ML20064A689
| ML20064A689 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 09/12/1990 |
| From: | Trevors G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20064A690 | List: |
| References | |
| NLS9000363, NUDOCS 9009270067 | |
| Download: ML20064A689 (25) | |
Text
.
.g' GENERAL OFFICE P.O. BOX 400. COLUMBUS. NERRABKA 00002 0490
, m.2 Nebraska Public Power District _
Tx "#ME" - . ~.
NLS9000363:-
September =12,,1990
- . J.
U. S. Nuclear Regulatory Commission
' Attention: Document Control Desk-Washington, D.C'.
20555 Gentlemen:
Subject:
Evaluation of the Qual'ification of Okonite T95/35-Tape Splices for Use in Instrumentation Circuits Cooper Nuclear Station NRC Docket.50 298/DPR 46 References': 1. Letter from S. J. Collins (NRC) to C. A. Trevors (NPPD)
. dated August 13, 1990, same subject.
- 2. Memorandum from G. M. Holahan (NRR) to Messrs. S. J. Collins and L. J. Callan (Region - IV) dated May 16, 1990,
" Qualification of Taped Splices-for Use in Instrument Circuits. Subject to Harsh Environments, Waterford Steam Electric Station, Unit 3."
. The Nebraska.Public Power District (District) hereby forwards the attached. .,
--evaluation of the qualification of Okonite T95/35' tape splicesL ni instru'nentation ' applications at Cooper Nuclear Station- (CNS) . The NRC requested'this information by letter dated August 13,:1990.l.(Reference 1).
.The- District maintains that Okonite T95/35 tape splices are fully qualified for use in CNS instrumentation circuits in harsh environments. The attached evaluation provides-the basis for this qualification and addresses the
" : concerns-identified in recent discussions with'the NRC and as discussed in'the May 16,-1990 internal NRC memorandum (keference 2).
LAdditionally,'due.to.the qualification concerns expressed by the NRC, the-(District has prepared a Justification for Continued Operation which establishes the basis ~ for interim operation in the event the NRC does not accept the District's basis for qualification of the Okonite splices for use in instrumentation circuits. A copy of this JC0 has been provided to the NRC.
Resident Inspector and11s available for NRC review.
At.the request of NRC - Region IV personnel, also at,tached is a copy of Patel Test Report PEI-TR-C70200 02. As discussed in @@ 6t$aghed evaluation, this 9009270067 900912L
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-i NLS9000363 U. S. Nuclear Regulatory Commission Page 2 of 2-test report' forms part of the District's qualification basis for qualification i of Okonite tape splices in instrumentation applications, Please call if you have any questions.
Sincerely, ,
, , Trevors Senior Staff Advisor i Nuclear Power Group
. CAT /mjb/ deb Attachments ,
I cc: NRC Regional Office ;
Region IV ;-
Arlington, TX NRC Resident Inspector Cooper Nuclear Station i
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Att:chment 1-to NLS9000363. .,
EVALUATION OF THE ENVIRONMENTAL QUALIFICATION OF.0KONITE T95/35 TAPE SPLICES IN INSTRUMENTATION APPLICATIONS AT COOPER NUCLEAR STATION
.I.. INTRODUCTION This evaluation has been prepared to address recent NRC concerns expressed to the !
Nebraska- Public Power District (District) regarding the environmental ,
qualification of Okonite T95/35 tape sp? ices for use -in instrumentation applications at Cooper Nuclear Station (CNS) in potentially harsh environments.
' During discussions held with the NRC - Region IV on August 8,1990, the District was made aware of an internal NRC memorandum and safety evaluation 1 written on the Waterford Nuclear Station Docket which disputes the qualification of Okonite tape.' splices for use in instrumentation applications at that plant.
- Accordingly, the NRC - Ree, ion IV electronically transmitted the NRC safety evaluation to the District. 'for review of its applicability to the District's
- environmental qualification program. The District's review has determined that the information contained in the NRC safety evaluation does not invalidate the basis for the environmental qualification of Okonite tape splices installed at CNS,-and therefore,;the District remains in compliance with 10 CFR 50.49.
. However, because of NRC concerns regarding this issue, the District has prepared, and has in place, a Justification for Continued Operation '(JCO) 8 addressin6 the ,
safety : significance = of the CNS configuration assuming an . unacceptable i
. qualification basis.. for the Okonite tape splices in affected instrumentation
. circuits. This JC0 demonstrates that, assuming an unacceptable. qualification .;
basis for the Okonite splices in the affected instrumentation circuits, redundant I
instrumentation;and inherent design characteristics and operational measures L : exist such that continued operation of CNS will not compromise plant safety or. ;
the health and safety of the general public. This JC0 has been provided to the CNS Resident Inspector 'and will remain in effect until final resolution of this issue. . ,
The L following discussion provides further background regarding this issue, l' '
outlines the District's basis for the environmental qualification of Okonite tape splicca for use in instrumentation applications, aw' addresses each concern raised by the~ internal NRC memorandum and safety evaluation. l l II. BACKCROUND The District's basis for qualification of Okonite tape splices is docunented by the District's Environmental' Qualification Data Package (EQDP) 224.3 EQnP 224 -
firmly estchlishes the basis for the qualification of Okoniu splices for use in instrumentation applications. This data package has received extensive review i :by the-NRC-and, as discussed below, meets the qualification requirements set M forth in 10 CFR.50.49.
During the week of November 3 - 7, 1986, an NRC Inspection Team completed its first round inspection of the District's environmental qualification program to verify compliance with 10 CFR 50.49. That inspection, documented by NRC Inspection Report 86-28,' identified only one issue impacting NRC acceptance of the District's basis for qualification of Ohonite splices. The NRC accepted the
Okonite qualification basis with the exception that it took issue with the District's qualification basis for use of Okonite tape splices-over fiberglass
-braided Limitorque motor leads.
It was the NRC's position that under accident conditions, water could travel along the insulation and into the splice through a " wicking" action, and therefore provide a path for leakage current from the splice. The NRC maintained -
that adequate similarity had not been demonstrated to qualify this configuration based on existing test reports.
By letter. dated June 17, 1987,8 the District submitted its response to Inspection Report 86 28. In this response, the District indicated that it had conducted additional testing to address the Okonite over braid concern, and would update the Okonite qualification data package (EQDP 224) to incorporate the new test data. As a result of further discussions with the NRC regarding this issue, on May 31, 1988,5 the District submitted to the NRC Patel Test Report No. PEI-TR-870200 02' documenting the Okonite over braid test.
In response' to the NRC's request made during a June 20, 1988 Enforcement Conference, on July 13, 1988, the District submitted an updated response to Inspection Report 86-28.s This response included an outline of the District's basis for qualification of Okonite splices and provided the NRC with further
' background on the Okonite splice history.
By letter dated October 19, 1988,' the NRC issued Inspection Report 88-26, which documented the results of the NRC's special EQ followup inspection conducted between June - September, 1988. Inspection Report. ' 88-26 issued a Notice of Violation (NOV) on the Okonite-over braid issue. The NRC maintained that the
-District did not have_an acceptable qualification basis for the Okonite-over-braid configuration for the period following the November 30, 1985 EQ deadline and prior to the additional testing documented by Patel Test Report No. PEI TR--
870200 02. The. NRC identified no other concerns with respect to the qualification of Okonite splices llowever, NRC Inspection Report 88 26 did acknowledge that the type testing documented by Patel Test Report No. PEI-TR-870200-02:
" ... demonstrates acceptance for applications of Okonite splicing tape to cable with a braided fiberglass jacket on motor operator power leads for postaccident operability times of less than 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br />."
Although NRC Inspection Report 88-26 did not specifically address use of Okonite in, instrumentation circuits, it did acknowledge thet insulation resistance (IR) measurements were taken, and that the IR values remained above 5 mogohms until a power loss anomaly occurred 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br /> into the test. The test anomaly is
-discussed in more detail below.
.By letter dated November 18, 1988," the District responded to NRC Inspection Report 88-26. Therein, the District reiterated the basis for qualification of the Okonite-over-braid configuration and indicated that all corrective actions had been completed. In a letter dated December 29, 1988," the NRC indicated 2
i that the District's reply was responsive to the concerns raised in the NOV, and Lthat it would review the ~ implementation of the District's corrective actions during a future; inspection. [
The NRC conducted the followup inspection during the period March 27 - 30, 1989, 5c as- documented by NRC Inspection Report 89-13." During this inspection, the NRC-4 again reviewed the District's EQDP 224 and Patel Test Report PEI TR-870200 02.
The NRC concluded that the test methodology and the District's rationale for
. qualification were acceptable. . Inspection Report 89-13 closed the NRC's concern with respect to Okonite qualification, and indicated with respect to the Okonite-
- over braid configuration that the type tests "have demonstrated these .
configurations can survive up to 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br /> during these accidents."
By'1etter dated April 20, 1990," the NRC transmitted NRC Inspection Report 90
- 09. This inspection report documer.ted the NRC inspection conducted during the period April 2 -6, 1990 which focused on instrumentation calibration and environmsntally qualified (EQ) Okonite tape splices. Inspection Report 90 09-identified no violations or deviations, but indicated that "the inspector found that the [0konite splicing) procedure [s] did not permit the use of taped splices in harsh environments for instrumentation circuits."
By, letter dated July 31, 1990," the District submitted a response to NRC Inspection Report 90 09 to clarify the record. In its response, the District
- acknowledged some ambiguity in its Okonite splicing procedures with respect to j the use _of Okonite in instrumentation applications,-but maintained that Okonite ;
taped splices were fully qualified for use in instrumentation applications. The i t
District committed to revise its Okonite splicing procedures to clarify this issue.
On August 8,1990, following receipt of the District's July 31, 1990_ letter, the NRC - Region IV contacted the District to further discuss the qualification of ,
Okonite in ' instrumentation applications.
During that discussion, Region IV ,
expressed concerns with respect to the qualification of Okonite tape splices in instrumentation'_ applications and advised the District 'of the internal NRC memorandum on the Waterford Docket 2 addressing the qualification of Okonite tape splices.
l Further discussion with Region IV indicated that their concerns centered on a instrumentation circuits, specifically 4 - 20 mA loops. Region IV staff l" indicated that they were not aware of any test report that sufficiently l; documenced the qualification of Okonite in these circuits. The District J l:- - expressed its position that the Okonite tape splices were fully qualified for ~use
-in instrumentation applications at CNS, but committed to evaluate its basis for E' qualification against the information contained in the internal NRC memorandum i
which the NRC -
Region IV subsequently transmitted electronically to the L . District.
K As a result of this discussion, the District immediately performed a walkdown of i all. environmentally qualified 4 - 20 mA loops to verify the location of all Okonite in-line splices in such applications. This walkdown confirmed application of Okonite splices in the CNS environmentally qualified loops listed 3
- h. ' '..$,
Li
- b'elow~ in Table 1'. These instrumentation loops are Regulatory Cuide 1.97 Category. f
- I indication oniv circuits,.and have no automatic safety related= functions.
TABLE 1.
CIC Descriotion RC 1.97 Cat PC-PT-30A- Torus Pressure Cat I !
PC PT-30B Torus Preasure Cat I
'NBI-LT 59A Rx Water Level Cat I' NBI LT-59B. Rx Water Level Cat I -[
NBI-LT-590 Rx Water Level Cat I NBI LT-91C Rx Water Level Cat I .
NBI LT 92 Torus Level Cat I
.PC DPT-3Al Torus Level Cat I
'PC DPT 3B2- Torus Level Cat I On August 13, 1990, the District contacted the NRC - Region-IV with the results- ,
L of'its walkdown-and evaluation of the Okonite qualification basis.in light of the information contained in1the NRC memorandum. The District indicated that its.
qualification basis adequately addresses the concerns raised in the NRC' memorandum, and that the qualification of Okonite tape splices for use in CNS. ;
instrumentation applications-remained valid, C
During this discussion, the NRC requested the District to submit a'JC0 addressing 4 i' this. issue. The District maintained-that since its basis for qualification of i l Okonite tape splices for ; use in instrumentation applications was valid,' and ,
laccordingly, it war. in compliance with 10 CFR 50.49, that a JC0 was not required.
- 7 1
However, following further discussions on this issue, the District agreed to.
prepare a JC0 to remain.in effect until final resolution of this issue. This JC0 has been provided to the NRC - Region IV staff. L L By letter dated August 13, 1990," the NRC documented their concerns regarding the qualification of Okonite tape splices in CNS. instrumentation applications subject to harsh environments, and requested the District to, within 30 days,1) 3 inform the NRC if tape splices-have been installed in instrumentation circuits
. subject to harsh environments,- and if so, identify which circuits are involved,: (
'and 2) if any such circuits are identified, demonstrate the qualification of the splices in accordance with 10 CFR 50.49, or perform an operability evaluation to i justify continued operation for a finite time until a qualified configuration can .
be installed. l As - discussed above, although' it is the District's position that the Okonite splices are fully qualified for use in 4 - 20 mA instrumentation circuits subject to harsh environments at CNS, the District currently has in place a Justificati.on
-forf Continued Operation which will remain in effect until final ~ resolution of H this issue. In addition, the District has identified, in Table 1 above' .the 4 -
'20'mA circuits containing Okonite splices. The following discussion describes the1 District's basis-for the qualification of Okonite tape splices for these applications and addresses the concerns identified in the internal NRC ;
memorandum.
4 i
E III. QUALIFICATION TESTING .
. The qualification of Okonite splices for use in instrumentation applications at CNS is based on the testing and analysis included in and referenced by EQDP 224.
EQDP 224 references two qualification test reports, Patel Test Report No. PEI-TR-842900 1" and PEI TR 870200 02.7 These test reports are summarized below. ,
' III . A'. Patel Test Report PEI-TR-842900 1 Patel Test Report No. PEI-TR-842900-1 documents the environmental qualification testing.of Okonite tape splices over lengths of #12 AVG crosslinked polyethylene (XPLE) Rockbestos Pyrotrol III and Firewall III control cables. This test was originally performed by the New York Power Authority for.the James A. Fitzpatrick
. Nuclear Power Plant.
The test assembly consisted of various configurations of inline and parallel t splices constructed using both bolted and crimped connectors, and insulated with Okonite No. T95 high voltage insulating tape and covered with Okonite No. 35 jacketing tape. 4 r
A total.of _16 splice assemblies were mounted in and mechanically fastened inside two grounded NEMA 4 junction boxes (8 splices per box) to provide a conservative simulation of ground paths. The junction box contained a 1/4 inch weep hole for condensate drainage. This test report also documents other costing performed on
~
the Rockbestos cable which will not be discussed here, V .
The test sequence for this qualification testing was as follows:
L :* Baseline functional' tests
- Radiation aging Functional tests
- . Thermal aging ,
l
- Functional tests- i
- Accident simulation
- Post-accident functional tests LThe splices were physically constructed and provided by the James A. Fitzpatrick .
Nuclear Power Plant staff in accordance with their procedures. (These procedures are included in the test report and form the basis for the CNS Okonite splicing procedures). The test splices were visually inspected for possible damage due l to shipping and handling; no damage was observed. The baseline functional test ,
consisted of measuring the'insulatic, resistance of the splice assemblies to the i grounded -junction box at 1000 VDC. These and all insulation resistance
- measurements conservatively neglect leakage current of - the spliced cables; L 'therefore, it is assumed that all leakage current originates from the splices.
All insalation resistance values were 4.0 EE10 ohms or greater.
The two junction boxes containing the Okonite splices were then subjected to a gamma radiation dose of not less than 1.2 EE8 rads at a rate not exceeding
. 0.41 EE6 rads / hour. Following the radiation exposure, the splice assemblies were subjected to a second functional test. Visual inspection of the splices revealed that the No. 35 outer jacketing tape had experienced cracking and unwinding; 5
f
-however,fthe_T95' inner' tape.(highvoltageinsulatingtape)hadremainedintact.
Later testing determined that the cracking of the No. 35 jacketing tape did not affect the electrical properties of the splice. The insulation resistance of the splice assemblies were again meacured at 1000 VDC. All insulation resistance values were 1.0 EE10 ohms or greater.
1 . The splice assemblies were then thermally aged at 275'F for 600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> to simulate the required qualified life. Following thermal aging, the splice assemblies were subjected to a third baseline functional test. _ Although no notation was made in the report covering the physical condition of the splices, discussions with the test engineer indicate that the physical condition at the T95 high voltage insulating tape was superior to its pre-aged condition. 'The compliant T95 tape had flowed around the wires and connections to form a ho:9ogeneous mass, devoid of the original, distinct wrapping lamination characteristics.
'> The insulation resistance of the splice assemblies was again measured at l
1000 VDC; all insulation resistance values were 1.0 EE10 ohms or greater. _The ;
l splice assemblies were.then subjected to a electric withstand test. -This test !
measured the leakage current to ground at 2400 VAC. All splice assemblies had less than - 1 mA current leakage at 2400 VAC, the lowest detectable leakage l current. .:
I The splice . assemblies were then subjected'to the accident simulation test. The ;
splice' assemblies were subjected to a accident profile (extended temperature of j 360*F, pressure of 50 psig, and deionized water spray) which conservatively _l envelopes the worst case accident profile at CNS, During the accident simulation .{
test, the splice assemblies were subject to a voltage of 696 VAC and set up-as j shown in: Appendix I._ Each splice assembly was provided with a 0.1 A fuse to ,
detect excessive leakage current. 1 Thir' teen of sixteen splice assemblies passed the accident' simulation test with '!
h no significant leakage current. Three splice assemblies experienced excessive !
leakage current. It was later determined that the cable insulation of the first j splice assembly _to exhibit excessive leakage current had experienced a through-
-wall crack in the cable insulation, external to the splice. This crack allowed-l' a pathway. for condensed steam, under the pressure of the simulation chamber, to
. travel along the conductor and out of the chamber to the fusebloch it was landed ;
on. This was evidenced by water staining on the plywood substrate to which the - )
'fuseblock was attached.
LThe water provided a current leakage path to ground outside the test chamber l
which caused the 0.1 A fuse to fail. This anomaly occurred upon the initial ramp ;
to 360,'F. The two remaining splice assemblies exhibiting excessive leakage. f L current did so at 47 and 100 minutes following test initiation. These two splice assemblies were attached to the same fuse block as the first assembly j experiencing the anomaly.. Therefore, the determination that the cracked wire )
insulation, and not the splices caused the anomaly was conclusive in that 1) the !
crack existed on the first assembly to experience an anomaly, 2) the hypothesized failure mechanism was evidenced by water staining on the plywood fuseblock substrate, 3) all'three test assemblies that experienced anomalies were landed '
on the same fuseblock evidenced to have water ingress (the second and third test assemblies to experience greater than 0.1 A leakage current were landed on either 6
f
1 .
i side of the assembly with the cracked wire anomaly), 4) the thirteen remaining- ;
splice; assemblies experienced no anomalc.7 behavior, and 5) the three splice -
assemblies laterisuccessfully passed a submerged dielectric withstand test at 2400 VAC,;as discussed-below. ,
Following the accident simulation, the splice assemblies were subjected to a-post-accident functional test. As discussed above, visual inspection-revealed- ,
cracked wiring insulation on the first splice assembly experiencing the excessive leakage current anomaly. .The insulation resistance of the sixteen splice assemblies were then measured at 1000 VDC. All assemblies with the exception of two measured IR valves of 1.0 EE9 ohm or greater. One splice assembly measured 1.6 EE7 ohms, which was somewhat lower than the other splices, but still met the. I test acceptance criteria of 1.0 EE6. ohms. The splice assembly with the cracked
-wire experienced an IR value of 2.0 EE5 ohms.
RThe splice assemblies were then subjected to a dielectric withstand test at 2400 VAC. 'All splice assemblies with the exception of the one with the cracked wire passed with less than 1 mA leakage current. This assembly, and the other two experiencing anomalous leakage current due to the cracked wiMe were . then subjected to a 2400 VAC dielectric withstand test immersed in watta, after all three assemblies were cut approximately 6 inches on either side of the splices.
This removed the cracked wire portion from the corresponding splice assembly.
-All three assemblies passed with less then 1 mA leakage current. .
III.B Patel'Tect Reoort PEl-TR-870200-02 Patel Test Report PEI-TR-870200-02 documents the qualification testing of 0konite -
tape splices over fiberglass braided Limitorque power and control cables. This test was performed for the District to demonstrate acceptance of Okonite tape splices over the fiberglass braided Limitorque cables.
- The test configuration consisted of two splice assemblies, each containing three bolted inline Okonite tape splices. The braided wire used to fabricate the test assemblies was naturally aged over 12 years of service at CNS. The lead wires for both test assemblies was Rockbestos Firewall SIS 16 AWG 600 V cable. .The i splice assemblies were constructed by CNS plant staff in accordance. with its
. applicable splicing procedure.
The two splice assemblies were mounted in and mechanically fastened to a grounded ;
NEMA-4 junction box to conservatively simulate ground paths. The test assembly was then' subjected to the following test sequence:
- Baseline functional test
- Accident simulation test
- Post accident functional test The splice assemblies were visually inspected upon receipt which revealed no obvious physical damage to the assemblies. The insulation resistance was then measured from the circuit to ground at 500 VDC. This measurement conservatively noglects the leakage current from the assembly wire. The insulation resistance for both splice assemblies was 1.0 EE9 ohms or greater. The circuit continuity 7
i l;
t-
was also verified by measuring the circuit resistance of each loop. The circuit -
resistance for each loop was 0.11 olue or less.'
The test ass _emblies were not subjected to radiation and thermal aging, as Patel
. Test - Report PEI-TR-842900 1 demonstrated that 1) no significant change in dielectric characteristics had occurred following radiation and thermal aging (i.e. , no significant IR change), and 2) as discussed in Section III. A above, the-physical' characteristics of the T95 high voltage insulating tape was superior following radiation and thermal aging. Therefore, it was determined that, over the irregular surface of the fiberglass braided cables, accident testing of unaged splices was the most conservative path.
-The test assembly for the steam accident test is as shown in Appendix II. Loop 1 was energized at 120 VAC, while Loop 2 was energized at 480 VAC. A leakage
. current monitoring loop, capable of measuring 1.0 mA was included in each test 4 splice assembly. l The splice assemblies were then subjected to the steam accident test. The I accident simulation profile (Appendix III) conservatively bounds the worst case .
accident profile at CNS. The test profile exceeded 300*F and 30 psig. Leakage l current and insulation resistance measurements were recorded periodically durin5 .,
1 the accident test.
The. insulation resistance for Loop 1 remained above 3.0 EE7 ohms throughout the '
stesa accident . test. The IR valves for Loop 2 remained above 5.0 EE6 ohms until f approximately 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> into the test. The leakage current in Loop 1 remained at -
L or below 2 mA throughout the test while leakage current in Loop 2 remained below 8 mA until approximately 52 hours6.018519e-4 days <br />0.0144 hours <br />8.597884e-5 weeks <br />1.9786e-5 months <br /> into the test.
l Following the steam accident test, the splice assemblies were visually inspected L for obvious damage. No visual damage was noted in Loop 1. However, visual
( inspection of Loop 2 revealed that one of the fiberglass braid wires had frayed, presumably from mishandling the test specimen, exposing the conductor. Arcing
, was evidenced by discoloration of the enclosure wall in the vicinity of- the ..
l/ frayed wire. Another fiberglass braid wire section in Loop 2 appeared to be. !
L . damaged but not quito as extensive. A surface layer of water was observed in the L bottom of the ~ enclosure. This and other observations made . during the . test
! indicated _that the NEMA-4 enclosure was completely submerged for approximately ten hours during the accident simulation test. The insulation resistance of both loops was then measured. Loop 1 recorded an IR of greater than 1.0 EE9 ohms, while.. Loop 2 with the damaged wire recorded an IR value between 6.0 - 8.0 EE5 ohms.
IV. SPLICE QUALIFICATION CRITERIA 4
--The qualification of Okonite tape splices in CNS instrumentation applications is based on the requirements of 10 CFR 50.49 and the guidance contained in IEEE 323 1974. The critical characteristics (which for Okonite splices are limited to !
the T95 high voltage insulating tape) for electrical splices which must be demonstrated through testing and analysis include:
8
' Physical- integrity - The splicing material'should maintain adequate physical integrity (i.e. ,- the splice material should not crack, fissure, etc.) during and ,
following exposure to - normal ' and - accident conditions to prevent moisture '
intrusion which might create unacceptable leakage current.
- Permanent - dielectric channes - The splicing material should not undergo any.
permanent dielectric changes which would significantly reduce its insulation
- resistance.
Temocrary dielectric channes - The splicing material. should demonstrate - no significant dielectric changes at ceak accident conditions, (e.g., due to increased electron mobility at elevated temperatures, etc.) which might create unacceptable insulation resistance.
e Sealing - Adequate sealing must exist between splice material and conductor ,
- insulation to prevent moisture-intrusion from the steam environment which might 3 create unacceptable current leakage. The District does not have Okonite splices in areas postulated to become submerged; therefore, the District is not inferring ?
qualification of Okonite for such applications.
r The District has adequately addressed each of the above issues with rerpect to-Okonite splices. This qualification is based upon the tests documenteo by Patel ,
Test Reports Mce. PEI TR 842900 1" and PEI TR 870200 027 discussed above, and the analyses presented in and referenced by ' EQDP 224. As discussed in the y' Background Section above, these reports and the District's corresponding analyses -
.have undergone extensive NRC review. The following discussion explains the I
- District's basis for meeting the above splice qualification criteria.
IV '. A , ' Physical Integrity and Permanent Dielectric Change The splicer ability to maintain physical integrity, (resist cracking, fissuring, p etc.) and to withstand significant permanent dielectric degradation due to normal 1 and-accident. environments (radiation, temperature, humidity, etc. ) has been
- demonstrated by Patel Test. Report PEI-TR 842900-1. . As discussed in Section III; A i I above, the splice assemblies performed well during the testing documented by (1 Patel Test Report PEI TR 842900 1. Following radiation and thermal aging, and-L - exposure to - accident conditions, fourteen of. sixteen splices demonstrated l; insulation resistances of 1.0 EE9 ohms or greater. One splice assembly measured '
l
' 1'.6 EE7 ohms, and the assembly with the cracked wire insulation anomaly measured
-2.0 EE5 ohms.
In addition, as discussed above, all splice assemblies with the exception of the assembly with the cracked wire passed the post accident dielectric test with '
leakage currents less that 1 mA at 2400 VAC. Further, the three splice assemblies experiencing excessive leakage current during the accident test due i to the cracked ' wire were subjected to a submerged dielectric withstand test at 2400 VAC. All three: experienced less than 1 mA leakage current.
l The testing documented by Patel Test Report PEI-TR-870200 also demonstrated l
the ability of the Okonite tape splices to maintain their physical integrity and withstand significant permanent dielectric change. As discussed in Section II.B above, the post accident testing demonstrated IR values of greater than 1.0 EE9 9
i
. 1 U
ohms for Loop 1 in that' test, while the IR values for Loop-2 were skewed after 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br /> due to thelfrayed wire anomaly.-
Each of the test sequences discussed above - the post accident IR test, the high ,
potential dielectric withstand test, and the submerged high potential withstand '
test conservatively neglects leakage current from the conductor insulation,, and' .
demonstrates acceptability of the splice material to maintain both its' physical ,
integrity and to. withstand any significant permanent dielectric change. If the - i physical integrity or the permanent dielectric strength or the splice had been significantly compromised, the pont accident IR and high potential witbetand tests would have produced significant leakage current. Therefore, the Dimirict ,
concludes that the tests documented by Patel Test Roport Nos. PEI-TR 842900-1 and PEI-TR-870200-02 demonstrate that okonite splicing material 1) maintains adequate physical integrity during and following normal and accident conditions, and 2) withstands any significant permanent dielectric change following normal and accident conditions.
IV.B Temocrary Dielectric Channe The capability of Okonite splice material to withstand significant temporary dielectric change during accident conditions (i.e. , maintain adequate insulation resistance) has been demonstrated during testing documented by Patel Test Report PEI TR 870200 02. During this accident test, leakage current and IR measurements were taken throughout the ecident simulation. Since at CNS, 'al10konite splices in the_4 - 20 mA instrumentation circuits are located in a mild environment after 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the-District used the IR values recorded during the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the low voltage test loop in conjunction with the effects of all other components to calculate the total accident error for all instruments installed with Okonite splices.
The District ~has also evaluated the accident induced uncertainty for all
' Regulatory Guide 1.97 instrumentation. This evaluation has concluded that the Regulatory Guide 1.97 instrumentation provides sufficient information for the operators to successfully carry out E0P instructions.
Therefore, since the IR and leakage current measurements were taken throughout the enveloping accident conditions, and the effects of the-leakage current has
~been evaluated and found not to produce unacceptable results, the capability of Okonite splice - material to maintain adequate IR throughout the accident conditions is demonstrated by Patel Test Report PEI-TR 870200-02. Therefore, it is the District's position that the test results provide sufficient evidence that Okonite splicing material does~not exhibit unacceptable temporary dielectric changes at CNS accident conditions.
IV.C Sen11nn Patel Test Reports PEI-TR-842900-1 and PEI-TR-870200-02 both demonstrate adequate sealing capability of the Okonite splicing material. Inadequate sealing, as _
defined in Section IV above, would manifest itself as unacceptable leakage current or lowered IR either during or following-the accident simulation. As discussed above, and as documented in Patel Test Report PEI-TR-842900-1, all the Okonite splices with the exception of the three affected by the cracked wire 10
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r anomaly demonstrated ' no significant- leakage current. In addition, the. three_ ,
-splice assemblies _affected by the cracked wire anomaly were immersed in water ,
L while subjected to a potential of. 2400 VAC. Even at this high voltage, leakage '
current ~for all three _ assemblies remained below 1 mA, which demonstrates' acceptability of Okonite splicing material sealing capability following normal and accident conditions.
The testing documented by Patel Test Report PEI-TR 870200-02 demonstrates, through'the' low leakage current and high IR values maintained during the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the test, the sealing capability of Okonite splicing material'over irregular (fiberglass braid) wire. These results demonstrate that the Okonite !
splicing material adhesion and compliant characteristics provide for adequate sealing between the splice material and the conductor insulation material during high pressure and temperature conditions. Therefore, the District concludes that !
Okonite splicing material provides sufficient sealing capabilities for its.
. applications-.at CNS.
T l Based on the testing documented by Patel Test Reports PEI-TR-8429001 and PEI-TR-L 870200 02, ~ the (nalysis provided in and referenced by EQDP 224, and the p discussion above, the District concludes that Okonite splicing material satisfies the four criteria for qualification in instrumentation circuits at CNS, and therefore is qualified for use in the Regulatory Cuide 1.97 post accident monitoring instrumentation listed above.
1: . V. RESOLUTION OF NRC CONCERNS -(
l:
The NRC has raised several concerns regarding the qualification 'of Okonite .;
l> splices' for use in instrumentation circuits. These .7ncerns have been raised in recent discussions between the District and the NRC - Region IV as discussed'in l
Section I above, - and include those concerns identified in the internal NRC ,
memorandum written on the Waterford Docket.1 Most of these concerns are D associated with the use of Patel Test-Report PEI-TR-842900 1 to demonstrate
i l qualification of Okonite tape si lices - for use in instrumentation circuits.
However, as' discussed above, the District has performed additional testing of Okonite splices, as documedted by Patel Test Report 870200 02, which supports the b _' qualification of Okonite for use in instrumentation applications. The NRC's l)
~ specific concerns are addressed below.
V.A. Patel Test Reoort PEI-TR-842900-1 Contained Several Anomalies Involving I Lenkare Current.
As' described in Section III. A. above, during the accident simulation portion of !
the testing documented by Patel Test Report PEI-TR-842900-1, three test splice- I assemblies experienced excessive leakage current anomalies. As discussed further L in Section III. A. , strong evidence exists to conclude that the anomalies were the i result.of an insulation crack in one of the wires, and were not related to the i splices. The following discussion addresses these anomalies in more detail.
Three of sixteen test splice assemblies experienced anomalies during this test.
These assemblies were designated as samples Nos. 2-2, 2-3 and 2-4. All splicos ,
were tested . with 696 VAC applied continuously during the LOCA/MSLB test.
Although the IR measurements were not directly taken at all points throughout the 11
m k
test, the circuits were monitored for excessive leakage current and for a ground t fault by use of a 0.1 ampere fuse.
During: the LOCA test, three samples listed above experienced excessive' leakage i current-as noted on page 13 of the report. Sample 2 3 and 2-4 were inline i splices and sample - 2 2 was a V- type . .The root cause of the anomaly which produced excessive leakage in the three splice circuits was attributable to a single-cable insulation crack in sample 2 3 but remote to the splice itself.
This insulation crack occurred on sample 2-3 inside the LOCA chamber but outside !
the ~ junction box where the tested splices were housed.
'- The insulation crack extended from the cable surface to the ccnductor on sample .,
2-3.' This allowed the pressurized steam and water to penetrate.the insulation
~-
and travel along the conductor underneath the insulation to.the outside of the LOCA chamber. The steam and water exited the cable at the fuse block, where samples 2-2 and 2-4 were also terminated, causing the fuse block and its plywood substrate to become moistened, creating a leakage current path to ground. The leakage current of sample 2-3 occurred during the initial 360*F temperature dwell followed by sample 2 2 forty seven minutes after test initiation and by sample ,
2 4 one hundred minutes after the start of the test. Since the three samples '
h were terminated to the same~ fuse block, they all experienced a similar increase in leakage current from the same anomalous condition. Therefore, it was evident ,
that the cracked wire insulation caused test assemblies 2-2, 2-3, and 2-4 to ,
L experience high leakage current.
H l This conclusion is further supported by the post accident testing conducted on L the splice assemblies. Upon completion of the-LOCA test, these three specimens L were- subjected : to IR measurements at 1000 VDC for one minute followed by. a dielectric. withstand test of 2400 VAC in water per Appendix IV of the report to isolate the cause of failure.
h Post LOCA insulation resistance (IR) tests at 1000 VDC -indicated an IR'value of 0.2 EE6 ohms .for the cracked cable sample 2-3 and values of greater than 1.0 EE9 .)
ohms for the. other. two samples, This indicates that the leakage current anomaly 1 was not attributable to a common mode failure of the tested splices. In addition, the remaining 13 splices completed the test without incident. l A subsequent dielectric withstand test at 2400 VAC was performed on the splices L themselves by cutting the cable on each side of the splice (i.e. removing the L cracked insulation from the . loop) and immersing them in water to confirm the l integrity of the splices. The results of the dielectric test indicated that the -
performance of all three. splices was- essentially the same with- the leakage current being less than 1 mil 11 ampere. This provided further evidence that oil e three splices maintained sufficient insulating characteristics after exposure to ,
N ~ normal.and accident conditions.
l '6
-Therefore, as. discussed in Section III.A., and as further detailed above, the anomalies associated with the Okonite splice test assemblies 2-2, 2-3, and 2-4 were the result of a crack in the conductor insulation, and are not attributable .
to splice performance. It should be noted further that in both tests which form l the basis for the District's qualification of Okonite splices, no evidence of splice' failure has-been identified.
T 12
- i. l 1
Another anomaly which occurred during the testing documented by Patel Test Report PEI-TR-842900-1 involved leakage current due to water penetration at the " shrink j
- fit. endL caps" located ' on cable specimens which were independently tested concurrent with' testing of the splice assemblies.; The NRC memorandum1 states:
"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 urrent leakage path, is an example that is analogous to the inherent weakness of the V-type tape splices."
.i, Cable test samples P2 and F2 experienced-excessive leakage current during the f dielectric withstand test. The leakage current resulted from water penetrating the cable jacket at the epoxy chamber entrance, located outside the LOCA chamber, ,
which resulted in water accumulating at the end caps. The end caps at issue are 1 net qualified items, were applied over non safety related cable jacketing which is. subject to cracking, and the cable test was independent of, and therefore not
. applicable to the qualification testing of the Okonite splices.
V.B. During Testine Documented by Patel Test Report PEI-TR 842900-1. the i Functional Performance of the Okonite Solices Was Not Measured Durine the i Accident Simulation.
' As discussed in Section IV above, the District uses Patel Test Report i
.PEI-TR-842900-1 to demonstrate-the ability of Okonite to maintain its' physical
. integrity, withstand significant permanent dielectric changes, and to support the F conclunion that Okonite provides adequate sealing capability. During the testing ,
documented by Patel . Test Report PEI-TR-870200-02, insulation resistance and l- leakage current were measured durine the accident simulation test, and therefore adequately address this' concern. [
p As -discussed earlier, the test program documented by Patel Test Report j PEI-TR-870200 02 consisted of testing six (two loops of three splices each) in- '
As discussed in . the Lline Okonite splices over fiberglass braided wire. ,
background section above, the test methodology has been evaluated by the NRC and ' l
- found to be acceptable. ]
i The six splice assemblies were securely fastened inside a grounded junction box and the leakage current at 120 volts for Loop 1 and 480 volts for Loop 2 was recorded throughout the accident simulation. In addition, insulation resistance was measured at 500 VDC periodically during the transient and thermal equilibrium
- phase of-the accident simulation. The test duration was approximately 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />; 7 a
however,: the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the test completely envelope the postulated harsh L environment of okonite splices !.n 4 20 mA loops (i.e. , environments outside' the drywell return to mild enviror. ment within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />).
$1 ~
The leakage current for Loop 1 remained below 2 mA throughout the accident test, while . the minimum. IR value recorded was 3.0 EE7 ohms. However, an anomaly f , -involving leakage current occurred in Loop 2 (480 VAC) 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br /> into the test, p At approximately the same time, the insulation resistance dropped to 5.0 EE3 L ohms.
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Post accident inspection revealed:that the braided wire external' to the splice.
was frayed, presumably due to mishandling of the test specimen. Discoloration 1
' of' the junction box indicated that arcing had occurred'at some time during the-test.':It was determined that_ the frayed wire was the- cause of the low IR values and high leakage current experienced by Loop 2 during .the test. This was
- verified' by a further IR measurement following the accident simulation. The '
- damaged' portion of the wire was moved away from the- junction . box, without disturbing the contact of the splices to the ground plane in that Loop. The IR values were again measured, resulting in a reading _of 4.0 EE7' ohms for Loop 2.
As stated in Section II, Background, the NRC has accepted the testing documented by. Patel Test Report PEI TR-870200-02 for demonstrating qualification for equipment with operability times up to 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br />. Since the Okonite splices at issue are located outside the drywell, the environment to which they are exposed returns to mild within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Therefore, the anomaly described above does not impact the qualification of these splices, and functional performance during ,
accident conditions is demonstrated.
V.C. Testine Documented by Patel Test Reoort PEI-TR-842900-1 was nerformed at
- j. a Much Higher Voltare than Used in Instrumentation Circuits and Therefore Does Not Take Into Account Drvine of the Solice Due to Leakare Current.
ll The-NRC, during cotr'ersations with District personnel, had expressed concerns
' regarding potential- drying of the splice junctions due to circuit resistance
. heating at high vol: age. As documented by Patel Test Report PEI-TR 870200-02,
- l. the District has conducted further testing of Okonite tape splices, performed at L a lower voltage than used_' in testing documented by Patel Test . Report
[' PEI-TR-842900-1. During the District's additional testing, Okonite ' test
[ specimens were continuously stressed at 480 VAC and 120 VAC open circuit voltage.
Therefore, _the only current available . for resistance heating in the splice is from the leakage current. This current was monitored continuously during the L teest. The leakage current did not exceed 1 mA for the 120 VAC loop or 8 mA for the 480 VAC loop during the first 46 hours5.324074e-4 days <br />0.0128 hours <br />7.60582e-5 weeks <br />1.7503e-5 months <br /> of the test.
Each test loop contained three Okonite splices. Assuming conservatively that the- ;
entire circuit resistance measured during the test program was centered in eng worst case splice,-(i.e., assuming zero resistance for the wire and two.of the splices) the power available for drying the splice would be 5 microwatts, _which '
corresponds to 1ess than 5 EE 9 Btu /sec. At this rate of heat input, it would
~
require over 5 days to . raise one gram of water l'F. Given the high temperature .'
of the accident simulation chamber, with periodic additions of steam to achieve.
and maintain the required temperature, the effects of circuit resistance heating are negligible. Therefore, the District's - qualification basis adequately 1
addresses this concern.
VI . . CONCLUSION
' Besed on the existing qualification basis as demonstrated by Patel Test Reports
'PEI-TR 842900 1 and PEI-TR-870200-02, and the analysis provided in and referenced by EQDP 224 as discussed above, the District has concluded that Okonite splices are qualified for use in instrumentation applications at CNS. As discussed in "
the Background Section, the District, by letter dated May 31, 1988, provided the.
14
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- NRC with' a copy of PEleTR-870200-02. This test report and the analysis discussed
~
.i
.- above adequately address each of the concerns expressed by the NRC memorandum,' !
- and- those expressed;by the NRC 'in recent discussions. - There fore , l it is the l
~'
p - District ?s : position 3 that Okonite splices : are qualified for use at . CNS in instrumentation, circuits in potentially harsh environments. .;
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J 9-REFERENCES e.
- 1. Memorandum from G.M. Holahan (NRR) to S. J. Collins and ' L.' J'. Callan (Region.IV) dated May 16, 1990, " Qualification of Taped Splices for Use in Instrumentation Circuits Subject to Harsh Environments, Waterford Steam Electric; Station, Unit 3."
- 2. Justification For Continued Operation No. 90 03, "Okonite Tape Splices in EQ Instrumentation Circuits," approved August 17, 1990.
- 3. Environmental Qualification Data Package (EQDP) 224, "Okonite T95/35 Taped Splices."
- 4. Letter from J. E. Gagliardo (NRC) to G. A. Trevors-(NPPD) dated' April 1, 1987, " Equipment Qualification (EQ) Inspection Cooper Nuclear Station-Inspection Report 50 298/86 28."
l-5.. Letter from G. A. Trevors (NPPD) to NRC dated June 17, 1987, " Nebraska Public Power District Response to Inspection Report Docket 50 298/86-28." J y
- 6. Letter from R-.'E. Wilbur (NPPD) to A. Johnson (NRC) dated May 31, 1988 transmitting Patel Report PEI TR 870200 02. .
- i
- 7. " Test Report on Steam Accident Simulation of Limitorque Control and q Power Wiring and Okonite Tape Splices," Report No. PEI-TR 870200 02, Patel Engineers.
- 8. Letter from C.' A. Trevors (NPPD) to NRC dated July 13, 1988, " Updated j Response.to Inspection Report 86-28, Cooper Nuclear Station, Docket 50 . 1 298, DPR-46."' '
- 9. Letter from L. J. ' Callan (NRC) to G. A. Trevors (NPPD)Tdated October 19, -)
1988, " Equipment Qualification (EQ) Inspection -' Cooper Nuclear Station j Inspection Report 50-298/88-26." l,
- 10. Letter from G. A. Trevors (NPPD) to NRC date November 18, 1988, "NPPD Response to Inspection Report 50-298/88-26."
- 11. Letter from L. J. Callan (NRC) to G. A. Trevors (NPPD) dated December j 4 .29, 1988, regarding the District's response to Inspection Report 50- l 298/88-26. .l i
- 12. . Letter from L. J. Callan (NRC) to G. A. Trevors (NPPD) dated April 17- ,
1989, transmitting Inspection Report 50-298/89 13.
i
- 13. ' Letter from S. J. Collins (NRC) to G. A. Trevors (NPPD) dated April 20, j 1990, transmitting Inspection Report 50-298/90-09.
16
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, 14 '. Letter from C.. A. - Trevors (NPPD) to NRC dated July 31,-1990, " Response to NRC Inspection Report No. 90 09, Cooper Nuclear Station, NRC' Docket
. 50 298, DPR-46."
- 15. Letter from S. J. ' Collins (NRC) to C. A. Trevors (NPPD)' dcLed August -13, 1990,- regarding the qualification of Okonite tape splices in-instrumentation circuits.
" Final Test Report of Okcaite Tape Splice Insulation for Power and 16.
Control Cables and-Rockbestos Pyrotrol III and Firewall III Cables,"
Report No.-PEI- TR-842900-1, Patel Engineers.
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