ML20127P588
| ML20127P588 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 01/25/1993 |
| From: | William Cahill, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TXX-93060, NUDOCS 9302020001 | |
| Download: ML20127P588 (17) | |
Text
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Log ( TXX-93060 File # 10010 909.5 r
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Ref. # 10CFR50.48 TUELECTRIC January 25, 1993 Wihrn J. Cahill, Jr.
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U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, OC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NO. 50-446 RESPONSES TO REQUEST FOR ADDITIONAL INFORMATION FOR CPSES UNIT 2 REF:
- 1) TV Electric Letter logged TXX-92626 from Mr. William J. Cahill, Jr. to the USNRC dated December 23, 1992
- 2) TV Electric Letter logged TXX-93038 from Mr. William J. Cahill, Jr. to the USNRC dated January 19, 1993
- 3) TU Electric Letter logged TXX-93023 from Mr. William J. Cahill, Jr. to the USNRC dated January 19, 1993
- 4) USNRC Letter from Suzanne C. Black to to William J. Cahill, Jr. dated October 29, 1992 Gentlemen:
After a review of the above referenced letters, TU Electric and your Staff met in Washington, DC., on January 21, 1993, to resolve issues which arose during your review of TV Electric's documents-listed or attached to the above referenced letters. Additionally, during a teleconference with your Staff on January 22, 1993, your staff requested additional clarifications regarding the Therno-lag testing data and the engineering evaluations.
TU Electric is hereby responding to the' additional information requested by your staff, during(as we understand them) are provided in the attachments to January 21, and 22, 1993 conversations. Responses to the staff's questions this letter.
The subjects addressed in the attachments are:
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i IXX-93060 Page 2 of 2 :
Cure time required to declare Thermo-Lag operable :
Combustibility (IN-92-82) : Thermoset cables and qualification of mineral insulated cable :
Clarifications specific to the test reports docketed via, Reference 3, and attachments TV Electric offers the folicwing in response to the NRC Staff's question regarding the completion of the calculations for the weight of raceways which have been covered with additional Thermo-Lag material, and if Safety Evaluations have been performed for these changes.
TU Electric did not perform 10CFR 50.59 Evaluations for these changes, since they were not under the auspices of 10CFR 50.59.
TV Electric performed calculations to verify design adequacy.
Should you require additional information or copics of documents not available to your Staff in Washington, OC., please feel free to contact Obaid Bhatty at (817) 897-5839.
Sincerely.
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William J. Cahill, Jr.
By:
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R. D. Nalker Manager of Regulatory Affairs for NE0 OB/ds Attachments c - Mr. J. L. Milhoan, Region IV Resident inspectors, CPSES (2)
Mr. T. A. Bergman, NRR Mr. B. E. Holian, NRR
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' to TXX-93060 Page 1 of 1 CURE T1HE The Thermo-Lag pref abricated panels and preshaped conduit sections, when shipped f rom Thernal Science Inc (TSI), are deemed capable of performing their design function.
These prefabricated shapes do not require additional or further curing. Appropriate certificates of conformance are submitted by T51 pertaining to curing of these prefabricated shapes, which are available for review at receipt inspection by TU Electric Quality Control inspectors.
TV Electric has subsequently consulted with the Thermo-Lag vendor (i.e.,
TSI) on this issue. During a teleconference with TSI, and a review of attachment 3 of TXX-93023 "Thermo-Lag Operability", TSI has concurred with TV Electric's position.
Additionally, TSI has provided TV Electric with a letter documenting such along with an explanation regarding it's June 3, 1992, comments on 30 day cure time.
Regarding the Thermo-Lag trowel grade material used to prebutter joints or use of tr wel grade material for the upgraded fire barrier configurations.
TV Electric contends that a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> cure time, or, a moisture meter reading of less than 100 using a Delmhorst Model DP moisture meter is adequate to declare the fire barriers operable.
TV Electric has demonstrateo the acceptability of using this cure time criteria prior to topcoat by applying this criteria in the fabrication of the samples tested at Omega Point Laboratory.
This issue was previously discussed with your staff and was docketed via TXX-93023 (Attachment 3).
Notwithstanding, if the Unit 2 low power operating license is issued prior to acceptance of TV Electric's position with respect to cure time, compensatory measures as required, will be established.
J 4 to TXX-93060 Page 1 of 7 i
C0leUSTIBILITY OF T11CRH0-LAG i
information Notice (IN) 92-82, "Results of Thermo-Lag 330-1 Combustibility Testing" was issued on December 15, 1992 to inform licensees of the results of small scale testing performed for the staff by the National Int,titute of StandardsandTechnology(NIST). These tests subjected 1/2 inch and 1 inch thick Thermo-Lag panel samples to two separate tests to investigate the combustibility properties of the material.
The subject tests were 1) ASTM E136. " Standard Test Method for Behavior of Material in a Vertical Tube furnace at 750 C" and 2) ASTM E1354, " Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products using an Oxygen Consumption Calorimeter." The results of the ASTM E136 tests were that Thermu-Lag 330-1 material failed criteria invoked by the standard to qualify it as noncombustible.
Since this test is a pure pass / fail determination, the material is defined by AS1H E136 criteria as combustible.
The results of the ASTM E1354 tests compared peak and total heat release rates (HRR) to values established for gypsum wa11 board. As such, the values obtained for peak HRR were determined to be equivalent to those for gyptum, while values obtained for total HRR were determined to be more than 8 times higher than those for gypsum.
The Information Notice conveyed these results to licensees for consideration of impact where Thermo-Lag is used for enclosure of intervenina combustibles to achieve a horizontal distan:e of 20 feet between redundant safe shutdown trains. Additionally, the results conveyed by IN 92-82 were provided for consideration of impact where Thermo-Lag is utilized inside noninerted containment structures as a noncombustible radiant energy shield to achieve protection of safe shutdown circuits.
Response to IN 92-82 a)
Therno-Lag is not utilized to eliminate intervening combustibles in order to obtain a horizontal distance of 20 feet with negligible intervening combustibles between redundant safe shutdown trains.
This is documented by the " Unit 2 Fire Safe Shutdown Analysis" (Ref.1) and the " Unit 2 Physical Separation Analysis and Unit 2 Cables and Components in Common Areas" (Ref. 2).
b)
Thermo-Lag is not utilized as a radiant energy shield inside Unit 1 or Unit 2 containment structures.
c)
There is no Thermo-Lag installed in non-raceway applications for Unit 2 (i.e., as used for protection of structural steel supporting 2-hour rated gypsum wall assemblies around stairwcys) which could act as an intervening combustible between redundant safe shutdown trains, d)
The. following information addresses those plant areas where Thermo-Lag installed on Unit 2 safe shutdown raceways could potentially constitute an intervening combustible between redundant equipment or components:.
. to TXX-93060 Page 2 of 7 1.
Auxiliary Buildina. 852'-6" Elevation. Room X-241 (Fire Area AA1 Fire safe shutdown analysis area AA-N is physically separated from the remainder of Fire Area AA by floors, w;11s and ceilings on the east and west which have a 1-hour minimum fire rating. The north and south boundaries are special separation area; (i.e., " buffer zones") separating Train A and Train B components, primarily MCC's.
These buffer zones are 20 foot wide areas with no intervening combustibles except as noted below, running north-south.
Cable trays containing non-essential cables which transverse the north and south boundaries of each buffer zone are provided with fire stops to prevent potential propagation paths across the buffer zones.
Raceways containing essential cables are protected with Thermo-Lag up to the boundary of their respective buffer zone.
One cable tray protected with Thermo-Lag extends through the north buffer zone and the north boundary of the south buffer zone at which point the tray terminates and the cables transition into two 4 inch diameter conduits and a 12 inch wide tray.
These commodities (also protected with Thermo-Lag) then extend south, out of the buffer zone (see Sketch 1). All other Thermo-Lag in the south buffer zone terminates since the associated raceways penetrate the west wall of the corridor oc the floor.
Fire propagation along the Thermo-Lag installed on the trays and conduits which transverse both buffer zones is not credible based on the properties of the material described below and overali lack of other combustibles to fuel such a fire.
Additionally, complete sprinkler system protection and ionization type fire detection system coverage is provided for the area.
2)
Electrical & Controls Buildina. 778'-0" Elevation. Room X-1158 (Fire Aret_aal As described in the Fire Protection Report (Section V, Appendix C) for Deviation Ib(2), separation of redundant safe shutdown components and raceways associated with the Unit 2 safety chilled water system is achieved via partial height 1-hour rated fire barriers, complete automatic suppression system coverage (including " water curtain" coverage at the partial barriers),
complete fire detection system coverage and cable tray fire stops at the partial barriers (Ref. 3).
In addition, all cables and raceways essential for operation of both trains of chilled water components are protected with Thermo-Lag barriers. Thermo-Lag is not used to enclose the negligible quantities of combustibles that exist in the room (predominantly exposed non-essential IEEE 383 cabling).
Some raceways (mostly conduit) protected with Thermo-Lagtransversethepartialheightbarriers(SeeSketch2).
Fire propagation along those raceways with Thermo-Lag, such that a fire 1
I to TXX-93060 Page 3 of 7 originating on one side of a barrier could affect both trains of cables or components is not credible based on the properties of the material described below, overall lack of other combustibles to fuel such a fire and the extensive fire protection features provided for the area.
3)
Auxiliary and Unit 2 Safeauards Buildina (Fire Areas AA. 2SB. 2SK)
Other locations exist in these fire areas where Thermo-Lag installed on safe shutdown cables and raceways is located within spaces separating redundant components.
In no instance is Thermo-Lag utilized to achieve 20 foot horizontal separation by enclosing the negligible quantities of combustibles (i.e., non-essential cat,1es) that exist in the areas.
In Fire Areaf 2SB and 2SK, the safe shutdown raceways protected with Thermo-Lag are n.inor quantities of conduit only.
In all cases, the in-situ combustible loading in the areas is low, consisting predominantiy of exposed IEEE 383 cabling and no viable propagation pathways exist. Fire propagation along raceways with Thermo-Lag such that redundant components could be affected is not credible based on the properties of the material described below and overall lack of other combustibles to fuel such a fire. Additionally, complete fire suppression and detection system coverage is provided for Fire Area 2SK and applicable portions of Fire Area 258 where redundant cables, raceways or components are located, in Fire Area AA, complete fire detection system is provided but only partial suppression system coverage.
in this instance, as described below, the inherently low in-situ combustible loading, administrative controls and the ionization type fire detection system coverage effectively minimize the potential for development of a fire of sufficient size and intensity to involve the Thermo-Lag.
3)
ASTM E136 is not considered to be an appropriate test to determine the inherent combustibility of Thermo-Lag, based on the intumescence and sublimation properties of the material. As noted in IN 92-82, gypsum wa11 board with the outer (paper) layer left in place will not pass this test.
Considering how and where Thermo-Lag is utilized, use of ASTM E84, " Surface Burning Characteristics of Building Materials" (used to measure the properties of the paper covering on gypsum board) is more appropriate, since the primary concern for Thermo-Lag 4.talled within a 20 foot horizontal separation zone is propagation potential (i.e, flame spread) between redundant shutdown trains. The ASTM E84 flame spread rating of 5 for Thermo-Lag 330-1 material and for 350 Topcoat (Ref 4) demonstrates that Thermo-Lag with Topcoat will not readily propagate a fire.
Based on this flame spread rating, NFPA 101 (Ref. 5) would define Thermo-Lag as a Class A material; i.e., allowable for interior finish I
E to TXX-93060 Page 4 of 7 b[-
u in building emergency egress travel paths. Another appropriate test ei hx' hod would be the ASTM E162 critical heat flux test (Ref. 6), which determines the heat energy required for a material to propagate a flame.
Thermo-Lag 330-1 with Topcoat has a high flash ignition temperature f
(1004 F) based on ASTM 01929 testing (Ref. 7) and requires a high 2
T radiant heat flux, estimated at 6.4 kw/m (Ref. 0), to sestain i
combustion.
Based on the above and fire modeling techniques utilized
}
fe determination of minimum fire sizes required to activate sprinkler syste' ' at CPSES (Ref. 9), sufficient basis exists to conclude that sprinkier systems installed in areas containing Thermo-Lag will activate h
prior to ignition of the Thermo-Lao, For the minor plant arets containing Thermo-Lag where sprink nr protection is not provided, inherently low in-situ combustible loading, administrative controls (i.e., transient combustible limitations and enforcement of "No Storage" requirements per Ref. 10) and complete fire detection syster enverage effectively minimize the potential for development of a fire of sufficient size and intensity to ignite the Thermo-Lag.
Therefore. based on the Fire Hazards Analysis, adequate fire protection features are provided in all plant areas to address the limited combustible pret rties of Thermo-Lag.
TU Electric is actively participating m the NUMAPC effort to address Thermo-Lag combustibility iss m in a generic industry basis, and may take future action based on NUMMC s findings and 7:connendations.
Refer s 1) salculation 2-ME-0282, Rev. O, " Unit 2 Fire Safe Shutdown Analysis."
2)
Calculation 2-ME-0279, Rev. O, " Unit 2 Physical Separation Analysis and Unit 2 Cables and Components in Common Areas".
3)
CPSES Engineering Report ER-ME-080, Rev. O, " Assessment of Fire Protection Features for Separation of Unit 2 Redundant Safety Chiller Components".
4)
Underwriter's L ooratories ASTM E84 Tests; "Thernc-Lag 330-1 Subliming Compound without Topcoat", UL File No. R6076, dated June 16, 1981 and "Thermo-Lag 350 Topcoat," UL File No. R0676B, dated June 16, 1981.
5)
National Fire Protection Association (HfPA), " Code for Safety to Life from Fire in Buudings and Structures." 1988 Edition.
_ _. ~
. to TXX-93060 Page 5 of 7 6)
American Society for Testing and Standards (ASTM), Publication E162-90,
" Standard Test Method for Surface Flammability of Materials using a Radiant Hcat Energy Source".
7)
Omega Point Laboratories Test Report 12340-93953, " ASTM 01929 Ignition Properties of Plastics; Thermo-Lag 330-1 (with Coating and Stress Skin)", dated July 10, 1992.
8)
Omega Point Laboratories Final Report (Draft) on OPL Project No. 94105,
" Evaluation of Heat Release Parameters of Thermo-Lag 330", dated September 3, 1992.
9)
Hughes and Associates, Inc., " Engineering Evaluation of HRC Unresolved Items for CPSES Unit 2." dated.lanuary 11, 1993.
- 10) CPSES Procedure STA-729, " Control of Transient Combustibles, Ignition Sources and Fire Watches," Rev. 4.
-Attachment-2 to TXX-93060
.Page 6 of-7
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. to TXX-93060 Page 1 of 2 CABLES Thermoset Cables In clarification of the response to question 12 in reference 2 (TXX-93023) attachment 2, page 4 of 14, TU Electric confirms that:
All cables contained in raceways protected by Thstmo-Lag for Fire Safe Shutdown requirements are IEEE-383 qualified and have thermo setting insulation (except for mineral insulated cable).
Mineral Insulated Cable Oualification Summary EEQDSP-THES-042-01 " Qualification Test Report for the RCS series Neutron Flux Monitoring System," which includes the following:
This qualification report includes the qualification of mineral insulation cables.
Section 5 " Specification and Test Result", of this report summarizes the specification and test results for different cable attributes at different temperatures.
The table in section 5 documents that the mineral insulated cable meets or exceeds all the specification requirements for the adequate transmission of signal at temperatures of 75 F to 420 F, (refer to pages 18-27 of-the report 6
for data sheets).
During these tests the minimum insulation resistance measurement at 420 F was 4000 M ohms which exceeds the specification requirement of 1000 M ohms. The mineral insulated cable for neutron flux monitoring is installed in an exclusive 3 inch conduit from the Reactor Building penetration to the amplifier. This conduit is protected by Thermo-Lag. Temperature eavironment inside the conduit during a fire scenario will be consistent with Thermo-Lag fire endurance qualification test for 3 inch conduit which is less than the 420 F for which the cable is qualified.
The qualification of the mineral insulated cable shows that this cable will perform its design function at temperatures to which it may be exposed, when protected by Thermo-Lag, during a fire scenario.
Cable Deratina
'In clarification of our previous response to question 9, in reference 2 (TXX-93023) attachment 2, Page 3 of 4,TV Electric concludes that:
'1
' to TXX-93060 Page 2 of 2 A cable derating factor of 31% was utilized using UL Report R6802.
However, due to concerns raised by the NRC's Inspector General Report, CPSES performed a calculation (2-EE-0053 Revision 0) to evaluate acceptability of a 40% cable derating factor. The "40% derating by calculation" in Appendix C refers to this calculation.
The reference to
!TL Test P.eport is an oversight and will be corrected to reference UL R6G02. Engineering report ER-ME-067 is being revised to reflect this correct test report for cable derating.
I
. to TXX-93060 Page 1 of 5 CLARIFICATIONS SPECIFIC TO Tile TEST REPORT Oualification of 36 inch (Stratqht Run) Cable Trav Unit 2 FSSA requires 1-hour fire barrier protection of cables which are routed in 36 inch wide cable tray in the Auxiliary Building.
Scheme 12-1; a 30 inch tray (straight run), and Scheme 14-1; a 30 inch tray with tee section were tested by TU Electric.
A brief description af the upgrades is prov*.ded in Appendix A of the Engineering Report ER-ME-067 (Reference 1).
Please note that for Scheme 14-1 joint reinforcements were limited to additional stress skin and trowel grade buildup.
Successful 1-hour fire endurance tests for the Thermo-Lag protective envelope installed on Scheme 12-1 and 14-1 were performed. The tests were conducted utilizing tne acceptance criteria provided in USNRC letter of October 29, 1992, the test results were:
a)
Maintained acceptable cable and side rail temperature.
It was noted that one thermocouple on Scheme 14-1 (located on the horizontal centerline of the tray rail on the tee section, opposite the mouth of the tee) recorded a maximum temperature of 6 F above the acceptance temperature of 395 F.
Visual cable inspection, however, was satisfactory, b)
The fire barriers were subjected to a post fire fog nozzle spray test at C
75 psi and the post fog nozzle visual inspection revealed that no barrier " burn through" occurred; c)
Visual cable inspection was satisfactory; and d)
Insulation resistance test results and circuit continuity results were
' [
acceptable.
These two tests demonstrated that for both the 30 inch tray (straight run) and the 30 inch cable tray with the tee section yielded similar and satisfactory test results.
A 36 inch wide tray with a tee section, Scheme 1, was also tested by TU 4
Electric. A brief description of the upgrades is provided in Appendix A of the Engineering Report ER-ME-067. A successful 1-hour fire endurance test for the Thermo-Lag protective envelope on Scheme 1 was performed. This test.
was conducted on June 22, 1992, prior to the issuance of USNRC letter is criteria provided in the October 29, 1992. The test results were:
a)
Maintained cable and tray side rail temperatures sufficiently below the values later established by the staff's coicurrence with tcst acceptance criteria for sebsequent tests;
.1
9
. to TXX-93060 Page 2 of 5 b)
No visual cable damage resulted in the test; and c)
Circuit continuity was maintained throughout the test and insulation resistance tests were performed, evaluated and were deemed acceptable.
The qualification of the 36 inch (straight run) cable tray is based on demonstration by satisfactory test, with consistent test data, of 30 inch wide tray (straight run), 30 inch cable tray (with tee section), and 36 inch cable tray (with tee section).
Differences between the Scheme 1 test assembly and associated test methodology and acceptance criteria and tests performed in November through December (i.e., Schemes 12-1 ar.d 14-1) are as follows:
The cable tray supports were protected with a single layer of 1/2 inch o
thick Thermo-Lag panels for a 9 inch distance from the raceway envelope and two layers of material for the remainder of the support lengths up to the test deck.
Subsequent tests utilized supports protected for the 9 inch distance only and demonstrated that protection of supports for the full length has no effect on barrier effectiveness or performance.
o Thermocouples were provided at 12 inch intervals on instrumented cables and the "outside" cables in the tray were located halfway between the centerline of the tray and the side rails.
Subsequent tests utilized cable thermocouples at 6 inch intervals and "outside" (instrumented) cables were positioned immediately adjacent to the side rails. However, since siderail temperatures were maintained sufficiently below values later deemed satisfactory by the staff, this had no bearing on the acceptance basis for the test, o
A 1-1/2 inch diameter smooth bore playpipe discharging a straight stream was utilized for conduct of the hose stream test.
Subsequent tests employed a fog nozzle for the hose stream test. However, since use of the fog nozzle on subsequent tray test including the two 30 inch tray tests, resulted in no adverse effect on barrier material, the results are considered applicable to Scheme 1.
The upgrade techniques utilized to construct the test assembly consisted o
of one of two independent methods to reinforce joints and seams:
Either " stitching" through the stress skin of abutting paneis using stainless steel tie wires or, Use of stress skin to cverlap adjacent panel surfaces by a 5 inch distance secured in place with staples and tie wires and covered with a trowel grade material buildup.
The actual plant configuration used both of these upgrades.
A l to TXX-93060 Page 3 of 5 Conclusion Based on the performance of Thermo-Lag material demonstrated by subsequent cable tray tests; i.e., Scheme 12-1 (30 inch wide tray), 12 2 (24 inch wide tray with " tee" section), Scheme 13-1 (12 inch wide tray) and 14-1 (30 inch wide tray with " tee" section), and maintenance of acceptable cabic and side rail temperatures as described above, sufficient basis exists to conclude that no barrier "burnthrough" occurred, it should be noted that for Scheme 14-1 (30 inch wide tray with " tee"), no " stitching" techniques were employed for joint reinforcement.
Therefore, use of the test results for Schemes 12-1, 14-1 and 1 for qualification of Unit 2 Thermo-Lag configurations with 36 inch wide cable trays (straight run) is justified.
The qualification test matrix provided in Engineering Report ER-ME-067 will be revised to include reference to test Schemes 12-1, 14-1 and 1 for the 36 inch wide cable tray.
Discussion on Test Scheme 11-1 a)
With respect to the discussion in the test report on page 22, the temperatures in the summary tables and actual thermocouple readings (TC
- 196, #197, Maximum Steel and Average Steel for 1" conduit) are all consistent with one another. The only statement that may be confusing is in the second paragraph on page 22, which states "the thermocouples located on the 1 inch conduit steel began reading excessively high temperatures," The term excessively high could be interpreted to he in excess of acceptance criteria. However, in this case, this paragraph was noting a major jump in temperatures at the 51 minute reading where thermocouple #196 jumped fror 190 F to 304 F in one minute and then proceeded to cool back to 240 F at the 60 minute reading. ' The intent of this paragraph was to identify what appears to be a false reading, not consistent with the typical steady rise for a E-119 exposure. This to a lesser extent appears to be the same anomaly which occurred in previous conduit tests. The term " excessive" in this case is describing what would be in excess of typical temperature rise.
It is, however, true that the temperature acceptance criteria was never exceeded on the 1 inch diameter conduit steel, b)
In accordance with the NRC acceptance criteria letter dated October 29, 1992, Test Scheme 11-1 was determined to be satisfactory based on the first two criteria for " Temperature" and " Barrier Condition".
- However, in order to obtain as much information as possible, TV Electric opted to gather all stipulated data for all tests performed. The cables were
n l
l to TXX-93060 Page 4 of 5 therefore, visually inspected and an " Insulation Resistance Test" was conducted on all cables. Visual inspection of the cables revealed slight "dange" (blistering) on the outside (exterior jacket) of three cables. The cable jackets were stripped away to inspect the condition of the conductors and conductor insulation.
Each of these cables did not have any visual evidence of damage to either the inside of the exterior jacket, onto the individual conductor insulation. The conclusions of the test report documents a " satisfactory" insulation resistance test. The test report states that W-020 Cable "R" acceptance criteria was 33.69 M ohms and the lowest reading was 5,000 M ohms W-023 Cable "T" acceptance criteria was 46.5 M ohms and the lowest reading was 5,000 M ohms, W-048 Cable "H" acceptance criteria was 45.94 M ohms and the lowest reading was 30,000 M ohms.
Therefore, all three cables were determined to be functional.
The thermocouple locations on this test assembly are identified both in the section entitled " Thermocouple Placement" and " Appendix C Thermocouple Locations."
In accordance with these sections, in 5 inch conduit, the instrumented power cable was located at the center of the cable bundle, while the instrumented control cable was located midway in the bundle and the instrumented instrumentation cable was located on the outside of the cable bundle. Thermocouples are located each six inches along the run of the bundle including through the free air drops attached to the conduits.
At the point where the blistering took place there were instrumented cables at each of those locations, however, the one control cable (midway) and instrumentation (outside) happened to be on the opposite side of the bundle.
This level of detail was not included in the test report since this was considered a satisfactory test by the acceptance criteria (October 29, 1992 letter).
Although TV Electric believes that there was no cletr definitive cause of blistering of the exterior jacket of these specific cables, the most likely cause is a twist in the cables which would cause the exttrior jacket to balloon and possibly touch the Thermo-Lag barrier.
TU Electric concludes that this was a satisfactory test because the temperatures were maintained be' low acceptable levels, and the fire barrier did not have any "burnthrough". Nevertheless, TV Electric did evaluate the slight blistering observed on three cables, and determined that undamaged conductor insulation and an acceptable Insulation Resistance Test furthei confirm this test as acceptable.
Discussion on_ Tnt _jitheme 12-2 Scheme 12-2; a 24 inch wide cable tray with tee section, was tested by TU Electric. A brief description of the upgrades is provided in Appendix A of
4 4
l to TXX-93060 Page 5 of 5 the Engineering Report ER-ME-067. The test was conducted utilizing the acceptance criteria provided in USNRC letter of October 29, 1992. The test results were:
a)
Maintained acceptable cable and side rail temperature, b)
The fire barrier was introduced to the fog nozzle spray test at 75 PSI.
During the hose stream test, the bottom Thermo-Lag panel below the fire stop at the tee area detached (sagged), which created an opening between the fire stop and the panel, c)
Post hose stream visual inspection was satisfactory with no "burnthrough" noted.
d)
Visual cable inspection was acceptable; and e)
Insulation resistance test results and circuit continuity results were acceptable.
The Thermo-Lag panel discussed in item b) above was bonded to the fire stop (seal) using trowel grade material; and no mechanical fasteners were used.
The Thermo-Lao trowel grade material did not provide adequate bond within the joint. This test was therefore considered satisfactory based on acceptable temperature during the fire test, and no burn through noted on the post fire fog nozzle test. Since there was a mechanical failure of one section of Therna-Lag, however, TU Electric further evaluated the post fire visual cable inspection and the insulation resistance checks to confirm that there was no cable damage.
Both of these evaluations were satisfactory, confirming that test Schenie 12-2 is satisfactory.
The CPSES design requirements were revised to provide mechanical attachment of the bottom Thermo-Lag to the fire stop. This design change has been implemented into Unit 2 via, Design Change Authorization (DCA) #104121 Rev.
O.
This detail was satisfactorily tested in Scheme 14-1 (30 inch cable tray withteeconnections).
l
,