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.