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Irregular Heterogeneous Effects in a LWR Reactor


Study of Irregular Heterogeneous Effects in an LWR-Type Reactor Core

Tech Area / Field

  • FIR-NOT/Nuclear and Other Technical Data/Fission Reactors
  • FIR-FUE/Reactor Fuels and Fuel Engineering/Fission Reactors

8 Project completed

Registration date

Completion date

Senior Project Manager
Tocheny L V

Leading Institute
Federal State Unitary Enterprise Research and Development Institute of Power Engineering named after N.A.Dollezhal, Russia, Moscow

Supporting institutes

  • ITEF (ITEP), Russia, Moscow


  • IRSN - Institut de Radioprotection et de Sûreté Nucléaire, France, Fontenay aux Roses

Project summary

The objective of investigations is

- to perform analytical and calculating studies of local effects of reaction rates (fission rate) distributions in peripheral rows of fuel elements in the fuel assemblies adjacent to inter-assembly gaps and in the assemblies near reflector of LWR type reactors,

- to perform corresponding calculating algorithm, including all necessery methods and codes,

- to study pin fuel caracteristics distribution influence on Doppler Effect.

Therefore, to achieve the project objective the solution of the following tasks is proposed:

1) To develop a TRIFON 2.1 code version for the calculation of a cluster group of fuel assemblies surrounded by the asymptotic area of sources in a LWR- core with real material contents, and to verify this new version using the available benchmarks;

2) To develop and perform additional verification of a software for precise, reference calculations – the RECOL code for a full reactor calculation by Monte-Carlo method with pin-wise (if needed, in-pin-wise) degree of detalization and continuous tracking of neutron energies within the same geometrical structure as used in calculations by performed with the TRIFON 2.1 code (for the development of a numerical test);

3) Based on the outputs of (1), to prepare group few cross-section libraries for calculations of LWR type reactors taking into account sub-zones with irregular geometry and material contents. This activity also includes verification of such libraries on a specially developed system of numerical tests (calculations with the RECOL, MCNP codes with B-645 library). It is also planned to verify group data libraries using fine numerical benchmarks.

4) Based on the MCCG3D code with irregular mesh:

- To perform calculation studies of neutron transport on a detailed mesh including the irregular zones of a reactor;

- While simultaneously using the RRSFGG code for calculation of sensitivity coefficients for various functionals of a reactor in a group approximation, to analyze the impacts of the cross-section and methodical errors on power distribution in peripheral rows of fuel elements within reactor fuel assemblies, including core periphery fuel assemblies.

5) Using cluster-oriented TRIFON 2.1 and UNK codes, to study the impact of taking into account the detailed geometry, isotopic vectors, and temperature distributions along fuel element sections on reaction rates in the volumes of the fuel elements, to ensure an enhanced accuracy of Doppler Effect calculation. of a LWR reactors. These studies would be conducted for separate fuel elements, for fuel elements within an assembly and, specifically, for peripheral fuel elements; they will also include a detailed analysis of Doppler Effect of the whole core taking into account all factors mentioned above.

Expected Results and Their Applications:

  • The outputs of the proposed project will include a set of methods, codes, nuclear data and group cross-section libraries altogether allowing to increase substantially the accuracy of calculation of neutron physical characteristics of LWR type reactors , to study the impacts of local irregular (heterogeneous) zones on pin-wise power distribution, including the peripheral assemblies of the core.
  • Other outputs of the project will include results of investigations of pin fuel characteristics influence on reactor Doppler Effect.


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