A leak in a seawater cooling system at Fukushima Daiichi 5 has shut down cooling to its spent fuel pool.
On 6 July, a leak was discovered in a valve from the auxiliary seawater cooling system, which also cools components in unit 5, but not the reactor pressure vessel; water flow was stopped that afternoon.
The water temperature of the spent fuel pool at that point was 23°C; assuming a temperature increase rate of about 0.01 C/hr, TEPCO would have until 15 July to restart cooling before the spent fuel pool heats up to 65°C. However, should it need to, TEPCO would plan to switch flows of cooling water between the reactor residual heat removal system and the spent fuel pool instead.
About 1.3t of seawater was estimated to have leaked out of the valve. Analysis of the water found no traces of gamma radiation.
In the meantime, TEPCO workers have applied a temporary repair on the valve.
Fukushima Daiichi 5&6 were officially shut down in December 2013, according to IAEA Power Reactor Information System.
Picture: Close-up of a hole in a cooling valve, since repaired with sealant.