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Cheryl Rofer: Is there a leak at Fukushima #3?

29 Mar, 11 | by BMJ Group

Cheryl RoferWe simply don’t know. There are enough radionuclides in the outflow to the sea and in the water in the plant that it looks like a leak is possible, but there are too many other things that we don’t know. If there is a leak, it is not a big one.

It’s not a big one, because reactor #3 has been pressurized. If you try to blow up a balloon with a big leak, nothing happens. You can blow up a balloon with a pinhole leak, though. The steel reactor containment vessel is equipped with pressure gauges to measure the pressure. With a big enough leak, the pressure wouldn’t rise, but it has been rising as water is pumped in and turns to steam.

So where is the radioactive water coming from?

The information available doesn’t allow strong conclusions. An enormous amount of seawater has been pumped into the reactors and the spent fuel pools. Some of it is evaporating, but the reactor containment is a closed system. The reactors have been vented when their pressures went too high; fission products would have been released with the steam. If the fuel is damaged, and it almost certainly is in reactors #1, #2, and #3, more fission products will be in the coolant and steam than there are normally. They may condense out in the buildings. Or it is possible that water has been released during the venting.

Standing water in the Unit #3 turbine building has high levels of radiation. Two workers have suffered radiation burns on their feet from stepping in it without protective gear. These burns are being treated as heat burns would be. Although the doses (180 mSv) are in a range that is close to producing symptoms of radiation sickness for whole body exposures (see chart), exposures to extremities are less likely to do so.

There are different kinds of fission products in the cores and in the spent fuel pools, because the short half life fission products, like iodine-131, have disappeared from the fuel in the pools. Sampling in Seattle seems to indicate that the releases are coming from the cores.

Electricity has been partially restored to the control rooms. Here’s a photo from the control room for Unit 2. Fresh water is being injected into Units 1, 2, and 3, which removes some of the concern about salt build up from the use of seawater. Fresh water may also be injected into Unit 4.

There has been some discussion about whether Tepco is holding back information about radiation levels. I’m inclined to think that if information is not being released in an entirely timely manner, it is because the operators’ and managers’ first priority is dealing with the emergency. But Tepco has been less than forthcoming on past accidents, so suspicion remains.

I’m making this assessment on 26 March, from IAEA reports and other sources.

Cheryl Rofer holds an A.B. from Ripon College and an M.S. from the University of California at Berkeley, both in chemistry. She is retired from the Los Alamos National Laboratory, where she worked from 1965 through 2001 on tthe nuclear fuel cycle, management of environmental cleanups, and other topics. She has also been involved with cleanups in Estonia and Kazakhstan of former nuclear sites. She is immediate past president of the Los Alamos Committee on Arms Control and International Security and a member of the Board of Trustees of Ripon College (Ripon, Wisconsin). She also blogs at Phronesisaical (http://phronesisaical.blogspot.com/)

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  • http://seekerblog.com Steve Darden

    Thank you for your highly informative dispatches. A followup question regarding unit 2 leaks.

    The latest IAEA presentation shows Unit 2 “Core and Fuel Integrity” has jumped to “Severe damage” today March 29. Yesterday was same as units 1,2 = “Damaged”.

    The RPV pressure reports are unit 1 = “Slightly increasing” (due to restricting core cooling water); units 2,3 = “Stable”. Looking for confirmation of Will Davis' thesis, I've examined the reactor status reports for evidence of RPV pressure drop on unit 2. I don't see it – TEPCO continues to operate unit 2 below one atmosphere – about 0.074 MPa, or 3/4 atmosphere absolute. I read unit 3 as stable around 1.3 atmospheres = 0.135 MPa. But if unit 2 is being operated below one atmosphere, why can't most of the flow leak out of the RPV + primary into the secondary circuit?

  • http://phronesisaical.blogspot.com/ Cheryl Rofer

    I'm not looking at the daily dispatches and trying to do particularly detailed analysis from them. There are several reasons for that. First, initial information is often erroneous or may be an accurate description of a rapidly changing situation. Second, many of the words used to describe the situation are not defined rigorously, like “Severe damage” and “Damaged.” They represent qualitative and indirect evaluations. So any nice theory I could develop on Tuesday might well be irrelevant by Thursday for a variety of reasons. In this post, I tried to use information that had been stable for a while.

    If Unit 2 is being operated below atmospheric pressure, it should be pulling in air and water. Laboratories handling radioactive materials are usually operated at less than atmospheric pressure to keep material from leaking out.

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