lochbaum on nuke plant aging

[Norman Cohen <ncohen12@HOME.COM>]

Julian, et al:



This is a text file, without illustrations, and without the UCS heading, etc. Word file availble, just ask me.

This was written by Lochbaum.



Norm





>   ------------------------------------------------------------------------

>

> Aging Nuclear Plants and License Renewal - Updated 09/13/2001

>

> The NRC allows nuclear plant owners to cut back on the number of safety tests and inspections. The NRC justifies this safety rollback on the notion that experience demonstrates improved equipment reliability. But the fact remains that nuclear plant equipment-just like virtually all living and inanimate objects-follows what is called the "bathtub" curve. Region A, or the break-in phase, and Region C, the wear-out phase, have high failure rates while Region B reflects peak reliability during middle life. The NRC uses the lower failure rate for equipment in Region B to relax testing intervals from once per quarter to once per year. Mathematical magic then falsely "proves" safety gains. For example, consider a component that fails every time it is tested. Going from quarterly to annual tests reduces the number of failures per year from four to one. On paper, safety is greatly improved. But in the plant, safety is unchanged. Every nuclear plant in the United States is in Region B!

 heading towards Region C, if it is not already into the wear-out phase. Cutting back on safety checks saves plant owners money, but it may someday cost lives.

>

> The NRC originally licensed nuclear plants for 40 years. Plant owners have the option of seeking a 20-year extension. The Nuclear Regulatory Commission (NRC) renews licenses after determining plant owners have aging management programs to monitor the condition of important equipment and structures so that repairs and/or replacements will take place to prevent failures. But failures are simply not being prevented because many nuclear plants have been forced to shut down since January 1, 2000, after aging equipment broke:

>

> 1. March 7, 2000: The owner reported that Nine Mile Point Unit 2 in New York had automatically shut down when the system controlling the level of water over the reactor core failed. The owner attributed the failure as "Specifically, the manual-tracking card failed to provide an output signal when the feedwater master controller was switched from automatic to manual mode of operation ... The manual-tracking card failed due to aging." [emphasis added]

>

> 2. March 14, 2000: The owner reported that Catawba Unit 1 in South Carolina had automatically shut down due to an inadvertent electrical ground problem. The owner reported "A detailed failure analysis determined that the root cause of the connector failure was the misapplication of the connector insert insulating material which is made of neoprene. ... The neoprene insert at the failure point on the connector exhibits signs of accelerated aging [emphasis added]. The inserts are hardened and there are charred deposits on the end of the inserts which are indications of electrical tracking."

>

> 3. March 17, 2000: The owner reported that Indian Point Unit 2 in New York had been forced to declare an emergency condition and shut down after a steam generator tube failed and resulted in approximately 19,197 gallons leaking from the reactor coolant system. The owner stated "Preliminary analysis indicates that the cause of the tube failure is primary water stress corrosion cracking (PWSCC)" [i.e., aging].

>

> 4. March 27, 2000: The owner reported that Catawba Unit 2 in South Carolina had automatically shut down due to an inadvertent electrical ground problem. The owner reported "A detailed failure analysis determined that the root cause of the connector failure was the misapplication of the connector insert insulating material which is made of neoprene. ... The neoprene insert at the failure point on the connector exhibits signs of accelerated aging [emphasis added]. The inserts are hardened and there are charred deposits on the end of the inserts which are indications of electrical tracking."

>

> 5. September 12, 2000: The owner reported that Oyster Creek in New Jersey had been forced to shut down because a system needed to provide containment integrity had failed a periodic test. The owner determined "The cause of the degradation in Secondary Containment was age-related degradation [emphasis added] of the automatic ventilation exhaust valve seals."

>

> 6. September 27, 2000: The NRC reported that Diablo Canyon Unit 1 in California had automatically shut down after an electrical transformer failed and interrupted the supply of electricity to the reactor coolant pumps. The NRC stated "The licensee's evaluation concluded that a center bus bar overheated at a splice joint, which caused a polyvinyl chloride boot insulator over the splice joint to smoke. Eventually, heat-induced failure of fiberglass insulation on adjacent phases resulted in phase-to-phase arcing" [i.e., aging].

>

> 7. February 16, 2001: The owner reported that North Anna Unit 2 in Virginia had been forced to shut down due to leakage exceeding ten gallons per minute from the reactor coolant system. The owner determined "The cause of the stem packing material failure below the lantern ring is attributed to aging" [emphasis added].

>

> 8. April 2, 2001: The owner reported that San Onofre Unit 3 in California automatically shut down after an electrical breaker failed and started a fire. The failed breaker was reportedly 25 years old and scheduled for inspection next year. The owner "will implement modifications to appropriate preventative maintenance [emphasis added] procedures to address the apparent failure causes."

>

> 9. April 23, 2001: The owner reported that South Texas Project Unit 2 in Texas had been forced to shut down after actions in the plant's electrical switchyard tripped all three pumps supplying cooling water to the main condenser. The pumps stopped running after workers took one electrical circuit out of service thinking that a backup circuit was available to take up the load. However, the backup circuit was also out of service because an electrical breaker had remained opened after workers tried to close it. The breaker's failure was attributed by the owner to "accelerated wear of the components" [i.e., aging].

>

> 10. April 24, 2001: The owner reported that Limerick Unit 2 in Pennsylvania had been forced to shut down when a pressure relief valve spuriously opened and remained open. The owner attributed the failure to "a sudden loss of material from the first stage pilot valve due to erosion and oxidation of the Stellite disc material in the area of the seating surface" [i.e. aging]. The owner additionally reported that "The SRV [safety relief valve] Leakage Determination Monitoring Process did not consider all possible failure mechanisms."

>

> 11. May 9, 2001: The owner reported that Beaver Valley Unit 2 in Pennsylvania had automatically shut down after a motor-driven pump supplying cooling water to the steam generator failed. The pump's failure was attributed by the owner to "a combination of long term heating, accelerated oxidation [i.e., aging], and marginal sizing of the motor cable and terminal lugs." [emphasis added]

>

> 12. July 17, 2001: The owner reported that Nine Mile Point Unit 2 in New York had automatically shut down after a relay in the reactor protection system failed. The relay manufacturer had notified its customers four years earlier that the relay was vulnerable to oxide buildup [i.e., aging] and recommended a modification to the relays along with periodic replacement. The owner opted not to implement either recommendation; at least, not until after this event.

>

> 13. August 13, 2001: The owner reported that Beaver Valley Unit 1 in Pennsylvania had been forced to shut down when the instrument air system pressure declined to the point where air-operated valves throughout the plant began closing. The owner attributed the pressure loss to "mechanical aging/cyclic fatigue" of the spring in a valve that caused the output from the air compressor to be vented rather than directed to the system piping. [emphasis added]

>

> 14. August 14, 2001: The owner reported that the Kewaunee nuclear plant in Wisconsin had automatically shut down due to insufficient instrument air supply to the regulating valve for feedwater flow to the steam generator. The regulating valve closed when the instrument air pressure dropped. The owner attributed the air pressure loss to a tear in a neoprene diaphragm that had not been detected due to a "running to failure" maintenance schedule. In other words, the part wore out and broke.

>

> 15. August 20, 2001: The owner reported that the Perry nuclear plant in Ohio had automatically shut down after a blown fuse stopped the flow of cooling water to the reactor core. The owner determined that the fuse blew from high electrical resistance "due to age related oxidation." [emphasis added]

>

> Nuclear power plants generate revenue by producing electricity. If their owners are unable to properly maintain the equipment needed to make them money, why should the public believe that they are able to properly maintain the equipment needed to make us safe?

>

> September 13, 2001



--

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