ML19254F321
| ML19254F321 | |
| Person / Time | |
|---|---|
| Issue date: | 10/26/1979 |
| From: | Bennett B NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Butcher E, Danielle Sullivan, Szukiewicz A Office of Nuclear Reactor Regulation, NRC OFFICE OF STANDARDS DEVELOPMENT |
| References | |
| NUDOCS 7911090039 | |
| Download: ML19254F321 (15) | |
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OCT 2 91979 Those on Attacheri List Gentlemen:
Subject:
Summary of Meeting of Qualification Testing Evaluation Research Review Group Enclosed is a summary of the meeting of the Qualification Testing Evaluation (QTE) Research Review Group held on October 5, 1979. The meeting was called to review the status of the Comission-directed connector tests, specifically the facility changes needed to meet the Review Group-specified test conditions.
The Peview Group members agreed with the actions Sandia is taking to upgrade the facility and noted the need to monitor the temperature of the connectors during the dry runs and the actual test.
Sincerely,
~
Gary L. Bennett, Chief Research Support Branch Division of Reactor Safety Research
Enclosure:
as stated 1301 182 79110 9 06M
a"r, e :- _
Addressees for Letter dated D. Sullivan, SD J. Zwolinski, DSS A. Szukiewicz, DSS D. Mcdonald, NRR E. Butcher, D0R F. Rosa, DSS R. Satterfield, DSS M Srinivasan, DSS W. Rutherford, IE V. Thomas, IE E. Blackwood, IE C. Long, DSS T. Dunning, D0R E. Sylvester, D0R R. Ferguson, D0R A. S. Hintze, SD A. Ungaro, DSS W. Haass, DPM M. Taylor, RES S. Hanauer, DSS L. Rubenstein, NRR D. Kirkpatrick, II C. Miller, DSS B. Brooks, MIPC W. Paulson, NRR H. Ornstein, ED0 H. Wilber, IE H. Conrad, DSS S. Ebneter, IE-I NRC PDR (2) File #1-25 D. Nowlin, AL l'.
Bonzon, Sandia D. Dugan, Sandia F. Thome, Sandia R. Saloman, Temple Univ.
W. Von Riesemann, Sandia W. H. Buckalew, Sandia D. Eisenhut, 00R T. Murley, RSR F. Schroeder, DSS R. Denise, DSE R. Vollmer, NRR G. Lainas, PSYB 1301 183
ENCLOSURE SUMARY OF MEETING OF QUALIFICATION TESTING EVALUATION RESEARCH REVIEW GROUP OCTOBER 5, 1979 Introduction The meeting was called by Gary Bennett as a means of informing the QTE Research Review Group about the activities relating to the Commission-directed connector tests and to obtain comments and concurrence from the members on these activities.
A list of attendees is enclosed as Attachment 1 to this enclosure.
Commission Connector Tests Bennett reported on the Sandia activities related to performing the Commission-directed connector tests. An advance copy of his trio reoort (suhinct-Visit tn Sandia Laboratories - September 25-28, 1979, now dated October 15,1979)was distributed to the attendees.
(NOTE: This trip report has since been sent to the QTE Research Review Group along with the other handouts so they are not included with this summary).
Bennett reviewed the test plan and test facility then reported that Sandia had attempted three dry runs on September 25 and 26, 1979. These dry runs were in preparation for performing a LOCA qualification test on two types of electrical connector assemblies from Browns Ferry Unit 3.
In each case the test chamber did not reach the minimum acceptable temperature (161 C) at twa minutes as required by the test plan. After reviews and discussions on Sette.;ber 27, 1979, the following actions for Sandia were agreed to at a joint NRC/Sandia meeting on September 28, 1979:
1.
Install the new 20-kW superheater 2.
Increase the pipe sizes 3.
Install the new one-inch regulator 4.
Develop and use a more sophisticated analytical model of the QTE facility (including calculations of what the final design should be) 5.
Mock up the connectors and cables in the next set of dry runs 6.
Remove and reinstall the chamber head between runs to simulate the insertion of the actual connectors 7.
Install a thermocouple (with spares) in a more central location such that the chamber free-space temperature can be recorded. This will be the test temperaturc 8.
Provide rigid..auntings for the thermocouples 9.
Provide extra diagnostic instrumentation (e.g., pressure taps, turbine meters) only on a non interfereice basis 10.
In parallel, plumb the two new accumulators
- 11. Accelerate the test schedule 12.
Start ordering the McGuire electrical connector assemblies for the next set of tests.
1301 184
. Bennett reported that as of October 4, 1979, Sandia had plumbed in the "new" (20-kW) superheater and the larger, one-inch lines and regulator. A pressure test showed the system had no leaks. Dummy connector loads were to be installed the af ternoon of October 4,1979 with a test scheduled for October 8 or 9, 1979.
In parallel with this work Sandia is assembling the two new accumulators.
The attendees discussed this test and the actions and expressed agreement with the actions. Several of the attendees noted that the thermocouples inside the cans were reading somewhat higher than the " free space" thermocouples.
In view of the possible influence of t:mperature and rate of temperature rise on the performance of the connectors, the attendees suggested that RSR review the logic of using the free space temperature if the temperatures inside the cans deviated from the free space temperature by more than 10 C (above or below).
The new test schedule is shown in Attact. ment 2 to this enclosure. NRR will send a witness to the test.
IE will arrange to have TVA witness the tcst.
Miscellaneous Bennett distributed advance copies of the Sandia report on "A Study of Strong Synergism in Polymer Degradation" (see Attachment 3).
E. Butcher discussad briefly his work on developing guidelines on the qualifica-tion of Class IE equipment.
Attachments:
3, as stated 1301 185
ATTACHMENT 1 LIST OF ATTENDEES QTE REVIEW GROUP October 5, 1979 Gary L. Bennett RES Ed Butcher D0R Herb Conrad DSS Roy Gustafson Consultant (MTEB)
Don Sullivan SD John A. Zwolinski DSS W. R. Butler DSS 1301 186
ATTACHMENT 2 9/28/79 Working Days Remarks Task Time / Cumu.
(days)
(days)
I.
Install large superheater Accumulators Build up dummy load system with being control loop 8
8 installed a multaneousk Redesign thermocouple Positioning System
- Increased piping and regulators size
+
II.
Load System
{
put dummies in cans in chamber 2
10 mount thermocouple positioning i
system, etc.
20 III.
First test-old procedure with new 4
S.H. preheated to 80% T max 1
11
+
IV.
T >>> T+AT (specification)
+
Establish T(superheated) VS T (Chamber),
+
(6 runs @ 1 run/ day = 6) 11 22 Establish repeatability 4-5 runs - 5d
{
IV.'
T = T spec (i.e., system marginal),
+
put in new accumulator 3
23 I
Establish T vs. T chamber 6 runs Repeatability runs 4-5 days 11 34 130l i87
AND ~79- 092 V C ATTACHMENT 3
[OWCW$
.17 A STUDY OF STRONG SYNERGISM IN POLYMER DEGRADATION
- l'11 %
R. L. Clough, K. T. Gillen and E. A. Salazar Sandia Laboratories, Albuquerque, New Mexico 87185**
ABSTRACT Anomalous strong interactions of radiation and thermal effects in the degradation of polyethylene and polyvinyl chloride are discussed.
The interactions are found to occur in both simultaneous i
and sequential radiation-elevated temperature experiments, and are totally blocked in the absence of oxygen.
A mechanism is proposed by which the effects can be understood in terms of a time-dependent thermal amplification of initial radiation damage; the phenomena results from thermal breakdown of peroxides as a rate limiting step in the radiation-induced degradation.
1301 i88
- This report documents part of the Qualification Testing Evaluation (QTE) Program (A1051-9) being conducted by Sandia Laboratories for the United States Nuclear Regulatory Commission under Department of Energy Contract #DE-AC04-76-DP00789.
- A U. S. DOE facility.
2 In depth studies of material degradation he.ve considerable significance for practical applications.
An understanding of the factors governing the degrada?.i"s process facilitates both inter-vention aimed at controlling the deterioration and prediction of a material's life expectancy under a given set of usage conditions.
Degradation behavior and degradation rate may not atways be inter-pretable in a straight-forward manner; attempts to compare or extrapolate results from one set of experimental conditions to another may lead to anomalous results.
We are investigating strong interactions between radiation and thermal envi:onments in the degradation of some polymeric materials, an effect which might be termed synergism.
Our interest in the possibility of strong interactive radiation-thermal effects was prompted by the recent discovery of degraded polyethylene insulation from cables used in a nuclear application where the total radiation dose received was estimated to be relatively modest, and the temperature was believed to be no greater than 50 C.
Unaged samples of polyethy;.ene-insulated, PVC-jacketed cable identical to the degraded cable were obtained and aged in various radiation and temperature environments; some of the results are outlined here.
RESULTS Radiation experiments were carried out in a cobalt-60 source under controlled temperature conditions, with continuous renewal of 4 surrounding air atmosphere.
Material deterioration was followed by monitoring the ultimate tensile elongation of the samples.
Figure I shows elongation as a function of time for the polyethylene samples submitted to the following environments:
1301 189
3 1.
Radiation at elevated temperature (4 krad/hr, 80 C),
2.
Radiation at low temperature (4 krad/hr, 25 C),
3.
Elevated temperature (80 C, no radiation),
4.
Radiation at elevated temperature under inert atmosphere (4 krad/hr, 80 C, sealed under N }'
2 The curves in the figure are numbered to correspond to the exper-iments listed above.
It is seen that simultaneous application of radiation and elevated temperature results in a striking increase in degradation over what one might expect, intuitively, based on the results for the radiation at low temperature and for the elevated-temperature exposure (compare curves 1-3).
This joint-action radiation-temperature degradation is also seen to be critically dependent upon the presence of oxygen (curve 4).
Also shown in Figure I are two data points (labelled 5 and
- 6) representing experiments in which elevated temperature exposure, and radiation at low temperature, were carried out secuentially.
The two points represent:
5.
83 days elevated temperature (80 C), followed by 83 days of room temperature radiation (4 krad/hr),
6.
83 days room temperature radiation (4 krad/hr), followed by 83 days of elevated temperature (80 C).
It is seen that the order in which the two environments are administered is crucial:
low-temperature radiation followed by elevated temperature is substantially more, damaging than elevated temperature followed by low-temperature radiation.
A corresponding set of experiments was carried out with polyvinyl chloride samples, and similar results were obtained 130l l90
4 (Figure II,:
the numbers 1-6 refer to the same experimental conditions described above.)
Once again, radiation and elevated temperatures, in the presence of oxygen, lead to a severe increase in degradation.
Again, low-temperature radiation followed by elevated temperature yields far greater degradation than a sequential application of the two environments in the opposite order.
The time-dependent degradation of PVC samples held in a thermal-only (80 C) environment, after an initial radiation exposure period (59 days, 4 krad/hr) is also shown in Figure II (curve 7);
it is clear that the initial radiation dose greatly affects the subsequent degradation rate in the elevated-temperature environment.
MECHANISM The results indicate that y-radiation inflicts initial damage on the material, and the degradation thus initiated becomes amplified thermally:
this can occur rapidly at elevated temperatures or more slowly at low temperatures.
In Figure III is shown the molecular mechanism by whien we believe this thermal amplification occurs.
The molecutar strue'ure of the original polymer is not substantially disrupted by thermal environments within the temperature range of interest.
- However, all the chemical bonds are susceptible to breakage by high energy radiation.
The radiation-cleaved bonds, in the form of radicals, react with oxygen to give degradation products including peroxides.
The peroxides are chemically weak links, which are susceptible to thermal cleavage:
this thermal peroxide cleavage gives more radicals, which, in the presence of oxygen, lead to more degradation i301 191
5 and more peroxides.
The mechanistic postulate may be viewed in terms of a thermally activated cleavage of peroxides being the rate deter-mining step in the radiation degradation pathway; results in Figures I and ]I can be readily rationalized by this picture.
Though our present work is being conducted on PVC and poly-ethylene, we believe that similar radiation-thermal degradation pathways may be important for other organic materials.
- Moreover, similer_ phenomena of peroxide-mediated, time dependent, thermal amplification of degradation may be operational in conjunction with other degradation-inducing factors, for example photochemical or mechanical degradation.
More experiments are underway'to further document and better understand both the interaction of radiation and thermal effects, and the proposed role of peroxides.
DISCUSSION It is instructive to imagine here three different empirical observations of anomalous degradation effects in radiation environ-ments, and to consider the interpretation that these observations might, individually, be assigned.
In the first instance, polymeric materials which have previously seen some finite radiation exposure are used along side other samples which had no radiation exposure, with the result that after some time the former are found to have suffered de' gradation.
The interpretation here would be " radiation sensitization."
I-the second instance two samples of a certain polymeric material, which is known to possess excellent high temperature properties, have received similar dosages of radiation but at low and elevated temperatures, respectively, with the result that the sample exposed at the higher temperature is found 1301 192
6 to be badly embrittled.
The interpretation here might be
" strong synergism."
In the third instance, two sets of polymeric samples have been irradiated to approximately the same total dosage, but the first set received the dosage during one week and was thea tested, while the second set received its dosage over the course of a year.
The degradation in the latter set is found to be much more severe, laading to an interpretation of " dose rate effects."
Armed, however, with a more fundamental understanding of the degradation < process, we see that the three foregoing obser-vations (sensitization, synergism, dose rate effects) can all be interpretable (and predictable) as manifestations of the same molecular process: radiction induced degradation involving a thermally activated (peroxide cleavage) rate determining step.
130i 193
~',
FIGURE I POLYETHYLENE DEGRADATION
_.7_1.__._1__@_R_A D [D A y T __80 1
Total AgingTime (Days) 10 1~00 4
500-E 3
x<
400 59
=
o
[300 o
~
200 I
aw 100 69 0
Numbers refer to experiments described in the text.
1301 194
FIGURE 11
~
POLYVINYL CHLORIDE DEG R AD ATI ON
_ 7_ i _ _ _1 @ _R A Q ] Q b_Y_T __80_oC_
Total Aging Time (Days)
~
10 100 300 4
3 2
5 200 95 7
x<
La e
m o
1 r
zo 100 06 Czo d
O Numbers refer to experiments described in the text.
1301 195
<. a.
FIGURE Ill PROBABLE M01.ECULAR MECHANISM Ehdct
.>- c - e ~
H H
Y
.S_u_b_s_t_a_n_i_i a 1_R e a c t,i_o_n (All chemical bonds are suscepti ble to Y )
N c.
P rodu ce Oxidat. ion Degradat. ion P roducts (Chain S cission),
Plus Peroxides:
c-o-o-c C-O-0-H
=""""
Thermal P e rox.de are i
suscepti le to th,e rm al deg rada-ti o n.
Result: m o'.e racicals c-o e More Degradation (
. g2 ce More Peroxides 1301 196