Uncertainty Budget and Efficiency Analysis for the 239Pu (n,2ny) Partial Reaction Cross-Section Measurements

PDF Version Also Available for Download.

Description

The {sup 239}Pu(n,2n{gamma}){sup 238}Pu partial reaction cross-section, {sigma}{sub (n,2n{gamma})}, has been measured as a function of neutron energy for several transitions in {sup 238}Pu. Partial {gamma}-ray cross sections for yrast, ''collector'' transitions, can provide especially valuable constraints on the magnitude and shape of the total (n,2n) reaction cross-section. In essence, nuclear reaction models will be used to infer the shape and magnitude of the total (n,2n) reaction cross-section from the measured partial {gamma}-ray cross-sections. The reason for undertaking this somewhat indirect approach is that previous measurements of the {sup 239}Pu(n,2n{gamma}) have been hampered by a variety of constraints. Activation measurements ... continued below

Physical Description

1600 pages

Creation Information

McNabb, D.P.; Archer, D.E.; Becker, J.A.; Bernstein, L.A. & Garrett, P.E. May 1, 2000.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Sponsor

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

The {sup 239}Pu(n,2n{gamma}){sup 238}Pu partial reaction cross-section, {sigma}{sub (n,2n{gamma})}, has been measured as a function of neutron energy for several transitions in {sup 238}Pu. Partial {gamma}-ray cross sections for yrast, ''collector'' transitions, can provide especially valuable constraints on the magnitude and shape of the total (n,2n) reaction cross-section. In essence, nuclear reaction models will be used to infer the shape and magnitude of the total (n,2n) reaction cross-section from the measured partial {gamma}-ray cross-sections. The reason for undertaking this somewhat indirect approach is that previous measurements of the {sup 239}Pu(n,2n{gamma}) have been hampered by a variety of constraints. Activation measurements have several hurdles: (1) intense flux and long counting times are required to overcome the relatively long half-life of {sup 238}Pu (87 years) and (2) isotopically pure samples of {sup 239}Pu in an environment free of {sup 238}Pu contamination are difficult to come by. Neutron counting experiments are subject to significant uncertainties because (1) large background statistics from fission neutrons and (2) the experimental fission neutron multiplicity spectrum is subject to systematic errors because the flux of low-energy neutrons which induce fissions in thermally-fissile {sup 239}Pu is very difficult to characterize. In this measurement, spallation neutrons are provided by the LANSCE/WNR facility, and reaction neutron energies are determined via time-of-flight. Neutron flux is monitored in-beam with one {sup 235}U fission chamber and one {sup 238}U fission chamber. The {sup 238}U is not sensitive to background from low-energy neutrons, whereas the {sup 235}U fission chamber has better statistics. Hence, in essence the partial {gamma}-ray cross sections are normalized to the evaluated fission cross sections of {sup 235}U and {sup 238}U. As a check of our normalization to provide additional constraints to the nuclear reaction modeling, benchmark measurements of {sup nat}Fe(n, n{prime}{gamma}) and {sup 235}U(n,2n{gamma}) have also been undertaken. The secondary {gamma}-rays are measured with the GEANIE array. GEANIE consists of eleven Compton-suppressed planar detectors, nine suppressed and six unsuppressed co-axial detectors. Any absolute cross section measurement requires a complete understanding of array performance, flux normalization, and target effects. Important items to consider in this experiment include intrinsic detector efficiency, beam and detector geometry corrections, target attenuation, and deadtime. Radioactive targets give rise to significant counting rates in the GEANIE array resulting a large deadtime. The magnitude, energy dependence, and uncertainties of these effects and other corrections are the subject of this paper.

Physical Description

1600 pages

Source

  • Other Information: PBD: 1 May 2000

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: UCRL-ID-139906
  • Grant Number: W-7405-Eng-48
  • DOI: 10.2172/793116 | External Link
  • Office of Scientific & Technical Information Report Number: 793116
  • Archival Resource Key: ark:/67531/metadc742164

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • May 1, 2000

Added to The UNT Digital Library

  • Oct. 19, 2015, 7:39 p.m.

Description Last Updated

  • May 6, 2016, 2:08 p.m.

Usage Statistics

When was this report last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 3

Interact With This Report

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

International Image Interoperability Framework

IIF Logo

We support the IIIF Presentation API

McNabb, D.P.; Archer, D.E.; Becker, J.A.; Bernstein, L.A. & Garrett, P.E. Uncertainty Budget and Efficiency Analysis for the 239Pu (n,2ny) Partial Reaction Cross-Section Measurements, report, May 1, 2000; California. (digital.library.unt.edu/ark:/67531/metadc742164/: accessed May 27, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.