Start-up predictions using PC1D, a personal-computer-based neutronics code

Conference · Mon Jan 01 04:00:00 EST 1990 · Transactions of the American Nuclear Society; (United States)

OSTI ID:7089479

Sarafian, P G; Alsop, B H

The determination of accurately estimated critical rod positions (ECP) is required for safe start-ups after plant shutdowns. Typical procedures employ point-core reactivity balance models to do such estimates. The point-core models generally are accurate enough for quasi-equilibrium conditions. These conditions exist when a plant operates near steady-state power level and rod position for a prolonged period of time prior to shutdown. Shutdowns from nonsteady conditions, however, result in transients in the spatial distribution of fission products such as xenon and samarium. Severe xenon transients could cause point-core model ECPs to deviate appreciably from plant critical conditions. These reactivity deviations can reach a significant fraction of the plant operating license limits. A dimensional neutronics model can be used for ECP calculations in large reactor cores with better accuracy than point-core models. The PC1D axial neutronics code was developed for this application for both steady-state and transient xenon conditions. Pacific Gas and Electric (PG and E) has utilized this code for the last two cycles of operation of two reactors. This paper describes the code and PG and E's experience using it for ECPs.

• OSTI ID: 7089479
• Report Number(s): CONF-901101--
• Conference Information: Journal Name: Transactions of the American Nuclear Society; (United States) Journal Volume: 62
• Country of Publication: United States
• Language: English

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