ProTec Tear-Offs: A Preliminary Assessment
The Savannah River National Laboratory (SRNL) has conducted a series of ''scoping'' tests (referred to as Phase 1) to assess the potential use of a Mylar{reg_sign} tear-off system as a primary or secondary protective barrier to minimize acid etching (''frosting''), accidental scratching, and/or radiation damage for shielded cells windows. Conceptually, thin, multi-layered sheets of Mylar (referred to as a ''tear-off'' system) could be directly applied to the Lexan{reg_sign} sheet or glovebox/hood sash window to serve as a secondary (or primary) barrier. Upon degradation of visual clarity due to accidental scratching, spills/splatters, and/or radiation damage, the outer layer (or sheet) of Mylar could be removed ''refreshing'' or restoring the view. Due to the multi-layer aspect, the remaining Mylar layers would provide continued protection for the window from potential reoccurrences (which could be immediate or after some extended time period). Although the concept of using a tear-off system as a protective barrier was conceptually enticing, potential technical issues were identified and addressed as part of this Phase 1 feasibility study. These included resistance to: (1) acid(s) (concentrated (28.9 M) HF, concentrated (15.9M) HNO{sub 3}, 6M HCl, and 0.6M H{sub 3}BO{sub 3}), (2) base (a simulated sludge with pH of 12.9), (3) gamma radiation (cumulative dose of {approx}200,000 rad), and (4) scratch resistance (simulating accidental scratching with the manipulators). Not only can these four factors play a significant role in determining the visual clarity of the integrated system, they can also contribute to the mechanical integrity issues which could dictate the ability to remove the outer layer when visual clarity has degraded. The results of the Phase 1 study clearly indicate that the Mylar tear-off concept (as a primary or secondary protective barrier) is a potential technical solution to prevent or retard excessive damage that would result from acid etching, base damage (as a result of a sludge spill or splatter), gamma radiation damage, and/or accidental scratching (due to manipulator/tool contact). The short term tests performed in this task showed that Mylar tear-offs can withstand the chemical and physical abuses expected in off-normal shielded cells operations. The ''tear-offs'' not only provide some measure of acid resistance, as reflected by the lack of visual degradation after being exposed to four acids, but also act as a protective barrier to accidental contact with the manipulators and/or tools. The conceptual ''erasing'' of scratches or marks was demonstrated in the shielded cell mock-up facility through the removal, with manipulators, of the outer layer tear-off. The successful removal of the outer layer tear-off with the manipulator, using tabs not specifically designed for remote operations, demonstrates that the system is ''manipulator-friendly'' and could be implemented in the shielded cells. The ability to remove the outer layer tear-off not only regains visual clarity but also reduces waste disposal volumes (i.e., disposal of a thin sheet of Mylar which is ''collapsible'' versus the bulk disposal of a rigid Lexan sheet or glovebox/sash window) which is more cost effective. The ''tear-off'' system could also reduce the number of cell entries needed to replace the Lexan sheet and increase the time interval between glovebox/sash window change outs which can be costly and time consuming. Although the primary focus of this report addresses the application of the Mylar tear-offs on shielded cells windows, the concept is also potentially applicable to glovebox and hood sash windows. In fact, the tear-off concept is potentially applicable to any system where visual clarity is compromised given the environmental conditions of the test. In addition, the tear-offs could be applied to walls or shelves where a protective barrier would reduce deterioration or discoloration. This concept is referred to as the ProTec{trademark} tear-off system as its primary intent is to protect windows or surfaces.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC09-96SR18500
- OSTI ID:
- 890198
- Report Number(s):
- WSRC-TR-2005-00386; TRN: US0604670
- Country of Publication:
- United States
- Language:
- English
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