REACTOR COOLANT PRESSURE BOUNDARY MATERIALS

Pressure-temperature limitations (P-T Limits) are determined, in part, using material property test data for Reactor Coolant Pressure Boundary materials, as required by Appendix G to Section III of the ASME Code. Based on considerations of existing material property test data, an initial for the reactor vessel beltline material of -20 F is assumed. " The initial RT m for the remaining material of the Reactor Coolant System of +lu F is also assumed. 

Criterion 32 - Inspection of reactor coolant pressure boundary. Components which are part of the reactor coolant pressure boundary shall be designed to permit (1) periodic inspection and testing of important areas and features to assess their structural and leaktight integrity, and (2) an appropriate material surveillance program for the reactor pressure vessel. 

A list of specifications for the principal ferritic materials, austenitic stainless steels, bolting and weld materials which are part of the reactor coolant pressure boundary is given in Table 5.2-2. 

Fracture toughness requirements for Reactor Coolant Pressure Boundary components are established in accordance with the ASME Boiler and Pressure Vessel Code, Section III. Fracture toughness testing of base, weld and heat affected zone materials will be conducted in accordance with the ASME Code. Data from these tests will be available after the required testing has been performed and may be examined upon request at the appropriate manufacturing facility. 

REACTOR COOLANT SYSTEM MATERIALS WELD MATERIALS FOR REACTOR COOLANT PRESSURE BOUNDARY COMPONENTS Materla1... 

The acceptance criteria for the resolution of GSI 029 are that proven bolting designs, materials, and fabrication techniques shall be employed. In addition, reactor coolant pressure boundary (RCPB) bolting shall meet the requirements of ASME Code, Section III (Reference 2). Also, for RCPB bolting the owner-operator shall use established industry practice in developing maintenance, assembly, and disassembly procedures. Furthermore for RCPB and its support bolting, inservice inspection shall meet the requirements of ASME, Section XI (Reference 2),... 

The reactor coolant system, its associated anxiliary systems, and the control and protection systems shall be designed with sufficient margin to ensure that the design conditions of the reactor coolant pressiue bonndaiy are not exceeded in operational states. Provision shall be made to ensure that the operation of pressure relief devices, even in design basis accidents, will not lead to nnacceptable releases of radioactive material from the plant. The reactor coolant pressure boundary shall be equipped with adequate isolation devices to limit any loss of radioactive fluid. 

A. The material used to manufacture the flywheel of the reactor coolant pump motor will be produced by a commercially acceptable process that minimizes flaws, such as the vacuum melt and degassing process. This provides adequate fracture toughness properties under reactor operating conditions. The acceptance criteria for flywheel design will be compatible with the safety philosophy of the Pressure Vessel Research Committee (PVRC) of the Welding Research Council (WRC) primary coolant pressure boundary criteria as appropriate considering the inherent design and functional requirement differences between the pressure boundary and the flywheel. 

Improved reactor coolant system materials to reduce the chance of reactor coolant system cracking, which can lead to reactor coolant system leakage and associated safety challenges and cleanup/repair operation radiation exposures. A specific example of this improvement is the elimination of Inconel 600, to prevent stress corrosion cracking affecting the reactor coolant system pressure boundary. 

In general, several successive physical barriers for the confinement of radioactive material are in place within a plant. Their specific design may vary depending on the radioactivity of the material and on the possible deviations from normal operation that could result in the failure of some barriers. The number and type of barriers that confine the fission products are dependent on the technology that has been adopted for the reactor. For the reactors under consideration these barriers include the fuel matrix, fuel cladding, pressure boundary of the reactor coolant system, and the containment or confinement. 

A relevant aspect of the implementation of defence in depth is the provision in the design of a series of physical barriers to confine the radioactive material at specified locations. The number of physical barriers that will be necessary will depend on the potential internal and external hazards, and the potential consequences of failures. The barriers may, typically for water cooled reactors, be in the form of the fuel matrix, the fuel cladding, the reactor coolant system pressure boundary and the contaimnent. 

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