Playing 'pick-up-sticks'

 “Did you ever play pick up sticks?” asked a foreign nuclear expert who has been monitoring Tepco’s efforts to regain control of the plant. “You had 50 sticks, you heaved them into the air and than had to take one off the pile at a time. “If the pile collapsed when you were picking up a stick, you lost,” 

Decommissioning Fukushima: how Japan will remove nuclear fuel rods from damaged reactor

Experts say no one has ever attempted such a procedure before and that a mistake could be disastrous

the Telegraph,

7 November, 2013

The operator of Japan's crippled Fukushima nuclear power plant is soon to begin the delicate and perilous process of removing 1,534 nuclear fuel rods from a storage pool at the site.

In the coming days it will begin a dry run of the procedure at the No. 4 reactor, which experts have warned carries grave risks. The operator had been scheduled to start the actual removal on Friday, but the Japan Nuclear Energy Safety Organisation this week insisted that Tokyo Electric Power Co. carry out a test to ensure that every part of its plan goes smoothly, delaying the operation for some two weeks.

The authorities' insistence on additional checks suggests there are serious concerns about the ability of the utility to handle the aftermath of the second-worst nuclear accident in history. Tepco's very public failures in the 32 months since the plant was devastated by the magnitude-9 earthquake and the tsunami that it triggered have shaken confidence in Japan's nuclear industry, both here and around the world.

And despite the fears of nuclear energy experts, the Japanese public, the government and environmental groups, all agree that the highly irradiated spent fuel must be removed from the damaged storage pool as swiftly as possible.

A key concern is that another major earthquake could cause cracks in the pool, which is nearly 100 feet above the ground, allow the cooling water to escape and expose the rods to the air. That would allow the zirconium alloy cladding to ignite and release radioactive material into the air.

Equally, a misjudgment during the operation to lift the rods out of the pool, transfer them individually to a water-filled cask, lower that to the flat-bed of a truck and then transport the rods to a more secure storage site in the grounds of the power station could lead to another massive release of radiation into the atmosphere.

Tepco says it is confident that the 18-month manoeuvre will go off without a hitch, emphasising that removing rods from a spent fuel pool "is a normal operation that has been done at any nuclear power station, even before the great earthquake."

The company admits there are risks, however, and has publicly vowed to do everything possible to ensure security "under safety-first principles".

Tepco has reinforced the pool containing the rods with concrete and steel and says that tests have determined that the building is still sufficiently strong to withstand another earthquake of the same magnitude as the March 2011 tremor.

An external crane to lift the rods out of the pool has been constructed in a way that no extra weight is added to the shell of the No. 4 reactor building, while the entire procedure will be carried out behind a shell to prevent radiation leaking into the surrounding atmosphere.

Despite all the security measures, experts and environmentalists point out that Unit 4 at the plant contains 10 times as much caesium-137 than was at Chernobyl and that nothing remotely similar has ever been attempted before.

"Did you ever play pick up sticks?" asked a foreign nuclear expert who has been monitoring Tepco's efforts to regain control of the plant. "You had 50 sticks, you heaved them into the air and than had to take one off the pile at a time.

"If the pile collapsed when you were picking up a stick, you lost," he said. "There are 1,534 pick-up sticks in a jumble in top of an unsteady reactor 4. What do you think can happen?

"I do not know anyone who is confident that this can be done since it has never been tried."

Even now, it is not clear whether any of the rods, containing transuranic and transplutonic elements, are cracked, he said.

"At the very least, if there was a catastrophic collapse, I assume there will be a major airborne release of radiation," he said. "But on the other hand, you have to do something."

Others have issued even more dire warnings, with Charles Perrow, a professor emeritus at Yale University, warning: "The radiation emitted from all these rods, if they are not continually cool and kept separate, would require the evacuation of surrounding areas, including Tokyo.

"Because of the radiation at the site, the 6,375 rods in the common storage pool could not be continuously cooled; they would fission and all of humanity will be threatened, for thousands of years."

Tepco has focused its efforts on Unit 4 at the plant because it was not operational at the time of the disaster and the reactor did not experience a meltdown. Experts say this makes it the easiest of the four reactors to deal with.