere on earth due to atmospheric bomb testing decades ago. You can find a map of it here:
As you can see Japan is a hot spot for weapons testing derived strontium-90.
Definitive proof of strontium emission of Fukushima is not there, at all.
Such proof would be there if they find significant amounts of strontium-89. This isotope is much shorter lived and the weapons testing decades ago would have allowed almost all of it to decay. If they find any, it will be from Fukushima.
Sr-89 has not been detected by TEPCO, to my knowledge.
Almost all of the exposure around Fukushima comes from cesium-137 and 134 that are powerful gamma emitters.
Evacuating over 20 mSv/year external gamma dose (Cs-137 and 134) is nonsense. Such dose appears to have strong beneficial effects on health (up to 525 mSv/year is beneficial) according to the Taiwanese cobalt-60 accident. (cobalt-60 is a strong gamma emitter, more powerful than cesium-137 due to its shorter half life)
Click to access low-dose-Cobalt-taiw-06.pdf
Cyril, please take the time to read my links. it said:
“TEPCO also said that strontinum-90 was detected at a level 170 times higher than the standard in samples also taken on May 16, near the water intakes outside reactor number 2. At the reactor number 3 water intakes, the level was 240 times higher than the legal safety limit.”
the idea that we have Strontium at 240 times the legal limit because of nuclear tests 50 years ago is utterly absurd. but perhaps you have a link that suggests that such levels of strontium are common?!?
@ Sod. Water intakes, yes because strontium forms water soluble species that go into the emergency coolant/leaked water on site. This isn’t what we are worried about here – we want to know about strontium fallout that was volatilized and thus spread out over a large land area. This is what happened to cesium because it is volatile so it comes with the vented containment pressure relief operations. Strontium isn’t very volatile at all, so land based fallout for strontium can be expected to be low.
There seems to be no mention of Sr-89, which is odd. Far more radioactive and easier to detect, and if found in land samples it would suggest clearly that the strontium was volatilized and comes from Fukushima.
The land based samples of Sr-90 are so low it is no threat and likely all/most due to the atmospheric bomb testing. Which is perfectly as expected.
For reference, here is a recent soil sample update from TEPCO:
Click to access 110614e4.pdf
All the volatiles are present, as expected, but there is no mention of strontium.
There is reference to typical weapons testing ‘background’ levels of plutonium:
Click to access 110614e3.pdf
Strontium has very roughly similar low volatility as plutonium. Also looking at Chernobyl gives a reference to how much of the nuclides are released (strontium roughly similar to plutonium).
If you’re not finding lots of plutonium from fallout, you won’t find lots of strontium from fallout. But there is lots of plutonium and strontium in the contaminated water, which TEPCO must now filter out.
Also notice from the Chernobyl radionuclides released that Sr-89 is 11x more activity released than Sr-90. If Sr-89 was there, it would be very easy to detect.
“Date City…problematic…40,000 residents’
The WSJ version –
Three of the four new hot spots are in the Ryozencho area of Date City, a neighborhood with 180 households
The Japanese authorities are doing what the should be doing, shrinking the size of the monitoring grids in order to identify hot spots.
What I am not hearing (perhaps because they don’t know) is what was really the “straw that broke the camel’s back” in terms of containment integrity. Was it the massive hydrogen explosions, or was it the high-G earthquake. It is odd to me that everyone focuses on the flooding (the initiating event), but not the hydrogen explosions or the earthquake. For everything that went wrong, the integrity of the containment is ultimately what must be protected.
Any speculation/information on why this failed. Did excessive pressure due to lack of venting pop the containment, or was it already opened up due to the earthquake? Or was it a combination of these factors plus the explosions?
Also, I’m having a lot of trouble finding information on exactly where the containment is breached in the three units. Are there data for the breach locations, size, etc?
Why did the containments fail, well it seems obvious that they would after taking that level of punishment. There are many challenges to the containment and its a wonder the things held up the way they did. Let’s break it down (pardon the pun).
First there’s an earthquake with 4 or 5 times the design ground accelleration.
Second there’s a huge wave of water putting forces on the building, with unknown damage effect to the containment (though fairly well known effect on site electrical infrastrure).
Third the crazy operators allow 2x design pressure (850 kPag) and at least 150 degrees Celcius higher temperature than design to build up in the containment, before they decided to vent to atmosphere. This must have ruined various pump and equipment seals as well as further stressing an already challenged containment.
Fourth the design flaw of venting potentially hydrogen rich gas and high activity material into the top section of the building, causing massive explosions that further shook the containments.
Fifth the decision not to flood the drywell means molten fuel likely dropped to the bottom bulb drywell section, causing heat and corium-concrete interactions.
Much of the containment problems above can be solved by having a passive automatic containment venting system that vents up a tall chimney. I’m thinking about a U-shaped pipe where the bottom is filled with water, connecting to the containment in one leg and to the outside stack on the other. Pressure rising means the water gets pushed down, up to the point that it reaches the bottom of the U-pipe, and then the excess pressure will bubble out through the stack, also scrubbing it of cesium and other radionuclides. There should be extra carbon filters on both ends of the pipe just in case.
TPL, on 15 June 2011 at 5:58 AM said:
Also, I’m having a lot of trouble finding information on exactly where the containment is breached in the three units.
That’s because the basements have radioactive water in them making it impossible to inspect for the leak.
More regarding the containment, the World Nuclear article suggests that most radioactivity was released by the rupture of the containment of unit 2 after the hydrogen explosion. That points to the hydrogen explosion as the culprit.
Rupture of the lower containment (torus) seems the most likely part that failed.
It almost suggests that the torus isn’t normally inerted, which would be a gross design flaw if true.
Cumulative radiation up to 82 mSv over the past three months in a part of Namie (outside the 20km no-entry zone), 23 out of 160 monitoring sites outside the no-entry zone exceeded 20 mSv:
Original in Kyodo News.
Ups, I didn’t know that Namie (the site with 82 mSv cumulative radiation) was evacuated at the end of April:
US DOE did airborne mapping. It would make sense that the Japanese have ‘enhanced monitoring’ in areas where the US DOE airborne radiation mapping indicated had problems.
> an earthquake with 4 or 5 times the design ground accelleration.
I realize this is the open thread, but would it be possible for you to cite a source for that claim anyhow, for credibility purposes? It would be good to know your reason for believing this.
The best info I recall was here:
“At Daiichi there is still no data for units 1, 2 and 5, but available figures put the maximum acceleration as 507 gal from east to west at unit 3. The design basis for this was 441 gal. Other readings were below design basis, although east-west readings at unit 6 of 431 gal approached the design basis of 448 gal.”
Again, I realize this thread is for assertions of belief and opinion and you aren’t required by the rules to give a reason for the numbers you’re posting.
It would be a kindness for those who want actual facts, if you’d do so.
A slightly different number (449, rather than 448) given here:
Figures Released On Fukushima-Daiichi Seismic Design Reference Values
Sunday, 20 March 2011
The maximum ground acceleration near unit 3 of the Fukushima-Daiichi nuclear plant from the earthquake that struck northern Japan on 11 March 2011 was 507 gal – or 507 centimetres per second squared – which is above the plant’s design reference values of 449 gal, the Japan Atomic Industrial Forum (JAIF) said today.
Correct Hank, the acceleration was only a small percentage above the limits. It was the total earthquake energy that was so much higher than expected, but of course that is not what is actually experienced at any one nuclear plant. My vague recollection is that the shaking went on for a very long time (reflecting the high energy). I don’t know if there is a time-based limit on how long the nuclear plant is designed to endure its maximum shaking; if not, perhaps there should be.
The World Nuclear website says the plants were upgraded in the 80s and 90s for higher earthquake protection. Too bad they didn’t increase the tsunami protection, despite the fact that a higher tsunami was predicted, according to the World Nuclear website.
Are the gal numbers for the lateral movement only, or are they also for axial movement? Some kind of normalized number?
For reference, here is the World Nuclear link, updated recently, a very nice summary with lots of numbers:
> if there is a time-based limit on how long the
> nuclear plant is designed to endure its
> maximum shaking
Good point, Joffan.
> gal numbers … axial
Three axes, different numbers for each, very much depending on the specific location; a combination number would lose the specifics.
Lots of detail on this page — using as an example a quake that hasn’t happened yet but would be one in a known pattern, not a surprise; it’s a worry site but the numbers seem cited to good sources.
“in Kobe, the shake of 800gal or more is recorded. The 818gal in the directions of north and south, the 617gal in the directions of east and west, and the 332gal in the vertical directions are recorded at the Kobe Marine Observatories at the Hyogo southern part earthquake in 1995. (Fig. 16)”
Ah, here’s the answer:
“PGA or Design Basis Earthquake Ground Motion is measured in Galileo units – Gal (cm/sec2) or g – the force of gravity, one g being 980 Gal. …
PGA has long been considered an unsatisfactory indicator of damage to structures, and some seismologists are proposing to replace it with Cumulative Average Velocity (CAV) as a more useful measure since it brings in displacement and duration.”
More and different measurements beyond the one World-Nuclear mentions turn up with searching:
“… The SAFER Project initiated the parameter optimization in the Istanbul Earthquake Early Warning System IEEWS (Fig. 24). The existing IEEWS utilizes band-pass filtered PGA and CAV values. A new parameter called Bracketed Cumulative Average Velocity (BCAV) has been proposed to be used in the IEEWS. As a new approach the specific window-based BCAV namely BCAV-W is planned to be used in IEEWS….”
Click to access SAFER_Final_Report.pdf
“SAFER (Seismic Early Warning for Europe) is a project funded by the European Commission in the context of Framework Program 6 under the Theme Sustainable Development, Global Change and Ecosystems.”
@Cyril R “… the crazy operators allow 2x design pressure … and at least 150 degrees .. higher … than design to build up in the containment, before they decided to vent to atmosphere. This must have ruined …. ”
It sure is crazy from a technical point of view. And the health fears were probably crazy from a radiation health expert’s point of view. However the environment of those decision-makers was not technical, so much as political, under a terrific pressure from a minefield of vindictive regulations.
There is currently underway a stress testing process across Europe’s reactors. Let us hope that it exposes the craziness of the restrictions imposed. Perhaps proportionate measures will be put in place for timely assessment of any health threats to the neighbourhood. Timely enough for operators to make rational decisions in crises.
Roger, yes, the fact that politicians can decide when to vent an overpressurized containment, is scary. That’s why I want this system to be fully passive. One way to do it is to put a U-shaped pipe in the containment, with one end sticking out to the outside air, the other connected to containment, and isolation achieved through water in the bottom of the U section. If the pressure rises, the water will be pushed down in the containment side of the pipe, until it reaches the bottom of the U pipe, causing it to vent out through the pushed up water column on in the other side of the pipe. This scrubs the fission products as well. These type of functions are so vital they should be fully passive and automatic. Operators shouldn’t be able to override them. Put extra carbon and particulate filters in the pipe just in case iodine and cesium make it through.
The European stress test looks good. They’re going to look at some really extreme events, such as a blackout combined with a 9/11 style aircraft crash attack. But I hope they will allow changes to be made to existing plants to make them resistant against all that, if it proves necessary. I hope no more plants are shut down.
via Mainichi news…
A somewhat speculative(lot’s of mays and could haves) article about the possibility that some of Fukushima #1 vent valves may have never opened
This is an interesting article published in the Journal of American Physicians and Surgeons on the biological effects of radiation:
Click to access luckey.pdf
> Journal of American Physicians and Surgeons
“I’m about to discuss a medical organization that is steeped in an utterly toxic brew of bad science and extreme ideology. So what? you might ask…. when it comes to medical science, this organization deserves every harsh word that I am about to write because it is a major booster of antivaccinationism, HIV/AIDS denialism, and the now discredited hypothesis that abortion causes breast cancer, while on its pages it regularly attacks the very concept of evidence-based medicine and peer-review. That it is an organization of physicians is all the more appalling….”
Always check the references.
(deleted violation of citation rule)
The author mounts a supporting case for the hormetic nature of ionising radiation. He has a significant number of papers listed in the U.S. National Library of Medicine (PubMed).
I was particularly intrigued by Figure 1 but I will treat the article with due caution.
(Deleted violation of citation policy)
@Martin Nicholson : They are a number of serious papers supporting radiation hormesis but this one is not one of them. A constant irradiation level near the 10 Gy/y range is extremely harmful and will cause fatal leukemia in most case, as is amply demonstrated by the unfortunate Kramatorsk nuclear poisoning incident :
There’s a good references site on hormesis here:
You can find a lot of articles on radiotoxic and chemically toxic induced hormesis – quite convincing I think. Be sure to check out the ‘newsletters’ section.
The June 27 “Industry talk” thing at http://world-nuclear-news.org/indtalk.aspx includes a brief item,
That seems to be the right currency conversion for ¥2500 billion, but isn`t it high by one power of ten? How much are they paying for natural gas?
I gave them feedback yesterday but they haven`t responded.
grlcowan, on 29 June 2011 at 2:10 AM said:
That seems to be the right currency conversion for ¥2500 billion, but isn`t it high by one power of ten?
Accordinging to Japan Times
Chubu Electric is under pressure to pay an additional ¥250 billion this year to burn more natural gas at thermal generators to offset declining output from reactors
It would appear world nuclear has an extra zero in it’s article.
Give me some clue how you want that cited, or if it’s inadmissable to mention that this has already been beaten to death here in prior topics, just say you won’t allow it to be disputed again.
You can state that it has been comprehensively dealt with on BNC and suggest that people do the research before commenting. It is OK to link to BNC pages after saying that. For the record it was probably a mistake of mine to delete these two instances – however they followed on the heels of two other non BNC links which were light on comment before posting the link, so they were dealt with in the same way. You have been inserting a lot of quick remarks with links and these have been let stand but it is important that regular contributors abide by the citation policy as well as newcomers.
@jmdesp Luckey suggests that 1 Gy/y is acceptable and 0.1 Gy/y is optimal. I don’t think he is advocating 10 Gy/y. Why do you consider that Luckey’s article is not a serious paper?
I have no view one way or the other about Luckey’s veracity but I notice that the material referred to by Cyril R has several references to Luckey’s work so presumable the authors published in BELLE take him seriously.
No fallout legacy for Japan’s farms: http://www.nature.com/news/2011/110713/full/475154a.html?WT.ec_id=NATURE-20110714
I asked earlier if anyone knew how prepared the accident site was to deal with a major typhoon? The question is now more than hypothetical with the predicted path of Typhoon Ma-On indicating a possible direct hit on the Fukushima Region:
Nuclear power is must for survival of the earth but it has to be safe also. Unfortunatily most of the persons in the nuclear industry feel that each plant design is safe. it is evident from the statements of heads of most of the NPPs just after the Fukushima accident. Every ECO was saying that their plants are safe and a Fukushima like incident can not happen in their plant even without knowing that what has actually happened in Fukushima. since at time very little and confusing information was available. It is surpising that how one can claim that a particular type of incident will not take place in his plant even without knowing the incident itself. it decreases creadibility and people start suspecting these statements and rightly so. I can say that many of the plants design is not safe but they have got licence to operate. Most the the safety reviews are just showpiece and they are meant to fool the public. I do not say that all the designs are unsafe and some are definitely not safe. It is important to accept the flaws and plug it but people in the industry are not ready to accept flaws. they have perceptional blindness and not able to see the other side (unfsafe side) of the coin. It is important that public put pressure on plant managements to be transparent and prove that their design safe. it is a fact that transparency is lagging in this industry and everyone tries to hide the facts not only from public but even among themselves.
For survival of nuclear power safe design is a must which is not right now.