Comprehensivte Testing to Measure the
I .S,es poqsb$of Juorocarjhon Rubber (FKM)
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Paul J. l)lifrey and Denn~s'L. Bolton
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"'P'''V'J----J Sandia National Laboratories
Albuquet#e, New Mexico 87185 and Livermore, California 94550
Sandi#s a multiprogram laboratory operated by Sandia Corporation,
a Lockheed Martin Company, for the United States Department of
Ene{gy under Contract DE-AC04-94AL85000.
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1' 1~1 Sandia National laboratories
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SAND2000-0325
Unlimited Release
Printed February 2000
COMPREHENSIVE TESTING TO MEASURE THE RESPONSE OF
FLUOROCARBON RUBBER @lCM) TO HANFORD TANK WASTE SIMULANT
Paul J. Nigrey and Dennis L. Bolton ~.
Transportation Safety and Security Analysis Department
Sandia National Laboratories
P. O. BOX5800
Albuquerque, NM 87185-0718
Abstract
This report' presents the findings of the Chemical Compatibility Program
developed to evaluate plastic packaging components that may be
incorporated in packaging mixed-waste forms for transportation. Consistent
v@h the methodology outlined in this report, we performed the second phase
of this experimental program to determine the effects of sirnulant Htiord
tank mixed wastes on packaging seal materials. That effort involved the
comprehensive testing of five plastic liner materials in an aqueous mixedwaste
simulant. The testing protocol involved exposing the materials to
-143,286,571, and 3,670 Krad of gamma radiation and was followed by 7-,
14-, 28-, 180-day exposures to the waste simulant at 18, 50, and 60"C.
Fluorocarbon (FKM) rubber samples subjected to the same protocol were
then evaluated by measuring seven material properties: specific gravity,
dimensional changes, mass changes, hardness, compression set, vapor
transport rates, and tensile properties. From the analyses, we determmed
that FKM rubber is not a good seal material to withstand aqueous mixed
wastes having similar composition to the one used in this study. We have
determined that FICM rubber has limited chemical durability after exposure
to gamma radiation followed by exposure to the Hdord tank sinmkmt
mixed waste at elevated temperatures above 18"C.
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ACKNOWLEDGMENTS
The support of our sponsor, the U.S. Department of Energy, Office of Transportation,
Emergency Management, and Analytical Services, EM-761, is gratefully appreciated.
Specifically, the encouragement provided by Arnie Justice and Mona Williams in the DOE
National Transportation Program Office is aclmowledged. The technical assistance provided
by Tatianna G. Dickens was very much appreciated.
ii
Contents
Introduction ............................................................................................................................... 1
Experimental ............................................................................................................................. 4
Materials ........................................................................................................................ 4
Simulant Preparation ..................................................................................................... 4
Sample Preparation ....................................................................................................... 5
Sample Quantities ......................................................................................................... 6
Sample radiation ......................................................................................................... 7
Sample Exposure to Simulant ....................................................................................... 8
Evaluation Approach .....................................................................................................
Results .................................................................................................................................... 1;
Specific Gravity ........................................................................................................... 12
Dimensional Properties ............................................................................................... 14
Hardness Propetiies ..................................................................................................... 16
Compression Set .......................................................................................................... 19
Vapor Transport Rates ................................................................................................ 23
Tensile Propeties ........................................................................................................ 25
Tensile Sfien@h ............................................................................................... 26
Elongation at Break or Ultimate Elongation ................................................... 30
Tensile Stress or 100% Modulus ..................................................................... 33
Discussion ............................................................................................................................... 37
Conclusions ............................................................................................................................. 45
References ............................................................................................................................... 46
Appendix A FKM Rubber Material Information .................................................................... 49
~; Appendix B FKM Rubber Specific Gravity Data ................................................................... 50
Appendix C FKM Rubber Mass Data ..................................................................................... 51
Appendix D FKM Rubber Dimensional Data ......................................................................... 52
Appendix E FKM Rubber Hardness Data ................................................................................ 54
Appendix F FKM Rubber Compression Set Data .................................................................. 55
Appendix G FKM Rubber Vapor Transport Rate Data ........................................................... 56
Appendix H FKM Rubber Tensile Strength Data ................................................................... 57
Appendix I FKM Rubber Ultimate Elongation Data ............................................................. 58
Appendix J FKM Rubber Tensile Stress Data ....................................................................... 59
Figures
1. Comprehensive Seal Testing Strategy .................................................................................... 11
2. Specific gravity (S.G.) changes in FKM rubber after exposure to -0, 143,286,571,
and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14 days,
(c) 28 days, and (d) 180 days to the aqueous simulant waste at 18,50, and 60"C ................. 12
3. Mass changes in FKM rubber after exposure to approximately O, 143,286,571, and
3,670 Krad of gamma radiation followed by exposure for(a) 7 days, (b) 14 days, (c)
28 days, and (d) 180 days to the aqueous simulant waste at 18,50, and 60°C ...................... 14
4. Volume (Vol.) changes in FKM rubber after exposure to -0, 143,286,571, and
3,670 Krad of gamma radiation followed by exposure for(a) 7 days, (b) 14 days,
(c) 28 days, and (d) 180 days to the aqueous simulant waste at 18,50, and 60"C ................. 16
. . .
111
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Figures (continued)
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Hardness charges in FKM rubber after exposure to -0, 143,286,571, and 3,670
Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14 days, (c)28
days, and (d) 180 days to the aqueous simulant waste at 18,50, and 60°C ............................ 18
Compression set fixture: (a) a partly assembled fixture with the 4.5-mm spacer bars
and rubber samples and (b) an assembled fixture with rubber samples ..................................2O
Compression set (C.S.) changes in FKM rubber after exposure to -143,286,571,
and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14 days,
(c) 28 days, and (d) 180 days at 18,50, and 600C...................................................................2l
Compression set (C.S.) changes in FKM rubber after exposure to -0, 143,286,571,
and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14 days,
(c) 28 days, and (d) 180 days to the aqueous simulant waste at 18,50, and 60"C,
respectively ..............................................................................................................................22
Vapor Transmission Rate Cells ...............................................................................................23
VTR for FKM rubber after exposure to -0, 143,286,571, and 3,670 Krad of gamma
radiation followed by exposure for (a) 7 days, (b) 14 days, (c) 28 days, and (d) 180
days to the aqueous simulant waste at 18,50, and 60°C, respectively. ..................................24
Tensile strength (T. S.) changes in FKM rubber after exposure to -143,286,571,
and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14 days,
(c) 28 days, and (d) 180 days at 18,50, and 600C...................................................................28
Tensile strength (T. S.) changes in FKM rubber after exposure to -0, 143,286,571,
and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14 days,
(c) 28 days, and (d) 180 days to the aqueous simukmt waste at 18,50, and 60"C. ................29
Ultimate Elongation (U. El.) changes in FKM rubber after exposure to -143,286,
571, and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14
days, (c) 28 days, and (d) 180 days at 18,50, and 60"C- ........................................................3l
Ultimate elongation (U. El.) changes in FKM rubber after exposure to -0, 143,286,
571, and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14
days, (c) 28 days, and (d) 180 days to the aqueous simulant waste at 18,50, and
600C........................................................................................................................................32
Tensile stress (T. Stress) changes in FKM rubber after exposure to -143,286,571,
and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14
days, (c) 28 days, and (d) 180 days at 18,50, and 60"C. ........................................................34
Tensile stress (T. Stress) changes in FKM rubber after exposure to -0, 143,286,
571, and 3,670 Krad of gamma radiation followed by exposure for (a) 7 days, (b) 14
days, (c) 28 days, and (d) 180 days to the aqueous simulant waste at 18,50, and
Compression set samples exposed for 180 days at 60°C – 286 Krad gamma radiaQon
alone (R23-Bottom) and a combination of 286 Krad gamma radiation and simukmt
(23.Top) ..................................................................................................................................4O
Tensile specimens afier completion of several tests showing cross section of
(a) fracture and (b) len=gh-wise view ......................................................................................42
Summary graph for FKM rubber samples exposed to radiation, simulant, and a
combination of both radiation and simukmt at 18,50, and 60"C............................................43
iv
INTRODUCTION
Hazardous and radioactive materials packaging is designed to facilitate the transport and storing
of materials without" posing 'a threat to the health or property of the general public. U.S.
regulations establish general design requirements for such packaging. While no regulations
have been written specifically for mixed waste packaging, regulations for the constituents of
.
mixed wastes, that is, hazardous and radioactive substances, have been codified by the U.S.
Department of Transportation (U.S. DOT, 49 CFR 173) and the U.S. Nuclear Regulato~
Commission (NRC; 10 CFR 71). The materials of the packaging and any contents must be
chemically compatible. Furthermore, Type A [49 CFR 173.412 (g)] and Type B (10 CFR 71.43)
packaging design requirements stipulate that there be no significant che~cal, galvanic, or other
,. -,-
reaction between the 'materials and contents of the package.
Based on the federal requirements, a Chemical Compatibility Testing Program was developed in
the Transportation Technology Department at Sandia National Laboratories/New Mexico
(SNL/NM). The program attempts to assure any regulatory body that the issue of certain
packaging material compatibility towards hazardous and radioactive materials has been
addressed. This program was dethiled' in a. 1993 milestone repoit' submitted to the Department
of Energy (DOE). The results of this program were reported to the DOE in various unpublished
milestone documents and in a number of externally published papers.2-G
The milestone report Chemical Compatibility Test Plan and Procedure Report (CCTP&PR)
describes a program to evaluate plastic transportation packaging components that maybe used
in transporting mixed waste forms. Consistent with the methodology in the CCTP&PR, the f~st
phase of this experimental program has been completed. This effort involved screening 10
plastic materials in four simulant mixed waste types.' All materials that include "rubber" in
their names are used as seals; the others are used as liners. These plastics were as follows:
Seals
. . butadiene-acrylonitrile copolymer rubber (nitrile),
. epichlorohydrin rubber (EPJ)
. isobutylene-isoprene copolymer rubber (R.@),
. ethylene-propylene rubber (EPDM),
. fluorocarbon @lKM) rubber, and
. styrene-butadiene (SBR) rubber
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Liners
. cross-linked polyethylene (XLPE),
l high-density polyethylene (HDPE),
e fluorocarbon (Kel-F~
o polytetrafluoroethylene (Generically PTFE or Teflon@),
e polypropylene (l?P).
The selected simulant mixed wastes were
l aqueous alkaline mixture of sodium nitrate and sodium nitrite,
l chlorinated hydrocarbon mixture,
* sirrmlant liquid scintillation fluid, and
e mixture of ketones.
The iirst phase of the testing protocol involved exposing the materials to 286,000 rad (286
Krad) of gamma radiation followed by 14-day exposures to the waste types at 60"C. After
radiation and chemical exposure, the seal or rubber materials were tested using ~apor ~ransport
gate (VTR) measurements, while the liner materials were tested using specific gravity as a
metric. For these tests, screening criteria of-1 @hr/mz for VTR and a specific gravity change
of 10°/0 were used. Materials that failed to meet these criteria for all four types of waste were
judged to have failed the screening tests and were excluded from the next phase of this
experimental program. Based on this work, it was concluded that while all seal materials passed
exposure to the aqueous sirnulant mixed waste, EPDM and butyl rubber had the lowest VTRS.
In the chlorinated hydrocarbon simulant mixed waste, only FKM rubber passed tie screening
tests. This means that only FKM rubber would be selected for further testing in the chlorinated
hydrocarbon sirnulant. In both the sirnulant scintillation fluid mixed waste and the ketone
mixture simukmt mixed waste, none of the seal materials met the screening criteria. For
specific gravity testing of liner materials, the data showed that while all materials passed the
screening criteria in the aqueous simukmt, Kel-Fw, HDPE, and XLPE offered the greatest
resistance to the combination of radiation and chemicals.
The next phase of this program was the comprehensive testing of liner materials in the aqueous
simulant mixed waste. Since screening tests showed that all liner materials met the screening
criteria when exposed to the aqueous sirnulant mixed waste, the five liner materials (HDPE,
XLPE, PP, Kel-Fm, and PTFE) were subjected to comprehensive testing. The testing protocol
2
involved exposing the materials to -143, 286, 571, and 3,670 Krad of gamma radiation
followed by 7-, 14-,28-, and 180-day exposures to the waste simulant at 18,50, and 60"C. The
radiation exposure values were calculated based on y-ray dose rate data available to us for the
components of a pump submerged in a specific storage tank at Westinghouse Hadord Co.
These data indicate a maximum y-ray dose rate in the range of 750 to 850 R/h.r. The maximum
dose rate of 850 radhr was used in calculating the dose that container materials will receive
from a cOCo source at Sandia National Laboratories. Using this dose rate, the four doses
described above were calculated for 7-, 14-,28-, and 180-day exposures, respectively. From the
data analyses, the fluorocarbon Kel-P was identified as having the greatest chemical durability
after having been exposed to gamma radiation followed by exposure to the Hdord Tank
simulant mixed waste. The most striking observation from this study was the extremely poor
performance of PTFE when exposed to the higher radiation doses. Even at lower radiation
exposures, PTFE exhibited significant losses in performance. These results were reported as a
Sandia Report.' We also published a synopsis of these test results in the proceedings of MIXED
WASTE '97?
In this report, we present the results of the second phase of testing in this program. It should be
recalled that since all seal materials passed the screening tests in the aqueous simulant mixed
waste, all seal materials would be subjected to comprehensive testing. While earlier studies
investigated the response of EPDM and butyl rubber, this study involved the comprehensive
testing of FICM rubber. The results of comprehensive testing of EPDM and butyl rubber have
been reported to the DOE. A synopsis of the comprehensive test results for EPDM and butyl
rubber was presented at the Fourth Biennial Mixed Waste Symposiumg and at PATRAM '98.10
The comprehensive testing protocol involved exposing FKM to a matrix of four gamma
radiation doses (- 143, 286, 571, and 3,670 Krad), three temperatures (18, 50, and 600C), four
exposure times (7, 14, 28, and 180 days) in the aqueous simukmt. The temperature and
exposure times were based on values found in 49 CFR 173, Appendix B. It should be
mentioned that while some FKM rubber samples were exposed to only the aqueous sinmhmt,
other samples were only irradiated, and still others were irradiated and then exposed to the
simukmt to mimic the action of mixed wastes. Following exposure to these conditions, the
FKM rubber samples were evaluated by measuring seven material properties: specific gravity,
dimensional changes, mass changes, hardness, compression set, V~ and tensile properties.
3
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EXPERIMENTAL
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In this section, we describe the experimental aspects of the comprehensive phase of the
chemical compatibility testing program for elastomeric materials.
Materials
The selected material, .FKM rubber, is an elastomer having known chemical resistance to brake
fluids, alcohols, and water. FKM rubber is also known by various tradenames. The most
widely recognized product is VITON@ manufactured by DuPont. Appendix A provides
additional information on FKM, including its properties.
Simulant Preparation
The simulant mixed waste form used in this testing phase was an aqueous alkaline simulant
Hanford Tank waste developed locally based on more complex formulations used by researchers
at the Hanford site. It was prepared by dissolving 536 g (6.3 moles) of sodium nitrate and 150
g (2.2 moles) sodium nitrite in deionized water (1800 mL) using a 4-L beaker. After these salts
had completely dissolved, 246 g (6.2 moles) sodium hydroxide was added under stirring and
slight heating using a magnetic hotplate (Corning, Model PC-320). To this hot (-70°C) stirred
solution, 51 g (0.30 moles) cesium chloride and 48 g (0.29 moles) strontium chloride were
added. Finally, 96 g (0.9 moles) of sodium carbonate dissolved in 800 mL of deionized water
was added to the solution. This latter addition resulted in the formation of a copious amount of
white precipitate. Based on its insolubility, it is believed that this precipitate is strontium
carbonate. To the resulting mixture was added another 400 mL of deionized water to bring the
total volume of water used to 3 L. After cooling to near ambient temperature, the stirred
mixture was stored in amber glass bottles (Fisher Scientific, 03-327-6). All chemicals used in
the preparation of the waste simulant were American Chemical Society reagent grade chemicals.
The above composition produced a mixture with the following chemical concentrations:
2.1 Molar (M) sodium nitrate
0.7 M sodium nitrite
2.1 M sodium hydroxide
4
0.3 M sodium carbonate
0.1 M cesium chloride
0.1 M strontium chloride