Nuclear Data Verification and Standardization Project, |
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Nuclear Data Verification and Standardization Project, |
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The objective of this project is to provide accurate neutron cross section standards needed for studies in fields such as astrophysics, personnel health and safety, nuclear waste disposal, treaty verification, national defense, and nuclear based energy production. Nearly all neutron reaction cross section measurements are made relative to one of these standards. Thus it is important to maintain and improve these standards. The work has involved the measurement of important standard reference data, leadership and participation in international intercomparisons and collaborations, and the preservation of standard reference deposits. An essential element of the program is the critical evaluation of neutron interaction standards including international coordinations. Experimental work is performed at NIST and at other appropriate facilities which are best suited for the measurements to be made.
The evaluation effort is now focused on a new international evaluation of the neutron cross section standards. This international standards activity, which is being coordinated by NIST, is being performed through a subgroup of the Nuclear Energy Agency. Work has been done defining the subgroup, determining the methodology for the evaluation and reviewing the experimental database.
Recent collaborative experimental work includes the following measurements, all of which have revealed significant differences with accepted evaluations:
Well characterized fissionable reference deposits originating both from NIST and other laboratories are included in the National Repository for Fissionable Isotope Mass Standards which is maintained by this project. This repository continues to obtain deposits from other laboratories where nuclear data programs are being reduced or terminated. One of the most important uses for this repository is preventing the loss of valuable isotopic samples which may otherwise have to be replaced at great expense at a future time. The deposits from the repository are available for use in nuclear data programs.
These activities are performed in the Neutron Interactions and Dosimetry group of the Ionizing Radiation Division at NIST. This group has additional capabilities which are useful for nuclear data applications. For example, there is a first class neutron interferometry facility which can be used for the determination of coherent neutron scattering lengths. These data are useful in evaluations of neutron cross sections. Also neutron fields are available using the NIST reactor or 252Cf sources which can be used for cross section measurements integrated over the source spectrum. Recently an NIST-Ohio University-Pennsylvania State University collaboration was formed to investigate deficiencies in the iron cross sections by performing spherical shell transmission measurements and making detailed transport calculations.| Name | Phone | Fax | |
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| Allan D. Carlson | (301)975-5570 | CARLSON@ENH.NIST.GOV | (301)869-7682 |
| David M. Gilliam | (301)975-6206 | GILLIAM@ENH.NIST.GOV | (301)926-1604 |
| Roald A. Schrack | (301)975-5569 | SCHRACK@ENH.NIST.GOV | (301)869-7682 |
| Oren A. Wasson | (301)975-5567 | WASSON@ENH.NIST.GOV | (301)869-7682 |
A general description of the Neutron Interactions and Dosimetry Group and other groups in the Ionizing Radiation Division may be found at http://physics.nist.gov/TechAct/Div846/div846h.html.
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