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"On October 11, 2005 Palo Verde Nuclear Generating Station (PVNGS) Units 2 and 3 at approximately 1602 and 1655 Mountain Standard Time (MST), respectively commenced reactor shutdowns required by Technical Specification 3.0.3.
"Engineering personnel were unable to demonstrate that the original design of the Emergency Core Cooling System (ECCS) could perform its safety function for its mission time under certain postulated accident scenarios. Specifically, the Refueling Water Tank (RWT) is designed with baffles to prevent a vortex from developing and air binding the Safety Injection pumps during a Loss of Coolant Accident (LOCA). On a LOCA, the High Pressure Safety Injection pumps take a suction from the RWT and inject borated water into the Reactor Coolant System (RCS). At 7.4 percent RWT level, the source of borated water by design automatically shifts from the RWT to the containment sump. However, for small break LOCA there may be insufficient containment pressure to ensure inventory is not continuing to be drawn from the RWT. This may allow the baffles in the bottom of the RWT to uncover. With the RWT baffles uncovered, a vortex may develop, leading to potential air binding of the Safety Injection pumps before the operator manually isolates the RWT. "
"It doesn't mean the system couldn't perform as it's supposed to," he said. "It just means we couldn't prove it would." eastvalleytribune
Problem with Palo Verde cooling system went undetected for years
A potential problem with the emergency reactor core cooling system at the nation's largest nuclear power plant went undetected since it began producing power in 1986, the Nuclear Regulatory Agency and the plant operator confirmed Thursday.
The design flaw put the plant outside of it licensing guidelines and operator Arizona Public Service shut down the two operating reactors immediately until a fix is put in place. The third reactor in the complex 50 miles west of Phoenix was already down for maintenance and refueling.
APS seeks rate hike to offset cost of Palo Verde outages
In July, APS asked the corporation commission to approve a fuel-cost "adjuster" that would hike the typical residential bill 2.1 percent and raise $100 million to offset rising energy costs
SRP board approves rate hike
Rates for business customers will increase 1.9 percent, and the combination of residential and business rates increase will create an average price increase of 2.9 percent.
The fact the potential problem took so long to be discovered should prompt the NRC to look at other plants and procedures, said David Lochbaum, a nuclear safety engineer for the Union of Concerned Scientists, a nuclear watchdog group.
Originally posted by Regenmacher
Why Now? It is very odd that ASP completely shut down Palo Verde:
• Is it in response to an undisclosed terror threat?
• Did APS shutdown the nuclear plant to push a rate hike agenda?
• Is it another facet of the "energy cabal" to stick it to Joe consumer?
LOS ANGELES California power officials called a Stage 1 power emergency for the southern part of the state this afternoon after higher than normal temperatures led to tight electricity supplies.
Part of that power shortage is due to the shutdown of the big Palo Verde Nuclear Generating Station west of Phoenix. That plant normally would provide more than 600 megawatts of power to Southern California Edison Company - enough for more than 600-thousand homes.
A containment building, in its most common usage, is a steel or concrete structure enclosing a nuclear reactor. It is designed to, in any emergency, contain the escape of radiation despite pressures in the range of 60 to 200 psi. The containment is the final barrier to radioactive release, the first being the fuel ceramic itself, the second being the metal fuel cladding tubes, the third being the reactor vessel and coolant system.
In the event of a worst-case emergency (called a "design basis accident" in NRC regulations) the containment is designed to seal off and contain a meltdown. (Redundant systems are installed to prevent a meltdown, but as a matter of policy, one is assumed to occur and thus the requirement for a containment building.)
NRC ANNOUNCES REAPPOINTMENT OF
COMMISSIONER EDWARD MCGAFFIGAN, JR
Prior to his appointment to the Commission, from February 1983 to August 1996, he served as a legislative assistant, then legislative director, and finally senior policy advisor to Senator Jeff Bingaman (D-NM). McGaffigan supported the Senator's work on defense policy, technology policy, personnel and acquisition reform, and nonproliferation and export control policy.
McGaffigan was a member of the Foreign Service from May 1976 to February 1983. From 1981 to1983 he served as a senior policy analyst and then assistant director in the White House Office of Science and Technology Policy, where he oversaw international scientific cooperation and export control matters. During much of this time, he held a dual appointment on the staff of the National Security Council.
Previously, Mr. McGaffigan carried out various assignments within the State Department dealing with U.S.-Soviet relations and politico-military issues. He was stationed as a science attache in the U.S. Embassy in Moscow from July 1978 to April 1980, where he reported on Soviet energy and atomic energy developments and managed bilateral science cooperation in those and other areas.
During a March 24, 2009 public meeting, the NRC announced that it cleared the Confirmatory Action Letter (CAL) and has returned Palo Verde to Column 1 on the NRC Action Matrix. The commission's letter stated that "The U.S. Nuclear Regulatory Commission has determined that the Palo Verde Nuclear Generating Station has made sufficient performance improvement that it can reduce its level of inspection oversight." “Performance at Palo Verde has improved substantially and we are adjusting our oversight accordingly,” said Elmo E. Collins, NRC’s Region IV Administrator. “But we will closely monitor the plant. We are reducing our oversight, but not our vigilance.”