SNL RML recommended dosimetry cross section compendium

Abstract. Characterization of the neutron environment in the central cavity of the Sandia National Laboratories' Annular Core Research Reactor (ACRR) is important in order to provide experimenters with the most accurate spectral information and maintain a high degree of fidelity in performing reactor experiments. Characterization includes both modeling and experimental efforts. Building accurate neutronic models of the ACRR and the central cavity "bucket" environments that can be used by experimenters is important in planning and designing experiments, as well as assessing the experimental results and quantifying uncertainties. Neutron fluence characterizations of two bucket environments, LB44 and PLG, are presented. These two environments are used frequently and represent two extremes in the neutron spectrum. The LB44 bucket is designed to remove the thermal component of the neutron spectrum and significantly attenuate the gamma-ray fluence. The PLG bucket is designed to enhance the thermal component of the neutron spectrum and attenuate the gamma-ray fluence. The neutron characterization for each bucket was performed by irradiating 20 different activation foil types, some of which were cadmium covered, resulting in 37 different reactions at the peak axial flux location in each bucket. The dosimetry results were used in the LSL-M2 spectrum adjustment code with a 640-energy group MCNP-generated trial spectrum, self-shielding correction factors, the SNLRML or IRDFF dosimetry cross-section library, trial spectrum uncertainty, and trial covariance matrix, to generate a least-squares adjusted neutron spectrum, spectrum uncertainty, and covariance matrix. Both environment character-izations are well documented and the environments are available for use by experimenters.

Section: Neutron Spectrum Adjustment/unfold Resultsmentioning

confidence: 99%

Neutron Environment Characterization of the Central Cavity in the Annular Core Research Reactor *

Parma

Naranjo

Lippert

et al. 2016

“…Our assessment of the general shape of the neutron spectrum has changed slightly through the years because of increased accuracy in the activation foil measurements and the continuous updating of the cross section libraries [13,14]. The last major update to the shape of the damage function occurred in the mid-1980s with a rather significant change to the value of F D,Eref for silicon.…”

Section: Shape Index and Hardness Parametermentioning

confidence: 99%

A Re-Evaluation of the Reference Environment at the WSMR Fast Burst Reactor

Sparks¹,

Flanders²

2016

Abstract. This paper reviews the primary reference field at 60.96 cm from core centreline and re-examines the reference environment with improved characterizations of the reactor structure, test fixtures and also addresses some smaller issues of non-tracking calculations by monte carlo methods with various cross section set generations. We are also addressing long standing issues of absolute normalization of integral fluence based on the original characterizations of the facility diagnostic instrumentation.

“…MCNP B-V is an MCNP4 calculation using primarily ENDF B-V cross sections. The SAND-II [9] unfolded spectrum is an adjusted spectrum using activation data from 14 activation and 3 fission foils, the SNL-RML cross section library [10], and the MCNP4 46 group spectrum as the trial. The MCNP B-VI calculation is a more recent full spectrum calculation and was used to evaluate the effects of changing from earlier cross section sets to the newer SNL-RML activation data library.…”

Section: White Sands Missile Range Molly-g Reactormentioning

confidence: 99%

Highly Perturbed Operational Test Configurations at the WSMR Fast Burst Reactor

Flanders¹,

Sparks²,

Daniel³

2016

Abstract. The White Sands Missile Range (WSMR) MoLLY-G reactor has a long history of producing a well characterized environment for testing electronic systems/devices in fission environments. As an unmoderated, unreflected, bare critical assembly, it provides a slightly degraded fission spectrum with a 1/E tail. For radiation hardness testing of electronics, the neutron fluence is usually reported as the 1-MeV Equivalent Neutron Fluence for Silicon. In this paper, we examine additional neutron environments and characterizations ranging from low intensity neutron fields to more extreme modifications of our normal test environment. White Sands Missile Range MoLLY-G ReactorThe WSMR MoLLY-G reactor is an unmoderated, unreflected bare critical assembly. The reactor can be operated in either the steady state mode at the several kilowatt level or made super prompt critical, producing a pulse with a full-width half-maximum time of 45 microseconds or longer. The neutron spectrum leaking from the reactor is a slightly degraded fission spectrum. The reactor is operated in an exposure cell approximately 15 m by 15 m by 6.1 m high. The exposure cell has thick concrete walls lined with gypsum and borated gypsum wall board. The free field neutron environment at any position in the cell is a combination of the slightly degraded fission spectrum leaking from the reactor and a wall-return component which ties to the fission spectrum at a few keV in energy [1][2][3].The MoLLY-G core is a cylindrical assembly consisting of six annular fuel rings made of enriched uranium-molybdenum alloy. The safety block is a large fuel element which is inserted into the central cavity of the core. The fuel rings are bolted to a stainless steel support plate by three Inconel metal bolts. There is a stainless steel retaining plate at the top of the core. The power level of the core is adjusted by two control rods of the same fuel alloy which are inserted into voids in the body of the rings. A third control rod can be pneumatically driven into the core for burst operations. The core is covered by a cylindrical decoupling shield containing a 10 B loaded silastic. The decoupling shroud minimizes the effect of reactivity changes due to experiments and other environmental considerations external to the core. The core geometry is shown schematically in Fig. 1 with a typical MCNP [4] model of the core shown in Fig. 2. A more comprehensive model used for spectral characterization at experimental a Corresponding