Reference flaw size for structural and fracture analysis of Types 1 and 2 waste tanks
High Level Waste Engineering (HLWE) is reviewing the Technical Standard requirements for tank level and minimum wall temperature. These requirements are necessary to minimize the probability of brittle fracture of the primary liner due to normal operating and/or seismic loads. The review includes the determination of a reference flaw size, a maximum through-wall crack length, which may reasonably be applied to structural and fracture analysis of the Type I and II waste tank primary liners. This memorandum briefly discusses the mechanism of crack initiation and propagation, the inspections of primary wall cracks, and a statistical analysis of the measured crack lengths. Recommendations on additional analyses which may increase the confidence in the reference flaw size will also be presented. The primary liner for Type I and II waste tanks is fabricated from ASTM A285, Grade B carbon steel (A285). The liner received no heat treatments to relieve residual stresses in the heat affected zones. Five Type I waste tanks and all four Type II waste tanks developed through-wall cracks. Leaks developed in tanks 9, 10,14 and 16 within less than two years. Small surface cracks were also observed on the interior of the tank primary. The cracks were perpendicular to the butt welds and extended through the heat affected zone before stopping shortly after penetrating the base metal. The largest leakage of radioactive waste, approximately 185,000 gallons from the primary into the annulus, occurred from Tank 16, a Type II waste tank. During inspections of this tank over 300 leaks were discovered with the longest observed crack being approximately 6 inches. Due to the large number of observed cracks and the amount of leakage, this wag the only tank that was surveyed for crack lengths. For this analysis, Tank 16 will be considered representative of all Type I and II waste tanks because the materials, construction practices, and tank chemistry represented a worst case.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC09-89SR18035
- OSTI ID:
- 10137647
- Report Number(s):
- WSRC-TR-94-041; ON: DE94009099
- Resource Relation:
- Other Information: PBD: Jan 1994
- Country of Publication:
- United States
- Language:
- English
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