Reactor physics calculations in the Nordic countries: Proceedings of the 11th Nordic Reactor Physics Meeting

The eleventh biennial meeting on reactor physics calculations in the Nordic countries was arranged by VTT Processes in Otaniemi, Espoo and on board Tallink's m/s Romantika on April 9-10, 2003. The previous meetings in this series were held in Göteborg 1983, Roskilde 1985, Espoo 1987, Oslo 1989, Stockholm 1991, Roskilde 1993, Espoo 1995, Kjeller 1997, Göteborg 1999 and Roskilde 2001. 18 technical papers on very different subjects in the field of reactor physics were presented by the 46 participants of 8 nationalities representing 13 organizations in 6 countries: research establishments, technical universities, utilities, consultants and suppliers. Thus, some participants from outside the Nordic countries were also present this time. Additionally, VTT's activities in the nuclear field and the "Finland-5" project were described. General reactor physics, calculational methods, a code system adapted for RBMK reactor analyses, and transmutation of nuclear waste were presented by representatives of universities and programme developers (Royal Institute of Technology, Chalmers University of Technology, Studsvik Scandpower). Computer programmes are the most important tools of reactor physics and new versions of old ones as well as entirely new ones based upon better and more accurate, alternatively faster and more efficient, methods and models are still evolving. At the meeting there were presentations of VTT Processes' new deterministic 3-dimensional radiation transport code MultiTrans and BWR simulator ARES based upon the AFEN (Analytic Function Expansion Nodal) model, and also of new features in internationally wellknown codes like CASMO-4E and POLCA (POLCA-T) together with results obtained by these programmes. A code for PWR loading pattern search, called LP-fun (Loading Patterns - for user s need) is being developed by Westinghouse and others. Experiments and measurements are necessary for the validation of the computer codes. Measurements on SVEA-96+ fuel bundles in the PROTEUS facility had been analyzed with the PHOENIX4 code, reactor scram experiments in the Loviisa and Mochovce VVER reactors using CASMO-4, MCNP4B and HEXTRAN, results of gamma scanning on fuel bundles by the PHOENIX4/POLCA7 combination. Some difficulties in predicting the power distribution in the reactor core with sufficiently good accuracy using any of the available code systems were reported by OKG. The importance of direct heating, i.e. transfer of fission energy to non-fuel regions by gamma radiation and neutrons had been investigated using the HELIOS lattice code. Calculational results for heat deposition from gamma radiation in the moderator tank of the Forsmark-1 reactor were reported by Risø. Measurements and calculations of the pressure vessel exposure to neutrons have been performed by VTT during the whole life of the Loviisa reactors. New and more efficient nuclear fuels are continuously being developed. Successful introduction of a new fuel type requires extensive numerical analyses as well as experimental measurements and feedback from users' experiences. Framatome ANP and Westinghouse described the development and characteristics of the SVEA-96 Optima and ATRIUM 10 fuels. The twelfth meeting in the series is preliminary scheduled to be arranged by Institutt for energiteknikk and Studsvik Scandpower AS in Norway in 2005.