Charles T. Kelsey

Coupled Multigroup Proton/Neutron Cross Sections for Deterministic Transport

Abstract The limited availability of coupled multigroup proton/neutron cross-section libraries has hampered the use of deterministic transport methods for solving shielding problems involving energetic proton sources. Libraries are developed from evaluated nuclear data for low-energy transport and the physics models of MCNPX for intermediate-energy transport. They allow deterministic solutions of orbiting spacecraft shielding problems. Evaluated cross sections for protons and neutrons are available for many nuclides up to 150 MeV. NJOY99 is used to produce coupled multigroup proton/neutron cross sections from these. For higher energies, MCNPX is run in its cross-section calculation mode where the XSEX3 program is used to tally double-differential cross sections. The XSEX3 program was modified to discretize the cross sections in energy and output Legendre expansions for angular dependence. The NJOY99 and modified XSEX3 output are combined to produce cross-section libraries for energies up to 400 MeV. The libraries are used to solve trapped proton flux shielding problems using the discrete ordinates transport code Attila. High-order Legendre expansions (P39) are required to accurately describe the highly anisotropic scattering. Attila applies the extended transport correction allowing accurate three-dimensional solutions at much lower degrees. Particle flux solutions for orbiting spacecraft shielding problems obtained with Attila and MCNPX compare favorably. Coupled multigroup proton/neutron cross-section libraries, for use with deterministic transport codes, can be prepared using NJOY99 and MCNPX. Our results using the Attila code demonstrate that multigroup deterministic methods are computationally efficient alternatives to Monte Carlo simulation.

2012-13 Blue Room Low Enriched Uranium Sample Irradiation, Associated Gas Handling System, and Subsequent Separation Chemistry

Author(s): May, Iain; Anderson, Aaron S.; Bitteker, Leo J. Jr.; Connors, Michael A.; Copping, Roy; Cover, Matthew; Crooks, William J.; Dale, Gregory E.; Dalmas, Dale A.; Gallegos, Michael J.; Garcia, Eduardo; Gioia, Jack G.; Gonzales, Robert; Graves, Debra; Hollis, W. Kirk; Janicke, Michael T.; Kelsey, Charles T. IV; Mocko, Michal; Pieck, Martin; Rawool-Sullivan, Mohini; Reilly, Sean D.; Rios, Daniel; Romero, Tobias J.; Stephens, Francis H.; Taw, Felicia L.; Thorn, David L.; Woloshun, Keith A.

Design and experimental activities supporting commercial U.S. electron accelerator production of Mo-99

99mTc, the daughter isotope of 99Mo, is the most commonly used radioisotope for nuclear medicine in the United States. Under the direction of the National Nuclear Security Administration (NNSA), Los Alamos National Laboratory (LANL) and Argonne National Laboratory (ANL) are partnering with North Star Medical Technologies to demonstrate the viability of large-scale 99Mo production using electron accelerators. In this process, 99Mo is produced in an enriched 100Mo target through the 100Mo(γ,n)99Mo reaction. Five experiments have been performed to date at ANL to demonstrate this process. This paper reviews the current status of these activities, specifically the design and performance of the helium gas target cooling system.

LANL Activities Supporting Electron Accelerator Production of 99Mo for NorthStar Medical Radioisotopes, LLC

Summary of LANL FY12 Activities are: (1) Preparation, performance, and data analysis for the FY12 accelerator tests at ANL - (a) LANL designed and installed a closed-loop helium target cooling system at ANL for the FY12 accelerator tests, (b) Thermal test was performed on March 27, (c) 24 h production test to follow the accelerator upgrade at ANL; (2) Local target shielding design and OTR/IR recommendations - (a) Target dose rate and activation products were calculated with MCNPX, (b) {sup 206}Pb({gamma},2n){sup 204m}Pb vs {sup 204g}Pb branching ratio unpublished, will measure using the LANL microtron, (c) OTR system nearing final configuration, (d) IR prototype system demonstrated during the recent thermal test at ANL; (3) Target housing lifetime estimation - Target housing material specifications and design to be finalized following the thermal test, lifetime not believed to be an issue; and (4) Target cooling system reliability - Long duration system characterizations will begin following the thermal test.

RADIONUCLIDE INVENTORY CALCULATIONS FOR THE MATERIALS TEST STATION

Abstract 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.

Lansce fail-safe radiation shutter design for isotope production facility

Dose rate modeling and post irradiation measurements of the Isotope Production Facility (IPF) beamline, at the Los Alamos Neutron Science Center (LANSCE) accelerator have determined that a radiation shielding shutter is required to protect personnel from shine from irradiated targets for routine beam tunnel entries. This paper will describe radiation dose modeling, shielding calculations, and the fail-safe mechanical shutter design.