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Title: Technical Basis Document No. 6: Waste Package and Drip Shield Corrosion

Abstract

The waste package and drip shield will experience a wide range of interactive environmental conditions and degradation modes that will determine the overall performance of the waste package and repository. The operable modes of degradation are determined by the temperature regime of operation (region), and are summarized here. Dry-Out Region (T {ge} 120 C; 50 to 400 Years): During the pre-closure period, the waste package will be kept dry by ventilation air. During the thermal pulse, heat generated by radioactive decay will eventually increase the temperature of the waste package, drip shield and drift wall to a level above the boiling point, where the probability of seepage into drifts will become insignificant. Further heating will push the waste package surface temperature above the deliquescence point of expected salt mixtures, thereby preventing the formation of deliquescence brines from dust deposits and humid air. Phase and time-temperature-transformation diagrams predicted for Alloy 22, and validated with experimental data, indicates no significant phase instabilities (LRO and TCP precipitation) at temperatures below 300 C for 10,000 years. Neither will dry oxidation at these elevated temperatures limit waste package life. After the peak temperature is reached, the waste package will begin to cool, eventually reaching amore » point where deliquescence brine formation may occur. However, corrosion testing of Alloy 22 underneath such films has shown no evidence of life-limiting localized corrosion. Transition Region (120 C {ge} T {ge} 100 C; 400 to 1,000 Years): During continued cooling, the temperature of the drift wall will drop to a level close to the boiling point of the seepage brine, thus permitting the onset of seepage. Corrosion in a concentrated, possibly aggressive, liquid-phase brine, evolved through evaporative concentration, is possible while in this region. However, based upon chemical divide theory, most ({ge} 99%) of the seepage water entering the drift is predicted to evolve as benign chloride-sulfate or bicarbonate brines. Less than one percent will evolve to aggressive calcium chloride brines, and these brines will have significant levels of nitrate inhibitor present. Thus, waste package life will not be limited by localized corrosion while in this region of operation. Rates of uniform general corrosion are relatively insignificant, and stress corrosion cracking is prevented by stress mitigation, and physical isolation of welded regions from corrosive environments. Low Temperature Region (100 C {le} T; 1,000-10,000 Years) Continued cooling will eventually lower the temperature below the boiling point of the seepage brine, thus minimizing the extent of evaporative concentration. Once the waste package temperature drops below the critical temperature for crevice corrosion, corrosion will no longer limit waste package performance.« less

Authors:
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Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
15005729
Report Number(s):
UCRL-LR-155288
TRN: US0305613
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Aug 2003
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ACID CARBONATES; BOILING POINTS; CALCIUM CHLORIDES; CORROSION; CREVICE CORROSION; CRITICAL TEMPERATURE; MITIGATION; MIXTURES; NITRATES; OXIDATION; SHIELDS; STRESS CORROSION; WASTES

Citation Formats

Farmer, J, Pasupathi, V, Nair, P, Gordon, G, McCright, D, Gdowski, G, Carroll, S, Steinborn, T, Summers, T, Wong, F, Rebak, R, Lian, T, Ilevbare, G, Lee, J, Hua, F, and Payer, J. Technical Basis Document No. 6: Waste Package and Drip Shield Corrosion. United States: N. p., 2003. Web. doi:10.2172/15005729.
Farmer, J, Pasupathi, V, Nair, P, Gordon, G, McCright, D, Gdowski, G, Carroll, S, Steinborn, T, Summers, T, Wong, F, Rebak, R, Lian, T, Ilevbare, G, Lee, J, Hua, F, & Payer, J. Technical Basis Document No. 6: Waste Package and Drip Shield Corrosion. United States. doi:10.2172/15005729.
Farmer, J, Pasupathi, V, Nair, P, Gordon, G, McCright, D, Gdowski, G, Carroll, S, Steinborn, T, Summers, T, Wong, F, Rebak, R, Lian, T, Ilevbare, G, Lee, J, Hua, F, and Payer, J. Fri . "Technical Basis Document No. 6: Waste Package and Drip Shield Corrosion". United States. doi:10.2172/15005729. https://www.osti.gov/servlets/purl/15005729.
@article{osti_15005729,
title = {Technical Basis Document No. 6: Waste Package and Drip Shield Corrosion},
author = {Farmer, J and Pasupathi, V and Nair, P and Gordon, G and McCright, D and Gdowski, G and Carroll, S and Steinborn, T and Summers, T and Wong, F and Rebak, R and Lian, T and Ilevbare, G and Lee, J and Hua, F and Payer, J},
abstractNote = {The waste package and drip shield will experience a wide range of interactive environmental conditions and degradation modes that will determine the overall performance of the waste package and repository. The operable modes of degradation are determined by the temperature regime of operation (region), and are summarized here. Dry-Out Region (T {ge} 120 C; 50 to 400 Years): During the pre-closure period, the waste package will be kept dry by ventilation air. During the thermal pulse, heat generated by radioactive decay will eventually increase the temperature of the waste package, drip shield and drift wall to a level above the boiling point, where the probability of seepage into drifts will become insignificant. Further heating will push the waste package surface temperature above the deliquescence point of expected salt mixtures, thereby preventing the formation of deliquescence brines from dust deposits and humid air. Phase and time-temperature-transformation diagrams predicted for Alloy 22, and validated with experimental data, indicates no significant phase instabilities (LRO and TCP precipitation) at temperatures below 300 C for 10,000 years. Neither will dry oxidation at these elevated temperatures limit waste package life. After the peak temperature is reached, the waste package will begin to cool, eventually reaching a point where deliquescence brine formation may occur. However, corrosion testing of Alloy 22 underneath such films has shown no evidence of life-limiting localized corrosion. Transition Region (120 C {ge} T {ge} 100 C; 400 to 1,000 Years): During continued cooling, the temperature of the drift wall will drop to a level close to the boiling point of the seepage brine, thus permitting the onset of seepage. Corrosion in a concentrated, possibly aggressive, liquid-phase brine, evolved through evaporative concentration, is possible while in this region. However, based upon chemical divide theory, most ({ge} 99%) of the seepage water entering the drift is predicted to evolve as benign chloride-sulfate or bicarbonate brines. Less than one percent will evolve to aggressive calcium chloride brines, and these brines will have significant levels of nitrate inhibitor present. Thus, waste package life will not be limited by localized corrosion while in this region of operation. Rates of uniform general corrosion are relatively insignificant, and stress corrosion cracking is prevented by stress mitigation, and physical isolation of welded regions from corrosive environments. Low Temperature Region (100 C {le} T; 1,000-10,000 Years) Continued cooling will eventually lower the temperature below the boiling point of the seepage brine, thus minimizing the extent of evaporative concentration. Once the waste package temperature drops below the critical temperature for crevice corrosion, corrosion will no longer limit waste package performance.},
doi = {10.2172/15005729},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {8}
}

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