GB/T 43062-2023 Nuclear energy—Determination of neutron fluence and displacement per atom(dpa) in reactor vessel and internals

Scope

This document specifies an evaluation process for the irradiation dose of components between the reactor core and the containment vessel in a given reactor core based on the neutron source. The irradiation dose can be expressed in terms of neutron fluence, dislocation per atom (dpa), or helium nuclei generation. The evaluation of irradiation can be conducted by calculating the neutron fluence rate or measuring the dose in the pressure vessel and the reactor cavity, as appropriate. This document is applicable to the determination of neutron fluence and dislocation per atom (dpa) in the pressure vessels and reactor internals of various reactor types, including pressurized water reactors (PWRs), boiling water reactors (BWRs), and pressurized heavy water reactors (PHWRs). It also establishes a process for evaluating the neutron damage characteristics of the reactor pressure vessel and reactor internals in PWRs, BWRs, and PHWRs. Damage primarily refers to direct damage caused by dislocation per atom due to neutron collisions and indirect damage caused by gas generation. The extent of both types of damage strongly depends on the neutron energy spectrum. Therefore, calculating the total cumulative dislocation per atom value for a given neutron fluence and neutron energy spectrum is an important data for reactor lifetime management. Note: In this document, "neutron source" refers to the distribution of fission neutrons in the reactor core.

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