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Title: Assessment of alternative mitigation concepts for Hanford flammable gas tanks

Abstract

This report provides a review and assessment of four selected mitigation concepts: pump jet mixing, sonic vibration, dilution, and heating. Though the relative levels of development of these concepts are quite different, some definite conclusions are made on their comparative feasibility. Key findings of this report are as follows. A mixer pump has proven to be a safe and effective active mitigation method in Tank 241-SY-101, and the authors are confident that mixer pumps will effectively mitigate other tanks with comparable waste configurations and properties. Low-frequency sonic vibration is also predicted to be effective for mitigation. Existing data cannot prove that dilution can mitigate gas release event (GRE) behavior. However, dilution is the only concept of the four that potentially offers passive mitigation. Like dilution, heating the waste cannot be proven with available information to mitigate GRE behavior. The designs, analyses, and data from which these conclusions are derived are presented along with recommendations.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest Lab., Richland, WA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10186043
Report Number(s):
PNL-10105
ON: DE95000770; TRN: 94:020377
DOE Contract Number:
AC06-76RL01830
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Sep 1994
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; HANFORD RESERVATION; RADIOACTIVE WASTE STORAGE; SAFETY ENGINEERING; TANKS; DEGASSING; MIXING; MECHANICAL VIBRATIONS; DILUTION; HEATING; MIXERS; COMPARATIVE EVALUATIONS; SOUND WAVES; COMPILED DATA; 054000; 052002; HEALTH AND SAFETY; WASTE DISPOSAL AND STORAGE

Citation Formats

Stewart, C.W., Schienbein, L.A., Hudson, J.D., Eschbach, E.J., and Lessor, D.L. Assessment of alternative mitigation concepts for Hanford flammable gas tanks. United States: N. p., 1994. Web. doi:10.2172/10186043.
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Stewart, C.W., Schienbein, L.A., Hudson, J.D., Eschbach, E.J., & Lessor, D.L. Assessment of alternative mitigation concepts for Hanford flammable gas tanks. United States. doi:10.2172/10186043.
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Stewart, C.W., Schienbein, L.A., Hudson, J.D., Eschbach, E.J., and Lessor, D.L. Thu . "Assessment of alternative mitigation concepts for Hanford flammable gas tanks". United States. doi:10.2172/10186043. https://www.osti.gov/servlets/purl/10186043.
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@article{osti_10186043,
title = {Assessment of alternative mitigation concepts for Hanford flammable gas tanks},
author = {Stewart, C.W. and Schienbein, L.A. and Hudson, J.D. and Eschbach, E.J. and Lessor, D.L.},
abstractNote = {This report provides a review and assessment of four selected mitigation concepts: pump jet mixing, sonic vibration, dilution, and heating. Though the relative levels of development of these concepts are quite different, some definite conclusions are made on their comparative feasibility. Key findings of this report are as follows. A mixer pump has proven to be a safe and effective active mitigation method in Tank 241-SY-101, and the authors are confident that mixer pumps will effectively mitigate other tanks with comparable waste configurations and properties. Low-frequency sonic vibration is also predicted to be effective for mitigation. Existing data cannot prove that dilution can mitigate gas release event (GRE) behavior. However, dilution is the only concept of the four that potentially offers passive mitigation. Like dilution, heating the waste cannot be proven with available information to mitigate GRE behavior. The designs, analyses, and data from which these conclusions are derived are presented along with recommendations.},
doi = {10.2172/10186043},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Sep 01 00:00:00 EDT 1994},
month = {Thu Sep 01 00:00:00 EDT 1994}
}
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Technical Report:
View Technical Report (10.13 MB)
DOI:  10.2172/10186043
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  • ; ; ; ...
    This report presents a preliminary assessment of concepts for the mitigation and/or remediation of the hydrogen gas generation, storage, and periodic release in Tank 241-SY-101 (101-SY) and 22 other tanks. The 22 other tanks exhibit much less hydrogen generation (volume and concentration of released flammable gases) than Tank 101-SY and have not had the focus nor attention that has been given to Tank 101-SY. These tanks have been listed as potential hydrogen gas-generating tanks from analysis of tank performance and data from flowsheets and Track Radioactive Constituents Reports (TRAC). These lesser hydrogen-generating tanks will also need to be revisited andmore » revalidated. Of the 23 hydrogen class tanks, 5 are double-shell tanks (DST) and 18 are single-shell tanks (SST). Options for mitigation or remediation are different for the two types of tanks because of age, configuration, and waste form. While this document principally focuses on Tank 101-SY, the information presented has been useful to address other tanks containing hydrogen-generating waste.« less

  • ; ; ; ...
    This report presents a preliminary assessment of concepts for the mitigation and/or remediation of the hydrogen gas generation, storage, and periodic release in Tank 241-SY-101 (101-SY) and 22 other tanks. The 22 other tanks exhibit much less hydrogen generation (volume and concentration of released flammable gases) than Tank 101-SY and have not had the focus nor attention that has been given to Tank 101-SY. These tanks have been listed as potential hydrogen gas-generating tanks from analysis of tank performance and data from flowsheets and Track Radioactive Constituents Reports (TRAC). These lesser hydrogen-generating tanks will also need to be revisited andmore » revalidated. Of the 23 hydrogen class tanks, 5 are double-shell tanks (DST) and 18 are single-shell tanks (SST). Options for mitigation or remediation are different for the two types of tanks because of age, configuration, and waste form. While this document principally focuses on Tank 101-SY, the information presented has been useful to address other tanks containing hydrogen-generating waste.« less

  • ; ; ; ...
    Radioactive nuclear waste at the Hanford Site is stored in underground waste storage tanks at the site. The tanks fall into two main categories: single-shell tanks (SSTs) and double-shell tanks (DSTs). There are a total of 149 SSTs and 28 DSTs. The wastes stored in the tanks are chemically complex. They basically involve various sodium salts (mainly nitrite, nitrate, carbonates, aluminates, and hydroxides), organic compounds, heavy metals, and various radionuclides, including cesium, strontium, plutonium, and uranium. The waste is known to generate flammable gas (FG) [hydrogen, ammonia, nitrous oxide, hydrocarbons] by complex chemical reactions. The process of gas generation, retention,more » and release is transient. Some tanks reach a quasi-steady stage where gas generation is balanced by the release rate. Other tanks show continuous cycles of retention followed by episodic release. There currently are 25 tanks on the Flammable Gas Watch List (FGWL). The objective of this report is to evaluate possible mitigation strategies to eliminate the FG hazard. The evaluation is an engineering study of mitigation concepts for FG generation, retention, and release behavior in Tanks SY-101, AN-103, AN 104, An-105, and Aw-101. Where possible, limited quantification of the effects of mitigation strategies on the FG hazard also is considered. The results obtained from quantification efforts discussed in this report should be considered as best-estimate values. Results and conclusions of this work are intended to help in establishing methodologies in the contractor`s controls selection analysis to develop necessary safety controls for closing the FG unreviewed safety question. The general performance requirements of any mitigation scheme are discussed first.« less

  • This safety assessment (SA) addresses each of the required elements associated with the installation, operation, and removal of a rotary-mode core sampling (RMCS) device in flammable-gas single-shell tanks (SSTs). The RMCS operations are needed in order to retrieve waste samples from SSTs with hard layers of waste for which push-mode sampling is not adequate for sampling. In this SA, potential hazards associated with the proposed action were identified and evaluated systematically. Several potential accident cases that could result in radiological or toxicological gas releases were identified and analyzed and their consequences assessed. Administrative controls, procedures and design changes required tomore » eliminate or reduce the potential of hazards were identified. The accidents were analyzed under nine categories, four of which were burn scenarios. In SSTS, burn accidents result in unacceptable consequences because of a potential dome collapse. The accidents in which an aboveground burn propagates into the dome space were shown to be in the ``beyond extremely unlikely`` frequency category. Given the unknown nature of the gas-release behavior in the SSTS, a number of design changes and administrative controls were implemented to achieve these low frequencies. Likewise, drill string fires and dome space fires were shown to be very low frequency accidents by taking credit for the design changes, controls, and available experimental and analytical data. However, a number of Bureau of Mines (BOM) tests must be completed before some of the burn accidents can be dismissed with high confidence. Under the category of waste fires, the possibility of igniting the entrapped gases and the waste itself were analyzed. Experiments are being conducted at the BOM to demonstrate that the drill bit is not capable of igniting the trapped gas in the waste. Laboratory testing and thermal analysis demonstrated that, under normal operating conditions, the drill bit will not create high enough temperatures to initiate a propagating reaction in the waste. However, system failure that coincides in a waste layer with high organic content and low moisture may initiate an exothermic reaction in the waste. Consequently, a conservative approach based on the current state of the knowledge resulted in limiting the drilling process to a subset of the flammable-gas tanks. Accidents from the chemical reactions and criticality category are shown to result in acceptable risk. A number of accidents are shown to potentially result in containment (tank liner) breach below the waste level. Mitigative features are provided for these accidents. Gas-release events without burn also are analyzed, and radiological and toxicological consequences are shown to be within risk guidelines. Finally, the consequences of potential spills are shown to be within the risk guidelines.« less

  • ; ; ; ...
    Of 177 high-level waste storage tanks on the Hanford Site, 23 have been placed on a safety watch list because they are suspected of producing flammable gases in flammable or explosive concentrate. One tankin particular, Tank 241-SY-101 (Tank 101-SY), has exhibited slow increases in waste volume followed by a rapid decrease accompanied by venting of large quantities of gases. The purpose of this study is to help determine the processes by which flammable gases are produced, retained, and eventually released from Tank 101-SY. Waste composition data for single- and double-shell waste tanks on the flammable gas watch listare critically reviewed.more » The results of laboratory studies using synthetic double-shell wastes are summarized, including physical and chemical properties of crusts that are formed, the stoichiometry and rate ofgas generation, and mechanisms responsible for formation of a floating crust.« less