CASTOR-V/21 multi-source computations

For the given model of the isolated CASTOR-V/21 cask, six source spactra cases are considered for the gamma type of radiation (see Table).

Average Initial Enrichment (%wt.) Average Burnup (GWd/MTU) Cooling Time (months) Spectra Structure Designation
2.91 30.0 26 18-group V-15
44-group V-15, revised
3.11 35.7 46 18-group T-Type
44-group T-Type, revised
2.56 26.9 172 18-group N-Type
44-group N-Type, revised

It is seen that the initial enrichment and burn-up are various from case to case, but the strongest parameter here is the cooling time.

These six cases in total have been completed in a single computation of total running time 9.9 hours using the multi-source Monte Carlo technique [2].
Figure 1: Gamma source spectra considered in the calculation

In this calculation, the following techniques are used:

  • Expected-value estimators;
  • Multi-source calculations;
  • Joint location-direction importance sampling from source (for primary gamma only);
  • Energy importance sampling from source (for primary gamma only);
  • Exponential transform;
  • Simplified adaptive splitting.

The primary computational gain is achieved here thanks to the simplified adaptive splitting, exponential transform (for both gamma), and multi-source calculation techniques.

Computed flux functional - ambient equivalent dose H*(10) [1] rates normalized to an emitted source particle.

Below, the obtained results of neutron-gamma and gamma problems calculations are presented (see details in [2]).
(a) 18 source energy groups
(a) 18 source energy groups
(b) 44 source energy groups
(b) 44 source energy groups
Figure: Gamma axial dose per source particle and 1σ relative error distributions for the single cask. Clickable.

References

  1. International Commission on Radiological Protection., International Commission on Radiation Units, and Measurements. Conversion coefficients for use in radiological protection against external radiation. Annals of the ICRP ; v. 26, no. 3/4. Published for the Commission by Pergamon Press, Oxford ;, 1st ed. edition, 1996 - 1997.
  2. V.G. Mogulian. An approach to radiation shielding evaluations using estimators by expected scoring. 2025. doi:10.5281/zenodo.16781416.