ML20210Q173
| ML20210Q173 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 08/12/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20210Q167 | List: |
| References | |
| NUDOCS 9908130167 | |
| Download: ML20210Q173 (4) | |
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UN"eD iTATES j
j NUCLEAR REGULATORY COMM!SSION
't WASHINGTON, D.C. 20555-0001
.....,6 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 61 TO FACILITY OPERATING LICENSE NO. NPF-86 NORTH ATLANTIC ENERGY SERVICE CORPORATION SEABROOK STATION. UNIT NO.1 DOCKET NO. 50-443
1.0 INTRODUCTION
I By letter dated November 4,1998, the North Atlantic Energy Service Corporation (North Atlantic) submitted License Amendment Request (LAR) 98-17 which requests changes to the Seabrook Station Technical Specifications (TSs). Currently, TS Surveillance Requirement (SR) 4.5.2b.1 requires verification that the Emergency Core Cooling System (ECCS) is full of water by venting specific portions of the system. LAR 98-17 requests that the required verification method of venting be deleted. The requested change also includes a revision to the Bases associated with TS 3/4.5.2 that describes the intent of the surveillance requirement in greater detail.
2.0 BACKGROUND
I Title 10 of the Code of Federal Reaulations (10 CFR) Part 50, Appendix A, General Design j
Criteria for Nuclear Power Plants, Criterion 35 requires that 'A system to provide abundant emergency core cooling si,all be provided. The safety system function shall be to transfer heat J
from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts."
The ECCS at the Seabrook Station is designed to supply core cooling and negative reactivity to ensure the reactor is cooled and shut down following a postulated accident. Seabrook Station's ECCS consists of centrifugal charging pumps, safety injection pumps, a refueling water storage tank, residual heat removal pumps, a residual heat removal heat exchanger, safety injection accumulators, and associated valves and piping. To ensure that the ECCS at the Seabrook Station is able to perform its intended function, the Seabrook Station TSs includes various i
surveillance requirements to demonstrate operability of the ECCS. One of these, SR 4.5.2b.1,
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requires that each ECCS subsystem shall be demonstrated operable at least once per 31 days by " Verifying that the ECCS piping is full of water by venting the ECCS pump casings
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i (excluding the operating centrifugal charging pump) and accessible discharge piping high points...." Maintaining the ECCS piping full of water ensures that the system will perform j
ENCLOSURE 9908130167 990012 PDR ADOCK 05000443 P
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. properly and will be capable of performing its specified function by injecting its full capacity into the Reactor Coolant System upon domand. In addition, a full ECCS prevents hydraulic transients, pump cavitation, and pumping of non-condensable gas (e.g., air, nitrogen, or hydrogen) into the reactor vessel following a safety injection signal or during shutdown cooling.
The purpose of this amendment request is to eliminate from the TS SR the specific method of venting by which the ECCS piping is verified to be full of water. According to North Atlantic, it may not be appropriate from an ALARA, equipment reliability, and personnel safety standpoint to open valves for venting purposes.
In addition, North Atlantic's surveillance procedure associated with verification of SR 4.5.2b.1 currently employs ultrasonic testing (UT) as a backup method to assess the extent of air / gas / void in additional sections of ECCS piping if venting reveals the presence of air / gas at the accessible piping high points. The surveillance procedure has been demonstrated, contains the acceptance criteria, and describes required actions (e.g., evaluation, notification of shift management and support organizations, UT, etc.) to ensure the ECCS piping and pump casings remain full of water. North Atlantic's proposed TS SR would effectively allow the use of UT as the primary means of satisfying the SR. The proposed TS SR and basis for the SR are performance based and not prescriptive on how North Atlantic is to verify that the ECCS is full of water. Furthermore, the proposed changes are consistent with the Standard Technical Specifications for Westinghouse Plants, NUREG-1431, Revision 1, issued April 1995.
The use of UT to determine if ECCS piping is full of water is controlled by North Atlantic's
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procedures. Currently, North Atlantic uses either of two UT techniques, pulse-echo and through-transmission. Either technique is suitable to determine if ECCS piping is full of water.
Both techniques have been confirmed by North Atlantic as satisfactory for go-no-go testing with the use of either calibration test pieces of piping of similar diameter and material composition or
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calibrated on actual plant piping. The confirmation calibrations were also urn on piping under flow conditions. The confirmation methods employed are inherently conserr tive since a signal must be captured to show that the pipe is full of water. Any loss of signal would be identified as a pipe not being full of water.
The pulse-echo technique consists of exciting a transducer to generate a longitudinal sound wave that travels diametrically through dense materials. If the pipe is full of water, the sound will travel through the water, bounce off the far wall of the pipe and return to the transducer.
The time it takes for the sound wave to travel round trip is converted into distance which equals the diameter of the pipe. If the UT is performed from the high point of a partially water-fiiled pipe, the sound wave will not pass through the air gap, thus providing a go-no-go test.
The through transmission technique uses separate transducers for transmitting and receiving longitudinal sound waves. The transducers are placed diametrically opposite each other and the sound wave is passed from one transducer to the other. As with the pulse-echo technique, if an air gap is present the sound wave will not propagate through the air gap and no signal would be captured by the receiving transducer.
m, L 3.0 ' EVALUATION :
The proposed change is to eliminate from the Seabrook TSs SR 4.5.2b.1 the specific method of venting by which the ECCS piping is currently verified to be full of water. The proposed change also adds a section to th_e associated Bases that describes the potential for developing voids and the importance of their elimination.
Venting pump casings and piping high points has been a common industry practice to i
determine if ECCS piping is full of water and to remove any pockets of_ entrained gases and
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voids within piping systems. More recently, UT has been used as an alternative technique to determine if ECCS piping is full of water. In contrast to venting, the use of UT can determine if the piping is full of water without breaching the system, eliminating potential personnel hazards and safety system operability concerns, in conclusion, UT is appropriate for this application, provides safety benefits, meets the intent of the SR, and fulfills the applicable regulatory requirements. Furthermore, the proposed change would also result in the Seabrook Station TS SR 4.5.2b.1 being consistent with SR 3.5.2.3 and its associated Bases contained in NUREG-1431, " Standard Technical Specifications -
Westinghouse Plants," Rev.1, April 1995. Therefore, the proposed change to eliminate venting from SR 4.5.2b.1, as the only allowable method of determining if the ECCS piping is full of water, is acceptable. In' addition, the proposed change to the Bases to include an explanation
'of the potential development of voids and the importance of keeping the ECCS piping completely filled with water are appropriate.
4.0 - STATE CONSULTATION
- In accordance with the Commission's regulations, the New Hampshire and Massachusetts State officials were notified of the proposed issuance of the amendment. The State officials had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes
-surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that
- may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.' The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (64 FR 4157). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 1
51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
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6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: John Harrison Date: August 12, 1999
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