Dramatyczna walka o chłodzenie MOX (po ang.)

Special firetruck hoses down No. 3's fuel rods

The hosing operation, however, is just a desperate stopgap measure aimed at preventing the pool from drying up and exposing the MOX rods, which would then ignite and send radioactive ash into the atmosphere. MOX, reactor perpetually deluged as Tepco works to restore power

Sunday, March 20, 2011

http://search.japantimes.co.jp/cgi-bin/nn20110320a1.html

By KANAKO TAKAHARA and KAZUAKI NAGATA Staff writers

Battling to avert an atomic catastrophe, firefighting teams at the Fukushima No. 1 power station sprayed tons of seawater Saturday at its crippled No. 3 reactor in a seven-hour operation aimed at keeping its spent nuclear fuel rods from combusting. In the evening, the hosing operation was extended until 30 minutes past midnight at the government's request, the Tokyo Fire Department said.

Elsewhere at the plant, engineers raced to connect a power line to the plant in an effort to restart its crippled cooling system.

Shortly past 2 p.m., a "Super Pumper" from the fire department started continuously pumping seawater to an unmanned high-tech firetruck that is hosing down the spent-fuel storage pool at the No. 3 reactor at a rate of three tons per minute from a height of 22 meters.

This arrangement allows the truck to spray the storage pool without exposing firefighters to the deadly radiation. Some 1,260 tons of water was expected to be used in the seven-hour operation.

Just after midnight Friday, the rescue team had shot an estimated 60 tons of water at the sizzling storage pool, which contains highly toxic MOX, a mixed-oxide fuel that contains weapons-grade plutonium.

The hosing operation, however, is just a desperate stopgap measure aimed at preventing the pool from drying up and exposing the MOX rods, which would then ignite and send radioactive ash into the atmosphere.

A more concrete way to avert the crisis is to get the reactor's crippled cooling system working again by restoring power to it. While there's no guarantee it will work, reviving the system could get water in the pool circulating again to cool the fuel rods.

"Our priority is to have the regular cooling system cool the reactor and storage pool, instead of pouring in seawater," said Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency, an industry watchdog.

A power line was connected to the No. 2 reactor later in the day, but restoring electricity was postponed until Sunday after the teams decided to focus on the water-spraying operation for the rest of the day.

Working around the clock, Tepco plans to finish setting up new power lines to reactors 3 and 4 on Sunday.

Re-connecting the power cables is only the first step in defusing the crisis. Tepco officials need to check which devices are working and which aren't. Some may need to be repaired and others replaced before the cooling system, which was damaged by the March 11 tsunami, can be reactivated, a Tepco official said.

Still, expectations are high that Tepco will be able to get the bigger picture of the disaster via video feeds and other devices and come up with a detailed plan of action.

In another glimmer of hope, an emergency diesel generator was reactivated early Saturday to cool off the spent nuclear pool for the No. 5 reactor.

With another power generator that survived the tsunami, the No. 5 and No. 6 reactors now have two power generators, while Tepco is trying to set up a power line for the two as well.

After the power generator started working, the temperature of the storage pool at the No. 5 reactor dropped from 68.8 degrees at 5 a.m. to 67.6 degrees at 9 a.m.

Earlier, the water temperature at the pool had been gradually rising, reaching nearly 70 degrees, up from the normal 40 degrees.

According to the nuclear watchdog, the radiation level rose to 830.8 microsieverts per hour at 8:10 a.m. but the amount dropped to 364.5 microsieverts at 9 a.m.

More than a week after the threat of multiple nuclear meltdowns surfaced, questions started to emerge over what caused the biggest nuclear crisis since the 1986 Chernobyl disaster.

Was there human error or a defect in the plant design that caused the Fukushima No. 1 plant to face a possible meltdown?

Critics say the coastal plant was designed to withstand an earthquake but not the tsunami, which apparently knocked out the cooling pumps.

The nuclear safety agency's Nishiyama agreed, saying the tsunami was "beyond the prediction."

"One of the problems that caused (the crisis) was that the emergency power generators were not placed inside the building complex," said Nishiyama. "I have heard that generators in some other nuclear power plants are placed inside."

At the plant, almost all of the emergency power generators, a backup system in case the power shuts down, were damaged by the tsunami.

The Nuclear and Industry Safety Agency raised the severity level of the crisis-hit reactors to 5 from 4 on an international scale Friday, the same level as the Three Mile Island accident in the United States in 1979.

[Bezczelne kłamstwo, wobec znanych już faktów MD]