TEPCO has reported on a leak from the desalination equipment at the Fukushima Daiichi nuclear power station earlier this month, which led to around 150 liters of water containing radioactive strontium (and some cesium) draining into the sea.
The leak was discovered at approximately 11:33 on 4 December 2011 when workers found a puddle inside the barrier around the water desalination equipment (the evaporative condensation apparatus). The apparatus was stopped within 20 minutes and leakage had ceased by 12:41.
TEPCO later identified a crack in the concrete floor in the housing for evaporative concentration apparatus. Water was leaking from the crack into a gutter outside the barrier. TEPCO conducted sampling surveys, which revealed that water leaked from the apparatus had flowed into the sea via the outlet of the general drainage canal. TEPCO estimates that of around 240 liters of water that leaked from the housing, 150 liters of water flowed into the sea. Thus, its provisional estimates put the radioactivity that flowed into the sea at 2.6 x 10^10 Bq. TEPCO said that this would have ‘little influence.’
Efforts to stop the leakage included piling sandbags around the gutter. Later around 15 cubic meters of water that had accumulated in the barrier was pumped to a wastewater supply tank.
On 8 December TEPCO submitted its report on the leakage to the Japanese regulator the Nuclear and Industrial Safety Agency (NISA).
In the report TEPCO notes that it will continue to investigate the cause of the leakage, establish countermeasures and investigate the soundness of other facilities.
An inspection to determine the cause of the leakage will be implemented by 15 December and countermeasures will be implemented by January 2012, the report stated. The 3A to 3C evaporative concentration apparatus will remain out of service until then.
TEPCO said that the damage and gap caused between the joint and concrete bottom will be repaired using epoxy paint and that it is considering painting the whole surface of the concrete bottom to prevent leakage. Going forward monthly inspections of the housing will be conducted as this was ‘one of the causes of the leakage’ TEPCO said.
On 12 December, TEPCO reported that it had recieved an additional directive from NISA regarding the leakage from the evaporative condensation device. At the time of writing an English translation of this directive was not available.