29th Symposium on Fusion Technology (SOFT 2016)

P2.142 Propagation of decay gamma source uncertainties to dose rate in SDR calculations with R2SUNED

6 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 142

Poster G. Vessel/In-Vessel Engineering and Remote Handling P2 Poster session

Speaker

Juan-Pablo Catalan (Energy Engineering Department)

Description

Shutdown dose rate (SDR) analysis plays a key role in the design of fusion facilities like ITER and DEMO. One of most used methodology to carry out SDR calculations is the rigorous-two-step (R2S) based on the coupling of transport and activation calculations. Currently, one of the most relevant lacks of this method is the possibility to propagate the effect of the uncertainties accumulated along the calculation process to the error in the final dose evaluation. This error propagation represents an active and relevant frontier in neutronics research. In SDR calculations using computing tools based on Monte Carlo (MC) transport simulations, the most important source of uncertainty is the statistical error. In SDR calculation statistical uncertainty arise from neutron and decay transport simulations. Thus, in R2S methodology, the neutron flux uncertainties must be propagated to the decay gamma source, and then the error on decay gamma source has to be propagated consistently with statistical uncertainties due to the gamma transport process to the final dose value. In this work the scheme implemented in the R2SUNED tool to propagate uncertainties from the decay gamma source to final dose is described and applied. This method use the knowledge of the contribution of each phase space element of the decay gamma source (i.e. the contribution of the each energy group of each emitting volume) to the final dose to propagate the decay source error to the dose error value. This scheme has been applied to the ITER benchmark exercise in order to check its applicability to problems where the decay source has a large spatial extension (requiring a large number of mesh elements). In this exercise the decay gamma source were obtained using a direct-one-step method which can provide both decay source intensities and their relative errors due to the neutron flux statistical uncertainty.