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AGING
Nuclear reactors are similar to cars or any other piece of complicated machinery in that they
have limited shelf life. When they get old, they break down more often and maintenance
activities become too costly and difficult. Pilgrim is old and no exception - time to quit.
More than 30% of nuclear power reactor equipment failures can at least be partly attributed
to age-related degradation (Stephen Koff, “Nuclear Plant equipment Problems Worsening as
reactors Age,” Newhouse News Service, December 9, 2002).
Current federal regulations governing reactor re-licensing allow owners to ignore the
realities of age-related degradation that base risk calculations on the assumption that all
equipment fails at the same rate. This ignores hundreds of technical reports by the NRC about
age degradation of specific components such as valves, pipes, motors, cables, concrete, and
switches.
These reports indicate that failure rate of these parts follows a standard bathtub curve
(Susan Stanahan, “Reactor Revival; Old Reactors Being Re-licensed,” Mother Jones, November
2001). This means a high rate of failure at the beginning of the license, followed by a low
and rather constant failure rate, concluding with a wear-out period showing an increased rate
of failure as the original license is coming to a close.
Just because the NRC has re-licensed old reactors does not mean that they are fit; rather it
means that NRC’s re-licensing process is a “rubber stamp.” For example, the NRC inspected,
gave a clean bill of health and issued a re-license to the Oconnee reactor. Shortly after it
passed the re-licensing process, workers discovered the reactor’s cooling system, critical to
preventing a meltdown, had sprung a leak – due to aging metal on nine nozzles (NRC
Information Notice 95-17;NUREG/CR-6677-01).
Important Reports on
Aging
1. U.S. Nuclear Plants in
the 21st Century: The Risk of a Lifetime -
A report by the Union of Concerned Scientists
2. NRC and Oak Ridge
National Laboratory Report, “Boiling Water Reactor Internals Degradation
Study” NUREG/CR-5754, September, 1993; NRC/BWORG Meeting, “Core Shroud and
Vessel Internals Concerns,” Rockville MD, June 28, 1994
Source: Fact Sheet, Nuclear Resource Service, Paul Gunter
Deterioration of BWR Systems and Components:
It is becoming increasingly clear that aging of reactor components poses serious economic and
safety risks at BWRs. Pilgrim is a boiling water reactor (BWR).
A report by NRC published in 1993 confirmed that age-related degradation in BWRs will damage
or destroy many vital safety-related components inside the reactor vessel before the forty
year license expires. The NRC report states "Failure of internals could create conditions
that may challenge the integrity the reactor primary containment systems." The study looked
at major components in the reactor vessel and found that safety-related parts were vulnerable
to failure as the result of the deterioration of susceptible materials (Type 304 stainless
steel) due to chronic radiation exposure, heat, fatigue, and corrosive chemistry.
Core Shroud Cracking: One such safety-related component is the core shroud and it is also an
indicator of cracking in other vital components through the reactor made of the same
material. The core shroud is a large stainless steel cylinder of circumferentially welded
plates surrounding the reactor fuel core. The shroud provides for the core geometry of the
fuel bundles. It is integral to providing a re-floodable compartment in the event of a
loss-of-coolant-accident.
Cracking of circumferential welds on the core shroud has been discovered in a growing number
of U.S. and foreign BWRs – including Pilgrim. A lateral shift along circumferential cracks at
the welds by as little as 1/8 inch can result in the misalignment of the fuel and the
inability to insert the control rods coupled with loss of fuel core cooling capability. This
scenario can result in a core melt accident.
A German utility operating a GE BWR where extensive core shroud cracking was identified
estimated the cost of replacement at $65 million dollars. The Wuergassen reactor, Germany's
oldest boiling water reactor, was closed in 1995 after wary German nuclear regulators
rejected a plan to repair rather than replace the reactor's cracked core shroud.
Rather than address the central issue of age related deterioration, U.S. BWR operators now
opt for a dangerous piecemeal approach of patching cracking parts at least cost but increased
risk. Pilgrim opted to patch their cracks instead on following the German, safer example of
replacement.
See: NRC and Oak Ridge National Laboratory Report “Boiling Water Reactor Internals
Degradation Study” NUREG/CR-5754, September, 1993; NRC/BWORG Meeting, “Core Shroud and Vessel
Internals Concerns,” Rockville MD, June 28, 1994
More Structural Issues
PilgrimWatch.org
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