Fukushima Daiichi update: Saturday, June 18, 2011

Note: I am keeping track of the situation at the Ft. Calhoun station in the USA, which is in the midst of a flood of the Missouri River and which is getting no small amount of press on the anti-nuclear media front. However, the situation at the station is from all official and reliable sources not dangerous at this time, does not now and never did constitute any sort of accident and there is no danger to any fuel on site at the present time. The situation will be detailed here if and when necessary. Click here for official information, for now... and thanks to the ANS Social Media List's members for alerting me to this OPPD page.

Fukushima Daiichi I have had a chance to review some official documents from TEPCO and NISA, and one of the points of the accident sequence that has been the source of some conjecture can be clarified as of now. It appears that the isolation condenser system at No. 1 plant was manually shut down prior to the onset of the tsunami, upon reaching a cooldown limit. This cooldown limit is 55C/hr or 131F/hr. Upon reaching this limit, operators secured the IC system per operating instructions. At this moment, it does appear that the operators were unaware of the approach of the tsunami, given some other reports (IAEA being one source) that indicate that while many thousands of citizens were made aware of the tsunami's likelihood by automated warnings on TV and radio, the plant operators had no such warning available. This latter point is still not confirmed absolutely, but the timing of the shutdown of the IC system at No. 1 plant seems pretty firm now. We might then suspect that operators had no reason to think that they would lose all offsite power and all diesel power from on site... given that they probably did not know the location of the earthquake epicenter (off shore), and therefore could not realistically be expected to predict that there would be a tsunami. We will surely see much more official, and unofficial, commentary on these two things -- namely, the shutdown of the IC system, and the entire nature of the notification of, and/or knowledge of, any tsunami at the site.

Having said that I might point out that the operators would in all probability NOT have suspected that any tsunami they DID suspect was coming would overrun the plant's defenses against this sort of thing, given the known "worst case" design basis for the plant's tsunami defense.

Why all the conjecture about impending tsunami knowledge on site? Because this leads to the direction of actions on site, if one suspects he will very soon lose AC power, all heavy rotating electric machinery, and a great deal of (or all of) his I&C equipment. This very point might be pivotal in saying something like "yes, we've hit a cooldown limit on the RPV but we're about to lose all power and get hit with a wall of water so leave it run and to hell with the cooldown limit if we won't be able to start it again" .. or some such supposed, similar, thought process. The deepness of just what the accident investigation will reveal might now be a bit clearer to those outside the loop, as it were, as we see the interplay between system and equipment operating limits, operational abilities with equipment deranged and probable knowledge thereof, and any effects on decision making vis a vis those two things made by knowledge of, or lack of knowledge of, a further impending natural disaster.

Having now gotten one of the first known critical questions in the accident sequence at least briefed for the first time in good detail, we can proceed to an update of the site conditions.

I decided not to update last evening because a number of conflicting reports were being made about the water purification system on site, which is a combo of components supplied both by Kurion and Areva. It seems that some leaks occurred, so that the system was tested and then shut down (introduce wave of "oh no" posts on anti-nuclear blogs) followed by more testing which went well until one component in the system reached a total radiation flux exposure limit, at which point operations were again shut down while a replacement part was found and also while it was determined whether or not the dose rate on this component was actually valid. As such, then, there have been a number of rapid status changes regarding the system and as of now it appears to be temporarily suspended while components are replaced.

The seawater purification system, acting on that body of water contained inside the silt fence which surrounds the water inlets of Nos. 1 through 4 plants, is now in operation.

As to the reactor cores, No. 1 through No. 3 plants... Injection rates are down a little, at 4.5 and 4.9 cubic meters per hour for No. 1 and No. 2 respectively while No. 3 remains at 11.2 or so where it's been for days now. All plants are stable in temperature, with No. 3's the highest (feed nozzle 150C and lower head 140C.)

TEPCO continues to install the support beams, shown on this site a while back, below the spent fuel pool of No. 4 plant.

It has come to our attention via the ANS Social Media list that one purported expert is running about claiming that there are 20 total cores in danger on the Fukushima Daiichi site. Nonsense. Each of the plants, No. 1 through No. 3 contains one core in the plant. For No. 1 plant, that is 400 fuel elements, for No. 2 and No. 3 that is 548 fuel elements. The number of fuel elements in each plant's spent fuel pools in order of plant number is 292, 587 and 514 or we could say maybe three more cores worth, being very generous. No. 4 plant's core was removed, and there are 1331 fuel elements in No. 4 plant's spent fuel pool or roughly 2.5 cores worth. Thus, at the damaged plant buildings there is a (generous) total of about 8.5 core loads worth of fuel elements. These are the facts, not suppositions.

Conditions at No. 5 and No. 6 plant on the site are not of any dangerous nature. Their fuel element total is irrelevant, as is the total at the not too distant Fukushima Daini generating station, which is also in no danger.

Fresh water and hydrazine continue to be injected to the spent fuel pools as is needed. As noted before, the hydrazine is a corrosion inhibitor.

In a related note, Banri Kaeda, the Minister of Economy and Industry has requested that the local authorities all around Japan restart the nuclear plants in their jurisdictions, having ensured them that the added inspections and quake / tsunami provisions required by the government have been met. Japan will be seriously short of energy if all of the shut down plants remain shut down; however, public opinion seems to be bad for nuclear at the moment given the public displeasure of the Japanese government's handling of the situation and the feeling that the government didn't tell the truth about nuclear plant safety in the past. I would expect some plants to start up, and others not to -- on a case by case basis. Not right away, anyway.

Finally, an APR YouTube Channel note: I have marked as a "favorite" the IAEA inspection team tour video at Fukushima Daiichi, so that it's visible right from the APR YouTube page linked from Atomic Power Review's side bar. This video is not stunningly revelatory, but given the dearth of real-time, personal level onsite footage it is worth seeing.

6:45 PM Eastern Saturday June 18, 2011
ATOMIC POWER REVIEW