ML20097G868
| ML20097G868 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/10/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20097G865 | List: |
| References | |
| NUDOCS 9206180025 | |
| Download: ML20097G868 (7) | |
Text
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..r l day UNITED STATES V <
[i NUCLEAR REGULATORY COMMISSION WAsHINoToN. D C. 20666 '
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TEMPORARY EXEMPTION FROM APPENDIX J INTERVAL FOR LOCAL LEAK RATE TESTING OF CONTAINMENT PENETRATIONS BROWNS FERRY NUCLEAR PLANT. UNIT 2 DOCKET NO. 50-260
1.0 INTRODUCTION
By letter dated December 20, 1991, the Tennessee Valley Authority, (TVA or the
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licensee),. requested a temporary schedular exemption to extend the interval for Type B and C (local leak rate) testing of certain containment penetrations at the Browns Ferry Nuclear Plant (BFN), Unit 2, beyond the 2-year limit of Appendix J to 10 CFR Part 50.
. Appendix J requires these tests to be performed at every refueling outage, but with the interval not to exceed 2 years.
Browns Ferry, Unit 2, was in cold shutdown from September,-1984 until May 24, 1991. Type B and C testing began July 30, 1990, in anticipation of a seemingly impending restart.
However, the return-to-power sequence-took longer than expected,'and startup did not occur until May 24, 1991.
Leak rate testing was also spread out and was finished in May, 1991,. shortly before startup.
Since the next refueling outage is scheduled to begin January 29, 1993, the expiration of the 2-year interval for some of the Type B and C-tests would force a plant shutdown in July,1992,
-because many of the tests cannot be performed at power.
At the time of the restart, the licensee had expected that an extensive mid-cycle outage would be necessary due to problems which usually or. cur following restart after an extended outage. The licensee planned to conduct Type B and C testing during this expected mid-cycle outage.
TVA has since decided that this mid-cycle outage is not necessary.
Therefore, the licensee is unable to perform the-required testing within required time frames without a shutdown solely for the performance of the testing. The licensee believes a shutdown only to perform the Appendix J testing is unnecessary and expensive in-terms of time, money, and radiation exposure. -Therefore, the licensee requested a temporary or schedular exemption to extend the test interval for the Type B and C testing'for certain components.
Originally,159 containment boundary components, or approximately 58 percent of the total in' the plant, were in need of Type B or C testing before January 29,.1993. However, during two forced outages in October and December, 1991,-the licensee was able to perform some of the tests and reduce the-number
-to 121, or approximately 44 percent of the total. This was the number of components for which the licensee requested an' exemption-in their December 20, 1991, letter.
In February 1992, another outage brought the number down to I
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.. 87 components, or approximately 32 percent.
The 87 components (see attuhed Table li include containment isolation valves, expansion bellows, flanges, and valve bonnets / packing. The maximum requested extension of the interval beyond 2 years for any one component is 177 days, or slightly less than 6 months.
Sixty-two of the 87 components would be extended no more than 3 months.
Further, the licensee is committed to performing additional Type B and C tests during any forced outages of sufficient duration that may occur before the next refueling outage.
2.0 EVALVATION The licensee has addressed the following factors to justify the requested exemption.
2.1 Components not testable at power For the components listed in Table 1, it is either not possible to test with the unit at power, or it is inadvisable to test at power, as discussed below:
1)
Approximately half of the components cannot be tested without R
entering the primary containment, which must remain inerted with nitrogen when the unit is operating.
2)
The 24 expansion bellows are hot (both thermally and radioactive-ly) during unit operation.
The high temperature could affect the accuracy of leak rate measurements. The stability of the leak rate data obtained from the testing apparatus could be affected, and the measured leak rate could be different from that which would be obtained under cold conditions, due to expansion /contrac-tion of the test volume.
In addition, testing at power would result in significant radiation doses to the testing personnel.
For these reasons, testing the bellows at power is inadvisable.
3)
Eleven components (valves and bonnets / packing) in the HPCI and RCIC systems cannot be tested without entering a Technical Speci-fication Limiting Condition for Operation for the system being tested.
In addition, certain Surveillance Instructions must be performed to demonstrate operability before returning the system to service. These constitute avoidable challenges to safety systems. Therefore, testing these components at power is inadvis-able.
4)
For 8 valves in the Residual Heat Removal (RHR) containment spray system and 2 valves in the Pressure Suppression Chamber (PSC) level control line, a system train must be made inoperable to conduct the tests. This degrades safety systems and is inadvis-able at power.
.-c 5)
For one bonnet in the High Pressure Coolant injection (HPCI)
I-turbine exhaust line, 30-ft-high scaffolding must be erected in the HPCI room to allow access to the bonnet for testing, at some hazard to personnel and the HPCI system.
The interval extension for this component is only 16 days.
This short extension is not significant enough to warrant the scaffolding exercise.
6)
One flange in the containment ventilation system requires a 3-day interval extension and must have a 20-ft scaffold erected for the test. This very short extension is insignificant.
2.2 Good leak rate history for components The licensee has performed a detailed analysis of the past leak rate history of the 87 components in question. Most of these components are historically
" good performers," and those few that are not were repaired or replaced during the last extended refueling outage. The licensee has used historical leak rate data to conservatively project the leak rate expected to exist on January 29, 1993, the date to which interval extension is requested.
The expected incremental increases in component leakage rates due to the extension are small, less than 18 percent of 0.6 times the maximum allowable leakage rate, La.
The quantity 0.6 La is the acceptance criterion set by 10 CFR 50, Appendix J for Type B and C testing.
The projected increase in total leakage rate due to the test interval extension reduces the margin between as-left leakage rate and 0.6 La by less than 22 percent.
This provides reasonable assurance that the requested test interval extension will not result in the Type B and C leakage rate total exceeding the 0.6 La limit of Appendix J.
2.3 Improvements made to testing program During the extended outage, numerous actions were taken to upgrade the plant's Appendix J program. The following is a summary of actions taken to upgrade the program:
Block valves, test connections, and vent valves to enable isola-tion valves to be tested by flow in the accident direction were added.
Block valves and test connections were added to simplify testing of bonnet and packing seals.
Valves were reoriented to allow packing and bonnet seals to be tested during the normal Type C test.
Lines no longer used were capped to remove potential leak paths.
Changes in valve type were made to improve leakage characteris-tics.
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Stainlets steel overlays were added to ventilation valves to improve leakage characteristics.
problem valves to improve leakage performance we during the outage.
As a result of these upgrades, modifications, and improved maintenance practicos, the possibility of significant degradation of containment compo-nents is reduced.
2.4 Intent of Appendix J The staff notes that the 2-year interval requirement for Type B and C com nents is intended to be often enough to prevent significant deterioration from occurrin outages.g and long enough to permit the tests to be performed during plant Leak rate testing of the penetrations during plant shutdown is preferable because of the lower radiation exposures to plant personnel Moreover, as noted before, some penetrations cannot be tested at power penetrations that cannot be tested during power operation, or for which For testing at power is inadvisable as discussed above, the increase in confiden of containment integrity following a successful test is not significant eno ce to justify a plant shutdown specifically to perform the tests within the 2-year time period, considering the factors discussed in Sections 2 2 and 2 3 above.
3.0 CONCLUSION
Based on the above evaluation, the staff finds the requested temporary exemption, to allow the Type B and C test intervals of the 87 components listed in Table 1 to be extended to the refueling outage which will begin no later than January 29, 1993, to be acceptable.
Attachment:
Components Requiring Extension -
Table 1 Principal Co...ributor:
J. Pulsipher Date: June 10, 1992
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TAllLE 1 COMPONENTS REQUIRING EXTENSION TYPE B TESTI'D COMPONENTS COMPONENT IT.NT11 TAT 10N DESCRD'T10N EX1tN5 TON Doy:
M11D%1 X.7 A inked Beliows M5 line A 27 W11DW1 X 7A outtoard Bellose M5 Lire A 21 MLLOW1 X.78 Inteerd Bellows M5 Lane B 10 NLtD%1 X.75 Oviboard Be' lose MS L4ne B 10 W11DWS X.7 C Intmard Bellosa MS Line C I0 IGLLD%1 X.7C Outtoard Bellows M5 Lire C 10 lu11D%1 X 7D intnerd Bellose MS Line D I0 N11D%1 X.7 D Outtmerd Bellows M1 (Jte D 10 E11D%1 X.8 Intnoard Bellows M5 Drain 27 N11Dn1 X.C Outtinerd Ballows MS Dran 17 III11D*1 X 9A Inbuerd Bellows FW Lens A 11I M11DW1 X 9A Owaboard Bellose W IJns A i11 s
TH1D*1 X.9B Inboatd Bellows FT Lire B 11I
/AIDn1 X 98 Ovitinard Betnown lv LAns B 111 sJ11D%1 X.10 inhovd Bellows RCIC 5taarn 120 stri r rs%1 X.10 Ovibeerd Bellows RCIC 5taarn 120 M11DW1 X.it intowd Bdlene itPCl Siemn 9
M11D%1 X.ii Oviboeid Benoon llPCI Staan 9
IE11D%1 X.12 inboard Bellows SDC Sucuan 42 nn t ry*1 X.12 Ovibond Bellows 3DC Section 42 M11DW5 X.13A Inboard Bellows Rim Discharge 42 BRID%1 X.13A Outboard Bellows RHR Discharge 42 BRID*1 X.139 Inbeerd Bdiove RilR Dacharge 42 IW11DW5 X.13B Outhoard Bellows RHR Dacterse 42 ILANGE N/A Stwar Les Access Cover O' 12 I1ANGE N/A Stav Lug Access Cova 43' 12 IIANGE N/A Bev Leg Access Cover 90' 13 ILANGE
'/A shes las Access Cover 113' 13 ILANGE e/A Shew Lug Access Cover 270*
I2 ILANGE N/A Shew Le6 Access Cover 313' 12 DONNETNACKING X.2tl 24CV 7139/601 9
BONNFT&ACKING X.220 2.FCV.73 64/642 9
BONNETNaCKING 71 22 RCIC Veceon Pump Dischese 64 BONNISMACKING 73 24 IIPCI Tert >ine Ethaust Dram 167 BONNET 73 23 IIPCI Turbine EAbasst 16 TLANGE 64 19 Containrnent Ventilat6en 3
TABLE 1 (CONTINUED)
COMPONENTS REQUIRING EXTENSION TYPE C TESTED COMPONENT 8 COMPONENT IT.NI'TRA.ON DE50UPT10N CrlTN$10N Days 2 3.$38 X.9A Resciar Feedesier A 14 23334 X.9 A Reaciar Feedester A f4 2.FCV.73 45 X 9A HPCItercuan 14 23372 X.9B Raaetor Fe*4* ster B 137 2 3.$68 X.98 Reactor Feedwater B 137 2 69.$19 X.98 RWCU Return 137 2.FCV.71 40 X.9B RCIC inpevan 137 2.t$.576 X.98 CRD Return 137 2 63 523 X.42 Standby Uquid Control 173 2 63 526 X.42 8Landby Uquid Contrel l73 2 68.$00 X.37C RCP Seal Weser 24 2 68 350 X.37C RCP Seal Weser 24 2 FCV 691 X.14 RWCU sucum 146 2 FCV.69 2 X.14 RWCU 8ecem I46 2.FCV.70 4*,
X.23 RBCCW Rearn S5 2 70 506 X.24 RBCCW Supply 177 2.FCV.71 2/3 X.10 RCIC Sisasa Supply 1
2.'4CV 73 23/603 X 214 HPCI Turtnen Ethaest 16 2.FCV.74 47 X.12 RHR Shutdown Cooltag 91 2.FCV.74.48 X.12 RHR Shutdoen Cooling 91 2 74 661/662 X.12 RHR Shandown Coolmg 9l 2.FCV.77 2A X.ll Drywell Floor Drain Sump 60 2.FCV.77 29 X*ll Dryvell Floor Draia $mn, 60 2.FCV 7715 A X 19 Drywell Equipment Draw.twe 60 2.FCV.77 158
- 19 Drywell Equipment Drst, sane 60 2.HCV 713;,$92 X.221 RCic Vacuum Pump Discharys 64 2.HCV.73 24/609 X.222 HPCI Turbine Ethavst Drain 167 2 FCV.7118 X.227A RCIC Pung Secuan 6
2.FCV.74.$3
'(.13 A RHR Return g7 2.FCV.74.$ 4 X.13 A RHR Return 37 2.FCV.74 57/$8 X.211 A RHR Contamment $ pray
- 3 2.FCV.74 60 X.398 RHR Contamment Spey ag 2.FCV.74 61 X.39B RHR Contatamect $ prey gg 2.FCV.74 67 X.138 RHR Return g,
2.FCV.14 68 X.138 RHR Return gg 2.FCV.74 71/72 X.2 tlB RHR C-"-
5pey 73 2.FCV 7414 X.39 A RHR Containment 5 prey 69 2.FCV.74 75 X.39A RHR Containment Spray 39 2 FCV.73 25 X.16A Core Spey Ingcuan 173 2.FCV.73 26 X.16A Core Spey injecuan 173 2.FCV.75 53 X.KJi Core Spey inpcuan 172 2.FCV.75 54 X.169 Core sprey Inpcuan 137 2.FCV.75 57/5 8 X.227A PSC Level Control 147
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