ML051330038
| ML051330038 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/12/2005 |
| From: | Abney T Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MC1704, TAC MC1705, TAC MC1706 | |
| Download: ML051330038 (10) | |
Text
May 12, 2005 10 CFR 54 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop: OWFN P1-35 Washington, D.C. 20555-0001 Gentlemen:
In the Matter of
) Docket Nos. 50-259 Tennessee Valley Authority
) 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - UNITS 1, 2, AND 3 -
LICENSE RENEWAL APPLICATION (LRA) - RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION CONCERNING T-QUENCHERS (TAC NOS.
By letter dated December 31, 2003, TVA submitted, for NRC review, an application pursuant to 10 CFR 54, to renew the operating licenses for the Browns Ferry Nuclear Plant, Units 1, 2, and 3. As part of its review of TVAs LRA, the NRC staff, through an informal request on March 29, 2005, requested additional information concerning the T-Quenchers.
The enclosure to this letter contains the specific NRC request(s) for additional information and the corresponding TVA response(s). Additionally, this letter provides followup information for RAI 7.2.5-2 concerning the supports for the T-quenchers.
If you have any questions regarding this information, please contact Ken Brune, Browns Ferry License Renewal Project Manager, at (423) 751-8421.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 12th day of May, 2005.
Sincerely, Original Signed by:
T. E. Abney Manager of Licensing and Industry Affairs
U.S. Nuclear Regulatory Commission Page 2 May 12, 2005 Enclosure cc (Enclosure):
State Health Officer Alabama Department of Public Health RSA Tower - Administration Suite 1552 P.O. Box 303017 Montgomery, Alabama 36130-3017 Chairman Limestone County Commission 310 West Washington Street Athens, Alabama 35611 (Via NRC Electronic Distribution)
Enclosure cc (Enclosure):
U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 Mr. Stephen J. Cahill, Branch Chief U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Senior Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611-6970 NRC Unit 1 Restart Senior Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611-6970 cc: continued page 3
U.S. Nuclear Regulatory Commission Page 3 May 12, 2005 cc: (Enclosure)
Margaret Chernoff, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Eva A. Brown, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Yoira K. Diaz-Sanabria, Project Manager U.S. Nuclear Regulatory Commission (MS 011F1)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Ramachandran Subbaratnam, Project Manager U.S. Nuclear Regulatory Commission (MS 011F1)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739
U.S. Nuclear Regulatory Commission Page 4 May 12, 2005 TLE:BAB Enclosure cc (Enclosure):
A. S. Bhatnagar, LP 6-C K. A. Brune, LP 4F-C J. C. Fornicola, LP 6A-C R. G. Jones, NAB 1A-BFN K. L. Krueger, POB 2C-BFN R. F. Marks, Jr., PAB 1A-BFN F. C. Mashburn, BR 4X-C N. M. Moon, LP 6A-C J. R. Rupert, NAB 1F-BFN K. W. Singer, LP 6A-C M. D. Skaggs, PAB 1E-BFN E. J. Vigluicci, ET 11A-K NSRB Support, LP 5M-C EDMS, WT CA-K s://Licensing/Lic/BFN LR Clarification Concerning T-quenchers.doc
ENCLOSURE TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1, 2, AND 3 LICENSE RENEWAL APPLICATION (LRA)
RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION (RAI)
CONCERNING T-QUENCHERS (SEE ATTACHED)
E-1 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1, 2, AND 3 LICENSE RENEWAL APPLICATION (LRA)
RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION (RAI)
CONCERNING T-QUENCHERS By letter dated December 31, 2003, TVA submitted, for NRC review, an application pursuant to 10 CFR 54, to renew the operating licenses for the Browns Ferry Nuclear Plant, Units 1, 2, and 3. As part of its review of TVAs LRA, the NRC staff, through an informal request on March 29, 2005, requested additional information concerning the T-Quenchers.
This enclosure contains the specific NRC request(s) for additional information and the corresponding TVA response(s).
Additionally, this enclosure provides follow-up information for RAI 7.2.5-2 concerning the supports for the T-quenchers.
NRC QUESTION 1 NRC issued the following Information Notices on problems in BWR containments.
Determine if the applicant considered these operating events in the aging management of the T-Quenchers.
Determine the measures taken to avoid degradation by debris plugging the holes of the T-quenchers. (If particle can clog the strainers, they can clog the holes of the T-quenchers too.)
- 1. Information Notice No. 88-82: TORUS SHELLS WITH CORROSION AND DEGRADED COATINGS IN BWR CONTAINMENTS.
This relates to an incident at Nine Mile Point.
- 2. NRC INFORMATION NOTICE 94-57: DEBRIS IN CONTAINMENT AND THE RESIDUAL HEAT REMOVAL SYSTEM
- 3. NRC INFORMATION NOTICE 95-06: POTENTIAL BLOCKAGE OF SAFETY-RELATED STRAINERS BY MATERIAL BROUGHT INSIDE CONTAINMENT
- 4. NRC INFORMATION NOTICE 95-47: UNEXPECTED OPENING OF A SAFETY/RELIEF VALVE AND COMPLICATIONS INVOLVING SUPPRESSION POOL COOLING STRAINER BLOCKAGE
E-2
- 5. NRC BULLETIN 96-03: POTENTIAL PLUGGING OF EMERGENCY CORE COOLING SUCTION STRAINERS BY DEBRIS IN BOLING-WATER REACTORS
- 6. NRC BULLETIN 93-02: DEBRIS PLUGGING OF EMERGENCY CORE COOLING SUCTION STRAINERS TVA Response to NRC QUESTION 1 Debris plugging of the T-quencher holes does not create a significant issue at Browns Ferry. The ECCS suction strainers draw water as well as debris into the strainers, where as the T-quenchers discharge high pressure steam to the suppression pool which makes the T-quenchers less prone to debris plugging.
The holes in the T-quenchers are 0.391 inch diameter. In order for debris to plug the T-quencher holes, the debris would have to enter the main steam relief valve discharge lines (SRVDLs). There are two paths for debris to enter the SRVDLs: 1) from the reactor vessel through the MSRVs, or 2) through the SRVDL vacuum breakers inside the drywell. It is highly unlikely that a significant amount of loose debris large enough to obstruct a 0.391 inch diameter hole would be present inside the reactor vessel/main steam lines and thus highly unlikely for debris to enter the SRVDLs through this path. The SRVDL vacuum breakers are inside the drywell and are only accessible during outages. The vacuum breakers are check valves open to the drywell atmosphere which are held closed by a spring and are located several feet above the nearest floor grating. Since the vacuum breakers are spring loaded and are a significant distance above the floor grating, it would be impossible for debris to spuriously enter the SRVDLs through the vacuum breakers.
Additionally, the following measures provide reasonable assurance that the T-quenchers holes are not plugged with debris:
1-TI-368, 2-TI-359, and 3-TI-368 are the procedures for the suppression pool cleaning and sludge generation rate measurement and documentation. Their scope includes desludging of suppression pool shell, immersed piping components (including T-quenchers), and structural steel.
Inspection reports for the above work provide verification that the T-quenchers are in good condition and their holes are free of debris.
E-3 Foreign material exclusion evaluations are performed prior to any suppression pool work activity per procedure SPP-6.5 (FOREIGN MATERIAL CONTROL), providing assurance that uncontrolled introduction of foreign material such as dirt or debris is prevented.
During testing per Technical Specifications Surveillance Requirement 3.4.3.2, each main steam safety relief valve is required to be held open for 1 to 5 seconds when manually actuated once every operating cycle not to exceed 24 months. The steam blowing out of the SRV is dispersed through the T-quencher holes, providing assurance that the holes of the T-quenchers are not blocked by debris.
NRC QUESTION 2 The ends of the carbon steel downcomers are welded to the top of the stainless steel T-quenchers. The fluctuation temperatures can cause stress corrosion cracking. The T-quenchers are either bolted or welded to the base of the suppression pool liner plate.
How does the applicant plan to manage the aging of the integrity of the dissimilar welds immersed in water, and subject to fluctuating temperatures?
If the T-quenchers are bolted to the base of the suppression pool liner plate, how does the applicant plan to manage the aging of the bolts?
TVA Response to NRC QUESTION 2 Stress corrosion cracking (SCC) occurs through the combination of high stress (both applied and residual tensile stresses), a corrosive environment, and a susceptible material. Elimination or reduction of any of these three factors will decrease the likelihood of SCC. The minimal level of stress required for SCC depends not only on material but also on temperature and the environment. In general, SCC very rarely occurs in austenitic stainless steel below 1400F.
The likelihood of SCC occurring is considered minimal for the following reasons:
For power > 1% RTP, the Technical Specifications specifies a suppression pool average temperature limit of < 95°F when no testing that adds heat to the suppression pool is being performed.
E-4 For power > 1% RTP, the Technical Specification specifies a suppression pool average temperature limit of < 105°F when testing that adds heat to the suppression pool is being performed.
For power < 1% RTP, the Technical Specification specifies a suppression pool average temperature limit of < 110°F.
Even though the possibility exists that during SRV testing the T-Quenchers stainless steel internal surface may reach temperatures above 140°F, the testing is infrequent and the temperature is experienced for a short time (each valve is required to be held open for 1 to 5 seconds when manually actuated once every operating cycle not to exceed 24 months). With the T-Quencher fully immersed in water at < 105°F, through wall temperatures above 140°F for any significant period is unlikely.
The T-Quenchers are supported such that the stress levels during normal plant operating conditions are low.
The Chemistry Control Program maintains the contaminant levels for the treated water in the suppression pool below the minimum levels for SCC.
Galvanic corrosion is considered as a potential effect for the dissimilar metal connection. This is addressed in line 7 of Table 3.1.2.3 of BFNs LRA, where galvanic corrosion is shown as an aging effect for the carbon steel fittings connected to the stainless steel T-Quenchers.
Since there are no bolts associated with the T-Quencher supports, aging of the bolts for these supports are not addressed. The T-quencher supports are all welded construction and are constructed of stainless steel (SS) and carbon steel (CS) material in a submerged environment. LRA Table 3.5.2.26 addresses the aging management review (AMR) for stainless steel in a submerged environment in line item number 11 of Table 3.5.2.26. The AMR for CS in a submerged environment was inadvertently omitted from Table 3.5.2.26.
The line item on the next page should be added to Table 3.5.2.26 to address the AMR for a material/environment of carbon steel in a submerged environment.
E-5 Component Type Intended Function Material Environment Aging effect requiring management Aging Management Program NUREG-1801 Vol. 2 Item Table 1 Item Notes ASME Equivalent Supports and Components SS Carbon and Low Alloy Steel Submerged Loss of material due to crevice corrosion, general corrosion, pitting corrosion, galvanic corrosion.
Chemistry Control Program (B.2.1.5)
One Time Inspection (B.2.1.29)
III.B1.2.1-a None G,1