Spills at Hamaoka
02 December 2009
Workers were exposed to a small amount of radiation at Hamaoka 3 yesterday after liquid waste backed up in a drainage system.
Concentrated liquid from the treatment of cooling water is kept for a certain time to allow its radiaoctivity to decay further before handling. It is kept in a large tank and this was being drained to a secondary tank to allow a regular inspection.
An alarm sounded during the process, alerting managers to heightened radiation levels in a room containing a pool connected to the overall system. Managers stopped the drainage immediately. They then found that some 50 litres of the waste water had escaped the pool in the alarm area, while three other much smaller spills had occurred elsewhere in the system. One other pool room was affected by 0.4 litres and another area by two spills of 0.4 litres and 2 litres.
All this took place within plant buildings and there was no effect on the environment while normal power generation continued. However, 23 workers were exposed to 0.05 mSv in additional radiation - around one thousandth of the average annual regulatory maximum.
Plant owner and operator Chubu Electric Power Company is investigating the cause of the incident, while the Nuclear Industrial Safety Agency has its own experts on site.