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Title: DEVELOPMENT OF VISUAL CRITERIA FOR EVALUATION OF CORRODED TRANSURANIC (TRU) WASTE DRUMS AT THE DEPARTMENT OF ENERGY (US/DOE) HANFORD SITE

Fluor Hanford, Inc., at the Department of Energy (DOE) Hanford Site, has recently begun retrieving some 37,000 contact-handled, suspect-Transuranic or ''Retrievably Stored Waste'' (CH-TRU) waste drums from its Low Level Burial Grounds (LLBG). The drums are being retrieved, processed and prepared for eventual shipment to the DOE Waste Isolation Pilot Plant (WIPP). Immediately upon retrieval, the drums are visually inspected against requirements identified in the facility Authorization Basis to ensure they are safe for handling and fit for on-site transfer. A number of the retrieved drums did not meet specified corrosion criteria and as such required structural evaluation by Ultrasonic Test (UT) thickness checking (including mechanical surface prep) or overpacking into a Conex-type container prior to transfer. The additional evaluation and overpacking increases personnel exposure to the radioactive waste and reduces efficiency of the retrieval process. Based on historic Hanford CH-TRU waste drum corrosion data, showing very low general corrosion rates, there was reason to believe that existing Hanford site-transfer corrosion criteria were more conservative than needed. In an effort to demonstrate this belief, a corrosion investigation was performed. Eleven CH-TRU waste drums not meeting the corrosion criteria were included in the investigation and from these, 92 separate locations, ormore » areas of corrosion, were evaluated. Each of these locations was visually characterized and evaluated for thickness using the UT method. Visual characterization consisted of ranking photographs for each location on a scale from 1 to 6, representing an increasing level of corrosion attack. UT thickness measurements were then plotted against the visual ratings to identify any significant correlation. Analysis of the data indicated that as the corrosion rating increased, wall thickness decreased. It was concluded that drum surfaces characterized by a corrosion rating of 1-4 could be expected to have wall thickness values exceeding site minimum, calculated structural integrity requirements. The investigation concluded that existing corrosion criteria were in fact conservative and provided a technical basis for a new corrosion rating system. Application of the new system reduces the amount of evaluation and overpacking needed, while maintaining the transportation safety basis and worker safety. In addition, Engineering has developed an on-going data sampling program in which UT thickness checking of drums, as they are retrieved from the burial grounds, is performed. Evaluation of this data will determine the impact, if any, on the technical basis established for the rating system and will allow appropriate adjustment, as necessary. Sampling will also allow evaluation of potential surface conditions not observed in the original 11-drum investigation. It is noted that the safe, on-site transfer of drums is determined by all of the elements in the Hanford CH-TRU waste drum retrieval program, including design analyses, radiological controls, operational procedures, inspection requirements, etc. This paper addresses a single aspect of this process and the conclusions drawn regarding corrosion criteria were considered in the context of the overall program.« less
Authors:
Publication Date:
OSTI Identifier:
834443
Report Number(s):
HNF-22365-FP, Rev.0
TRN: US0407243
DOE Contract Number:
AC06-96RL13200
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Nov 2004
Research Org:
FH (US)
Sponsoring Org:
ENVIRONMENTAL MANAGEMENT (US)
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; CONTAINERS; CORROSION; EFFICIENCY; IMAGES; PERSONNEL; PHOSPHORS; RADIOACTIVE WASTES; SAFETY; SAMPLING; THICKNESS; ULTRASONIC WAVES; US DOE; WASTES; WIPP