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
ATOMIC POWER REVIEW