Testing of SRS and RFETS Nylon Bag Material
This report compares the effects of radiation and heating on nylon bagout materials used at the Savannah River Site (SRS) and the Rocky Flats Environmental Technology Site (RFETS). Recently, to simplify the processing of sand, slag, and crucible (SS and C), FB-Line has replaced the low-density polyethylene (LDPE) and polyvinyl chloride (PVC) bags normally used to package cans of plutonium-bearing material with nylon bags. LDPE and PVC are not soluble in the nitric acid dissolver solution used in F-Canyon, so cans bagged using these materials had to be repackaged before they were added to the dissolver. Because nylon dissolves in nitric acid, cans bagged in nylon can be charged to the F-Canyon dissolvers without repackaging, thereby reducing handling requirements and personnel exposure. As part of a program to process RFETS SS and C at SRS, RFETS has also begun to use a nylon bagout material. The RFETS bag materials is made from a copolymer of nylon 6 and nylon 6.9, while the SRS material is made from a nylon 6 monomer. In addition, the SRS nylon has an anti-static agent added. The RFETS nylon is slightly softer than the SRS nylon, but does not appear to be as resistant to flex cracks initiated by contact with sharp corners of the inner can containing the SS and C.2 FB-Line Operations has asked for measurement of the effects of radiation and heating on these materials. Specifically, they have requested a comparison of the material properties of the plastics before and after irradiation, a measurement of the amount of outgassing when the plastics are heated, and a calculation of the amount of radiolytic gas generation. Testing was performed on samples taken from material that is currently used in FB-Line (color coded orange) and at RFETS. The requested tests are the same tests previously performed on the original and replacement nylon and LDPE bag materials.3,4,5. To evaluate the effect of irradiation on material properties, tensile stresses and elongations to break w ere compared for unirradiated and irradiated samples. A standard ASTM method for the measurement of tensile plastic properties6 was used. Properties were measured both parallel to the direction of machining (MD) and transverse to the direction of machining (TD). Tensile strength measurements showed that the ultimate strengths of the SRS replacement bag material decreased by 22 percent in the MD orientation and 17 percent in the TD orientation after irradiation with 5 x 106 rad, a dose equivalent to about 8-9 months exposure in a plutonium can. For the RFETS material, the decreases were 23 percent in the MD orientation and 56 percent in the TD orientation. Although the 5 x 106 dose significantly degraded the properties of both materials, their strengths remained superior to those previously measured for LDPE,4 even after irradiation. Elongations to break also decreased, especially for the SRS material. The decrease for the SRS material were 86 percent in the MD orientation and 95 percent in the TD orientation. For the RFETS material, elongations to break decreased at least 18 percent in the MD orientation and 29 percent in the TD orientation. When samples of both the SRS and RFETS materials were heated in a sealed container to the maximum expected storage can temperature of about 95 C, they outgassed at pressures ranging from 16 to 22 psig. These pressure increases would not cause a can to fail. Using a representative G value of 1.6 molecules/100 ev, the amount of outgassing due to radiolysis was calculated to be negligible. In conclusion, it may be stated that the results of the strength tests and the outgassing measurements and calculations demonstrate that the SRS and RFETS replacement bag materials are acceptable substitutes for LDPE with respect to mechanical properties.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC09-96SR18500
- OSTI ID:
- 4936
- Report Number(s):
- WSRC-TR-98-00293; TRN: US0101591
- Resource Relation:
- Other Information: PBD: 3 Nov 1998
- Country of Publication:
- United States
- Language:
- English
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