ML20043A567
| ML20043A567 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 05/16/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043A566 | List: |
| References | |
| NUDOCS 9005220252 | |
| Download: ML20043A567 (4) | |
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SAFETY EVALUATION BY.THE OFFICE OF NUCLEAR REACTOR REGULATION PLANT SYSTEMS BRANCH ENVIRONMENTAL QUALIFICATION OF TAPED SPLICES FOR USE IN INSTRUMENTATION CIRCUITS SUBJECTED TO HARSH ENVIRONMENTS WATERFORD UNIT 3 DOCKET,NO. 50-382 During a recent inspection at Waterford Steam Electric Station Unit 3 conducted by NRC Region IV, a concorn was raised regarding the use of taped splices in instrumentation circuits located in potentially harsh environments that would result from design basis accidents such as a loss of coolant-accident (LOCA) er a high energy line break (HELB). The specific concern involved a lack of information to demonstrate that the splices in question are environmentally qualified in accordance with the requirements of 10 CFR Part 50.49.
The licensee subsequently provided-a submittal that included five test reports.
and an analyses describing the applicability of each report.
It is our
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understanding that it is the licensee's intent to use the five reports together rather than to produce' a new single report as a sole means of demonstrating environmental qualification.
- We have completed our review of the licensee's submittal and our conclusions are as follows:
.1.
Test Report No. PEI-TR-842900-1 for New York Power Authority " Final Test Report on Okonite Tape Splice Insulation for Power and Control Cables and Rockbestos Pyrotrol III and Firewall III. Cables."
The purpose of this test was to qualify the specimens for power and control circuits. Therefore, the test assembly was electrically stressed with:696 volts AC continuously during the LOCA tust. However, the' functional performance (i.e., insulation resistance) of the specimens was not monitored during the LOCA simulation. The insulation resistance was measured only before and after the LOCA simulation.
In addition, there were several anomalies involving leakage currents. Therefore, it is our conclusion that this test' report does not demonstrate qualification of Okonite T95/35 tape splices for instrumentation circuits.
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- We further conclude that this report should be scrutinized very carefully l-on a case-by-case basis before it is used to demonstrate qualification E
for any purpose. We also believe that the description of the anomaly in Figure 2 of Appendix VIII, where water entered the end cap of a cable specimen and provided a current leakage path, is an example that is analogous to the inherent weakness of the V-type tape splices.
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Test Report No. PEI-TR-84-704-1 for New York Power Authority," Final Report on the Qualification of Parallel Splice Insulation Systems Used on Power and Control Cables in the James A. FitzPatrick Nuclear Power Plant."
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This test was also conducted to qualify splices for power and control circuit applications.
Insulation resistance data was not recorded during LOCA simulation but, instead, before and after LOCA simulation.
Consequently, this test is of no significant value in determining the functional performance of T95/35 tape splices during a design basis LOCA.
3.
Wyle Test Report No. 17947-01, for Farley Nuclear Generating Station, i
" Qualification Test Program on Splices Fabricated with 3M Scotch Super 33+ Vinyl Plastic Electrical Tape and Okonite Splicing Tape No. 35 and T-95 for the Alabama Power Company for Use in the Farley Nuclear Generation Station."
This report contains the results of tests for several specimer.s. The majority of the specimens were wired for_ testing power and control circuits.
However, six of the specimens were energized with 137.5 VDC and 200 ne'(low power). Of the six, only two were energized continuously.
The other four were de-energized prior to the introduction of chemical spray. Therefore, of the six specimens (10.1A,10.18,11.1,12.1,13.1, and 14.1) powered at 137 V ' and 200 ma, insulation resistance measurements were not recorded during LOCA simulation and only two were energized continuously. Once again, the functional performance of the specimens during.LOCA simulation with chemical spray was not determined during the tests.
There are three additional specimens of interest (7.1, 8.1, and 9.1) because-of their use by Arkansas Nuclear _ Power Station. These specimens are powered at 632 VAC and 20.2 amperes. They were powered for the first 65 minutes of the LOCA simulation, de-energized until the 46-hour ruint, and then re-energized for 2 minutes. These specimens, as with the specimens previously mentioned, did not receive chemical spray before they were de-energized nor were insulation-resistance-data taken during LOCA simulation. Therefore, the functional performance of the specimens during LOCA simulation is not known. Moreover, the duration of the LOCA simulation was only 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br />. The licensee is apparently extended the i
45-hour period to 33 days by use of the Arrhenius equation. There is reason for.some concern in this area because the staff has always held the position that the transient portion'of a temperature vs. time curve that is generated from a LOCA test should not be used in an Arrhenius calculation.
Therefore, the only portion of-the test curve that is considered available y
for use by the Arrhenius technique to extend the test to 33 days is the portion after 167 minutes when the temperature stabilized at 245'F and remained constant for the remainder of the test. The design bases main steam line break curve in the Waterford FSAR Figure 6.2-8b indicates that the: temperature stabilizes around 230*F.
Review of this curve suggests L
that perhaps the test can be extended to 2.6 days, which is far less than l,
the 33 days suggested by the licensee.
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i 7 Based on our review, we have concluded that environmental qualification of the specimens in this test report for use in instrumentation circuits inside containment has not been demonstrated.
4.
Test Report No. NQRN-3, "LOCA ' qualification Report for Okoguard Insulated
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Cables and T-95 and No. 35 Splicing Tapes."
This report represents the results of testing of T95/35 inline splice configurations on one aged and one unaged cable specimen of 5KV rated #6 AWG with 0.090 inch thick Okoguard EPR insulation and no jacket. The i
E results of the tests indicate that this splice configuration is environmentally qualified. The staff has reviewed the test report and concluded that the inline splice configuration is environmentally qualified for the profile and power level outlined in the test report. However, it should be understood that this report does not demonstrate that the splices in question are qualified for submergence, nor does it demonstrate qualification for instrumentation circuits.
5.
"Okonite Long Tenn Water Immersion Test, Dated January 10, 1983, Supplemented with Report Excerpt from Illinois Power Company, Transmitted March 7, 1989."
This test was conducted on three samples of a 1/C #4 AWG Okonite EPR insulated cable which was imersed in 90'C water at a minimum depth of 2.5 feet.
Each of the three samples contained a single insulation splice in the form of an insulation repair constructed of cement and T-95 insulation splicing tape. The sam;.es in this test were unaged.
This test was conducted by the Okonite Company, and the results were provided in a letter to the licensee. The licensee's analysis of the information provided in the letter concluded that the T-95 taped splice is environmentally qualified for submergence. The analyses accounted for the samples being unaged by assuming the 90*C water temperature to be the aging temperature and the imersion times to be the aging time, and taking 50'C as the service temperature for the splice. Using the Arrhenius equation and an activation energy of 1.07 ev, the licensee concluded that the splice has a qualified life of 62.4 years at 50 C.
The samples were not LOCA tested and, therefore, no infonnation is provided by the tests on the functional performance of.these samples during and following a LOCA. There is some discussion related to specific insulation resistance which may be appropriate for a 1/C #4 AWG cable that is expected to carry
.large current loads.
However, there is no persuasive discussion on insulation resistance or leakage current that can be applied to the instrumentation circuits of interest during accident conditions. Therefore, we cannot determine the functional performance of the samples during and following a LOCA. Since we consider that a LOCA is the event that would cause the most damage, we cannot conclude that these samples are qualified for submergence during and following a LOCA.
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V In sunmary, we have reviewed the licensee's submittal, including the five test reports and the accompanying analyses. The principle objection the i
staff has with the information provided by the licensee is that neither insulation resistance (IR) nor leakage current were measured at the most critical times during the various tests.
In instances where IR or leakage current or both are to be measured, the measuring device must be capable of detecting a small amount of leakage current and measuring IR censistent with the requirements of instrumentation circuit (s). A typical instrumentation circuit may operate at a power level of 4 to 20 J
ma and 40 volts, whereas control circuits typically operate at higher currents and voltages; e.g.
7 to 10 amps and higher and 120 volts and higher. Consequently, leakage of a few milliamperares could result in an instrumentation circuit being inoperable whereas a control circuit may not be noticeably affected.
We have concluded that test report NQRN-3 is sufficient to demonstrate environmental qualification for the Okonite T95/35 inline tape splices for power and control circuits in areas where the splices will not be subnerged. We further concluded that none of the reports individually, nor a combination of the five reports, demonstrated' that the tape splice (s) of interest are environmentally qualified for use in instrumentation circuits inside containment.
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