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Track Record - Evidence of Problems

 

Scrams: Scrams are emergency plant shutdowns, different from a gradual decrease in power when a plant intentionally shuts down. To scram a reactor is like suddenly slamming on the brakes in a car - it is a sudden violent shutdown of a nuclear reactor. Too many scrams stress the reactor - important for Pilgrim NPS, a reactor showing signs of early degradation. In 2003, for example, Pilgrim reported three scrams.

Licensee Event Reports: are filed with the NRC each time there is a failure or breakdown of nuclear plant systems or procedures. Events for which an LER must be filed include: conditions outside the design basis of the plant, phenomena that pose an actual threat to the safety of the nuclear plant, and events that result in the degradation of the plant’s principal safety barriers. The NRC reporting guidelines state that these reports provide “detailed narrative description(s) of potentially significant safety events” --mishaps or conditions that “might lead to serious accidents.” 

Licensee Event Reports (LERs) by no means reflect harmless or trivial events. According to the NRC, LERs provide a “basis for assessing the performance trends of the industry as a whole and those of individual licensees.” U.S. NRC. Annual Report 1988 Vol. 5 NUREG-1145, June 1989, p.48.

The NRC reports current and archived event reports on their website daily http://www.nrc.gov/


Engineering Review of Operating Transients: Pilgrim in 1994 had already exceeded the 40-year design standards for 6 kinds of events that put stress on the reactor before license expiration, according to a February 24, 1994 NRC Inspection Report. 

Transient 
Description

Design Cycles
40 years 

Cycles to-date
 21 years

 Projected Cycles
40 years

Startup 120 187 368
Power Increase 120 133 264
T/G Trips 40 26 49
Other Scrams 147 134 346
Loss of FW Pumps 10 26 64
SR Valve Blowdown 2 13 23


A look at the NRC chart shows that if transients continued at the same rate of application until the end of the licensed period that they will exceed the number anticipated during design of the plants components. 

Several transients had already exceeded the design number of transients for a 40 year operation by 1994. For example, Pilgrim had 50% more plant restarts in its first 22 years than it was designed to have over a 40 year life. 

The report found that Pilgrim had more shutdowns and startups, more water pump failures, and more emergency steam releases than the other 10 plants studied by that date. These events expose key parts of the reactor to sudden changes of temperature and pressure, increasing the wear. 

More Structural Issues

 

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