ISO 18077:2018 PDF Download

Pressurized Water Reactors (PWRs) startup reactor physics tests are covered by ISO 18077:2018, a standard. This standard specifies the minimally acceptable test regimen that must be carried out after refueling or making changes to a PWR's core. These tests serve to ensure that the core can be operated as intended by confirming whether the operating characteristics of the core match the design predictions. 

It is significant to remember that ISO 18077:2018 does not cover monitoring reactor physics parameters while it is operating or other necessary tests like mechanical testing or fuel assembly loading verification. For both core design and starting test predictions, the standard presupposes the employment of previously established analytical techniques. It also presupposes that the projected operation of the core falls within the bounds of the plant's historical record.

When considerable modifications are made to the core design, such as new fuel cycle designs, significant changes in fuel enrichments, or unanticipated short cycles, the standard advises that extensive testing may be necessary. Given that they might not be covered by the plant's experience database, these modifications might necessitate an additional test program.

While the physics test program for the initial core of a commercial PWR is not covered by ISO 18077:2018, it is suggested that some of the good practices included in the standard might be taken into account for use in the physics test program for the initial core. The hot-zero-power to hot-full-power reactivity measurement, for instance, is suggested as a helpful test that yields important information without requiring additional test time.