DisastersJapan attempts "cold shutdown" at reactor no. 1
Officials at the Tokyo Electric Power Company (TEPCO) hope to bring reactor no. 1 at the beleaguered Fukushima Daiichi nuclear plant to a “cold shutdown” by the end of the week; plant operators will attempt to bring the temperature inside the reactor below the boiling point of water so that it will no longer produce radioactive steam; the building housing reactor no. 1 must be vented so that all the radioactive air that has accumulated is released allowing workers to approach the reactor; once inside workers will inject cold water into the reactor’s primary containment structure; injecting tons of water into a damaged containment unit that houses uranium makes some scientists uneasy
Workers preparing to enter Fukushima reactor 1 // Source: asiaone.com
Officials at the Tokyo Electric Power Company (TEPCO)hope to bring reactor no. 1 at the beleaguered Fukushima Daiichi nuclear plant to a “cold shutdown” by the end of the week.
Since the 11 March earthquake and tsunami crippled the nuclear power plant’s cooling systems, officials have struggled to contain the overheating reactors that have been steadily spewing radioactive particles for the last two months.
In their latest efforts, plant operators will attempt to bring the temperature inside the reactor below the boiling point of water so that it will no longer produce radioactive steam, but scientists from around the world question the safety and wisdom of such a move.
Once inside workers will inject cold water into the reactor’s primary containment structure.
The thought of injecting tons of water into a damaged containment unit that houses uranium makes some scientists uneasy, as the water could leak or damage the unit further.
“They’re basically getting ready to run a big experiment,” said Dr. Edwin Lyman, a nuclear expert with the Union of Concerned Scientists, a nuclear watchdog group.
“It sounds like they’re assuming that the structural issues [with the primary containment structure] aren’t that serious – and there’s debateover that.”
Last week TEPCO revised the damage estimates of reactor units one, two, and three. According to the new estimates, Unit 1’s damage was downgraded to 55 percent from 70 percent, while Unit 2 and 3 were increased to 35 percent and 30 percent respectively.
Dr. Lyman conceded that injecting water into the containment structure “[seemed] like a reasonable thing to do if they can’t cover the cores in any other way.”
“They’re just stuck with doing whatever is going to work. The problem is, they’re learning by experimentation – not by some well-thought through contingency plan,” he said.
Given the risks, TEPCO is taking several cautionary steps before attempting the cold shutdown.
On Tuesday, the company began installing ventilation equipment in the unit’s damaged turbine building to extract the radioactive air. In addition, to prevent the contaminated air from escaping, workers have built special negative pressure doors around the building so that air can flow into the building but not out of it.
No workers have set foot in the building housing Unit 1 since a hydrogen explosion on 12 March left the building badly damaged and leaking radiation.
Despite these safety measures, U.S. nuclear officials are concerned about the company’s decision as it has made little progress in containing the damaged plant.
On Wednesday before the House Energy and Commerce Committee, Gregory Jaczko, the chairman of the Nuclear Regulatory Commission (NRC), said, “While we have not seen or predicted any new significant challenges to safety at the site, we have only seen incrementalimprovements towards stabilizing the reactors and spent fuel pools.”
In addition last Friday radiation levels taken from the seabed near the nuclear facility were found to be 100 to 1,000 times above normal levels.
The elevated radiation levels are believed to be the result of an undiscovered leak. In response to this development, Britain has offered to send a team of experts to help monitor sea radiation.
