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Title: SNM holdup assessment of Los Alamos exhaust ducts. Final report

Abstract

Fissile material holdup in glovebox and fume hood exhaust ducting has been quantified for all Los Alamos duct systems. Gamma-based, nondestructive measurements were used to quantify holdup. The measurements were performed during three measurement campaigns. The first campaign, Phase I, provided foot-by-foot, semiquantitative measurement data on all ducting. These data were used to identify ducting that required more accurate (quantitative) measurement. Of the 280 duct systems receiving Phase I measurements, 262 indicated less than 50 g of fissile holdup and 19 indicated fissile holdup of 50 or more grams. Seven duct systems were measured in a second campaign, called Series 1, Phase II. Holdup estimates on these ducts ranged from 421 g of {sup 235}U in a duct servicing a shut-down uranium-machining facility to 39 g of {sup 239}Pu in a duct servicing an active plutonium-processing facility. Measurements performed in the second campaign proved excessively laborious, so a third campaign was initiated that used more efficient instrumentation at some sacrifice in measurement quality. Holdup estimates for the 12 duct systems measured during this third campaign ranged from 70 g of {sup 235}U in a duct servicing analytical laboratories to 1 g of {sup 235}U and 1 g of {sup 239}Pumore » in a duct carrying exhaust air to a remote filter building. These quantitative holdup estimates support the conclusion made at the completion of the Phase I measurements that only ducts servicing shut-down uranium operations contain about 400 g of fissile holdup. No ventilation ducts at Los Alamos contain sufficient fissile material holdup to present a criticality safety concern.« less

Authors:
Publication Date:
Research Org.:
Los Alamos National Lab., NM (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10126202
Report Number(s):
LA-12700
ON: DE94007116; TRN: 94:004585
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Feb 1994
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; FISSILE MATERIALS; NONDESTRUCTIVE ANALYSIS; DEPOSITION; GLOVEBOXES; EXHAUST SYSTEMS; FUME HOODS; DUCTS; SURFACE CONTAMINATION; LANL; NUCLEAR FACILITIES; SAFETY ANALYSIS; PROGRESS REPORT; URANIUM 235; PLUTONIUM 239; CRITICALITY; EXPERIMENTAL DATA; RADIATION DETECTORS; STATISTICS; 054000; HEALTH AND SAFETY

Citation Formats

Marshall, R.S.. SNM holdup assessment of Los Alamos exhaust ducts. Final report. United States: N. p., 1994. Web. doi:10.2172/10126202.
Marshall, R.S.. SNM holdup assessment of Los Alamos exhaust ducts. Final report. United States. doi:10.2172/10126202.
Marshall, R.S.. 1994. "SNM holdup assessment of Los Alamos exhaust ducts. Final report". United States. doi:10.2172/10126202. https://www.osti.gov/servlets/purl/10126202.
@article{osti_10126202,
title = {SNM holdup assessment of Los Alamos exhaust ducts. Final report},
author = {Marshall, R.S.},
abstractNote = {Fissile material holdup in glovebox and fume hood exhaust ducting has been quantified for all Los Alamos duct systems. Gamma-based, nondestructive measurements were used to quantify holdup. The measurements were performed during three measurement campaigns. The first campaign, Phase I, provided foot-by-foot, semiquantitative measurement data on all ducting. These data were used to identify ducting that required more accurate (quantitative) measurement. Of the 280 duct systems receiving Phase I measurements, 262 indicated less than 50 g of fissile holdup and 19 indicated fissile holdup of 50 or more grams. Seven duct systems were measured in a second campaign, called Series 1, Phase II. Holdup estimates on these ducts ranged from 421 g of {sup 235}U in a duct servicing a shut-down uranium-machining facility to 39 g of {sup 239}Pu in a duct servicing an active plutonium-processing facility. Measurements performed in the second campaign proved excessively laborious, so a third campaign was initiated that used more efficient instrumentation at some sacrifice in measurement quality. Holdup estimates for the 12 duct systems measured during this third campaign ranged from 70 g of {sup 235}U in a duct servicing analytical laboratories to 1 g of {sup 235}U and 1 g of {sup 239}Pu in a duct carrying exhaust air to a remote filter building. These quantitative holdup estimates support the conclusion made at the completion of the Phase I measurements that only ducts servicing shut-down uranium operations contain about 400 g of fissile holdup. No ventilation ducts at Los Alamos contain sufficient fissile material holdup to present a criticality safety concern.},
doi = {10.2172/10126202},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1994,
month = 2
}

Technical Report:

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  • Quantitative (Phase II) holdup measurements were made on ventilation exhaust ducts at three Los Alamos facilities to assess the quantity of fissile material deposited inside the ducts. The ducts requiring rigorous, quantitative measurements were identified through a comprehensive but less quantitative Phase I measurement program. From the Phase I and II measurements, ducts servicing two rooms at TA-21 (DP Site) are estimated to contain 385 g of [sup 235]U(room 313) and 381 g of [sup 235]U (room 413R). Uncertainties in these estimates are discussed in detail and are assigned one standard deviation values of 153 g of [sup 235]U formore » room 313 and 139 g of [sup 235]U for room 413R. These ducts are in rooms that have been inactive since 1985 and are scheduled and funded for removal in 1992 or 1993. The one room identified at TA-55, PF-4 for Phase II measurement has been measured and the estimated duct holdup is 39 g of [sup 239]Pu with a one standard deviation uncertainty of 28 g. Fissile material holdup has also been estimated from Phase I and Phase II measurements on lengthy ducts servicing three rooms at TA-3/SM-29 (CMR Building). These room ducts are estimated to contain a maximum fissile holdup of 345 (room 4023), 119 (room 4034), and 88 (room 5034) g of [sup 235]U. With the exception of one segment of duct (estimated to contain 0.8 g of [sup 239]Pu), no ducts displayed gamma spectra from fissile isotopes.« less
  • Prompted by a request from the US Department of Energy to quantify the amount of fissile material holdup in glovebox exhaust ducts, the Los Alamos National Laboratory developed a two-phase measurement plan and began initial (Phase 1) measurements in the fall of 1990. The Phase I measurements were designed to provide a comprehensive, semiquantitative survey of all ducting at Los Alamos associated with the direct handling of kilogram quantities of fissile materials. The Phase I measurements and follow-on measurements were competed in June 1991. The instruments, the resources required, and the semiquantitative results are presented. Tables list the {sup 235}Umore » and {sup 239}Pu holdup found in ducts at eight technical areas. Holdup quantities are listed for the ducts in individual rooms housing exhaust ducting at these technical areas. Of the 280 rooms surveyed, the estimated duct fissile holdup is summarized as follows: 239 rooms with <5 g, 27 rooms with >5 g but <50 g, and 14 rooms with >50 g. The holdup in one room has yet to be determined but is expected to be <50 g. The highest estimated duct holdup for any room is 683 g of {sup 238}U. This is the only room with estimated holdup in excess of the 400-g limit specified by the Department of Energy. Final, quantitative, Phase II measurements will follow the Phase I effort and will be conducted on those ducts showing potential holdup approaching or exceeding 400 g fissile material. The Phase II effort and results will be published in a final report.« less
  • Prompted by a request from the US Department of Energy to quantify the amount of fissile material holdup in glovebox exhaust ducts, the Los Alamos National Laboratory developed a two-phase measurement plan and began initial (Phase 1) measurements in the fall of 1990. The Phase I measurements were designed to provide a comprehensive, semiquantitative survey of all ducting at Los Alamos associated with the direct handling of kilogram quantities of fissile materials. The Phase I measurements and follow-on measurements were competed in June 1991. The instruments, the resources required, and the semiquantitative results are presented. Tables list the {sup 235}Umore » and {sup 239}Pu holdup found in ducts at eight technical areas. Holdup quantities are listed for the ducts in individual rooms housing exhaust ducting at these technical areas. Of the 280 rooms surveyed, the estimated duct fissile holdup is summarized as follows: 239 rooms with <5 g, 27 rooms with >5 g but <50 g, and 14 rooms with >50 g. The holdup in one room has yet to be determined but is expected to be <50 g. The highest estimated duct holdup for any room is 683 g of {sup 238}U. This is the only room with estimated holdup in excess of the 400-g limit specified by the Department of Energy. Final, quantitative, Phase II measurements will follow the Phase I effort and will be conducted on those ducts showing potential holdup approaching or exceeding 400 g fissile material. The Phase II effort and results will be published in a final report.« less
  • Quantitative (Phase II) holdup measurements were made on ventilation exhaust ducts at three Los Alamos facilities to assess the quantity of fissile material deposited inside the ducts. The ducts requiring rigorous, quantitative measurements were identified through a comprehensive but less quantitative Phase I measurement program. From the Phase I and II measurements, ducts servicing two rooms at TA-21 (DP Site) are estimated to contain 385 g of {sup 235}U(room 313) and 381 g of {sup 235}U (room 413R). Uncertainties in these estimates are discussed in detail and are assigned one standard deviation values of 153 g of {sup 235}U formore » room 313 and 139 g of {sup 235}U for room 413R. These ducts are in rooms that have been inactive since 1985 and are scheduled and funded for removal in 1992 or 1993. The one room identified at TA-55, PF-4 for Phase II measurement has been measured and the estimated duct holdup is 39 g of {sup 239}Pu with a one standard deviation uncertainty of 28 g. Fissile material holdup has also been estimated from Phase I and Phase II measurements on lengthy ducts servicing three rooms at TA-3/SM-29 (CMR Building). These room ducts are estimated to contain a maximum fissile holdup of 345 (room 4023), 119 (room 4034), and 88 (room 5034) g of {sup 235}U. With the exception of one segment of duct (estimated to contain 0.8 g of {sup 239}Pu), no ducts displayed gamma spectra from fissile isotopes.« less
  • The 327 Building Post Irradiation Testing Laboratory is used for temporary storage and for destructive and nondestructive examination of irradiated reactor fuels and structural materials. The facility contains 12 shielded hot cells, two water-filled basins, and dry storage. This report describes the measurements performed to determine the radionuclide content and mass of Pu in ducts, filters, and piping in the basement of the 327 Building at the Hanford Site in Washington State. This information is needed to characterize facility radiation levels, to verify compliance with criticality safety specifications, and to allow more accurate nuclear material control using nondestructive assay (NDA)more » methods. Gamma assay techniques typically employed for NDA analysis were used to determine the gamma-emitting isotopes in the ducts, filters, and piping. Passive neutron counting was selected to estimate the Pu content because high gamma levels from fission and activation products effectively mask any gamma emissions from Pu. A high-purity gamma-ray detector was used to measure the mixed fission and activation radionuclides. A slab neutron detector containing five {sup 3}He proportional counters was used to determine the neutron emission rates and estimate the mass of Pu present. Estimated Pu mass in the basement ductwork and filters is 7.2 grams. The radioactive liquid waste system line has 4.2 grams and Special Environmental Radiometallurgy Facility cell recirculating system contains 8.7 grams in the lower filter housing and associated piping. Total Pu mass holdup estimates range from 20.1 grams, assuming that the Pu is weapons-grade Pu, to a best estimate of 11.0 grams Pu, assuming 11% {sup 240}Pu.« less