APR: your source for nuclear news and analysis since April 16, 2010

Saturday, August 4, 2012

Hamaoka No. 5 seriously contaminated with seawater

New interviews given by representatives of Chubu Electric Power Company and Japanese regulatory bodies now indicate that the previously announced seawater leakage into Hamaoka No. 5 and the resulting damage may be far worse than had previously been released or assumed.

On May 6, 2011, the Prime Minister requested that Chubu Electric shut down Hamaoka No. 4 and No. 5 reactors, which were operating at the time, due to seismic and tsunami considerations. Chubu agreed (and also agreed not to restart No. 3; the other two older plants are shut down permanently and decommissioning.)

During the May 14th shutdown of No. 5 plant, which is an ABWR type boiling water reactor rated 3926 MWt / 1325 MWe, there was a rupture of tubes in the plant's main condenser, which uses seawater on the secondary side. Chubu detected the seawater's ingress when conductivity measurements began to rise in the condenser and in the reactor. Following achievement of cold shutdown, Chubu entered the main condenser and discovered damaged tubes. Of course, Chubu had notified NISA immediately upon detection of the problem, and NISA has been involved ever since.

Chubu's investigation indicates that something over 400 cubic meters of seawater were added to the reactor system water inventory. A recent Reuters report is quoted as indicating about 5000 liters of seawater may have entered the reactor.

Detailed inspection by Chubu shows seawater contamination, and either detected or probable damage, to the following components: Reactor recirculation pumps, control rod drive mechanisms, turbine driven feed pumps, condensate pumps, RHR pumps, RCIC pumps, HPIC system pumps, all intermediate stage feedwater heaters / reheaters, gland exhaust condensers, condensate filters and demineralizers. (This list is not all inclusive.) Seawater has also caused damage in much of the control rod drive system.

It is extremely likely given all of the information above that seawater has caused some degradation in the reactor core - whether the effect is as simple as salt blockage, or worse, such as salt plating out on surfaces, or even worse, such as corrosion. Chubu's recent press releases do not speculate at all on this scenario.

Recently, some water tankage has begun to leak, leading to new public attention to the problem since concurrent with this discovery Cobalt-60 has been found in leaked water in the turbine building.

The overall corrosion / damage condition of the plant is not fully known at this time; Chubu continues to inspect the plant as this is written. When details are available, they'll be printed here.

Click here for a fresh Reuters report on the subject.

9:45 AM Eastern 8/4/2012


  1. Roughly, as far as you can tell, how does this rate on a plant damage and public health concern scale as opposed Fukushima? You know the Japanese press are going to have a non-discrimnate hayday over this news even though it appears the injury and public property damage score remains the same.

    James Greenidge

  2. I don't get it. How could they not flush everything out with demineralized water as soon as the plant achieved cold shut down? It sounds as if they just let everything sit with all of that seawater inside.

    The Reuters article starts out by saying this is the first known instance of seawater leakage into a plant? What, no BWR has ever had a condenser tube leak? That doesn't make sense either.

  3. @James: Threat level ZERO. @T: It sounds as if they got the conductivity alarms as they were in cooldown, and I'm not sure how long the contaminated water was in the plant. I believe only the Japanese use seawater directly in their condensers, so that this problem is something we have not seen here.

  4. Seawater is used directly for condensers in one BWR in Ringhals Sweden and brackish seawater for three BWR:s in Oskarshamn Sweden, three at Forsmark Sweden and two at Olkiluoto Finland.

  5. Thanks, Magnus. I don't have access to any of those plants' records to see if they've had condenser tube failures - do you?

  6. There's one thing that is not totally clear to me, did the seawater go from the secondary to the primary ? (sounds yes since you talk of possible damage to the core). If so, it's a very serious breach of containment integrity. Something that should not have been possible without a big failure of the maintenance and missing all precursory signs of weakness in those tubes.
    As one the most modern reactor in Japan, Hamaoka 5 would be expected to be one of the strongest and better conceived, such a major (in industrial terms) problem after as basic an operation as a shutdown gives quite a bleak picture of it instead.

  7. @jmdesp: That's right - this is a BWR, so the water in the main condenser's secondary side goes right to the reactor. Many of us await further and much more detailed reports on the actual shutdown's events, minute by minute and on the plant's condition. This isn't the kind of thing that immediately constitutes a public threat at all, but it should be spread around to all the other BWR plants in Japan as a "Lessons Learned" example so that it isn't duplicated. Not only will the plant's owner-operator be down a significant amount of generating capacity and lose money, but Japan can't afford to keep losing any kind of generating capacity at all (assuming the public will allow all nuclear plants fully checked out to restart to allow their economy to restart.)