G. Muhrer

Implementation of Neutron Mirror Modeling Capability into MCNPX and Its Demonstration in First Applications

Abstract Reflection of thermal and cold neutrons by polished surfaces and so-called supermirrors effect radiation fields in and around neutron beamlines. To allow the prediction of these radiation fields with MCNPX 2.5.0, two new input cards were implemented for defining mirror properties of surfaces. Mirror properties can be linked to any type of surface, in contrast to other neutron optics codes, where the mirror properties are part of component descriptions, allowing the simulation of very complex neutron optical devices. First calculations are under way to verify the new capability against combinations of MCNPX and MCSTAS (neutron optics code) simulations. Also, simulations are under way to compare the predicted neutron beam characteristics against measurements conducted at Paul Scherrer Institut.

Shield Design of the Materials Test Station’s Camera Room

Abstract The Materials Test Station (MTS) is a project funded by the Advanced Fuel Cycle Initiative with the goal to build a facility that allows large-scale irradiation for potential future nuclear fuel and material samples to obtain the knowledge and understanding of the nuclear processes necessary to close the nuclear fuel cycle and thereby reduce the amount and the toxicity of the nuclear waste. The MTS is proposed to be built in Area A of the Los Alamos Neutron Science Center and operated at up to 2 MW (2.5 mA at 800 MeV). As part of this operation, a so-called camera room will need to be installed upstream of the target cell. Because of the uniqueness of this functionality, the camera room requires a special shielding design, which will be discussed in this paper.

Design of the Shielding of the Materials Test Station

Abstract The Materials Test Station (MTS) is a project by the Advanced Fuel Cycle Initiative to build a facility that allows for irradiating nuclear fuel and material samples to acquire the necessary knowledge to close the nuclear fuel cycle and thereby reduce the amount and the toxicity of the nuclear waste. This facility is proposed to be located in Area A of the Los Alamos Neutron Science Center at the Los Alamos National Laboratory. The MTS is proposed to be a spallation target facility operated up to 2 MW (2.5 mA at 800 MeV). To safely operate a facility of this size, a large amount of shielding needs to be put into place. In this paper we will discuss the shielding design proposed for the MTS.

FLAT TARGET NEUTRONICS

Abstract In this paper we will discuss the possibility of using a flat tungsten target as the target of a neutron spallation source. Therefore we investigated what influence the components of the target station, such as reflector material, moderator geometry, decoupler and target geometry, have on the neutronics of the target.

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.