ML18114A777

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Safety Evaluation on Environ Qualification of safety-related Cable
ML18114A777
Person / Time
Site: Surry  Dominion icon.png
Issue date: 05/30/1979
From:
Office of Nuclear Reactor Regulation
To:
Shared Package
ML18114A776 List:
References
NUDOCS 7907110148
Download: ML18114A777 (8)
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Text

{{#Wiki_filter:INTRODUCTION SAFETY EVALUATION REPORT ON ENVIRONMENTAL QUALIFICATION OF SAFETY RELATED CABLE IN SURRY POWER STATION, UNITS 1 AND 2 e Virginia Electric and Power Company (VEPCO) by letter dated s*eptember 29, 1978, submitted its proposed qualification test program for determining whether certain electrical instrument cables manufactured by Continental Wire and Cable Corporation will function under environmental conditions simulating those expected within the containment of Surry Power Station Units 1 and 2, during a postulated loss of coo*lant accident (LOCA) or during a main steam line break (MSLB). The test program was intended to include irradiation and additional aging of the cable samples which have been in service at Surry for more than seven (7) years, exposure of the cables to a combined steam and chemical spray while electrically energized, and a comparison of the physical properties of the samples before and after the environmental exposures. Separate tests were proposed to be conducted, one to simulate the LOCA conditions and a second to test the MSLB environment. The sample cable us~d in the test program was 300V, two conductor, No. 16 AWG, stranded with cross-linked polyethylene insulation and hypalon jacket (see Figure A for details). The test program required seven ( 7) test samples to be prepared - three for the LOCA test, three for the MSLB test and one for measuring initial physical and electrical properties. The acceptance criteria for LOCA and MSLB tests were established as follows: A. Short term for safety system initiation following an incident: The cable shall be considered*acceptable ff the current measurement remafos between 24 and 26 mi 11 i amps during the first five minutes of the**test. B, Long term for monitoring and o_perator action following an incident: The cable shall be considered acceptable if the current measurement remains between 22 and. 28 milliamps throughout the

test, VEPCO by letter dated December 15, 1978, submitted the test report of the environmental qualification perfonned by Conax Corporation on the Continenta1 Instrument Cable 1n accordance with the_ test procedure.

Additional information on the test was submitted by letter dated May 5, 1979. The cable samples supplied by VEPCO were cut into test samples and .uti 1 ized for testing as s*hown in F1gures B and C. These test samples that had been thermally aged for 60 hours at. l00°C and irradiated to 20 MR were installed i-n the test chamber, connected, instrumented and*subjected to the LOCA environment (t"emperatureipressure/chemi cal spray. environment). The test chamber temperature profile is shown in Figure D. Data was collected

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i-r,. e e of the measurements of voltage and current throughout the 48 hours of the test. Three test samples, thermally aged for 60 hours at 100°C and irradiated to 20 KR, were installed in the test chamber and subjected to the specified MSLB test environment. The test chamber profile is shown in Figure E. Data was also continuously collected throughout the test period of 48 hours. DISCUSSION The test procedure and the tests done for qualification of the Continental Instrument Cable followed the general guidelines of IEEE Std. 323-1974. TEST SEQUENCE The cable samples were thermally aged, irradiated and subjected _to steam pressure temperature/chemical spray as outlined in the approved test procedure. The sequence of the test was in line with the sequence of IEEE Std. 323-1974~ 'AGING The cable samples were subjected to accelerated aging at 60°C for 100 hours to put the samples in a condition e~uivalent to end-of-life condition. From the Arrhenius curve applicable to the cable and based.on the licensee maintaining the:.containment bulk average temperature at 40°C, it is seen that at 40°C a 150 year life of the cable is indicated and at 45°C a 53 year life is indicated, (The Arrhenius Life Curve is based on retention of 40% of original elongation of the cable insulation materiaU. MARGIN By comparing the test d.ata and the plant's temperature and pressure profiles of LOCA and MSLB events, it was seen thati:.iadequate margin per IEEE Std. 323-1974 was provided~ (The temperature peak of 420°F during 2*0 to 90 second *interval of the incident was not obtained during the test; however, the test temperature of 350°F was sustained for a period of 15 minutes to compensate f6r this. This deviation was found acceptable and was approved in the test procedure itself). . RAD'! A TI ON The samples were divided into two batches - one for the LOCA test and the other for the MSLB.test. The samples for the LOCA tests were irradiated to obtain an integrated gamma dose of 20 MR at 1 MR/hr and the samples used in the MSLB. test we~e irradiated to 20 KR at 1 Kr/hr. Measurement of electrical and physical pr.operites were made in conformance with applicable industrial standards. The data presented for the test are considered saUsfactory for Surry Units l and 2 service conditions.

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I ! I* [ t I I ' t I r f. =~ ~ 3 - OPERATION UNDER NORMAL.AND.ACCIDENT.CONDITIONS The electrical connections made in the test to keep the samples energized supplying simulated loads during the period when the samples were exposed to simulated environmental conditions are satisfactory. The review of the continuous readings of the current and voltage of the samples taken during the test show that the currents were within the required limits of the accept~nce criteria (one sample of the three used in the MSLB test had current readings beyond the limits of the acceptance criteria. However, analysis and measurement taken after the test traced this discrepancy to a decrease in resistance of a variable resistor outside the test chamber. Conax Corporation's report has conclusively established that the increased current flow in that particular test sample circuit was directly caused by the resistance decrease in the variable resistor used and in no way was a result of any change in the test cable). Based on this it is concluded that all 1he cable samples conformed to the acceptance criteria of the test procedure. CONCLUSION Based on our review of the test result we conclude that the instrumentation cable tested can perform its required functions during and following the specified abnormal environmental conditions. The acceptability is on the basis that the tests performed were generally.. in line with the requirements of Regulatory Guide 1,89 [IEEE Std, 323-1974). a

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