The ORNL-SNAP shielding program

The effort in the ORNL-SNAP shielding program is directed toward the development and verification of computer codes using numerical solutions to the transport equation for the design of optimized radiation shields for SNAP power systems. A brief discussion is given for the major areas of the SNAP shielding program, which are cross-section development, transport code development, and integral experiments. Detailed results are presented for the integral experiments utilizing the TSF-SNAP reactor. Calculated results are compared with experiments for neutron and gamma-ray spectra from the bare reactor and as transmitted through slab shields

Shielding experimental methods

Benchmark, parametric, and design-confirmation shielding measurements are made at the Tower Shielding Facility (TSF) in Oak Ridge. A powerful reactor (to 1 MW thermal) is used with spectral modifiers to provide neutron spectra close to those associated with the various parts of an LMFBR. The source strength allows measurements through shields of full reactor thickness using sensitive detectors. The detectors include spectrometers and dosimeters for both neutrons and gamma rays. A large exclusion area provides much flexibility in arranging shield assemblies to be studied

Determination of the neutron energy and spatial distributions of the neutron beam from the TSR-II in the large beam shield

The TSR-II reactor of the ORNL Tower Shielding Facility has recently been relocated within a new, fixed shield. A principal feature of the new shield is a beam port of considerably larger area than that of its predecessor. The usable neutron flux has thereby been increased by a factor of approximately 200. The bare beam neutron spectrum behind the new shield has been experimentally determined over the energy range from 0.8 to 16 MeV. A high level of fission product gamma ray background prevented measurement of bare beam spectra below 0.8 MeV, however neutron spectra in the energy range from 8 keV to 1.4 MeV were obtained for two simple, calculable shielding configurations. Also measured in the present work were weighted integral flux distributions and fast neutron dose rates. (auth

Measurements for the JASPER Program Axial Shield Re-measurement Experiment

With one modification, this series of measurements is a repeat of several of the mockups that were investigated during the Axial Shield Experiment performed earlier for the Japanese-American Shielding Program for Experimental Research (JASPER) program at the Tower Shielding Facility (TSF). For these re-runs, slabs of lithiated paraffin, 10.16 cm thick and 152.4 cm on an edge, were placed between the spectrum modifier and the axial shield and directly behind the axial shield. Each of the slabs contained a void area that corresponded in dimension and location,to the surface area of the seven hexagons in the axial shield plus the boron carbide (B{sub 4}C) collar that surrounded them. The lithiated paraffin was made part of the mockup to reduce the neutron contributions to the detector from those neutrons passing through the concrete surrounding the hexagon assemblies. The slabs were present in all of the mockups except one, for which the lithiated paraffin following the axial shield was removed. Spectral and integral flux measurements were made behind the axial shield for six B{sub 4}C homogeneous-type assembly containing: (1) the B{sub 4}C rod bundle assembly; (2) the B{sub 4}C central blockage type; (4) the B{sub 4}C central sodium type; and (4) another B{sub 4}C homogeneous-type assembly. The neutron source was the Tower Shielding Reactor II (TSR-II) modified to give a flux typical of that incident on the axial shielding in a Liquid Metal Reactor (LMR)

Measurements for the JASPER Program Flux Monitor Experiment

The Flux Monitor Experiment was conducted at the Oak Ridge National Laboratory (ORNL) Tower Shielding Facility (TSF) during the months of May and June 1992, as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) program that was started in 1986. This series of experiments was designed to examine shielding concerns and radiation transport effects pertaining to in-vessel flux monitoring systems (FMS) in current reactor shield designs proposed for both the Advanced Liquid Metal Reactor (ALMR) design and the Japanese loop-type design. The program is a cooperative effort between the United States Department of Energy (US DOE) and the Japanese Power Reactor and Nuclear Fuel Development Corporation (PNC). The Tower Shielding Reactor H (TSR-II) neutron source was altered by the spectrum modifier (SM) used previously in the Axial Shield Experiment, and part of the Japanese Removable Radial Shield (RRS) before reaching the axial shield. In the axial shield were placed six homogeneous boron carbide (B{sub 4}C) hexagons around a center hexagon of aluminum used to represent sodium. Shield designs to be studied were placed beyond the axial shield, each design forming a void directly behind the axial shield. Measurements were made in the void and behind each slab as successive slabs were added

Liquid Metal Reactor Program: JASPER US/DOE/PNC Shielding Research Program : Technical progress report, April 1-May 31, 1987

This progress report details activities on the JASPER Shielding Program for the time period of April 1, 1987 through May 31, 1987

Measurements for the JASPER Program Special Materials Experiment

The Special Materials Experiment was conducted at the Oak Ridge National Laboratory (ORNL) during 1992 as the final experiment in a series of eight experiments conducted for the Japanese-American Shielding Program for Experimental Research (JASPER) program that started in 1986. This experiment completes the experimental program providing support for the development of current designs proposed for advanced liquid metal reactor (LMR) systems both in Japan and the United States. The Tower Shielding Reactor II (TSR-II) source was modified to provide a neutron spectrum that would be typical of that to be found both radially and axially surrounding the LMR core. The experimental program plan was divided into two phases. In phase I, the mockups consisted of stainless steel followed by slabs of polyethylene and zirconium. For phase II, the stainless steel and zirconium were eliminated, leaving only the different thicknesses of polyethylene. Integral neutron flux measurements were obtained behind each of the mockups accompanied by spectral measurements for each configuration except one

Measurements for the JASPER program In-Vessel Fuel Storage experiment

The In-Vessel-Fuel-Storage (IVFS) experiment was conducted at the Oak Ridge National Laboratory`s (ORNL) Tower Shielding Facility (TSF) during the first nine months of 1991 as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) that was started in 1986. This is the fourth in a series of eight experiments that were planned, all of which are intended to provide support in the development of current reactor shield designs proposed for liquid metal reactor (LMR) systems both in Japan and the United States. The program is a cooperative effort between the United States Department of Energy (US DOE) and the Japanese Power Reactor and Nuclear Development Corporation (PNC). This document provides a description of the instrumentation and experimental configuration, test data, and data analysis

Measurements for the JASPER Program Gap Streaming Experiment

The Gap Streaming Experiment was conducted at the Oak Ridge National Laboratory (ORNL) Tower Shielding Facility (TSF) during the three month period from February to April, 1992, as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) program that was started in 1986. This series of experiments which are intended to provide support in the development of current reactor shield designs proposed for Liquid Metal Reactor (LMR) systems both in Japan and the United States. The program is a cooperative effort between the United States Department of Energy (USDOE) and the Japanese Power Reactor and Nuclear Development Corporation (PNC). The program was designed to study neutron streaming in annular gaps typical of those anticipated in future reactor enclosure systems for advanced LMRs. The two configurations studied in this experiment were: (1) an iron-lined, concrete-filled, vessel that was designed to allow changes in annular gap widths and/or their locations; or (2) a solid piece of concrete. In two of the studies, Items IIID and IIIE, stainless steel slabs were added to simulate the effect of a cover plate above the reactor head. The configurations were preceded by either a spectrum modifier that modeled the sodium pool above the LMR core or the bare Tower Shielding Reactor H (TSR-II) beam. Bonner ball measurements were made behind each configuration and neutron spectra and Hornyak button measurements were made behind selected configurations

Measurements for the JASPER program Axial Shield Experiment

The Axial Shield Experiment was conducted at the Oak Ridge National Laboratory (ORNL) during 1990--1991 as part of the continuing series of eight experiments planned for the Japanese-American Shielding Program for Experimental Research (JASPER) program starting in 1986. The program is intended to provide support for the development of current designs proposed for advanced liquid metal reactor (LMR) system both in Japan and the United States. As in the previous two experiments, the same spectrum modifier was used to alter the Tower Shielding Reactor source spectrum to one representing the LMR neutron spectra directly above the core in the area of the fission-gas plenum. In one of the measurements the spectrum was further modified by the fission gas plenum. In all cases the modified spectrum was followed by combinations of seven hexagon assemblies that represented different coolant flow and shielding patterns within the assemblies. The varied configuration permitted not only a study of the different designs, but also allowed a comparison to be made of the relative neutron attenuation effectiveness of boron carbide and stainless steel in such designs. This experiment was the third in a series of eight experiments to be performed as part of a cooperative effort between the United States Department of Energy (US DOE) and the Japan Power Reactor and Nuclear Fuel Development Corporation (PNC). This experiment, as was the previous Radial Shield Attenuation and Fission Gas Plenum Experiments, intended to provide support for the development of advanced sodium-cooled reactors. 5 refs