John Downey
Group says AP1000 design ‘flawed’
Wednesday, April 21, 2010, 2:31pm
AP1000 cutaway diagram. The containment vessel is in gold.
An anti-nuclear coalition says design flaws in Westinghouse’s AP1000 reactor could allow radiation leaks during an accident, and it is calling on federal authorities to suspend licensing and loan guarantees for plants that use it.
The AP1000 Oversight Group, made up of 11 environmental organizations, released a report Wednesday detailing what it calls a serious safety issue that the Nuclear Regulatory Commission has not addressed on the AP1000 reactor.
The report contends Westinghouse designed the reactor without a corrosion-proof backup to protect against leaks from the containment vessel. In a reactor accident, the reactor’s safety systems would allow any radioactive material that had leaked over time to be released into the air and spread to nearby populated areas, the group contends.
Preclude corrosion
Westinghouse spokesman Vaughan Gilbert dismisses that argument. “In the highly unlikely event that corrosion would occur, routine inspections would detect it very early on,” he says. “The facility is designed to preclude corrosion.”
Arnold Gunderson of Vermont-based nuclear consulting firm Fairewinds Associates Inc. prepared the coalition’s report. He contends Westinghouse and the NRC have not properly considered the corrosion issue.
His report outlines six cases in the last 20 years in which pitted corrosion ate through metal containment vessels in nuclear plants. In each of the plants, the metal containment vessel was surrounded by a concrete containment building. The concrete back-up containment system in those cases would have prevented any radiation leak in the event of an accident in the reactors.
Venting gas
The AP1000 has no concrete containment building, Gunderson says. And the design of the safety systems calls for dousing the containment vessel with water from an 8 million-gallon tank in an accident and venting the steam to cool the vessel.
If there were a small rust leak in the metal vessel, he argues, radioactive gas would automatically be vented from the nuclear plant from the safety system.
At a press conference releasing the report, Louis Zeller of the Blue Ridge Environmental Defense League said the NRC should suspend licensing proceedings for plants that use the AP1000 reactor. He also called on the Obama administration to hold off on loan guarantees offered to Southern Co. for its plans to build two AP1000 units at its Vogtle Nuclear Station in Georgia. Those guarantees were announced last month.
Blue Ridge is one of the environmental organizations in the AP1000 Oversight Group.
Lee plant
The AP1000 is also the unit Scana and Santee Cooper intend to use at the V.C. Sumner plant. And Duke Energy plans to use it at its proposed Lee Nuclear Station in Gaffney, S.C.
The AP1000 is also important to the Shaw Power Group, based in Charlotte, which is the contracting partner for Westinghouse on AP1000 projects in the United States.
Gilbert says the containment vessel on the AP100 is 1.75 inches thick — more than twice as thick as vessels in existing plants cited in Gunderson’s report. Westinghouse does not consider the vessel to be subject to undetected corrosion.
"Nuclear is Unclear " -- A confucian in confusion. 
发表于 2010-9-15 17:35:16