Speaker
Description
Accurate evaluation of shutdown dose rate (SDDR) represents a key requirement in fusion reactor design and operation and is essential to ensure personnel safety throughout the entire lifetime of fusion facilities, in particular during maintenance and their decommissioning. SDDR tools have been developed for this purpose, among which JSIR2S, developed at the Jožef Stefan Institute, implements the rigorous two-step (R2S) methodology. In this approach, neutron transport simulations are first carried out using the Monte Carlo transport code MCNP, followed by activation and inventory calculations of irradiated materials with FISPACT code, to produce the gamma source of the subsequent MCNP run. In the second step, photon transport calculations are performed to determine the resulting dose rates from radioactive decay.
The JSIR2S code has previously been benchmarked against experimental data from the TRIGA research reactor, and the present study extends its validation to fusion-relevant conditions using SDDR measurements after the second deuterium-tritium campaign (DTE2) at JET. The calculated SDDR is compared against some selected experimental measurement points and against the predictions of the other computational tools involved in the same benchmark campaign, thus enabling a comprehensive assessment and critical comparison of the methodology and of the specific tool. SDDR calculations at JET following DTE2 are presented in this work with the primary objective of validating the computational predictions of JSIR2S in a fusion-relevant environment as JET.
The comparison shows good agreement between calculated and measured values over the considered cooling times, up to 29 days after shutdown. For the last set of pulses of the campaign, C/E values for ionisation chambers in Octant 1 range between (0.75 ± 0.08) and (1.36 ± 0.07). In Octant 2, lower agreement is observed, with C/E values around (0.11 ± 0.01). For Octant 1, the C/E values are comparable to those obtained with the Advanced D1S method, whereas for Octant 2 the Advanced D1S shows better agreement with experimental data.
These results indicate that the applied approach with the JSIR2S code provides generally reliable predictions of SDDR in fusion environments, although the observed discrepancies warrant further investigation.
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