Instances of flux thimble tube wear and leakage observed in operating Westinghouse designed reactors with bottom mounted instrumentation have been attributed to flow-induced vibrations in the lower internals support column area. As a result, the U.S. Nuclear Regulatory Commission (NRC) issued Bulletin 88-09, “Thimble Tube Thinning in Westinghouse Reactors,” which instructs affected utilities to establish and implement inspection programs to periodically confirm thimble tube integrity.

The Westinghouse Solution Westinghouse is committed to bringing efficient, large-scale hydrogen production to nuclear facilities through operating plant integration and advanced reactor designs. Clean hydrogen supports societal decarbonization while yielding a significant, yet flexible revenue stream to utilities around the world. Westinghouse is positioned to be a full-scale hydrogen partner, maximizing power output, modernizing plants for long term operations and monetizing hydrogen production.

Background During a severe accident or a beyond-design-basis accident (BDBA), the reaction of water with zirconium alloy fuel cladding, radiolysis of water, molten coriumconcrete interaction (MCCI) and post-accident corrosion can generate hydrogen (H2). The total mass of H2 produced in-vessel depends on several factors. For most reactors, it is on the order of 1,000 kilograms. High peak rates for H2 release to the containment of up to several kg/s can result from discontinuous releases from the reactor pressure vessel. The detonation of H2 can result in damage to structures such as containment buildings or spent fuel buildings. In all reactor designs, H2 monitors can be utilized to monitor the risk of containment or spent fuel building damage due to H2 detonations.

Starting with the first commercial Westinghouse-design nuclear power plants, Westinghouse has been involved in the development of generic, as well as plant specific, guidance for response to plant events. Following the Three Mile Island (TMI) accident, the U.S. Nuclear Regulatory Commission (NRC) issued NUREG-0899, which provided requirements for utility preparation and implementation of emergency operating procedures (EOP), including development, writing and maintenance. This was followed by NUREG-1358, in which the NRC reinforced its expectations with respect to the plantspecific technical guidelines, EOP writers guide, EOP verification and validation (V&V) and EOP training. Together, these regulations comprise the plant-specific procedure generation package (PGP).

Virtually all nuclear utilities are facing ever-increasing personnel and financial pressures. The aging work force and demand for talent from regulators and new nuclear plants are creating skill gaps. Financial pressures are increasing in today’s sluggish economy, forcing utilities to optimize the size and skill sets of their staffs.

The goal of Valve Program Management (VPM) is to maintain the safety-related and important-to-safety-related valves’ reliability so that they can perform the design basis requirements for the life of the plant. While this may be simply stated, the actual management and implementation of the program is a complex and comprehensive task that, if performed effectively, results in increases in both plant reliability and capacity factors.