ML17164B005
| ML17164B005 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 04/09/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17164B004 | List: |
| References | |
| GL-92-08, GL-92-8, NUDOCS 9904160167 | |
| Download: ML17164B005 (9) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SUPPLEMENTAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION GENERIC LETTER 92-08 AMPACITYDERATING ISSUES PP8 L INC.
SUS UEHANNASTEAM ELECTRIC STATION UNITS 1 AND 2 DOCKET NOS. 50-387 AND 50-388
1.0 BACKGROUND
During the public meeting held on March 14, 1995, with PP&L, Inc.(the licensee), the staff responded to the question "Willthe resolution of the ampacity derating concern be deferred until agreement on the appropriate testing protocol (i.e., Institute of Electrical and Electronic Engineers (IEEE) Standard P848)?" by reiterating the position which had been previously cited in the Request for Additional Information (RAI) dated September 23, 1994, that stated that the ampacity derating concern could be resolved independently of the fire endurance concerns.
During the subject meeting the staff noted that after a review of the industry test results which had been performed under the existing draft IEEE Standard P848, the staff transmitted comments (see Attachment 1(a)) which were designed to ensure repeatability of test results to the IEEE Working Group responsible for the test procedure.
The licensee was requested to submit its ampacity derating evaluations, including any test reports in order to provide an adequate response to Generic Letter (GL) 92-08.
By letters dated August 2, 1995, and February 4, 1997, the licensee submitted its response to the NRC RAI dated June 13, 1995, and December 18, 1996, respectively related to cable ampacity due to application of Thermo-Lag fire barrier for Susquehanna Steam Electric Station (SSES), Units 1 and 2.
In its submittal dated February 4, 1997, the licensee stated that a preliminary evaluation of the ampacity derating for Thermo-Lag enclosed electrical raceways installed at SSES indicated that for all cases except the 3-hour fire rated conduits on Unit 2, the allowable derating is greater than the factors derived from the Texas Utilities Electric Company (TUEC) configurations tested for Comanche Peak Steam Electric Station, Unit 2. Further, the licensee stated that destructive examinations and detailed walkdowns would be utilized to confirm that the Thermo-Lag configurations installed at SSES are representative of the TUEC-tested configurations.
This commitment was to be completed by the Spring of 1997.
In a letter dated January 6, 1998, the licensee provided the results'of the subject examinations; revised their previous findings relative to ampacity derating factors for electrical raceways protected by Thermo-Lag; and clarified their position with respect to the use of Thermo-Lag as a Regulatory Guide 1.75 electrical separation barrier.
9904i60ih7 990409 PDR ADQCK 05000387 P
PDR Enclosure
The staff had reviewed the licensee's submittals and concluded that although two open items arose due to the licensee submittal dated January 6, 1998, there exists adequate assurance that Thermo-Lag protected cables installed at SSES, Units 1 and 2 were operating within acceptable ampacity limits. By letter dated December 8, 1998, the licensee submitted a revised response to address the two open items related.to ampacity derating issues due to the application of Thermo-Lag fire barriers at SSES, Units 1 and 2.
2.0 EVALUATION After reviewing the licensee's submittals, the staff makes the following observations and findings. The ampacity derating analysis questions, the licensee's response, and the staff's evaluation of the responses follow.
Ampacity Derating Analysis Review
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Question 1
In your submittal dated August 2, 1995, you did not specify a derating value for the 3-hour fire rated conduit configurations since TUEC did not include any of the subject barriers in their test program.
Florida Power Corporation (FPC) has recently completed ampacity derating tests of 3-hour Thermo-Lag-enclosed conduit configurations.
These tests were conducted in accordance with the Institute of Electrical and Electronic Engineers (IEEE) Standard P848, Draft 16, "IEEE Standard Procedure for the Determination of the Ampacity Derating of Fire-Protected Cables," at the Underwriters Laboratories Northbrook Testing Station in Northbrook, Illinois. Given this new test data for 3-hour fire rated conduit configurations please describe how you have incorporated this information and what are ampacity derating factors now being utilized for the 3-hour Thermo-Lag fire barriers in SSES electrical design calculations.
Licensee Res onse In its submittal of February 4, 1997, the licensee stated that a review has been completed which compared the ampacity derating value of 21% for the 3-hour conduit installations.
Specifically, the licensee reviewed the testing performed by Tennessee Valley Authority (TVA)and FPC. The licensee obtained copies of the TVATest Report entitled Project No. 11960-97337897338 and a verbal summary of the FPC test results.
The licensee reviewed the TVAtests associated with the 3-hour Thermo Lag 330-1 installation constructed with post-buttered joints and upgraded with two layers of 770-1 material. The subject tests, which were conducted in accordance with IEEE P848 Draft 14, provided the following results: 4"-conduit ampacity derating value =
13%; 1" conduit ampacity derating value = 10%. Given that SSES 3-hour installations do not have any,770-1 material present and the TVAtest barriers possessed additional thermal resistance provided by the two layers of 770-1 material, the licensee considers the subject test results to be conservative relative for their existing Thermo-Lag installations.
The FPC testing results obtained pertained to tests performed in accordance with IEEE P848, Draft 16 on conduits protected with a 3-hour Thermo-Lag 330-1 fire barrier. The licensee cited the following results:
4"-conduit ampacity derating factor (ADF) = 2.7%;
1"-conduit ADF = 4.2% [Staff Comment: FPC reported an ADF value of - 4.3%. This error has no impact on summary finding].
The licensee concludes after reviewing the results of the TVA and FPC tests that their ampacity derating value of 21% for 3-hour rated conduit installations is conservative and provides a significant margin of safety.
Staff Assessment The information provided by the licensee was responsive to the question.
uestion 2 Describe whether the results of your destructive examinations and detailed field walkdowns to date demonstrate that all of the installed configurations are
~ representative with the TUEC-tested configurations.
In the event of any deviations with the TUEC-tested configurations, the licensee is requested to ascertain their impact on previous ampacity derating determinations.
Licensee Res onse In its submittal of February 4, 1997, the licensee stated that the destructive examinations and detailed field walkdowns are approximately 75% complete and are scheduled to be completed by the end of the Unit 2 eighth refueling outage scheduled for Spring of 1997. The results of these efforts had indicated that the baseline installations at SSES are generally consistent with the baseline portions of tPe cable trays and conduits tested by TUEC. The licensee found, however, instances where non-standard configurations exist for a limited percent of the total installation population. The non-standard configurations can be divided into two groups:
(1) minor discrepancies that come in contact with the protected envelope, such as thermal shorts; (2) common enclosures where multiple raceways are included within a single protected envelope.
The licensee considered the items falling into the classification of minor discrepancies as having a negligible effect on the ampacity derating and, as such, no adjustment in the factors provided above or as represented in their August 2, 1995, submittal. The licensee has not found any instances where multiple cable trays are enclosed within the same protected envelope.
The licensee has, however, identified situations where multiple conduits are contained within the same protected envelope.
In some instances, the other conduit contained in the enclosure is a non-power raceway.
In
some cases, two or more power conduits may share a common protected envelope for a portion of their routing.
The licensee contends that since the SSES ampacity derating value of 21% for the 1-hour and 3-hour conduits exceeds test derived values by TUEC and TVA (See Table below), the difference or margin bounds the single r0w of conduits in a single enclosure configuration.
Conduit Fire Rating SSES Ampacity Derating Value Derating Value from Testing Margin Over Test 1-hour 3-hour 1%
21%
10.7% (TUEC Testing) 13.0% (TVATesting) 10.3%
8.0%
Staff Assessment The information provided by the licensee was responsive to the staff's question.
Application of Ampacity Derating Methodology In general, licensees have sought resolution of GL 92-08 ampacity issues by two approaches.
Both approaches have been found acceptable to the staff. One approach involves the development of a mathematical model to estimate the ampacity derating factor or penalty associated with the application of a specific Thermo-Lag fire barrier configuration. The second approach utilizes industry ampacity derating tests conducted in accordance with the IEEE Standard P848, "IEEE Standard Procedure for the Determination of the Ampacity Derating of Fire-Protected Cables" authored by Task Force 12-45 of Tests and Measurement Subcommittee No. 12 of the Insulated Conductors Committee for the IEEE Power Engineering Society.
As of the February 4, 1997, the licensee had adopted the approach to utilize industry test data (i.e, TUEC, TVA)to estimate the ampacity derating factors for SSES Thermo-Lag configurations.
It should be noted that the purpose of the detailed examinations and walkdowns of installed configurations was to confirm the applicability of the selected industry test data to SSES configurations.
On the basis of the licensee's determination in its August 2, 1995, and February 4, 1997, submittals, that the selected ampacity derating factors are bounded for the Thermo-Lag applications at SSES, the staff finds that the licensee has provided adequate assurance that the subject cables are operating within acceptable ampacity limits.
The licensee submittal dated January 6, 1998, described the results from the completion of the detailed examinations and walkdowns discussed above.
However, the subject submittal raised the two open items which were subsequently addressed by a licensee submittal dated December 8, 1998. The open items, the licensee response, and the staff disposition of the items follow:
Open Items The licensee did not provide sufficient technical justification for the ampacity derating reduction approach cited in its January 6, 1998, submittal.
Discussion:
The staff has been extensively involved in the development of industry ampacity derating test standard IEEE P848.
One example of this involvement is evident in the staff concerns on the draft procedure contained in the letter from C. Berlinger, NRR Electrical Engineering Branch Chief to A. K. Gwal, IEEE Task Force 12-45 Chairman dated October 13, 1994, (Attachment 1(a)). The subject letter provided the subject IEEE task force with detailed information regarding concerns which arose during TUEC and TVAampacity derating tests.
The staff participation in the subject task force led to the resolution of those outstanding issues and the issuance of a test procedure which provides consistent and conservative test results.
It should be noted that the tests utilized by the licensee in its January 6, 1998 ampacity derating methodology were the subject of staff's original concerns (see (a)) to the IEEE.
In addition,. the n'w licensee methodology is inconsistent with IEEE Standard P848.
Therefore, staff finds that the licensee has not provided sufficient technical justification for its ampacity derating methodology as described in its January 8, 1998, submittal.
~Dis osition In its submittal of December 8, 1998, the licensee revised the ampacity derating factors for electrical power raceways protected with Thermo-Lag 330-1 fire barriers based upon FPC, TUEC, and TVAampacity derating test results (See Table below).
Raceway Type Conduit/Air Drop -1 Hr Pull IJunction Boxes - 1 Hr Conduit [non-std] - 1 Hr Conduit/AirDrop - 3 Hr Pull IJunction Boxes - 3 Hr Cable Tray (with tray covers)
Wireway Cable Tray (w/o tray covers)
SSES Ampacity Derating Factor 10.7%
15 7%
13 0%/
10 7%
(non-upgraded raceways) 41 0%
31 5%
Industry Test Reference FPC Project No. 95NK17030 TVAProject No. 11960-97335 TVAProject No. 11960-97337 &
97338/FPC Project No.
95NK17030 for non-upgraded raceways FPC Project No. 95NK17030 TUEC Project No. 12340-95169 Staff Comments
',1) SSES Value exceeds -3.3%
FPC test result 7.7% margin added above the TVAtest result 13.0% SSES Value consistent with TVAtest I See Comment 1
(2) SSES Value consistent with test result See Comment 2
Although the licensee installed Thermo-Lag configurations at SSES Units 1 and 2 utilized the design and construction of FPC tested configurations the licensee appropriately selected ampacity derating factors for implementation based upon conservative positive TUEC (10.7%) and TVA (13%) test results.
Although the licensee referred to the acceptance by the staff of the FPC test results in its submittal dated December 8, 1998, the applicable NRC safety evaluation for Crystal River, Unit 3 did not address the application of those test results to the Crystal River design ampacity margins.
The use of negative or zero ampacity derating factors for fire barrier application is inconsistent with the known thermal insulating properties of the Thermo-Lag material. Therefore, the conservative arnpacity derating values selected by the licensee adequately resolves the subject open item.
The licensee should state explicitlywhether the destructive examinations and walkdowns performed confirm that the installed SSES Thermo-Lag fire barrier configurations are representative in terms of design and construction of those tested configurations which provided the SSES design ampacity derating factors for the applicable Thermo-Lag barriers.
~Dis osition In its submittal of December 8, 1998, the licensee stated that the installed SSES Thermo-Lag fire barrier configurations are representative in terms of design and construction of those tested configurations which provided the SSES design ampacity derating factors used for the applicable Thermo-Lag barriers.
See Table (Open Item1) above for the specific industry test results which was utilized by the licensee.
This information resolves the subject open item.
The staff finds that licensee submittal dated December 8, 1998, adequately resolves all of the subject open items.
3.0 CONCLUSION
S The staff found that the above open items did not affect the staff finding that adequate assurance exists to support the licensee assertion that SSES Thermo-Lag protected cables are operating within acceptable ampacity limits and that these items can be resolved independently of the original GL 92-08 ampacity concerns.
Moreover, after a review of the supplemental information provided in the licensee submittal dated December 8, 1998, the staff finds that the subject open items have been resolved for SSES, Units 1 and 2.
Attachment:
Letter from C. Berlinger, NRC, to A. Gwal, Defense Nuclear Facilities Safety Board, dated October 13, 1994 Principal Contributor:
R. Jenkins Date: