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Title: DISPOSAL OF REACTOR DEIONIZER VESSELS HIGHLY CONTAMINATED WITH 14 CARBON IN THE INTERMEDIATE LEVEL VAULT FACILITY AT SRS

Abstract

At the Savannah River Site (SRS), nuclear production reactors used deionizers to control the chemistry of the reactor moderator during their operation to produce nuclear materials primarily for the weapons program. These deionizers were removed from the reactors and stored as a legacy waste with no path to disposal due to the relatively high {sup 14}C contamination (i.e., on the order of 20 curies per deionizer for 48-50 deionizers) and the low disposal limit of 4.2 Ci previously established for the Intermediate Level Vault (ILV). The ILV is considered most appropriate facility within which to dispose these items due to the method of solidifying waste items with cementitious material inside concrete vaults. In previous analyses the {sup 14}C ILV disposal limit was established at 4.2 Ci resulting from the use of a very conservative method to analyze the dose received from atmospheric releases of gaseous {sup 14}C. This investigation implemented a more rigorous evaluation of the physical and chemical processes influencing the release and migration of gaseous {sup 14}C (as CO{sub 2}) to obtain a more realistic estimate of atmospheric dose and to determine new ILV disposal limits.

Authors:
;
Publication Date:
Research Org.:
SRS
Sponsoring Org.:
USDOE
OSTI Identifier:
908025
Report Number(s):
WSRC-STI-2007-00271
TRN: US0703384
DOE Contract Number:
DE-AC09-96SR18500
Resource Type:
Conference
Resource Relation:
Conference: American Nuclear Society - Decommissioning, Decontamination and Revtilization Technology Expo.
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; CARBON; CHEMISTRY; CONCRETES; CONTAMINATION; DECOMMISSIONING; DECONTAMINATION; EVALUATION; MODERATORS; PRODUCTION REACTORS; SAVANNAH RIVER PLANT; WASTES; WEAPONS

Citation Formats

Hiergesell, R, and Daniel Kaplan, D. DISPOSAL OF REACTOR DEIONIZER VESSELS HIGHLY CONTAMINATED WITH 14 CARBON IN THE INTERMEDIATE LEVEL VAULT FACILITY AT SRS. United States: N. p., 2007. Web.
Hiergesell, R, & Daniel Kaplan, D. DISPOSAL OF REACTOR DEIONIZER VESSELS HIGHLY CONTAMINATED WITH 14 CARBON IN THE INTERMEDIATE LEVEL VAULT FACILITY AT SRS. United States.
Hiergesell, R, and Daniel Kaplan, D. Mon . "DISPOSAL OF REACTOR DEIONIZER VESSELS HIGHLY CONTAMINATED WITH 14 CARBON IN THE INTERMEDIATE LEVEL VAULT FACILITY AT SRS". United States. doi:. https://www.osti.gov/servlets/purl/908025.
@article{osti_908025,
title = {DISPOSAL OF REACTOR DEIONIZER VESSELS HIGHLY CONTAMINATED WITH 14 CARBON IN THE INTERMEDIATE LEVEL VAULT FACILITY AT SRS},
author = {Hiergesell, R and Daniel Kaplan, D},
abstractNote = {At the Savannah River Site (SRS), nuclear production reactors used deionizers to control the chemistry of the reactor moderator during their operation to produce nuclear materials primarily for the weapons program. These deionizers were removed from the reactors and stored as a legacy waste with no path to disposal due to the relatively high {sup 14}C contamination (i.e., on the order of 20 curies per deionizer for 48-50 deionizers) and the low disposal limit of 4.2 Ci previously established for the Intermediate Level Vault (ILV). The ILV is considered most appropriate facility within which to dispose these items due to the method of solidifying waste items with cementitious material inside concrete vaults. In previous analyses the {sup 14}C ILV disposal limit was established at 4.2 Ci resulting from the use of a very conservative method to analyze the dose received from atmospheric releases of gaseous {sup 14}C. This investigation implemented a more rigorous evaluation of the physical and chemical processes influencing the release and migration of gaseous {sup 14}C (as CO{sub 2}) to obtain a more realistic estimate of atmospheric dose and to determine new ILV disposal limits.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 21 00:00:00 EDT 2007},
month = {Mon May 21 00:00:00 EDT 2007}
}

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  • At the Savannah River Site (SRS), nuclear production reactors used de-ionizers to control the chemistry of the reactor moderator during their operation to produce nuclear materials primarily for the weapons program. These de-ionizers were removed from the reactors and stored as a legacy waste with no path to disposal due to the relatively high {sup 14}C contamination (i.e., on the order of 20 curies per de-ionizer for 48-50 de-ionizers) and the low disposal limit of 4.2 Ci previously established for the Intermediate Level Vault (ILV). The ILV is considered most appropriate facility within which to dispose these items due tomore » the method of solidifying waste items with cementitious material inside concrete vaults. In previous analyses the {sup 14}C ILV disposal limit was established at 4.2 Ci resulting from the use of a very conservative method to analyze the dose received from atmospheric releases of gaseous {sup 14}C. This investigation implemented a more rigorous evaluation of the physical and chemical processes influencing the release and migration of gaseous {sup 14}C (as CO{sub 2}) to obtain a more realistic estimate of atmospheric dose and to determine new ILV disposal limits. The results are in terms of an emanation rate of {sup 14}C activity at the land surface. There is a rapid buildup to the maximum emanation rate of 1.42 E-8 Ci/year within 0.4 years. This rate continues steadily for the remainder of the simulation. The maximum emanation rate was used to calculate the dose to the Maximally Exposed Individual (MEI) at a point 100 m from the ILV, which is the most restrictive exposure point. The dose to the MEI at this location was calculated to be 3.83 E-05 mrem/yr. which is minuscule compared to the exposure limit defined in US DOE Order 435.1 as 10 mrem/yr. Considering the tiny dose to the MEI calculated in this analysis, no atmospheric pathway limit needed to be applied to the Intermediate Level Vault for {sup 14}C. This is justified in that no matter how much {sup 14}C is disposed in the ILV disposal environment, only a set, relatively small quantity can move into the air space as gas due to the solubility control limitation. Consequently, the groundwater pathway disposal limit for resin-based {sup 14}C in the Intermediate Level Vault became the most restrictive limit among the various pathways, this limit being 2.6 E+06 Ci, which easily allows for disposal of all the Reactor Moderator De-ionizers.« less
  • At the Savannah River Site (SRS), nuclear production reactors used de-ionizers to control the chemistry of the reactor moderator during their operation to produce nuclear materials primarily for the weapons program. These de-ionizers were removed from the reactors and stored as a legacy waste and due to the relatively high carbon-14 (C-14) contamination (i.e., on the order of 740 giga becquerel (GBq) (20 curies) per de-ionizer) were considered a legacy 'waste with no path to disposal'. Considerable progress has been made in consideration of a disposal path for the legacy reactor de-ionizers. Presently, 48 - 50 de-ionizers being stored atmore » SRS have 'no path to disposal' because the disposal limit for C-14 in the SRS's low-level waste disposal facility's Intermediate Level Vault (ILV) is only 160 GBq (4.2 curies) per vault. The current C-14 ILV disposal limit is based on a very conservative analysis of the air pathway. The paper will describe the alternatives that were investigated that resulted in the selection of a route to pursue. This paper will then describe SRS's efforts to reduce the conservatism in the analysis, which resulted in a significantly larger C-14 disposal limit. The work consisted of refining the gas-phase analysis to simulate the migration of C-14 from the waste to the ground surface and evaluated the efficacy of carbonate chemistry in cementitious environment of the ILV for suppressing the volatilization of C-14. During the past year, a Special Analysis was prepared for Department of Energy approval to incorporate the results of these activities that increased the C-14 disposal limits for the ILV, thus allowing for disposal of the Reactor Moderator De-ionizers. Once the Special Analysis is approved by DOE, the actual disposal would be dependent on priority and funding, but the de-ionizers will be removed from the 'waste with no path to disposal list'. (authors)« less
  • Disposal of depleted ion exchange resins from the primary system of the Savannah River Site (SRS) reactors is complicated by the presence of Carbon-14. Because Carbon-14 has a long half-life (5,730 years) and high mobility in soils, burial of the resins is no longer a viable option. Consequently some 35 spent reactor deionizers have accumulated that are to be stored aboveground in H-Area for an indefinite period. Spent deionizers containing Carbon-14 will continue to accumulate with operation of the present production reactors and would also accumulate from the proposed heavy water new production reactor. Removal of the Carbon-14 from themore » resins would reduce the volume of Carbon-14 bearing waste and enable the resins to be disposed of as low-level waste. Studies at SRS have indicated that the Carbon-14 from reactor primary coolant is mostly retained by the resins as the bicarbonate anion. Thus Carbon-14 removal might be accomplished by an acidification operation with trapping of the carbon dioxide released, for separate disposal. Conversion of the bicarbonate from the resin to barium carbonate, for example, would reduce the volume of waste more than a hundredfold. Displacement and recovery of Carbon-14 dioxide from reactor coolant deionizers by acid treatment has been reported by the Canadians. This memorandum recommends that a process be developed for Carbon-14 dioxide removal from SRS spent reactor deionizer resins, drawing on the Canadian experience.« less
  • Disposal of depleted ion exchange resins from the primary system of the Savannah River Site (SRS) reactors is complicated by the presence of Carbon-14. Because Carbon-14 has a long half-life (5,730 years) and high mobility in soils, burial of the resins is no longer a viable option. Consequently some 35 spent reactor deionizers have accumulated that are to be stored aboveground in H-Area for an indefinite period. Spent deionizers containing Carbon-14 will continue to accumulate with operation of the present production reactors and would also accumulate from the proposed heavy water new production reactor. Removal of the Carbon-14 from themore » resins would reduce the volume of Carbon-14 bearing waste and enable the resins to be disposed of as low-level waste. Studies at SRS have indicated that the Carbon-14 from reactor primary coolant is mostly retained by the resins as the bicarbonate anion. Thus Carbon-14 removal might be accomplished by an acidification operation with trapping of the carbon dioxide released, for separate disposal. Conversion of the bicarbonate from the resin to barium carbonate, for example, would reduce the volume of waste more than a hundredfold. Displacement and recovery of Carbon-14 dioxide from reactor coolant deionizers by acid treatment has been reported by the Canadians. This memorandum recommends that a process be developed for Carbon-14 dioxide removal from SRS spent reactor deionizer resins, drawing on the Canadian experience.« less
  • This Special Analysis (SA) evaluated a unique waste disposal item, the initial Tritium Extraction Facility (TEF) waste container, to determine its suitability for disposal within the intermediate Level Vault (ILV). This waste container will be used to dispose 900 extracted Tritium Producing Burnable Absorber Rods (TPBARs) and the Lead Test Assembly (LTA) container, which will hold 32 unextracted TPBARs. Suitability was determined by evaluating the contribution of the expected radionuclide inventory of the initial TEF waste container versus the disposal limits derived for it. The conclusion of this SA is that the TEF disposal container described in this investigation willmore » not cause any exceedance of U.S. Department of Energy (DOE) Order 435.1 performance measures over the 1000-year PA compliance period and may therefore be disposed of within the ILV.« less