The presence of cesium-134 and cesium-137 indicates that fission took place in the fuel rod holding pools.
SunFresh nuke plant woes, as police search for bodiesTOKYO – A new glitch in the cooling of used fuel at Japan's crippled nuclear plant prompted a surge in radiation, but an overall decline in leaks allowed police Thursday to search for missing tsunami victims closer to the complex than ever before.......
.....This week's glitch at the plant involved declining water levels at the pool for spent fuel rods in the Unit 4 reactor building. Water inadvertently sprayed into an overflow tank prompted a false reading that the main pool was full when it wasn't. That prompted workers to suspend the injection of water into the main pool for several days until Wednesday, when spraying resumed.
Strong aftershocks might also have affected the readings, officials said.
The suspension of spraying allowed temperatures and radiation levels to rise, though the rods were still believed to have been covered with water, said Hidehiko Nishiyama of Japan's Nuclear and Industrial Safety Agency.
"I believe fuel rods in the pool are largely intact, or still keeping the normal shape of what they should look like," Nishiyama said. "If they were totally messed up, we would have been looking at different sets of numbers from the water sampling."
A new burst of radiation this week leaking in Unit 4's fuel pool suggests damage to the fuel rods and complicates efforts to stabilize them, officials said. TEPCO manager Junichi Matsumoto said analysis of the pool's water detected higher levels of radioactive iodine-131, cesium-134 and cesium-137. Normally, those elements would not be found in the pool.
Three of the plant's reactors also have about 20,000 metric tons of stagnant, radiation-contaminated water and it is proving difficult to reduce the amount spilling from the reactors, Nishiyama said.
Until cooling systems can be fully restored, flooding the reactors with water is the only way to help prevent them from overheating, but those many tons of water, tainted with radioactivity, pose a separate threat.
"It is the problem of being stuck with reactors that constantly need to be fed water," Nishiyama said. Setbacks in preparing tanks to store the contaminated water mean new options may need to be considered, he said. He did not elaborate.
The beleaguered plant operator, Tokyo Electric Power Co., or TEPCO, is seeking ways to eventually remove spent fuel rods from reactor storage pools as the plant is closed down for good. The glitch at Unit 4 makes those plans more urgent.
Eventually the rods must be stored permanently in dry, radiation-proof casks, but that process is far off, he said.
TEPCO, meanwhile, is working to stabilize conditions at the plant's No. 1 reactor by pumping nitrogen into its containment vessel to reduce risks of a hydrogen explosion. It also is installing steel plates and silt screens along the coast to help reduce radiation leaks into the sea....
http://www.foxnews.com/world/2011/04/13/spent-fuel-rods-add-trouble-japan-nuke-plant/
