While performing an extent of condition review associated with the adequacy of air operated equipment inside containment to withstand containment main steam line break (MSLB) and loss of coolant accident (LOCA) temperatures, it was discovered that the Reactor Coolant System (RCS) Loop 1A Charging Line Stop Valve, the RCS Loop 2A Charging Line Stop Valve, and the Pressurizer RC-4 Auxiliary Spray Inlet Valve have nitrile based elastomers used in the air filter regulator and actuator. The design temperature limit for the nitrile elastomers used in the valves is 180°F which is acceptable for the normal operating conditions inside Containment of 120°F. However, during the MSLB and LOCA accident the temperature inside Containment is analyzed to reach 370°F. Since these valves have both open and close functions supported by an air accumulator, failure of the nitrile based elastomers could prevent the valves from fulfilling their intended safety function.
The causal analysis did not determine why the nitrile elastomers were installed during original plant construction. However, it was determined that a procedural deficiency and human error resulted in the wrong type of elastomer material being used in the instrument air filter regulators when the air accumulators were added to the valves to support their safety function.
Should disclose how if these valves all failed in the worst accident..how much harder it would be for the control room operators if these valved for a unknown surprise reason...what would be the poorest outcome of a plant in their DBA accidents? That is the only thing that matters. The public has a right to be protected thoroughly in these accidents.
Since these valves have safety functions, the failure of the nitrile based elastomers could have prevented the valves from fulfilling their intended function. However, FCS has not experienced any event that would have subjected this material to a temperature above the design temperature limit for the nitrile elastomers of 180°F.
1) Request nationwide all nuclear plants be notified this make and model "air filter regulator and actuator" is defective and needs to be replaced. To shutdown immediately and replace defective components.
2) Request nationwide all nitrile elastomers and buna seals, gaskets and 0-rings in nuclear safety component and especially containments be immediately checked for inappropriate (my Peach Bottom and Vermont Yankee SRV actuator threaded seals 2.206...their inspection reports and LERs) environmentally unqualified and unsafe sealing materials much like Fort Calhoun, Peach Bottom and Vermont Yankee.
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