Authors & Affiliations
Usheva K.I.1, Kuten S.A.1, Khruschinsky A.A.1, Babichev L.F. 2
1Institute for Nuclear Problems, Belarusian State University, Minsk, Belarus
2Joint Institute for Power and Nuclear Research - Sosny, National Academy of Sciences of Belarus, Minsk, Belarus
Kuten S.A. – Cand. Sci. (Phys.-Math.), Senior Researcher (Higher Attestation Commission of the USSR), Head of Laboratory, Institute for Nuclear Problems, Belarusian State University.
Khruschinsky A.A. – Cand. Sci. (Phys.-Math.), Senior Researcher (Higher Attestation Commission of the USSR), Leading Researcher, Institute for Nuclear Problems, Belarusian State University.
Babichev L.F. – Cand. Sci. (Phys.-Math.), Head of Laboratory, Joint Institute for Power and Nuclear Research - Sosny, National Academy of Sciences of Belarus.
XS libraries for the core and reflector should be prepared for the calculation of neutron-physical characteristics of the reactor core in the diffusion codes, such as DYN3D. The details related to the modeling of the radial reflector for the VVER reactor core in Monte Carlo code Serpent (version 2.1.26) are discussed in the paper. Due to design features of the baffle of VVER reactor five types of the radial reflector model can be considered. The structure of the model of each type of radial reflector is determined by the features of the boundary conditions in the Serpent. A separate model, which takes into account the impact of the three bordering FAs, has been developed for the reflector cells, located on the corners of the core. Model of each type of radial reflector under consideration consists of two layers of hexagonal nonfuel assemblies.
Testing of the reflector XS library has been performed using typical first loading of VVER core based on six different FA types. The library has been prepared for radial reflector as well as for each of individual FAs using Serpent. The two-group cross sections were calculated taking into account discontinuity factors at the "FA-FA", "FA-reflector" boundaries (so-called ADF and RDF factors, re-spectively). RDF factors were additionally corrected to account for the influence of nearby FAs.
Verification of the two-group XS’s for reflector was carried out by comparing the results of the full core calculations in DYN3D and Serpent codes. The Serpent model of the core considered as reference includes a two-layered reflector, an analogous model was developed in DYN3D. For correct work of the DYN3D two-group version the fast-to-thermal transfer cross-sections (Σs12) were adjusted taking into account the heating of the thermal neutrons (Σs21). The resulting XS libraries have been used in DYN3D for calculating the criticality and power distribution in the reactor core during operation at zero power. The relative error in calculating criticality in the model of "core+radial reflector" was 10 and 150 pcm for the boric acid concentration of 0 and 8 g/kgH2O, respectively. In both cases the maximum error in the calculation of power distribution does not exceed 5%, its average value is less than 2%.
reactor, VVER, radial reflector, Monte Carlo method, Serpent, two-group XS, criticality, power distribution
1. Rohde U., Kliem S., Grundmann U., Baier S., Bilodid Y., Duerigen S., Fridman E., Gommlich A., Grahn A., Holt L., Kozmenkov Y., Mittag S. The reactor dynamics code DYN3D – models, validation and applications. Progress in Nuclear Energy, 2016, no. 89, pp. 170-190.
2. Leppдnen J. Serpent – a Continuous-energy Monte Carlo Reactor Physics Burnup Calculation Code. User’s Manual. VTT Technical Research Centre of Finland, 2015. 164 p.
3. Ovdiienko I., Ieremenko M., Kuchin A., Khalimonchuk V. Development of cross-section library for DYN3D code. Journal Yaderna ta Radyiatsyjna Bezpeka, 2014, no. 4(64), pp. 22-25.
4. Leppдnen J., Pusa M., Fridman E. Overview of methodology for spatial homogenization in the Serpent 2 Monte Carlo code. Annals of Nuclear Energy, 2016, no. 66, pp. 126-136.
5. Smith K.S. Nodal diffusion methods: understanding numerous unpublished details. Proc. PHYSOR-2016. SunValley, ID, USA, 2016, pp. 1227-1241.