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Challenging Test Problems for Coupled Transient Simulations of Pressurized Heavy Water Reactors

Abstract of the technical paper/presentation to be presented at:
M&C 2019 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering
August 25-29, 2019

Prepared by:
A. Trottier and N. Aydemir, Canadian Nuclear Laboratories
M. Krause, International Atomic Energy Agency
M. Dahmani, SNC-Lavalin Nuclear
D. Serghiuta, Canadian Nuclear Safety Commission


Several countries operating Pressurized Heavy Water Reactors (PHWR) have active research programs to investigate multi-physics code simulations. The choice of a coupling algorithm is expected to involve several considerations such as applicability of the proposed multi-physics system to different reactor transients, the state of existing and prototype codes, and the required accuracy in the results of the analyses. Open access to standardized numerical test problems, representative of PHWR transients, facilitates testing of different codes and coupling methods and provides a means to test current transient simulation methods, which are generally based on coupling few-group diffusion neutronic codes to thermalhydraulic codes.

To address this need, the International Atomic Energy Agency initiated in 2016 an International Collaborative Standard Problems (ICSP) to facilitate the development of a set of standardized numerical test problems for selected postulated transients in PHWR. These manufactured test problems are different from the typical benchmark problems in that the specification is designed for a stylized model of a generic CANDU-6 PHWR and a reference solution is not postulated. Currently, twelve institutes from seven Member States plus the Organisation for Economic Co-operation/Nuclear Energy Agency are participating in the ICSP.

It is expected that differing participant’s simulation codes and methods will lead to variation in the submitted solutions to the test problems. The objective is to decompose these variances, in order to gain insight on the impact of different simulation approaches to coupled simulation accuracy.

The paper provides an overview of the process for developing the specifications for the proposed challenging test problems and a brief description of each problem. The “inadvertent withdrawal of adjuster rods” challenging problem and selected results for this problem are used for illustration.

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