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Title: Experimental Quantification of the Background Neutron Flux in the Advanced Test Reactor Fuel Storage Canal

Abstract

The Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL) is one of only a few high-power research reactors (HPRR) of its type in the world, with a variety of missions involving accelerated testing of nuclear fuel and other materials in a very high neutron flux (5.0x1014 n/cm2 -s) environment, medical and industrial isotope production, and other applications. It typically runs several cycles per year with lengths varying from 40-60 days depending on specific experimental requirements for each cycle. The highly radioactive used fuel elements that are discharged from the ATR after each cycle are stored in an adjacent canal (Figure 1) and can be used for as many as three cycles before being retired. The ATR canal features a gamma irradiation facility that has various uses. It is composed of a simple dry tube that extends down into one of the fuel storage rack positions. This tube is surrounded by used fuel elements that can be selected from the inventory to produce the desired gamma radiation level and, to some extent, spectrum within the dry tube. Typical gamma fields that can be produced in this manner can be as high as several megarads per hour. The gamma fieldmore » within the dry tube is accompanied by a small background neutron flux, produced by photoneutron production in the small fraction of heavy water (D2O) that is naturally present in light water at a concentration of approximately 0.015% by weight, and by a very low level of photofission and spontaneous fission in the fuel elements. The measurement technique used is very sensitive and provided self-consistent results in terms of raw activation data quality. The background neutron fluxes in the gamma facility are very low, but still detectable. The total neutron flux in the energy region from 0.414 eV to 1 MeV and the thermal neutron flux (below 0.414 eV) were estimated from the activation measurements to be 1.0x104 and 2.0x102 n/cm2 -s, respectively. ncertainties of approximately an order of magnitude apply to both results. No neutrons above about 1 MeV were detected. The high uncertainties quoted here are primarily due to uncertainties in the a priori neutron fluxes computed by MCNP6 as well as uncertainties in the spectrum-averaged foil activation cross sections used in the few-group least-squares flux adjustment procedure that was applied. Detailed analyses are currently underway with the aim of reducing these sources of uncertainty.« less

Authors:
 [1]; ORCiD logo [1];  [2]
  1. Idaho National Laboratory
  2. University of New Mexico/University of New Mexico
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1492835
Report Number(s):
INL-CON-18-50140-Rev000
DOE Contract Number:  
AC07-05ID14517
Resource Type:
Conference
Resource Relation:
Conference: Radiation Protection and Shielding Division of ANS, Santa Fe, New Mexico, 08/26/2018 - 08/31/2018
Country of Publication:
United States
Language:
English
Subject:
21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; 22 - GENERAL STUDIES OF NUCLEAR REACTORS; Advanced Test Reactor; ATR; Neutron Activation Spectrometry

Citation Formats

Nigg, David W., Miller, David T., and Beling, Kyle S. Experimental Quantification of the Background Neutron Flux in the Advanced Test Reactor Fuel Storage Canal. United States: N. p., 2018. Web.
Nigg, David W., Miller, David T., & Beling, Kyle S. Experimental Quantification of the Background Neutron Flux in the Advanced Test Reactor Fuel Storage Canal. United States.
Nigg, David W., Miller, David T., and Beling, Kyle S. Wed . "Experimental Quantification of the Background Neutron Flux in the Advanced Test Reactor Fuel Storage Canal". United States. https://www.osti.gov/servlets/purl/1492835.
@article{osti_1492835,
title = {Experimental Quantification of the Background Neutron Flux in the Advanced Test Reactor Fuel Storage Canal},
author = {Nigg, David W. and Miller, David T. and Beling, Kyle S.},
abstractNote = {The Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL) is one of only a few high-power research reactors (HPRR) of its type in the world, with a variety of missions involving accelerated testing of nuclear fuel and other materials in a very high neutron flux (5.0x1014 n/cm2 -s) environment, medical and industrial isotope production, and other applications. It typically runs several cycles per year with lengths varying from 40-60 days depending on specific experimental requirements for each cycle. The highly radioactive used fuel elements that are discharged from the ATR after each cycle are stored in an adjacent canal (Figure 1) and can be used for as many as three cycles before being retired. The ATR canal features a gamma irradiation facility that has various uses. It is composed of a simple dry tube that extends down into one of the fuel storage rack positions. This tube is surrounded by used fuel elements that can be selected from the inventory to produce the desired gamma radiation level and, to some extent, spectrum within the dry tube. Typical gamma fields that can be produced in this manner can be as high as several megarads per hour. The gamma field within the dry tube is accompanied by a small background neutron flux, produced by photoneutron production in the small fraction of heavy water (D2O) that is naturally present in light water at a concentration of approximately 0.015% by weight, and by a very low level of photofission and spontaneous fission in the fuel elements. The measurement technique used is very sensitive and provided self-consistent results in terms of raw activation data quality. The background neutron fluxes in the gamma facility are very low, but still detectable. The total neutron flux in the energy region from 0.414 eV to 1 MeV and the thermal neutron flux (below 0.414 eV) were estimated from the activation measurements to be 1.0x104 and 2.0x102 n/cm2 -s, respectively. ncertainties of approximately an order of magnitude apply to both results. No neutrons above about 1 MeV were detected. The high uncertainties quoted here are primarily due to uncertainties in the a priori neutron fluxes computed by MCNP6 as well as uncertainties in the spectrum-averaged foil activation cross sections used in the few-group least-squares flux adjustment procedure that was applied. Detailed analyses are currently underway with the aim of reducing these sources of uncertainty.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {8}
}

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