ML20058J725
| ML20058J725 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 08/02/1982 |
| From: | Steptoe P CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.), ISHAM, LINCOLN & BEALE |
| To: | Atomic Safety and Licensing Board Panel |
| References | |
| ISSUANCES-OL, ISSUANCES-OM, NUDOCS 8208110187 | |
| Download: ML20058J725 (35) | |
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UNITED ETATES OF AMERICA l' NUCLEAR REGULATORY COMMISSION , ; ,,
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^9 n , ,;cJ BEFORE THE ATOMIC SAFETY AND LICENSING BOARDe. q
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~ v; A .Cli In the Matter of )
) Docket Nos. 50-329-OM CONSUMERS POWER COMPANY ) 50-330-OM '
) 50-329-OL (Midland Plant, Units 1 ) 50-330-OL' and 2) )
APPLICANT'S RESPONSE TO NEW CONTENTION 14 OF MARY P. SINCLAIR AND REQUEST FOR ADDITIONAL TIME TO RESPOND TO NEW CONTENTION 13 On July 23, 1982 Intervenor Sinclair submitted two additional new contentions in-this proceeding. ,,
Sinclair New Contention 13 states:
- 13. Albert T. Howard, formerly of the Zack Company, has provided a signed affidavit stating that substandard materials have been used in the heating and ventilating system of the Midland nuclear plant that will not be able to withstand the temperatures and the radioactive and chemical environments that are part of the operating l
conditions for the Midland nuclear plant. Since these materials that went into the ductwork are built-in all through the plant, including all safety related structures, no assurance cah.be given for the safe operation of this plant as far as the workers or surrounding population is concerned.
Ms. Sinclair did not provide a copy of the re-ferenced affidavit of Albert T. Howard, which apparently forms the I
i only basis for this contention. Applicant did not have a copy of this affidavit, nor was it able to obtain a copy from l
8208110167 820802 D
PDR ADOCK 05000327 G PDE
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' the NRC Staff until August 2, 1982.b! Accordingly, Applicant was not able to respond to Ms. Sinclair's new contention 13 within five days from service, as provided by this Board's Memorandum and Order (Telephone Conference Call of May 5, 1982). Applicant respectfully requests permission to respond to new contention 13 at the prehearing conference on August 12.
Sinclair New Contention 14 states:
- 14. The issue of synergism between chemicals and radiation (Contention 55, Contentions of Mary Sinclair, 1978) must be re-opened based on a new study. Scientists at Sandia National Laboratory, Albuquerque, New Mexico, have conducted tests spon'sored by the Nuclear Regulatory Commission on polymer caole insulation and jacketing used in nuclear power containment buildings."- '(Industrial Research and Development, June, 1982) They have found that long-term low doses of gamma radiation degrades many **
polymers more than do equal doses administered at higher rates in shorter testing times. Besides the dose rate effect, the researchers have also found.that synergistic effects can occur when polymers are exposed to radiation
- l and mildly elevated temperatures. Dr. Roger Clough, of Sandia National Laboratory, has stated that the present testing method underestimates the long-term effects of radiation exposure on polymers by not t; king into account l
l
-1/ Isham, Lincoln & Beale had received a copy of the Howard affidavit from another client, which received it from the NRC. However, that client told IL&B that it could not communicate the contents of this affidavit to Applicant without the permission of the NRC Staff. The IL&B attorneys l presently working on the Midland case therefore did not read l the Howard affidavit until informed by Mr. Paton on the I afternoon of august 2, 1982 that the Howard affidavit could
[
be communicated to CPCo. The Howard affidsvit is 27 pages in length and therefore resists hurried review.
l
' dose rate effects and synergisms that display themselves only in 1cnger tests. Thi's study indicates that the useful life of the plant will be shortened considerably because of this problem. It also confirms our earlier contention that chemical compounds such as polymers (and, therefore, human and other biological systems which can also be classed as organic polymers) ~ will be adversely effected through synergistic action with low Tevel radiation to a degree that is much greater than the present standards would indicate. Therefore, this plant's operation will have an unacceptable adverse health effect on the people of this region as well as workers in the plant.
This Licensing Board in its Special Prehearing Con-ference Order dated February 23, 1979 . (at p. 12) dismissed Sinclair Contention 55 on the grounds that synergism was thoroughly considered in the construction permit hearing and therefore relitigation of this issue is barred by the doctrine of res judicata. See Consumers Power Company (Midland Plant, Units 1 and 2), LBP-72-34, 5 AEC 214, 226 (1972) ; ALAB-123, 6 AEC 331, 344-45 (1973).
The article in Industrial Research and Development does not provide any. basis for reopening the record on l synergism. It appears that the Sandia study referred to in the Industrial Research and Development is NUREG/CR-2156, attached l hereto. Even a casual look shows that the " low level radiation" l
l which Sandia found acts synergistically with elevated temperatures to degrade polymer cable insulation was 4,000-4,500 Rad /hr, far above the lethal dose for humans and, of course, far above present NRC radiation protection standards. See NUREG/CR-2156 at p. 9 and p. 11, Table 1.
t 1
These results may have relevance for equipment qualification testing. However, equipment qualification methods including synergistic effects and aging are the subject of a current rulemaking and therefore can not be accepted for litigation in this proceeding.
47 Fed. Reg. 28363 (June 30, 1982).
The Sandia report hardly provides a basis for this proposed contention to the extent it seeks to challenge present NRC radiation protection standards, and questions the
" health effect" of radioactivity released by the plant on workers and the general public.
In view of the obvious irrelevance of the Sandia test conditions to present NRC radiation protection standards, ..
this Board need not grapple with the issue of whether people and other biological systems.can properly be cl.assified as
" organic polymers", as Ms.- Sinclair asserts.
Respe ull m tted,
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J Ph(Jip P.
o W[ ' ty teptoe '-
Isham, Lincoln & Beale 3 First National Plaza 52nd floor Chicago, Illinois 60602 DATED: August 2, 1982 l
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. UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION .n
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BEFORE THE ATOMIC SAFETY AND LICENSING BOARD . . . .
9 In the Matter of )
) Docket Nos. 50-329-OM CONSUMERS POWER COMPANY ) 50-330-OM
) 50-329-OL (Midland Plant, Units 1 ) 50-330-OL and 2) )
CERTIFICATE OF SERVICE I, Philip P. Steptoe, one of the attorneys for Consumers Power Company, hereby certify that a copy of
" Applicant's Response to Additional New Contentions by Mary P. Sinclair" was served upon all persons shown in the attached service list by deposit in the United St;ates mail, '
. first class, this 2nd day of Augus .
82.
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0 Phili'p P.
m Ste]} toe Mn'
- SUBSCRIBED a d SWORN before me this day of August, 1982.
m >d 11, l Notary Public l My Commission Expfres January,161983 l
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SERVICE LIST Frank J. Kelley, Esq. Steve Gadler, Esq.
. Attorney General of the 2120 Carter Avenue State of Michigan St. Paul, Minnesota 55108 Carole Steinberg, Esq.
Assistant Attorney General . Atomic Safety & Licensing Environmental Protection Div. Appeal Panel 720 Law Building U.S. Nuclear Regulatory Cortm.
Lansing, Michigan 48913 Washington, D. C. 20555 Myron M. Cherry, Esq. Mr. C. R.'Stephens Cherry & Flynn Chief, Docketing & Services Suite 3700 U.S. Nuclear Regulatory Comm.
Three First National Plaza Office of the Secretary Chicago, Illinois 60602 Washington, D.C. 20555 Mr. Wendell H. Marshall Ms. Mary Sinclair 4625 S. Saginaw Road 5711 Summerset Street Midland, Michigan 48640 Midland, Michigan 48640 Charles Bechhoefer, Esq. William D. Paton, Esq.
Atomic Safety & Licensing Counsel for the NRC Staff Board Panel U.S. Nuclear Regulatory Comm.
U.S. Nuclear Regulatory Comm. Washington, D. C. 20555 Washington, D. C. 20555 Atomic Safetyon Licensing Dr. Frederick P. Cowan .
Board Panel 6152 N. Verde Trail U.S. Nuclear Regulatory Comms-Apt. B-125 Washington, D. C. 20555 Boca Raton, Florida 33433 Barbara Stamiris Admin. Judge Ralph S. Decker 5795 North River Road Route No. 4, Box 190D Route 3 Cambridge, Maryland 21613 Freeland, Michigan 48623 D. F. Judd Jerry Harbour Babcock & Wilcox Atomic Safety & Licensing P. O. Box 1260 Board Panel Lynchburg, Virginia 24505 U.S. Nuclear Regulatory Comm.
. Washington, D. C. 20555 James E. Brunner, Esq.
Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201 l
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RADIATION-THERMAL DEGRADATION OF PE AND PVC:
MECEANISM OF SYNERGISM AND DOSE RATE EFFECTS I .
{
1 Roger L. Clough and Kenneth T. Gillen l
Date Published: June 1981
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Sandia National Laboratories Albuquerque, New Mexico 87185 operated by Sandia Corporation
. for the U. S. Department of Energy l Prepared for Electrical Engineering Branch Division of Engineering Technology
- Office of Nuclear Regulatory Research **
Washington, DC 20555 Under Interagency Agreement DOE 40-550-75 NRC FIN No. A-1051-0
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- t t TABLE OF CONTENTS PAGE Abstract 7 Keywords 8 Introduction 8 Results 9 Discussion i 17 Experimental ,
20 Acknowledgement i 21
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References ; 21 l '.
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12 Figure 3 14 Figure 4 16 Table 1 11 Table 2 17 I
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ABSTRACT Polyethylene insulation and polyvinyl chloride jacketing materials that had been in use in a nuclear application were recently found to be substantially deteriorated. The damage had occurred under conditions where both the total estimated dose (about 2.5 Mrad) and the operating temperatures (about 43 C average) seemed relatively moderate. These results prompted us to initiate a program to study polyvinyl chl'oride and polyethylene degradation under conditions of combined y-radiation and elevated temperature environments. A number of interesting aging effects were observed, including 1) a striking synergism between radiation and temperature and 2) strong dose-rate dependent effects which occur over a wide -
range of dose rates. The aging effects are explained in terms of a chain branching degradation' mechanism involving thermally induced breakdown of peroxides which are formed in reactions initiated by the radiation. Evidence for this mechanism is derived from infrared spectra, from sequential radiation-elevated temperature' experiments including experiments under f inert atmosphere, from activation energy estimates and from a new technique involving treatment of intact samples with PH f r chemical reduction of peroxides. The results of our 3
studies raise significant doubts about the utility of earlier compilations which purportedly serve as radiation life expect-ancy guides by indicating " tolerable radiation doses" for a -
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variety of polymers.
- 7
KEYWORDS Polymer degradation; radiation effects, dose rate effects; synergistic effects; radiation-thermal interactions; hydro-peroxide breakdown; polyethylene; polyvinylchloride; oxidative
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sC1ssion.
INTRODUCTION -
Lengths of cabling material which had been in service in a nuclear application for a period of 12 yr (Sandia, 1977) . were recentiy examined and found to exhibit substantial deterioration.
This cabling consisted of polyethylene (PE) insulation having a thin nylon sleeve, with an outer jacket of polyvinyl chloride (PVC). In certain areas, the polyethylene was visibly embrittled; h .
it readily cracked and fell off the wire when subjected to ..
bending. Adjacent areas along the s me cable exhibited no I apparent damage and were found by tensile test's to possess good mechanical proper, ties (elongation about 500%). Tensile tests revealed that for areas of the cable showing strong PE embrittlement, the PVC jacketing also showed decreased elonga-tion (as low as 170%, compared with 300% for undamaged areas) .
Dosimetry mapping revealed a correlation between damaged areas of the cable, and areas of elevated radiation intensity within the application environment. However, the maximum dose rate experienced was estimated to be about 25 rad /hr, giving a I total 12 yr integrated dose of about'2.5 Mrad. The ambient temperature during reactor operation was estimated to average about 43 C. The extent of damage incurred by the cable was 8
rather curpricing in light of industry guidalinas which suggast only inor effects at this level of total absorbed dose.
The discovery of the damaged cabling prompted us to under-take an investigation of the radiation-thermal aging behavior of these PTterials. Radiation experiments were performed on PE insulation and carbon black filled PVC jacketing similar in formulation to the degraded materials from the nuclear applica-tion. Samples were irradiated using a Co-60 facility which is
) capable of delivering a range.of dose rates and which has provision for temperature regulation. The air atmosphere surrounding the samples was continuously replenished during '
irradiation.
s RESULTS Tensile' elongation data for PE samples aged in environments of: 1) room temperature radiation (4.5 krad/hr, 25 C) , 2) elevated temperature radiation (4. 5 krad/hr, 80 C) 'and 3) elevated temperature in the absence of radiation (80 C) are presented in Fig.'l'. It is seen that the combined effect of radiation and elevated temperature results in dramatically enhanced degradation compared with elevated temperature alone or radiation at room temperature. The joint effect of y-radiation and elevated temperature was also found to occur
~
when the two environments were applied in a s'auential' e fashion, ,
but only when the experiments were performed in th.e order:
radiation at room temperature followed by elevated temperature.
This rapid thermal degradation of preirradiated samples is 9
1 illustrated in Fig. 1 and Table 1. The apparent strong synergism observed with PE was also seen to occur with PVC, when similar aging experiments wer'e performed (see Fig. 2 and Table 1).
A further interesting aging behavior was found when radiation experiments were carried out at 60 C but at a variety of different dose rates. Tensile elongation data from these experiments, performed with PVC, are plotted in Fig. 3 as a function of total absorbed dose. The results demonstrate the existence of a strong dose-rate dependent degradation effect.
PE behaves similarly.
The aging behaviors of the PE and PVC can be understood in terms of a peroxide-mediated-oxidative degradation mechanism. ..
v-Irradiation of the polymers results in bond cleavage giving free radicals, which, in the presence of oxygen, react by a chain mechanism to form oxidation products that include hydro-peroxides (Dole, 1974; Rabek, 1975; Reich and Stivala, 1971).
The hydroperoxides are thermally labile; breakdown yields more free radicals which can initiate new chain reactions with oxygen to give further oxidation including formation of more hydroperoxides. The radical steps set in motion during the ,
course of the reactions include pathways which lead to polymer chain scission and crosslinking. Evidence for formation and subsequent breakdown of hydroperoxides in the thermo-oxidative degradation of PE has been cited before (Cheng, Schilling and Bovey, 1976; Decker, Mayo and Richardson, 1973; Decker, 1976).
10
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100 200 AGING TIME (Days) ,.,
l- Fig. 1. Aging of PE in various environments.
Sample tensile elongation divided by initial (unaged) elongation is plotted l
Versus aging time.
f TABLE 1 Sequential Aging Experiments:
Tensile Elongation Data EXPERIMENT * , e/eg**
1 i Unaged, Material 1.0 1 0.05 1.0 10.1 0.68 + 0.09 y; no subsequent T 0.80 + 0.04 T (in air) ; y (in air) 0.68 7 0.04
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- y = gamma radiation - 4.5 krad/hr (for PE), 4 krad/hr (for PVC) - both at 250C for 83 days l T = thermal exposure of 80oc for 83 days
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Fig. 2. Aging of PVC in various environments. ,
Sample tensile elongation divided by' initial (unaged) elongation is plotted versus aging time.
Several lines of evidence supporting the importance of such a peroxide-mediated oxidative degradation mechanism are outlined below. Infrared spectra obtained on polyethylene samples from our combined radiation-elevated temperature environment experiments showed a correlation titween deteriora-tion in mechanical properties and the formation and growth of strong peaks in the carbonyl region (1 ,,x N 1710 cm-1).
Spectra obtained at intervals along the cable from the nuclear applica-tion showed that embrittled regions exhibited strong carbonyl absorption bands essentially identical to those obtained in
the lcboratory aging exparimnnts; in contrast, undamngcd portions of the cable showed no carbonyl absorption. Representative IR spectra are given in Fig. 4. The close match obtained between the carbonyl bands of samples from our aging experiments and the carbonyl bands of the degraded cable under investigation provides evidence that the aging mechanism in the laboratory experiments parallels that in the use environment.
Further confirmation of the importance of oxygen to the degradation came from experiments performed in the simultaneous environment of radiation and elevated temperature, but under an inert atmosphere of nitrogen; here, the degradation was found to be completely blocked. For the secuential experiments, an oxidative degradation mechanism involving substantial amounts of thermally-induced peroxide breakdown, as ' described earlier, would require the participation of oxygen in both the radi*ation step and the thermal step. To test this, inert atmosphere
' secuential aging experiments were performed as follows: 1) ,
l l
irradiation at room temperature in nitrogen followed by l elevated temperature treatment in air; 2) irradiation at room temperature.in air followed by elevated temperature treatment in nitrogen. In both cases the mechanical degradation was found to be blocked, in contrast to the rapid deterioration resulting when the sequential experiment is performed with an air environment throughout (see Table 1). Thus in the case of the first inert atmosphere sequential ex.periment, the lack of oxygen in the radiation environment prevented the radicals generated by the radiation from inducing oxidative 13 i-- . _ _ - - _-. _- ___
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chain reactions, and hence from forming any peroxides. In the second inert atmosphere sequential experiment, the lack i
o'f oxygen during the elevated temperature treatment prevented the radicals generated by thermal breakdown of previously formed peroxides from inducing further oxidative chain reactions. In 1
either case, radicals generated in the absence of available oxygen largely disappear by recombination and disproportionation reactions.
1.0 , ,
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C 0.5 -- -
c 938 krad/hr ,
3.5 356 krad/hr 17.6 71 krad/hr krad/hr I '
0.0 O 20 40 60 RADIATION DOSE (MRAD)
Fig. 3. Aging of PVC at 60 C at a series of radiation dose rates. Sample tensile elongation divided by initial (unaged) elongation is plotted versus total
- absorbed radiation dosage.
14
. Tosproyida furthar cvidenes for the role of paroxidos in the degradation effects observed, a chemical technique was developed.
This technique is based on an' analytical solution chemistry method in which hydroperoxides are reduced to alcohols by treatment with triphenylphosphine (Mair and Hall, 1971). In our experiments, we treated intact polymer specimens with gaseous PH 3
f r 24 hr. The PH 3 diffuses into the polymer to react with existing peroxide sites. Unreacted PH 3 is then allowed to diffuse out of the sample. Sequential aging experiments were performed in which polymer samples were y-irradiated at 25 C, treated with PH 3, then exposed to an elevated temperature. The results (Table 2) show that the thermally-induced mechanical degradation was blocked, in contrast to the result for samples identically aged except for omission of the PH3 treatment.
Additionally, infrared analysis of the samples that were irradiated and then treated with PH 3 showed that subsequent thermal treatment resulted in no change in the carbonyl absorption, whereas strong carbonyl growth was observed during l thermal treatment of samples similarly irradiated but not treated with PH 3*
Further sequential experiments were performed in which samples were irradiated at 25 C, and then thermally aged at i
several temperatures (60 C, 70 C, and 78 C in the case of PE; 70 C, 78 C and 90 C in the case of PVC). An Arrhenius plot made to estimate the activation energy of the' thermally-induced degradation step gave E, = 16 1 3 kcal/ mole for PE, These numbers correspond i and E, = 23 1 3 kcal/ mole for PVC.
1.
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well withl activation energies for bimolecular decomposition of hydroperoxides in solution (which largely range between 15 and 26 heal / mole) (Chien, 19 7 5 ; Hiatt , -19 71) , and are comparable to values for the thermo-oxidative degradation of polymers at low temperatures (Gilroy , 1979 ; Howard and Gilroy, 1975) . The data are not consistent with activation energies for oxygen diffusion in polymers (E a 10 kcal/ mole (Stannett, 1968)).
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2000 1600 1200 800' 2000 1600 1200 000 WAVENUMBERS WAVENUMBERS Fig. 4. FTIR spectra of PE insulation from laboratory aging studies and from the cable section which had been in the nuclear environment for 12 yrs: 1) unaged sample (c/eo =0 1.0); 2) sample aged at 42 krad/hr, 90 C to a total dose of 7.1 Mrad (e/eo= .43); 3) sample aged at 42 krad/hr, 900C to a total dose of
- 17. 9 Mrad '(e/co = .16); 4) section of cable from nuclear application which did not show mechanical damage (e = 5021) ; 5) section of cable from nuclear application which was 16 highly embrittled (e N 01).
TABLE 2
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Saquantial Exparimsnts With cnd Without .
Tensile Elongation Data PH3:
EXPERIMENT
- e/e g**
~
Unaged Material 1.0 + 0.05 1.0 + 0.1 y 0.74 7 0.04 0.71 7 0.08 y; T 0.38 7 0.03 0.03 7 0.03 y; PH 3; 0.74 [ 0.04 0.75 [ 0.08
- y = gamma radiation - 4.5 krad/hr (for PE), 4 krad/hr (for PVC) both at 25 0 C for 96 days in air T = thermal ex osure of 80 0C for 25 days in air 0
PH3 = 1.4 x 10 Pa (200 psi) of PH3 at 25 C for 1 day Sample tensile elongation divided by initial elonga-tion. eg = 310% for PVC; eo = 540% for PE DISCUSSION The increased production of radicals due to time dependent thermal breakdown of peroxides accounts for then.aging ~ behaviors l
observed in both our laboratory experiments and under the ,,
conditions of the nuclear application. The mechanism is variously manifested as an apparent radiation-elevated temperatur synergism, as an ordering effect in sequential aging experiments, .
and as a dose rate efiect. (The latter results from the fact that at progressively lower dose rates, the material simply has a longer time period over which the thermally-induced breakdown can occur. ) Thus, the degradation of the cable material which had experienced only 2.5 Mrad at 43 C during its 12 yr service life could be viewed in terms of either of two empirical terminologies: 1) an apparent " synergistic inter-action" involving a moderate radiation dose in combination with a moderatel'y elevated temperature during a long time period, or 2) a " dose rate effect."
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The occurrence of the aging effects described above is cuite significant for understanding and predicting material ~
~
lifetimes in radiation environments. Comprehensive studies made in the past have often tended to overlook the type of aging phenomena described here. For example, CERN has generated extensive radiation aging data during the past decade for a wide variety of polymers; this data was compiled and published as a " Selection Guide to Organic Materials for Nuclear Engineering" (Schonbacher and Stolarz-Izycka, 1979; Vandevoorde and Restat, 1972). The data in these' publications indicate that radiation effects on mechanical properties of PVC and PE should be virtually nonexistent for the 2.5 Mrad dose s received by the degraded cable under investigation by us. The CERN report (VandeVoorde and Restat, 1972) further presents a Table of " Radiation Stabilities" at temperatures of "> 75 C" in which no major effects of combined radiation and elevated temperature are indicated for PVC or PE. -The reason for the 1
discrepancies between the CERN results and the damage actually found in the nuclear environment is clear in light of Fig. 3, l sinc,e we observe very large dose rate effects over the range of 4 krad/hr to 950 krad/hr. The dose rate in the nuclear application environment (25 rad /hr) is two or'ders of magnitude below the lowest dose rate of Fig. 3, whereas all aging tests performed by CERN were apparently done at 10 Mrad /hr, an order of magnitude higher th'an the highest dose rate shown in Fig. 2. At such high dose rates, radiation-thermal synergisms Clearly, and/or dose rate effects were simply never observed.
2 18
, for materials such as PVC and PE wharo the tima dcpandant peroxide breakdown.can play a major role in the degradation mechanism, the total " tolerable dose" for a given material will be critically dependent upon the environmental temperature and the time period over which the dose is ' administered. For such materials, radiation degradation predictions arrived at from high dose rate experiments are meaningful only at the same l dose rate employed in the test; generalized statements about a ,
f material's " tolerable dose" are meaningless. I Experimental observations made during the past three decades on radiation experiments performed under nitrogen or vacuum have led to a general conclusion (often cited in review articles) (Chapiro, 1962; Makhlis, 1975) that dose rate effects
- n. ,
are not important under inert atmosphere. Clearly this con- i clusion is not valid for radiation experiments in the presence _ .
of oxygen.
The evidence gathered in the present study indicates I that a predominant cause of the observed dose rate effects for PE and PVC results from the peroxide-breakdown m'echanism.
Other effects such as oxygen diffusion (Schnabel, 1978) also could play some contributing role here.
Whether peroxide breakdown and/or oxygen diffusion become important factors in determining the degradation rate will depend, in the general case, on the material type, the specimen geometry, and the particular environmental conditions involved.
Two additional consequences of peroxide breakdown which relate to material lifetimes and to aging predictions are worth mentioning. First, the buildup of peroxides at 19 l
l i
moderate temperatures means it is possibiri that a ap_lymmric material could ba eged into a condition of low apparent damage, yet be preconditioned to a state of susceptibility to rapid _
deggadation ir, the event of an inc.aase in ambient temperature.
~
Second, the strong ordering effect in the sequential aging experiments is of practical consequence for aging studies since sequential aging experiments have been used in the past in an effort to replicate usage environments having both radiation and elevated temperature (IEEE Inc. , 1979) ; such tests have often been designed without regard to ordering.
EXPERIMENTAL Radiation dosimetry was performed using a Victoreen Model 550 Radocon III Integration / Rate Electrometer. n, The resulting dose rates were verified by the thermoluminescen~ce ,,
method using CaF 2 wafers. Tensile elongation tests were per-formed using an Instron Model 1020. Fourier Transform Infrared spectra were obtained on KBr pellets made from polymer samples that had been ground at -196 C. A Nicolet Model 7199 FTIR spectrometer was employed. For inert atmosphere experiments, samples were held under. vacuum for 24 hr, then sealed under nitrogen. Treatment of samples with PH 3 was carried out at ambient temperature at 200 psi in a Parr Bomb for a period of 24 hr. Samples were left standing 3 days in air prior to elevated temperature treatment. .
20 8
O
ACKNOWLEDGEMENT The authors are grateful to Dave Haaland for performing the FTIR spectroscopy.
REFERENCES Chapiro, A. (1962). Radiation Chemistry of Polymeric Systems.
Wiley, New York. p. 361.
Cheng, H. N., F. C. Schilling and F. A. Bovey (1976). C-13 nuclear magnetic resonance observation of the oxidation of polyethylene. Macromolecules, 9, 363.
Chien, J. (1975). Hydroperoxides in degradation and stabilization of polymers. In G. Geuskens (Ed.),
Halsted Press, Degradation and Stabilization of Polymers.
New York. p. 95.
Decker, C., F. Mayo and H. Richardson (1973). Aging and de-gradation of polyolefins. III. Polyethylene and ethylene-propylene copolymers. J. Polvm. Sci., Polym. Chem. Ed.,
11, 2879.
Decker, C. (1976). Oxidative degradation of poly (vinylchloride) .
J. Accl. Polym. Sci., 20, 3336.
Dole, M. (1974). Radiation chemistry of polyethylene. In M.
Burton and J. Magee (Eds.), Advances in Radiation Chemistry, Vol. 4, Wiley, New York. p. 307.
Gilroy, H. M. (1979). Long term photo- and thermal oxidation
'of polyethylene. In R. B. Eby (Ed.), Durability of Macromolecular Materials, American Chemical Society, Washington, DC. Chap. 5, p. 62.
Hydroperoxides. In D. Swern (Ed.), Organic Hiatt, R. (1971).
Peroxides, Vol. II, Wiley, New York. Chap. 1, p. 94.
Howard, J. B. and H. M. Gilroy (1975). Some observations on the long term behavior of stabilized polyethylene.
Polym. Eng. Sci., 15, 268.
IEEE, Inc. (l~974). IEEE standard for qualifying class lE Institute equipment for nuclear power generating statio'ds.IEEE Std.
of Electrical and Electronics Engineers, Inc.,
(323-1974), New York.
Mair R. and R. Hall (1971). DeterminationTreatise of organic percxides.
on In I. Kolthoff and P. Elving (Eds.),
21
Analytical Chnnistry, Wiley, New York. Chap. 14, pt. 2,
- p. 295.
Makhlis, F. (1975). Radiation Physics and Chemistry of Polymers, Halst'ed Press, New York. p. 150.
Rabek, J. (1975). Oxidative degrad'a tion of polymers. In C.
Bamford and C. Tipper (Eds.), Comprehensive Chemical Kinetics, 14, Degradation of Polymers, Elsevier, Amsterdam.
Chap. 4, p. 425.
Reich, L. and S. Stivala (1971). Elements of Polymer Decradation.
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Sandia (1977). Qualification Testing Evaluation Program Light Water Reactor Safety Research Quarterly Report, Oct.-Dec.
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Schnabel, W. (1978). Degradation by high energy radiation.
In H. H. G. Jellinek (Ed.), Aspects of Degradation and Stabilization of Polymers. Elsevier, Amsterdam. Chap. 4, pp. 169, 172.
Schonbacher, J. and A. S.tolarz-I:ycka (1979). Compilation of Damage Test Data. CERN 79-4, Geneva, n.
Stannett,V. (1968). Simple gases. In J. Crank and G. Park (Eds.), Diffusion in Polymers. Academic Press, New York. p. 41.
VandeVoorde, M. H. and C. Restat (1972). Selection Guide to Organic Materials for Nuclear Engineering.
CERN 72-7, Geneva.
O m
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