Fuel-rod pool now 'major concern' - French watchdog
A pool containing spent fuel rods at Fukushima's No. 4 reactor "is the major concern" in Japan's nuclear crisis, presenting the risk of radioactivity being released directly into the air, a French safety agency said on Wednesday.
The deep tank at the reactor unit contains used fuel rods which are extremely radioactive and normally are kept immersed in cooling water.
Unlike the fuel rods that are used in the reactor vessel, the spent rods are not surrounded by a steel-and-concrete containment vessel, which is designed to confine leaks of radioactive gas and particles.
Instead, they are housed in the overall building covering the No. 4 unit, which has been "badly damaged," the Nuclear Safety Authority (ASN) said in a statement.
Fires broke out on Tuesday and again early Wednesday in the area of the fuel-rod pool before being extinguished, the agency said.
"The state of the fuel rods stored in this pool, which have been potentially affected by the fire, is not known," it said.
"The evaporation of water in the pool is continuing," the ASN said.
If the tanks run dry, the rods can overheat and the metal sheaths that surround the fuel can be ruptured, the ASN said.
"The Japanese authorities have consequently indicated there is the possibility of releases of radioactivity directly into the atmosphere."
© 2011 AFP