Nuclear Technology / Volume 168 / Number 3 / December 2009 / Pages 957-964
Miscellaneous / Special Issue on the 11th International Conference on Radiation Shielding and the 15th Topical Meeting of the Radiation Protection and Shielding Division (PART 3) / Materials for Nuclear Systems
Radionuclide inventory calculations support design and accident analyses for the Materials Test Station (MTS). MTS is a spallation source facility being designed to irradiate reactor fuels and materials in a fast neutron spectrum. Calculated radionuclide inventories are used to provide decay heat input to cooling system design, decay radiation source terms for hot cell design, and material-at-risk input to accident analyses. CINDER'90 is a transmutation code that uses MCNPX-calculated spallation product yields and neutron fluxes to calculate residual nuclide concentrations based on irradiation history. The code also calculates decay heat and photon spectra for the resulting radionuclide inventories. A total activity of 2 × 1017 Bq is created during MTS operation. Decay heat is an important factor since in loss of primary cooling scenarios, this heat must be removed. The major sources at shutdown are 3000 W for the tungsten target plates and 6000 W for fuel pins being irradiated. Decay photon spectra result in unshielded dose rates that hot cell design must accommodate on the order of 1000 Sv/h. The MTS design includes lead-bismuth eutectic (LBE) coolant. For accident analysis 210Po activity in the LBE is a significant concern. The calculated 210Po activity following 2.5 yr of operation is 2 × 1014 Bq. Radionuclide inventory calculations are important for MTS design. The CINDER'90 code is a valuable tool for this purpose.