The design of a nuclear plant includes “hot” containment penetration assemblies designed to protect the containment building concrete walls from the effects of localized high temperature and degradation due to thermal cycling resulting from the process piping. Typically, a penetration assembly is jacketed by coolers inside and outside a sleeve originating at a flued head on the process pipe and penetrating the containment wall. The coolers are supplied by either chromated component cooling (CC) or raw service water. Recently, a minor leak of chromated water from the penetration coolers rendered the Class 3 safety-related CC system inoperable and was isolated. Subsequently, Non-Destructive Examination (NDE) inspections of the sleeve were conducted and significant degradation was noted. The root cause of the degradation under the jacketed cooler was due to raw service water, which was used in the cooler prior to switching to CC water. Weld repairs were subsequently performed to restore degraded areas. The coolers were also removed since the air gap could provide adequate insulation to keep the sleeve below a threshold temperature for degradation of concrete. An evaluation of past functionality was still required, however, to demonstrate that the degradation did not affect the structural integrity of the sleeve and breach containment boundary. The NDE data was processed to characterize the degradation for analysis. A novel application of ASME Section XI Non-mandatory Appendix C with a simple extension of the methodology was used in the evaluation to assist the operability determination. The paper concludes that a simple extension of the code methodology was useful in establishing plant operability.
Structural Evaluation of Degraded Containment Penetration Sleeves
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Vasquez, DJ, Smith, AJ, & Dwivedy, KK. "Structural Evaluation of Degraded Containment Penetration Sleeves." Proceedings of the ASME 2008 Pressure Vessels and Piping Conference. Volume 1: Codes and Standards. Chicago, Illinois, USA. July 27–31, 2008. pp. 307-312. ASME. https://doi.org/10.1115/PVP2008-61514
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