Affordable Cleanup? Opportunities for Cost Reduction in the Decontamination and Decommissioning of the Nation's Uranium Enrichment Facilities (1996) / Chapter Skim
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E: RADIONUCLIDE CHARACTERIZATION AND DETECTION
E: RADIONUCLIDE CHARACTERIZATION AND DETECTION
Pages 220-232
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From page 220... ...
These salts exist outside the cascades due to leaks or to seals being breached for repairs or changes. Moisture changes the chemical form of the uranium gas by hydrolysis from uranium hexafluoride (UFO)
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From page 221... ...
Uranium-236 (236U) is produced by neutron activation of 23sU (competing with the fission process)
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From page 222... ...
Progress in removing uranium must be monitored for cascade components in situ and, after disassembly, for recyclable materials, building surfaces, and scrap. Sufficient information is available from plant upgrading and from the Capenhurst decommissioning to prepare plans for characterization during cascade disassembly, component decontamination, and site cleanup, with associated waste processing and radiation protection of personnel.
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From page 223... ...
The vast expanse of the cascade buildings presents a challenge for applying innovative monitoring techniques. For surface monitoring, robotic monitors that can move independently across floors at a rate controlled by the collected radiation count rates and that process measurements for data analysis and mapping could be highly cost-effective.
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From page 224... ...
Values given are indicative of achievable detection limits. SOURCE: Information on in situ alpha-particle, beta-particle, and gamma-ray survey detection limits was provided in March 1995 as personal communications to Bernd Kahn, member of the committee, from Steven Meiners and Chris Blewett, Martin Marietta Energy Systems, Paducah, Kentucky; Ron Brandenburg, Martin Marietta Energy Systems, Oak Ridge, Tennessee; Richard Mayer, Martin Marietta Utility Services, Portsmouth, Ohio; and James Berger, Auxier and Associates, Knoxville, Tennessee.
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From page 225... ...
The sensitivity of laboratory analysis can be improved by processing a sample of several grams to separate uranium from the bulk of the sample medium and other radionuclides and then measuring alpha particles with a solid-state detector or liquid scintillation system and spectrometer for as many as 1,000 minutes. The effort of chemical separation can be avoided by counting gamma rays from a kilogram sample in a calibrated container with a Ge detector and a spectrometer.
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From page 226... ...
239Pu and 237Np may be characterized with the same detection limits as uranium by radiochemically separating the elements and counting them, by distinguishing alpha particles by their energies with a spectrometer, or by distinguishing x and gamma rays with a spectrometer. 99Tc is measured by counting it with gas-filled ionization or liquid scintillation detectors.
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From page 227... ...
is also developing guidance for releasing radioactive materials. The Nuclear Regulatory Commission (Nuclear Regulatory Commission, 1974)
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From page 228... ...
When removal contanunation on objects of less surface area is determined, the pertinent levels should be reduced proportionally, and the entire surface should be wiped. SOURCE: Nuclear Regulatory Commission Regulatory Guide 1.86 (Directory of Regulatory Standards, 19741.
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From page 229... ...
. TABLE E-6 EPA Review Draft Generic Site Concentration Values for Various Exposure Scenarios (dose equivalent of 15 mrem/yr)
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From page 230... ...
Other important local factors in developing decommissioning guides for these plants are the contaminated areas contiguous to the GDP structures, the valuable metals on site, and the large structures. For example, the maintenance of access restrictions at a contiguous site may negate the rationale for decontaminating parts of the plant for free access; the radionuclide limit for freely releasing metals may be driven upward by their value or downward by concerns about subsequent radiation-sensitive applications; decisions on retaining structures versus tilrninsr them ;~^ Ho Bier ~ an_ d~ ~:~1 __~1___ _~1__ a_ ~ .~ it.
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From page 231... ...
The detection limit is the net amount of radionuclide of interest that can be distinguished reliably from the selected background value, and depends on the variability in these background values. Natural uranium concentrations in rock, soil, and concrete typically range from near zero to several pCi/g.
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From page 232... ...
1994. Regulatory Guide on Release Criteria for Decommissioning: Nuclear Regulatory Commission Staff's Draft for Comment.
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