Fukushima Daiichi 4 frame takes shape

Tuesday, 15 January 2013

The first layer of steel framing for a cover that will allow removal of used fuel from Fukushima Daiichi unit 4 has been completed.

The completed first layer of the frame and its position within the structure (Image: Tepco)

Work began on the six columns and seven beams comprising the first layer of the frame on 8 January. The cover is the second to be built over the damaged reactors at the site: a cover was completed over unit 1 in 2011. A third cover is planned for Fukushima 3. The three covers are all different in function and appearance, reflecting the different conditions at each unit.

Unit 4 was off line for maintenance when the earthquake and tsunami struck on 11 March 2011. Its full core load of fuel, plus used fuel from previous operation, was being stored in a pool at the top of the reactor building. Although this meant there was no possibility of a reactor accident at unit 4, there was a possible risk of the pool overheating. The safety of the pool was then reduced by major structural damage to the building after the ignition of hydrogen that leaked through ventilation systems shared with unit 3.

Plant operator Tokyo Electric Power Company (Tepco) had already put in place additional support including a steel cover over the used fuel pool before work began on unit 4's cover. The cover will contain ventilation, filtration and handling gear to facilitate the removal of fuel from the pool, which remains one of the highest decommissioning priorities at the site.

Researched and written
by World Nuclear News