Diesel Problems Keep Seabrook nuke Off-linegreenspun.com : LUSENET : Grassroots Information Coordination Center (GICC) : One Thread
Diesel Problems Keep Seabrook Off-line
LCG, Dec. 15, 2000--The 1,150 megawatt Seabrook nuclear power plant in southeastern New Hampshire shut down October 21 to refuel and was expected back on-line by November 21, but continuing problems with a back-up diesel generator have prevented a restart and it appears they will continue to do so, a minority owner of the plant said yesterday.
Bay Corp Holdings Ltd., the parent company for Great Bay Power Corp. and Little Bay Power Corp., said that repairs to the diesel had been expected to be accomplished by the middle of this month, but haven't been. When mechanics tested one of the diesel generators recently, they broke it.
Seabrook is mostly owned by Northeast Utilities subsidiary Public Service Co. of New Hampshire and is operated by North Atlantic Energy Service Corp. North Atlantic is now projecting that the plant will be returned to service at the end of January.
Bay Corp got out a news release to explain the outage is costing it a lot of money for replacement power it must purchase at high rates to cover the 174 megawatts it isn't getting from Seabrook
-- Martin Thompson (email@example.com), December 15, 2000
It's not that they broke it, it's more like they have a 2% failure rate, and that means they were lucky to have it break when it was not an emergency!!!! BTW [I think - remember reading something to the effect that] they have two backup gennys, and both are down?? Wow this is not good. Or maybe they can't start with out both gennys fixed.
-- (firstname.lastname@example.org), December 15, 2000.
I thought diesel generators were only needed if the whole grid went down. Why can't they use grid power to start up? They have a connection to the grid, or did managment forget that? Last time I checked (I'm typing this on line) the grid was up!
-- James Fitzgerald (JamesJFitz@Juno.com), December 17, 2000.
STATION BLACKOUT RISKS INCREASING
Most people are not aware that an operating reactor does not provide itself with its own alternating current (AC)used to power,control and monitor reactor safety systems, such as emergency shutdown and core cooling capability. That power comes offsite through transmission lines from the electrical grid to the reactor site. With the experience of loss or instability of the grid, nuclear power stations are designed to automatically SCRAM ("Single-Control-Rod-Ax-Man")to rapidly shut down the fissioning of the core. A tremendous amount of residual heat from the atomic chain reaction must then be efficently managed to keep the reactor core from overheating and melting. Hence the importance of emergency diesel generators (EDG).
In the event of loss of the electrical grid and the shift to EDGs, a number of safety systems are prioritized with some safety systems shut off. Should multiple EDG failure occur, there is a large back up battery bank which uses stored direct current (DC)for generating AC power to a further limited number of safety systems for a shorter amount of time of several hours.
The importance and significance of unreliability of emergency diesel generators should not be underestimated.
By the Nuclear Regulatory Commission's own studies into accident events leading to core melt, fully 50% of the risk originates from a condition called "station blackout," where grid failure is followed by the common mode failure of the onsite emergency diesel generators used to provide altnating current to and running down the backup DC power. The recent Seabrook Station outage raised a significant safety concern which has been further borne out by the multiple maintenance failures. During the now extended refueling/maintenance outage, Seabrook operators took a daring and irresponsible move by simultaneously taking both emergency diesel generators off standby readiness to do a full overhaul of both the "A" and "B" trains used for emergency backup power to safe reactor shutdown and cooling systems. The move at one point intentionally disabled both trains to go to full reliance on the grid after the 'B' EDG failed during a 24 hour surveillance test on November 1.
According to NRC records, between October 29 and November 1, 2000, Seabrook attempted to perform a 24-hour endurance surveillance test on the "B" EDG. The attempts on October 29 and 30, 2000, resulted in operators securing the EDG based on high differential pressure across the lubricating oil filter. The attempt on November 1 encountered "crankcase high pressure" and "EDG high vibration" alarms and required emergency EDG shutdown. In addition, the operators in the EDG room noted a flash from the turbo-charger area and heavy black smoke. Subsequent preliminary assessment by the licensee has revealed damage to at least one of the EDG cylinder liners.
The licensee formed an Event Team on October 31, 2000, to assess the problems with the lubricating oil system, and expanded the scope of that team on November 1, 2000, based on the last test failure.
On December 3, the licensee stopped a 6 hour break-in run of the 'B' emergency diesel generator about 25 minutes into a post maintenance test run due to an increase in lube oil strainer differential pressure. Preliminary visual inspections indicate that damage had occurred to the No. 5 main bearing.
All the main bearings on the 'B' EDG were replaced during the overhaul. The 'A' EDG was successfully restored to service on November 28.
Seabrook initiated an 'event team' to investigate this most recent failure of the 'B' EDG. Region I received initial notification of the third test failure resulting in damage to the EDG by telephone on November 1 from the senior resident inspector. On November 2, Region I, in consultation with NRR, decided to send a Special Inspection Team to the site to monitor and assess the licensee's root cause evaluation and corrective actions, independently evaluate the risk significance of the EDG test failures, and determine possible generic implications.
For Seabrook station, this is not an isolated incident. During the summer of 1999, operators undertook to intentionally disable one EDG train while at full power, providing the safety analysis that the alternate EDG train would be available. Some months later, it was discovered that in fact, that alternate train was degraded by faulty relays and would not have automatically started. The NRC dismissed the faulty safety analysis by saying that the EDG could have been manually started and anyways, the grid was functional.
It is significant to note that the NRC and industry continue to assume that the electrical grid is a stable and every reliable entity. All studies to date on the risks associated with "station blackout" have assumed the grid is basically stable. A number of events over the past several years, do not lend to that high confidence factor. The California situation in particular suggests that the grid is growing more and more unstable and subject to higher risks of severe disturbances which can critically affect safety systems at nuclear power stations. The fact that EDG reliability and stability is coming under ever more question from watchdog groups should further raise safety concerns for increased regulatory scrutiny, not less and mount public pressure for permanently shutting down this inherently dangereous technology.
Paul Gunter Nuclear Information and Resource Service 1424 16th Street NW Suite 404 Washington, DC 20036 Tel. 202-328-0002 http://www.nirs.org
-- Paul Gunter (email@example.com), December 18, 2000.
it was discovered that in fact, that
alternate train was degraded by faulty
relays and would not have automatically
Scary indeed :-§
Thanks Paul for the info and the link to
the NIRS site.
I have compiled info on SCRAMs for the
last 3 years. In January 2000 there were
a record 12 SCRAMs. Here is a link to the
Your comments would be appreciated.
-- spider (firstname.lastname@example.org), December 18, 2000.