Speaker
Description
Current experimental fusion systems and conceptual designs of fusion pilot plants (FPPs) are growing in complexity and size. Several radiation metrics are crucial to the safe operation of fusion machines, including the shutdown dose rate (SDDR). SDDR is caused by decay gamma rays from radionuclides that become activated by neutrons during the operation of a fusion system. The two state-of-the-art approaches for determining SDDR are the Direct 1-Step method (D1S) and the Rigorous 2-Step method (R2S).
The R2S method is divided in to 2 steps. In the first neutron transport step, spectra are calculated on a mesh covering the complete problem geometry. The calculated neutron spectra are then used in the intermediate isotope inventory calculation step where the decay gamma spectra and specific activities are calculated. The second transport step follows, where gamma rays originating from the activated radionuclides are transported through the system in question. The high computational demand of the R2S technique originates from the need for two transport simulations in complex and often highly attenuating geometries.
There is a clear need for computationally efficient R2S codes for high fidelity analyses of complex, realistic fusion geometries. The Multi Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) variance reduction method was developed with the SDDR problem in mind. The MS-CADIS methodology is implemented in the Oak Ridge National Laboratory R2S Code Suite (ORCS).
In this paper we will present the capabilities of individual codes that make up ORCS. The paper will also include examples of using ORCS to support experimental campaigns at Joint European Torus (JET), analysis of the Pellet Injection system in Port Cell 16 of ITER, and analysis of the Equatorial Port 9 at ITER.
ORCS is under active development with one of the main research areas on integrating the Shift Monte Carlo transport code.