How to shut down a nuclear reactor

12th April 2007, Comments 0 comments

PARIS, April 12, 2007 (AFP) - Deactivating a nuclear reactor such as the one in Yongbyon in North Korea can be done in a couple of days, but dismantling the whole facility would require up to a decade, according to an expert from France's Atomic Energy Commission.

PARIS, April 12, 2007 (AFP) - Deactivating a nuclear reactor such as the one in Yongbyon in North Korea can be done in a couple of days, but dismantling the whole facility would require up to a decade, according to an expert from France's Atomic Energy Commission.

The entire procedure consists of three steps, according to Robert Mogavero, who oversees the decommissioning of nuclear facilities in France, which derives around three-quarters of its electricity from nuclear power.

The first is to shut down the nuclear chain reaction, done by simply switching the control panels to a "safety" position. One must then wait "a few days, up to a week or two" for the residual power in the reactor core to diminish on its own, Mogavero said.

From there, one can proceed to step two, "the removal of the nuclear fuel that is in the core of the reactor," he explained in an interview.

This part of the operation could take "anywhere from a several weeks to a couple of months," depending on the size of the reactor and whether any contamination had occurred due to breaches in the barriers sealing off the fuel, he said.

The spent fuel must then be prepared for storage, either in specially designed pools buried underground or above-ground dry storage casks.

Because the spent fuel continues to emit radiation and heat, it must be transported in containers that shield and contain the radioactivity and dissipate the heat.

Step three is the dismantling of the reactor itself, which "requires a certain number of phases and can last many years," Mogavero said, depending on the power of the reactor.

The Yongbyon facility is small, a five megawatt, gas-graphite reactor that went into operation in 1987. It uses natural uranium for fuel, and is thought to be capable of a thermal power output of 20 to 30 megawatts.

American experts estimate that Yongbyon has produced 50-60 kilograms of weapons-grade plutonium, enough for six to 12 bombs. North Korea tested its first nuclear weapon last October.

In France, the average time needed to dismantle a reactor of comparable type and power is ten years, Mogavero said.


Copyright AFP

Subject: French news

0 Comments To This Article