REACTOR DYNAMICS MODELS FOR SAFETY ANALYSIS IN AERB

Obaidurrahman K., Avinash J. Gaikwad, Nuclear Safety Analysis Division, Atomic Energy Regulatory Board (AERB), India

24th Symposium of AER on VVER Reactor Physics and Reactor Safety (2014, Sochi, Russia)
Reactor dynamics and safety analysis

Abstract

REACTOR DYNAMICS MODELS FOR SAFETY ANALYSIS IN AERB
Obaidurrahman K., Avinash J. Gaikwad
Nuclear Safety Analysis Division, Atomic Energy Regulatory Board (AERB), Anushaktinagar, Mumbai, India, 400094 (
Corresponding author, e-mail: obaid@aerb.gov.in / obaid.iitb@gmail.com)
ABSTRACT
The nuclear power programme in India is being pursued with full regard for nuclear and radiation safety, which encompasses safety of plant personnel, public and the environment. The task of laying down necessary safety requirements and their enforcement are entrusted to the Atomic Energy Regulatory Board (AERB), which is the national authority to ensure that the use of ionizing radiation and nuclear energy in India does not cause undue risk to the health of workers and members of the public, and the environment. AERB is involved in safety review and licensing of variety of power reactors of different design and capacity. To provide technical support to its review process, AERB carries out independent safety analysis and research on selected important areas of nuclear and radiation safety. These safety studies help in taking important regulatory decisions during licensing process. Independent safety analysis requires a set of competent computational tools for which AERB has taken sincere initiatives to establish state-of-the-art best estimate analytical capabilities for analysis of core behavior, system thermal hydraulics, severe accidents and radiological impact assessment. Reactor dynamic is the integral part of any postulated initiating event (PIE) being analyzed. With induction of several types of reactors with diverse design in Indian nuclear map, it was imperative to develop detailed core modeling capability in AERB. Consistent with this objective a comprehensive 3D neutron kinetics code (TRIKIN) has been developed in AERB. TRIKIN model solves time dependent multigroup neutron diffusion to the highest level of approximation in full 3D core domain. This is achieved by flux factorization approach implemented by improved quasi static method. Finite difference method, assisted by a Chebychev’s acceleration scheme has been employed for spatial solution of neutron fluxes and Generalized Runge Kutta method has been used for time integration of amplitude function. Provision of triangular, hexagonal as well as square meshes in space solver renders high generality to the code, which allows its use for variety of reactors like PHWRs, VVERs, PWRs, BWRs and FBRs. For evaluation of core thermal state during evolving nuclear transient, a dedicated core thermal hydraulic model based on fuel pin simulation has been developed and internally coupled to the spatial kinetics model. Complete coupled TRIKIN model has been validated against a series of international benchmarks for VVER, PWRs and PHWRs. The present paper will describe salient features of AERB TRIKIN code and the glimpses of a few analytical studies carried out to support regulatory review process.

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