Using MCNP for fusion neutronics
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Doctoral thesis (article-based)
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en
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VTT publications,
699
Abstract
Any fusion reactor using tritium-deuterium fusion will be a prolific source of 14 MeV neutrons. In fact, 80% of the fusion energy will be carried away by these neutrons. Thus it is essential to calculate what will happen to them, so that such quantities as the tritium breeding ratio, the neutron wall loading, heat deposition, various kinds of material damage and biological dose rates can be determined. Monte Carlo programs, in particular the widely-used MCNP, are the preferred tools for this. The International Fusion Materials Irradiation Facility (IFMIF), intended to test materials in intense neutron fields with a spectrum similar to that prevailing in fusion reactors, also requires neutronics calculations, with similar methods. In some cases these calculations can be very difficult. In particular shielding calculations - such as those needed to determine the heating of the superconducting field coils of ITER or the dose rate, during operation or after shutdown, outside ITER or in the space above the test cell of IFMIF - are very challenging. The thick shielding reduces the neutron flux by many orders of magnitude, so that analog calculations are impracticable and heavy variance reduction is needed, mainly importances or weight windows. On the other hand, the shields contain penetrations through which neutrons may stream. If the importances are much higher or the weight windows much lower at the outer end of such a penetration than at the inner end, this may lead to an excessive proliferation of tracks, which may even make the calculation break down. This dissertation describes the author's work in fusion neutronics, with the main emphasis on attempts to develop improved methods of performing such calculations. Two main approaches are described: trying to determine near-optimal importances or weight windows, and testing the "tally source" method suggested by John Hendricks as a way of biasing the neutron flux in angle.Description
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- [Publication 1]: Heikinheimo, L., Heikkinen, J., Linden, J., Kaye, A., Orivuori, S., Saarelma, S., Tähtinen, S., Walton, R. and Wasastjerna, F. Dielectric window for reactor like ICRF vacuum transmission line. Fusion Engineering and Design 55 (2001), pp. 419-436.
- [Publication 2]: Bibet, Ph., Mirizzi, F., Bosia, P., Doceul, L., Kuzikov, S., Rantamäki, K., Tuccillo, A.A. and Wasastjerna, F. Overview of the ITER-FEAT LH system. Fusion Engineering and Design 66-68 (2003), pp. 525-529.
- [Publication 3]: Fischer, U., Pereslavtsev, P., Kotiluoto, P. and Wasastjerna, F. Nuclear performance analyses for HCPB test blanket modules in ITER. Fusion Engineering and Design 82 (2007), pp. 2140-2146.
- [Publication 4]: Norajitra, P., Bühler, L., Buenaventura, A., Diegele, E., Fischer, U., Gordeev, S., Hutter, E., Kruessmann, R., Malang, S., Maisonnier, D., Orden, A., Reimann, G., Reimann, J., Vieider, G., Ward, D. and Wasastjerna, F. Conceptual design of the EU dual-coolant blanket (model C). Proceedings of the 20th IEEE/NPSS Symposium on Fusion Engineering (SOFE 2003). San Diego, CA, USA. 2003. © 2003 IEEE. By permission.
- [Publication 5]: Simakov, S.P., Fischer, U., Möslang, A., Vladimirov, P., Wasastjerna, F. and Wilson, P.P.H. Neutronics and activation characteristics of the international fusion material irradiation facility. Fusion Engineering and Design 75-79 (2005), pp. 813-817.
- [Publication 6]: Fischer, U., Chen, Y., Simakov, S.P., Wilson, P.P.H., Vladimirov, P. and Wasastjerna, F. Overview of recent progress in IFMIF neutronics. Fusion Engineering and Design 81 (2006), pp. 1195-1202.
- [Publication 7]: Simakov, S.P., Vladimirov, P., Fischer, U., Heinzel, V., Möslang, A. and Wasastjerna, F. Tungsten spectral shifter: neutronics analysis (dpa evaluation, H, He and other impurities generation, recoil spectrum, etc) of different positions and geometries. Final report on the EFDA task TW5-TTMI-003, Deliverable 8. FZK (Forschungszentrum Karlsruhe) report (2006). 11 p. © 2006 Forschungszentrum Karlsruhe (FZK). By permission.
- [Publication 8]: Kotiluoto, P. and Wasastjerna, F. Calculating the neutron current emerging through the beam tubes in IFMIF (EFDA Task TW6-TTMI-001-D3a). VTT Research Report, VTT-R-06720-06 (2006). 9 p. © 2006 Technical Research Centre of Finland (VTT). By permission.
- [Publication 9]: Wasastjerna, F. A study of variance reduction methods in MCNP4C in a slot with a dogleg. Proceedings of the 12th Biennial Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society. Paper 14, Santa Fe, NM, USA. 2002. 11 p. © 2002 American Nuclear Society (ANS). By permission.
- [Publication 10]: Wasastjerna, F. Importances for MCNP calculations on a shield with a penetration. Proceedings of the 14th Biennial Topical Meeting of the Radiation Protection and Shielding Division of the American Nuclear Society. Carlsbad, NM, USA. 2006. Pp. 478-488. © 2006 American Nuclear Society (ANS). By permission.
- [Publication 11]: Wasastjerna, F. Application of importances or weight windows in MCNP4C to a geometry similar to an ITER equatorial port. Annals of Nuclear Energy 35/3 (2008), pp. 425-431.
- [Publication 12]: Wasastjerna, F. Calculating streaming with the "tally source" method, as applied to IFMIF. Annals of Nuclear Energy 35/3 (2008), pp. 438-445.