The Fukushima Daiichi nuclear crisis has moved off the front page of most newspapers, but a lot continues to happen, and the situation remains unresolved. Below I offer some personal perspectives on some of the things that have been widely reported over the last few days, and then I conclude with some official updates.

Disclaimer: What follows is my interpretation of the sparse and often confusing information being made available by TEPCO, NHK etc. Take or leave at your discretion.

1. Plutonium detected in the soil around the plant. A few isotopes of plutonium (Pu) have been found in soil at various test sites at the FD plant. This has sent some folks on Twitter apoplectic. So where does it come from?

One theory, and quite a reasonable one, is that it is the global residual left over from the extensive atmospheric atomic weapons testing of the 1950s — 1970s. That would help explain the presence of Pu-238, for instance — an isotope not readily created in a power reactor.

Another thought is that there was a local source, either from volatilisation of sloughed material in the drying spent fuel ponds, or perhaps from the reactor cores (that was then carried away in minute traces via the vented steam). Being a heavy metal, however, the Pu would not mobilse readily and would deposit very locally. Remember, Pu is present in all spent fuel, via the U-238 –> Pu-239 transmutation pathway. All reactor fuel elements that have been fissioning will contain plutonium. It is not something peculiar to mixed-oxide (MOX) fuel (which was being used in FD unit 3), as some have implied — there has been a lot of nonsense written about this during the past few weeks.

In short, Pu is a metal, not a demon. Indeed, from my perspective on the Integral Fast Reactor technology, I see Pu as THE fuel of the future, and boldly predict that it will be looked back on, by some far distant civilisation, as among the most important elements humankind ever encountered. However, that’s for another post for another day. But if you want the full review now, please read Cohen.

2. Containment integrity and core damage. The story that hit the headlines was this…

Richard T. Lahey, former chair of nuclear engineering at Rensellaer Polytechnic Institute, in Troy, N.Y., was quoted as saying that the evidence he had seen indicated that fuel melted through the pressure vessel of reactor No. 2 at some point after the crisis began. He told The Guardian: “The indications we have, from the reactor to radiation readings and the materials they are seeing, suggest that the core has melted through the bottom of the pressure vessel in unit two, and at least some of it is down on the floor of the drywell.”

While I respect his personal opinion as an engineer with professional experience with GE BWRs, I really don’t think he’s correct– to me, as a logical analyst, it’s just not consistent with the recent data. The reactor pressure vessel (RPV) outlet temperature, RPV internal pressure, and drywell pressure readings, have all remained relatively stable over the last few days (see latest FEPC and JAIF reports at the foot of this blog entry). I can’t see that this could possibly have been the case if chunks of molten metal had burned a gaping hole through the 8″ thick steel vessel and then fizzed through the concrete floor to boot. It certainly didn’t happen at TMI-2 in 1979, and I don’t think that it happened at Fukushima unit 2 either. Lahey seems to think his theory is supported by the high radiation readings in the water trench adjacent to unit 2… however, I disagree, as I explain in point 3.

3. Trench water. I think World Nuclear News had done an excellent recap on this: Tsunami likely filled trenches. In short:

Analysis of the trenches at Fukushima Daiichi indicates they were probably flooded by the tsunami. Low radioactivity in one trench may result from capture of radionuclides from the air but high levels in another are unexplained… …But while an answer appears close on the presence of the water, the levels of radioactivity remain unexplained. The trench at unit 2 is a serious concern due to radiation levels from surface measurement in excess of 1000 millisieverts per hour. Further sampling has not yet taken place due to this extraordinary level, and it is not clear if the dose rate is representative of the whole 6000 cubic metre body of water, although it does match the level in the basement of the turbine building. Unit 2 suffered suspected damage to its torus suppression chamber on the morning of 15 March.

The key to this riddle, I think, is the wetwell torus breech (which is likely to be a pinhole or crack) — there has clearly been damage to containment at unit 2, but NOT, I think, to the RPV. The radioactive water in the trench could also plausibly have come from cracked/burst piping or seals elsewhere in the containment/primary system (remembering that in a BWR, the cooling water/moderator also runs through the turbine directly, unlike in a PWR). But there is no reason to think that this water comes directly from the RPV or drywell (which is where the fuel would be if it had melted through the RPV). Indeed, I think the chances of a large steam explosion at this stage of events — more than two weeks out from the core damage event — is remote in the extreme, and even if this highly unlikely chain of events did occur, it would still not spread reactor fuel over a wide area, because most of the heavier material is very difficult to mobilise and disperse (remembering that there is no burning graphite in this situation, unlike Chernobyl, and even in that accident most of the actinides stayed put).

The weird theories of Caldicott and her ilk, in which she fantasises about some ‘magical’ mechanism that is able to spread fine particulates of Pu across the landscape and into the lungs of millions of humans, and so (she outrageously claims) render the Japanese islands uninhabitable as a result, is simply beyond a joke (from many angles). Actually, it’s nothing short of appalling, grossly unscientific, hyper-alarmism.

4. Spent fuel ponds. These continue to get serious attention, with regular injections of water. They have likely been the primary source of the Cs-137 releases. The current TEPCO plan is to switch to fresh water injection ASAP. The pools in units 5 and 6 are now stable and both below 40C (see reports given at the end of this post), but there is still some concern of the pools in units 2, 3 and 4 especially. There was even a report that authorities are still considering entombing them in concrete. It’s possible, but I really don’t think that will happen because it may solve a few short-term problems, and create other longer-term site-management headaches (personal judgement).

5. Radation levels in the ocean. These continue to be elevated close to the plant, due presumably to site run-off and the flushing/settling of airborne particles, but drop away rapidly with distance as the isotopes are spread in the ocean waters, as expected. The I-131 has a short half life, and the longer-lived Cs-137 does not bioaccumulate like mercury (for instance). I thought John Bennetts, writing in response to another BNC commenter who had earlier objected vociferously to my rather bland statement about the ‘disperse and dilute’ principle, summed it up rather well:

Firstly, to demand that a reference be provided to support the notion that 500ml of water, when mixed with the waters of an ocean, actually dilutes! I am shocked! Indeed, once the dilution factor achieves 128, then all reported isotope concentrations will be below the reporting limit, i.e. of no interest to the regulatory authorities. So what’s there to worry about? At that point, your own concerns will become baseless. As per the table at the head of this thread, three limits have been exceeded and publicly reported. With a half-life of 8 days, the offending isotope will naturally decay by a further factor of 128 in 7*8 = 56 days, after which time you can be doubly assured that no nasty exceedances remain. I have no doubt that assessment of the real world impacts will be reviewed and assessed and talked about for some time to come, but the fact remains, that once the waters have been diluted in the Pacific, there will be no cause for further alarm. There will be no ongoing public health threat and there will be no threat to the food chain. The only threats after dilution will be those which arise due to incomplete dilution, e.g. possible uptake in molluscs of certain species, or in aquatic vegetation, and even these will dissipate rapidly with time. I am sure that there are many suitably qualified people who will be involved in ensuring that hypothetical secondary effects are assessed and monitored and that, where doubt exists, actions such as bans on fishing are put in place. You have added precisely nought to the process of rational assessment, review and response which will ensure that the community’s health will not be damaged through these releases.

6. Future of Fukushima Daiichi site. TEPCO have announced that units #1 to #4 will be decommissioned once the crisis is finally closed off. Hardly surprising. I said about 2 weeks ago that 1-3 were write-offs, and although unit 4 didn’t have a fuel loading during the accident, the secondary containment has been so badly damaged by the hydrogen fires and problems with the drying spent fuel ponds that it was inevitable that it’d also be curtains. World Nuclear News has more on that story here. The decomm period is likely to take 5-10 years, based on TMI-2 experience (TMI-1 is still running, incidentally), and perhaps longer given the serious problems they’ve had with multiple reactor units. The fate of the undamaged units 5 and 6, which are some 200 m distance from 1-4, remains unresolved. I suspect they’ll eventually be put back into operation, as Japan really needs their electricity, but probably not for 12+ months. From that WNN story, there is also now speculation about whether the slated Gen III units (GE advanced boiling water reactors, similar to those built at Kashiwazaki-Kariwa in the 1990s) will be built on the Fukushima Daiichi site the future:

Tepco had planned to construct two 1380 MWe Advanced Boiling Water Reactors at Fukushima Daiichi and the start of work on these was slated for 2012. This was a delayed date as a result of additional earthquake engineering flowing from what the company learnt during a July 2007 earthquake that hit similar reactors at Kashiwazaki Kariwa. Tepco contracted for 1600 MWe of new coal generation and 4500 MWe of gas to bridge the supply gap.

So, at least that’s clear. Once again, it’s nuclear, or it’s coal and gas.

7. Other useful unofficial posts. Charles Barton from Nuclear Green looks at the good, the bad and the ugly side of reporting on the Fukushima crisis. George Monbiot comments on The double standards of green anti-nuclear opponents (We must apply the same standards to all energy-generating technology as we do to nuclear power). Will Davis, a former U.S. navy reactor operator, has an interesting blog going here: Atomic Power Review, with some informed theories and speculation on what the FD data mean. Worth checking out.

8. Donations to BraveNewClimate. Many people have asked about this, in the comments and privately, and I thank them for their generosity. However, I’ve always maintained that I’d rather pay for the running of the site myself ,on principle. That is, I don’t want to be seen to profit from this venture in any way, because I do it for non-monetary reasons. Indeed, it’s fair to say that I get more than enough reward out of the work by having people read my posts and for them providing a wonderful stream of comments that really makes this blog alive (even if I don’t always agree with them!). That community input makes me feel rich indeed.

(Oh, and I don’t get any $$ from the Google Ads that run — this is how WordPress extracts their pound of flesh for their otherwise largely free [and excellent] hosting service — I just pay them for domain redirection etc.).

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Okay, on to some (semi-) official stuff. The latest IAEA report is here (last updated on 30 March). NEI update status here. Some snips:

At the Fukushima Daiichi site, workers continued to inject fresh water into reactors 1, 2 and 3 to keep them cool, while at the same time dealing with water that has pooled in the basements of turbine buildings and in concrete trenches near the units. As available storage space in the reactors’ condensers is filled, Tokyo Electric Power Co. is looking to store the radioactive water in tanks that will be brought to the facility. TEPCO has switched to fresh water for spraying the spent fuel pools for reactors 1, 2, 3 and 4. All the units at Daiichi are operating on off-site electric power and work continues to connect equipment. High radiation levels and wet equipment still hampers restoration of the plants’ original machinery.

Here is the latest JAIF status update, as of 2100 on 31 March 2011:

Here are links to the latest reports from the Japanese Nuclear and Industrial Safety Agency (NISA):

Conditions of Fukushima Dai-ichi Nuclear Power Station Unit 1-6(As of 14:00 30th, 2011)

Fukushima Di-ichi Nuclear Power Station Major Parameters of the Plant (As of 14:00, March 30th)

March 30th, 2011 Fukushima Dai-ichi Monitoring points

Finally, the most recent FEPC report:

Radiation Levels At 8:51AM (JST) on March 31, it was announced that radioactive nuclide I-131 was detected from the seawater sampled near the seawater discharge point (south side) of Fukushima Daiichi Nuclear Station at 1:55PM on March 30. The level of concentration was approximately 4,385 times higher than the maximum permissible water concentration set by the government. At 2:00PM on March 31, radiation level at main gate (approximately 3,281 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 157 micro Sv/hour. At 2:00PM on March 31, radiation level at west gate (approximately 3,609 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 99.9 micro Sv/hour. Measurement results of environmental radioactivity level around Fukushima Nuclear Power Station announced at 7:00PM on March 31 are shown in the attached PDF file. English version is available at: http://www.mext.go.jp/english/radioactivity_level/detail/1304082.htm 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 At 8:00AM on March 31, pressure inside the reactor core: 0.329MPa. At 8:00AM on March 31, water level inside the reactor core: 1.65 meters below the top of the fuel rods. At 8:00AM on March 31, pressure inside the primary containment vessel: 0.21MPaabs. At 8:00AM on March 31, the temperature of the reactor vessel measured at the water supply nozzle: 480.9 degrees Fahrenheit At 9:20AM on March 31, transferring of the accumulated water at the trench (concrete tunnel which houses pipes and cables) outside the turbine building commenced, until 11:25AM. As a result, the water level at the trench was reduced from 0.14 meters to 1.14 meters below the top of the trench. At 1:03PM on March 31, TEPCO began to shoot freshwater aimed at the spent fuel pool, with a specialized vehicle normally used for pumping concrete. As of 3:00PM on March 31, the injection of freshwater into the reactor core continues. As of 3:00PM on March 31, preparation to recover and transfer the accumulated water at the turbine building continues.

Fukushima Daiichi Unit 2 reactor As of 3:00PM on March 29, the water level at the trench was 1.04 meters below the top of the trench. At 8:00AM on March 31, the temperature of the spent fuel pool: 131 degrees Fahrenheit. At 8:00AM on March 31, pressure inside the reactor core: -0.016MPa. At 8:00AM on March 31, water level inside the reactor core: 1.5 meters below the top of the fuel rods. At 8:00AM on March 31, pressure inside the primary containment vessel: 0.11MPaabs. As of 3:00PM on March 31, the injection of freshwater into the reactor core continues. As of 3:00PM on March 31, approximately 96 tons of water in total has been injected into the spent fuel storage pool. As of 3:00PM on March 31, preparation to recover and transfer the accumulated water at the turbine building continues.

Fukushima Daiichi Unit 3 reactor As of 3:00PM on March 29, the water level at the trench was 1.55 meters below the top of the trench. At 9:40AM on March 31, pressure inside the reactor core: 0.016MPa. At 9:40AM on March 31, water level inside the reactor core: 1.85 meters below the top of the fuel rods. At 9:40AM on March 31, pressure inside the primary containment vessel: 0.1066MPaabs. As of 3:00PM on March 31, the injection of freshwater into the reactor core continues. As of 3:00PM on March 31, approximately 4,697 tons of water in total has been shot to the spent fuel storage pool. As of 3:00PM on March 31, preparation to recover and transfer the accumulated water at the turbine building continues.

Fukushima Daiichi Unit 4 reactor As of 3:00PM on March 31, approximately 1,098 tons of water in total has been shot to the spent fuel storage pool.

Fukushima Daiichi Unit 5 reactor At 11:00AM on March 31, the temperature of the spent fuel pool: 86 degrees Fahrenheit.

Fukushima Daiichi Unit 6 reactor At 11:00AM on March 31, the temperature of the spent fuel pool: 78.8 degrees Fahrenheit.

Fukushima Daiichi Common Spent Fuel Pool At 8:20AM on March 30, the temperature of the spent fuel pool: 89.6 degrees Fahrenheit. As of 3:00PM on March 31, approximately 130 tons of water in total has been injected to the spent fuel storage pool.



Our official sources are:

Office of The Prime Minister of Japan

Nuclear and Industrial Safety Agency (NISA)

Tokyo Electric Power Company (TEPCO) Press Releases

Ministry of Education, Culture, Sports, Science and Technology (MEXT)



