On June 11, three months will have passed since the Great East Japan Earthquake and tsunami. This is a good time for an update on the current status of the Fukushima One nuclear power station. In this post, I will focus on key technical details, and try to cover the impacts on people separately on another day.
It was clear within a couple of weeks (even at FDL, story and comments) that there was a major tension between the need to keep adding water to cool the fuel in Units 1-3 and SFP 4 and the need to halt releases of radiation into the environment, and that that tension was not going to be resolved quickly. Here at the Lake, we talked about months of cooling without recirculation, which meant accumulating a lot of radioactive water.
How has that played out? The current estimated inventory of radiation onsite, in water, and not in designed containment, is approximately 750,000 TBq. In plainer language: there are 100,000 tons of water contaminated with radiation in the basements and trenches of the Fukushima One nuclear power station. These 100,000 tons of water contain as much radiation as was estimated by NISA (the Japanese watchdog agency, not the utility TEPCO, who originally estimated about half as much and have recently upped their estimate to match the NISA estimate) to have been released to the atmosphere so far. That amount of radiation — 750,000 TBq — was in turn approximately 15% of the total release to the atmosphere in the course of the Chernobyl accident. Thus, the Fukushima accidents have so far released about 15% as much radiation to the atmosphere as Chernobyl, and there is another 15% of the Chernobyl atmospheric release in the tanks, basements and trenches onsite at Fukushima.
A brief sidenote on how the atmospheric release estimates are generated: There is not a direct measurement of the total release to the atmosphere. The estimates are made based on modeling of the accident and therefore are subject to revision as new data becomes available that forces revisions of the modeled scenarios. One should therefore not be too surprised if the numbers change as time goes on. It is actually somewhat encouraging that the estimate from the utility now more closely matches the estimate from the watchdog agency. These estimates, corresponding to 15% of the scale of Chernobyl, already take into account the likelihood that Units 1-3 each suffered total meltdowns of their fuel assemblies, and probably each have holes in their reactor pressure vessels (RPVs), though these holes are currently thought to be “small”. These estimates are based on scenarios that do not take into account the possibility that substantial amounts of melted fuel have escaped any reactor pressure vessel and accumulated on the floor of the drywell. If that has happened, there are many additional worries to contend with.
The inventory of radiation onsite in water is actually measured, not estimated.
Each day, approximately 500 tons of water are pumped into the facility. Most of the 500 tons of water that is pumped in daily is used to cool the contents of the RPVs of Units 1-3, and is coming into direct contact with the melted fuel. That water emerges (as steam, vapor, water, whatever) contaminated with radioactive substances, at varying concentrations. From what I can discern, Units 1 and 2 have the most highly contaminated water streams. Some of the 500 tons added daily boils; that steam is visibly escaping and is presumably radioactive. I cannot find credible estimates of the associated daily atmospheric release but I see estimates ranging from 1-150 TBq per day. Because of that continuing uncontrolled release, the accident is officially still continuing. Some of the 500 tons of water pumped into the facility per day that boils into steam recondenses into water. That seems to be happening all over the place. The rest of the 500 tons is simply leaking out through unidentified breaches in the designed containment structures.
Within the next few days, the wastewater containment facilities on site will be full and basements and trenches will manifestly begin to overflow into the ocean. There is a new facility onsite that has been constructed to remove 99.9% of the radioactive materials from approximately 1,000 tons of water per day. It is not yet operational, but will reportedly be ready to begin operation in a few days. Unless it is greatly delayed, there will not be a large, manifestly obvious dump/loss of radiation to the ocean. The news will likely focus on this “race” over the next week or two, because it will be a visible race against a new, obvious environmental insult. As long as the facility works and can be brought online soon, the actual amounts of new radiation losses will be small compared to what has already happened.
You can do the math as well as I can, and deduce that at these rates it will take at least several months more to treat the water on site while keeping up with new injections. There is no plan yet in place for what to do with the radioactive materials that are removed from this water. There is also no plan in place for what to do with the hundreds of shipping containers that have been filled with rubble, some of which is highly radioactive. Presumably all these waste streams will accumulate on site and be dealt with after the accident is under control.
I have not seen any credible timeline for getting back to a system in which the water is recirculated rather than boiled off and leaked away. That will be a very big job and is obviously very important.
There are wells drilled onsite at some distance from the reactor and turbine buildings. Periodically, samples of groundwater are taken and tested. The tests show that there is an ongoing loss of water contaminated with radioactive substances into the underground environment. I rarely see much accounting of what that might mean going forward. Since it is unlikely that anyone will be living within many miles of the facility for a few decades, there has not yet been much official focus on this radiation contamination channel.
Earthquake specialists say that the chances of further major aftershocks are still very high — i.e., a major aftershock of M7+ should be considered likely in the coming weeks and months. The structural damage to the buildings of Units 1, 3 and 4 is of particular concern in this context. There are ongoing efforts to recover structural integrity, particularly for Unit 4. Recall that the Unit 4 spent fuel pond (SFP) contains a large amount of fuel because the total inventory of fuel for Unit 4 was in the pool on the day of the earthquake. (It had been taken out of the reactor to enable maintenance.) There is an elaborate plan for a large number of new steel columns to be installed to brace the Unit 4 SFP. That work will take a long time to perform.
The IAEA publishes a weekly update of the progress made on all elements of the “roadmap” on their Facebook page. That is a good place to check for the latest news.