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Title: Science based stockpile stewardship, uncertainty quantification, and fission fragment beams

Abstract

Stewardship of this nation's nuclear weapons is predicated on developing a fundamental scientific understanding of the physics and chemistry required to describe weapon performance without the need to resort to underground nuclear testing and to predict expected future performance as a result of intended or unintended modifications. In order to construct more reliable models, underground nuclear test data is being reanalyzed in novel ways. The extent to which underground experimental data can be matched with simulations is one measure of the credibility of our capability to predict weapon performance. To improve the interpretation of these experiments with quantified uncertainties, improved nuclear data is required. As an example, the fission yield of a device was often determined by measuring fission products. Conversion of the measured fission products to yield was accomplished through explosion code calculations (models) and a good set of nuclear reaction cross-sections. Because of the unique high-fluence environment of an exploding nuclear weapon, many reactions occurred on radioactive nuclides, for which only theoretically calculated cross-sections are available. Inverse kinematics reactions at CARIBU offer the opportunity to measure cross-sections on unstable neutron-rich fission fragments and thus improve the quality of the nuclear reaction cross-section sets. One of the fission productsmore » measured was {sup 95}Zr, the accumulation of all mass 95 fission products of Y, Sr, Rb and Kr (see Fig. 1). Subsequent neutron-induced reactions on these short lived fission products were assumed to cancel out - in other words, the destruction of mass 95 nuclides was more or less equal to the production of mass 95 nuclides. If a {sup 95}Sr was destroyed by an (n,2n) reaction it was also produced by (n,2n) reactions on {sup 96}Sr, for example. However, since these nuclides all have fairly short half-lives (seconds to minutes or even less), no experimental nuclear reaction cross-sections exist, and only theoretically modeled cross-sections are available. Inverse kinematics reactions at CARIBU offer the opportunity, should the beam intensity be sufficient, to measure cross-sections on a few important nuclides in order to benchmark the theoretical calculations and significantly improve the nuclear data. The nuclides in Fig. 1 are prioritized by importance factor and displayed in stoplight colors, green the highest and red the lowest priority.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
967718
Report Number(s):
LLNL-TR-417030
TRN: US200924%%165
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BENCHMARKS; CHEMISTRY; CROSS SECTIONS; EXPLOSIONS; FISSION FRAGMENTS; FISSION PRODUCTS; FISSION YIELD; ISOTOPES; MODIFICATIONS; NUCLEAR REACTIONS; NUCLEAR WEAPONS; PHYSICS; RUTHERFORD BACKSCATTERING SPECTROSCOPY; STOCKPILES; TESTING; WEAPONS

Citation Formats

Stoyer, M A, McNabb, D, Burke, J, Bernstein, L A, and Wu, C Y. Science based stockpile stewardship, uncertainty quantification, and fission fragment beams. United States: N. p., 2009. Web. doi:10.2172/967718.
Stoyer, M A, McNabb, D, Burke, J, Bernstein, L A, & Wu, C Y. Science based stockpile stewardship, uncertainty quantification, and fission fragment beams. United States. doi:10.2172/967718.
Stoyer, M A, McNabb, D, Burke, J, Bernstein, L A, and Wu, C Y. Mon . "Science based stockpile stewardship, uncertainty quantification, and fission fragment beams". United States. doi:10.2172/967718. https://www.osti.gov/servlets/purl/967718.
@article{osti_967718,
title = {Science based stockpile stewardship, uncertainty quantification, and fission fragment beams},
author = {Stoyer, M A and McNabb, D and Burke, J and Bernstein, L A and Wu, C Y},
abstractNote = {Stewardship of this nation's nuclear weapons is predicated on developing a fundamental scientific understanding of the physics and chemistry required to describe weapon performance without the need to resort to underground nuclear testing and to predict expected future performance as a result of intended or unintended modifications. In order to construct more reliable models, underground nuclear test data is being reanalyzed in novel ways. The extent to which underground experimental data can be matched with simulations is one measure of the credibility of our capability to predict weapon performance. To improve the interpretation of these experiments with quantified uncertainties, improved nuclear data is required. As an example, the fission yield of a device was often determined by measuring fission products. Conversion of the measured fission products to yield was accomplished through explosion code calculations (models) and a good set of nuclear reaction cross-sections. Because of the unique high-fluence environment of an exploding nuclear weapon, many reactions occurred on radioactive nuclides, for which only theoretically calculated cross-sections are available. Inverse kinematics reactions at CARIBU offer the opportunity to measure cross-sections on unstable neutron-rich fission fragments and thus improve the quality of the nuclear reaction cross-section sets. One of the fission products measured was {sup 95}Zr, the accumulation of all mass 95 fission products of Y, Sr, Rb and Kr (see Fig. 1). Subsequent neutron-induced reactions on these short lived fission products were assumed to cancel out - in other words, the destruction of mass 95 nuclides was more or less equal to the production of mass 95 nuclides. If a {sup 95}Sr was destroyed by an (n,2n) reaction it was also produced by (n,2n) reactions on {sup 96}Sr, for example. However, since these nuclides all have fairly short half-lives (seconds to minutes or even less), no experimental nuclear reaction cross-sections exist, and only theoretically modeled cross-sections are available. Inverse kinematics reactions at CARIBU offer the opportunity, should the beam intensity be sufficient, to measure cross-sections on a few important nuclides in order to benchmark the theoretical calculations and significantly improve the nuclear data. The nuclides in Fig. 1 are prioritized by importance factor and displayed in stoplight colors, green the highest and red the lowest priority.},
doi = {10.2172/967718},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Sep 14 00:00:00 EDT 2009},
month = {Mon Sep 14 00:00:00 EDT 2009}
}

Technical Report:

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  • Stewardship of this nation's nuclear weapons is predicated on developing a fundamental scientific understanding of the physics and chemistry required to describe weapon performance without the need to resort to underground nuclear testing and to predict expected future performance as a result of intended or unintended modifications. In order to construct more reliable models, underground nuclear test data is being reanalyzed in novel ways. To improve the interpretation of these experiments with quantified uncertainties, improved nuclear data is required. As an example, the thermonuclear yield of a device was often inferred through the use of radiochemical detectors. Conversion of themore » detector activations observed to thermonuclear yield was accomplished through explosion code calculations (models) and a good set of nuclear reaction cross-sections. Because of the unique high-fluence environment of an exploding nuclear weapon, many reactions occurred on radioactive nuclides, for which only theoretically calculated cross-sections are available. Surrogate nuclear reactions at STARS/LIBERACE offer the opportunity to measure cross-sections on unstable nuclei and thus improve the quality of the nuclear reaction cross-section sets. One radiochemical detector that was loaded in devices was mono-isotopic yttrium ({sup 89}Y). Nuclear reactions produced {sup 87}Y and {sup 88}Y which could be quantified post-shot as a ratio of {sup 87}Y/{sup 88}Y. The yttrium cross-section set from 1988 is shown in Figure 1(a) and contains approximately 62 cross-sections interconnecting the yttrium nuclides. The 6 experimentally measured cross-sections are shown in Figure 1(b). Any measurement of cross-sections on {sup 87}Y or {sup 88}Y would improve the quality of the cross-section set. A recent re-evaluation of the yttrium cross-section set was performed with many more calculated reaction cross-sections included.« less
  • This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project has been to develop and apply the methods of multi scale science to the problems of fluid and material mixing due to instability and turbulence, and of materials characterization. Our specific focus has been on the SBSS (science-based stockpile stewardship) issue of assessing the performance of a weapons with off-design, aged, or remanufactured components in the absence of full-scale testing. Our products are physics models, based on microphysical principles and parameters, and suitable formore » implementation in the large scale design and assessment codes used in the nuclear weapons program.« less
  • The statement of work for this contract is to activate the Nevada Terawatt Facility (NTF). Experimentally investigate z-pinch physics, in collaboration with SNL, LANL, and LLNL. Develop x-ray and laser diagnostics for the NTF, SNL-Z, and LANL-ATLAS. Refine atomic and radiation physics calculations and data to meet the challenges of EUV and x-ray diagnostic development. Progress to date is reported.
  • One aspect of Science Based Stockpile Stewardship (SBSS) is to improve the quality of neutron cross section data for certain isotopes. The isotopes of interest are used to monitor neutron and charged particle fluxes in environments of brief, intense neutron fluxes. The accuracy of flux determination is dependent on the accuracy of cross section data for the stable isotopes loaded into the system and the unstable isotopes produced when the neutrons are incident on the monitor. For isotopes with a half-life greater than one day it is possible, given the production rates of RIA, to make radioactive targets for neutronmore » irradiation. This would require the ability to harvest isotopes at RIA, an onsite radiochemistry facility for processing the harvested material into a target, and an onsite neutron source facility. The radiochemistry facility will need to handle activity levels on the order of 100's of Curie's while the neutron source facility will need to provide high intensity ''monoenergetic'' neutrons from 10's keV to 20 MeV. For isotopes with a half-life much less than one day, only indirect methods can be used to get information on the neutron cross sections because of the lack of a target. Both experimental techniques will be discussed with their impact on the infrastructure at RIA, as well as the general case for the interest of SBSS in RIA.« less
  • This document reports on these topics: Computer Simulations in Support of National Security; Enhanced Surveillance of Aging Weapons; A New Precision Cutting Tool: The Femtosecond Laser; Superlasers as a Tool of Stockpile Stewardship; Nova Laser Experiments and Stockpile Stewardship; Transforming Explosive Art into Science; Better Flash Radiography Using the FXR; Preserving Nuclear Weapons Information; Site 300Õs New Contained Firing Facility; The Linear Electric Motor: Instability at 1,000 gÕs; A Powerful New Tool to Detect Clandestine Nuclear Tests; High Explosives in Stockpile Surveillance Indicate Constancy; Addressing a Cold War Legacy with a New Way to Produce TATB; JumpinÕ Jupiter! Metallic Hydrogen;more » Keeping the Nuclear Stockpile Safe, Secure, and Reliable; The Multibeam FabryÐPerot Velocimeter: Efficient Measurements of High Velocities; Theory and Modeling in Material Science; The Diamond Anvil Cell; Gamma-Ray Imaging Spectrometry; X-Ray Lasers and High-Density Plasma« less