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Title: Refinement of Measurement Technique Using Delayed Neutrons To Determine Enrichment of Shielded Uranium (NA-22 Project)

Abstract

Final Presentation for the NSSC-LANL Keepin Nuclear Nonproliferation Program

Authors:
 [1];  [1];  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1375144
Report Number(s):
LA-UR-17-27120
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION

Citation Formats

Frame, Emily Anne, Andrews, Madison Theresa, and Myers, William L. Refinement of Measurement Technique Using Delayed Neutrons To Determine Enrichment of Shielded Uranium (NA-22 Project). United States: N. p., 2017. Web. doi:10.2172/1375144.
Frame, Emily Anne, Andrews, Madison Theresa, & Myers, William L. Refinement of Measurement Technique Using Delayed Neutrons To Determine Enrichment of Shielded Uranium (NA-22 Project). United States. doi:10.2172/1375144.
Frame, Emily Anne, Andrews, Madison Theresa, and Myers, William L. Thu . "Refinement of Measurement Technique Using Delayed Neutrons To Determine Enrichment of Shielded Uranium (NA-22 Project)". United States. doi:10.2172/1375144. https://www.osti.gov/servlets/purl/1375144.
@article{osti_1375144,
title = {Refinement of Measurement Technique Using Delayed Neutrons To Determine Enrichment of Shielded Uranium (NA-22 Project)},
author = {Frame, Emily Anne and Andrews, Madison Theresa and Myers, William L.},
abstractNote = {Final Presentation for the NSSC-LANL Keepin Nuclear Nonproliferation Program},
doi = {10.2172/1375144},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Aug 10 00:00:00 EDT 2017},
month = {Thu Aug 10 00:00:00 EDT 2017}
}

Technical Report:

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  • The goal of this project is to demonstrate and develop a nondestructive measurement technique for determining uranium enrichment of bulk samples using active delayed neutron reinterrogation.
  • Feasibility experiments conducted at Pacific Northwest National Laboratory demonstrate that either delayed neutrons or energetic gamma rays from short-lived fission products can be used to monitor the blending of UF{sub 6} gas streams. A {sup 252}Cf neutron source was used to induce {sup 235}U fission in a sample, and delayed neutrons and gamma rays were measured after the sample moved {open_quotes}down-stream.{close_quotes} The experiments used a UO{sub 2} powder that was transported down the pipe to simulate the flowing UF{sub 6} gas. Computer modeling and analytic calculation extended the test results to a flowing UF{sub 6} gas system. Neutron or gamma-raymore » measurements made at two downstream positions can be used to indicate both the {sup 235}U content and UF{sub 6} flow rate. Both the neutron and gamma-ray techniques have the benefits of simplicity and long-term reliability, combined with adequate sensitivity for low-intrusion monitoring of the blending process. Alternatively, measuring the neutron emission rate from (a, n) reactions in the UF{sub 6} provides an approximate measure of the {sup 235}U content without using a neutron source to induce fission.« less
  • Assay and analysis procedures were developed for nondestructive fissile isotopic measurement of mixed /sup 233/U--/sup 235/U fuel samples. For /sup 233/U much fewer delayed neutrons are released per fission than for /sup 235/U, although the number of prompt neutrons is approximately the same. By separately counting prompt and delayed neutrons released by a sample exposed to neutron irradiation, the amounts of /sup 233/U and /sup 235/U present in the sample can be estimated. Equations of delayed- and prompt-neutron counts versus /sup 233/U and /sup 235/U contents are solved simultaneously for the /sup 233/U and /sup 235/U contents of a sample.more » Eleven samples containing mixtures of /sup 233/U and /sup 235/U from no /sup 233/U to nearly 100% were prepared and assayed in prompt- and delayed-neutron assay devices. Constants for calibration equations, which are derived in this report, were fitted to data from nine of the samples. The maximum differences between counts calculated by the calibration equations and measured counts were 2.3% for delayed neutrons and 1.2% for prompt neutrons, indicating a good selection of the form for the calibration equations. The two remaining samples were treated as unknowns, and the uranium contents of these samples were estimated by simultaneously solving the two calibration equations. The maximum difference between estimated /sup 233/U or /sup 235/U content and actual content for either sample was 1.5%.« less
  • Section 1 describes the repackaging and recharacterization of 19 approximately 1-kg lots of uranium oxides, with enrichments (/sup 235/U at. %) ranging from 0.7 to 91 at. %, for use primarily as working standards in gamma-ray enrichment measurements. The results of all characterization analyses are given. Section 2 describes demonstration gamma-ray enrichment measurements on the Los Alamos National Laboratory standards and on the National Bureau of Standards (NBS) certified enrichment reference standards (NBS SRM-969). We consider in some detail both the theoretical and experimental considerations of doing accurate gamma-ray measurement of uranium enrichment, including particularly the extraction of the netmore » area of spectral full-energy peaks, correction for deadtime and pileup losses, correction for the chemical composition of the measured materials, and correction for the attenuation in containers. We conclude that with proper procedures and careful work, gamma-ray enrichment measurements based on a minimum set of standards (perhaps only one of high enrichment) can be made over the whole range of enrichments greater than or equal to0.7% with biases of less than or equal to0.1%. 6 refs., 34 figs., 8 tabs.« less