ML080030300
| ML080030300 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 01/03/2008 |
| From: | Polson K Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MD6280 | |
| Download: ML080030300 (6) | |
Text
Keith J. Polson Vice President-Nine Mile Point 0"\\. Constellation Energy"
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- Nine Mile Point Nuclear Station
- u. S. Nuclear Regulatory Commission Washington, DC 20555-0001 P.O. Box 63 Lycoming, New York 13093 315.349.5200 315.349.1321 Fax January 3, 2008 ATTENTION:
SUBJECT:
REFERENCES:
Document Control Desk Nine Mile Point Nuclear Station Unit No.2; Docket No. 50-410 Response to Request for Additional Information:
Revision to Drywell Spray Nozzle Testing Frequency (TAC No. MD6280)
(a) Letter from K. J. Polson (NMPNS) to Document Control Desk (NRC), dated July 30, 2007, License Amendment Request Pursuant to 10 CFR 50.90:
Revision to Drywell Spray Nozzle Testing Frequency (b) Letter from M. J. David, (NRC) to K. J. Polson (NMPNS), dated December 4, 2007, Request for Additional Information Regarding Nine Mile Point Nuclear Station, Unit No.2, Revision to Drywell Spray Nozzle Testing Frequency (TAC No. MD6280)
Pursuant to 10 CFR 50.90, Nine Mile Point Nuclear Station, LLC (NMPNS) requested, in Reference (a),
approval of an amendment to the Nine Mile Point Unit 2 Renewed Operating License NPF-69 to revise the testing frequency for drywell spray nozzles specified in Technical Specifications (TS) Surveillance Requirement (SR) 3.6.1.6.3 from "10 years" to "following maintenance that could result in nozzle blockage." The purpose of this letter is to provide responses to the request for additional information (RAI) transmitted to NMPNS in Reference (b).
The response to the RAl is attached.
The response does not affect the No Significant Hazards Determination analysis provided by NMPNS in Reference (a). Pursuant to 10 CFR 50.91(b)(1), NMPNS has provided a copy ofthis response, with attachment, to the appropriate state representative.
Document Control Desk January 3, 2008 Page 2 Should you have any questions regarding this submittal, please contact T. F. Syrell, Licensing Director, at (315) 349-5219.
Very truly yours,
~~
STATE OF NEW YORK TO WIT:
COUNTY OF OSWEGO I, Keith J. Polson, being duly sworn, state that I am Vice President-Nine Mile Point, and that I am duly authorized to execute and file this response on behalf of Nine Mile Point Nuclear Station, LLC. To the best of my knowledge and belief, the statements contained in this document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other Nine Mile Point employees and/or consultants. Such information has been reviewed in accordance with company practice and I believe it to be reliable.~
Subscribed and sworn before me, a Notary Public, in and for the State of New York and County of
~,this Sr'dayof T
_y,2008.
WITNESS my Hand and Notarial Seal:
My Commission Expires:
Date KJP/JID 7
Notary Public SANDRA A. OSWALD Notary PUblic, State of New York
.~o. 01086032276 o.ual.lfled in Oswego Countv vommlSS,on Expires
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Attachment:
Response to Request for Additional Information Regarding Drywell Spray Nozzle Testing Frequency cc:
M. 1. David, NRC S. J. Collins, NRC Resident Inspector, NRC J. P. Spath, NYSERDA
ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING DRYWELL SPRAY NOZZLE TESTING FREQUENCY Nine Mile Point Nuclear Station, LLC January 3,2008
ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING DRYWELL SPRAY NOZZLE TESTING FREQUENCY By letter dated July 30, 2007, Nine Mile Point Nuclear Station, LLC (NMPNS) submitted a license amendment request (LAR) for Nine Mile Point Unit 2 (NMP2) Renewed Operating License NPF-69. The proposed amendment would revise the testing frequency for drywell spray nozzles specified in Technical Specifications (TS) Surveillance Requirement (SR) 3.6.1.6.3 from " 10 years" to "following maintenance that could result in nozzle blockage."
The NRC issued a request for additional information (RAJ) concerning the NMP2 LAR on December 4, 2007. The NMPNS responses to the RAJ questions follow.
NRC Question 1 The request states that pre-operational testing in 1986 and subsequent tests in 1992 and 1998 indicate no blockage of the spray nozzles.
However, at the initiation of the air flow tests, a momentary fme dark orange cloud (assumed to be rust particles) was observed exiting the nozzles. The request attributes this to a small amount of water entering the system during quarterly stroke testing ofthe isolation valves. The request further states that the method of stroke testing will be revised to ensure that the drywell spray system remains dry.
Are the revisions to the method of stroke testing in effect, now? Please explain the revisions and how they ensure that water does not enter the system?
Are the headers equipped with any drains to remove water that inadvertently enters the system?
What action will be taken if water enters the spray piping upstream ofthe nozzles?
NMPNS Response 1 The revisions to the method of stroke timing are not in effect now, but as committed to in the LAR, will be implemented prior to revising the drywell spray nozzle surveillance frequency.
The piping to the drywell spray nozzles is normally filled with water up to the inboard isolation valve. With the existing method for the quarterly stroking of the isolation valves, the inboard valve is normally cycled prior to the outboard valve. This allows some of the water that was in the pipe between the isolation valves to enter the piping in the drywell when the inboard valve is opened. In the future, to prevent water from entering the piping inside the drywell, the installed vent and drain between the isolation valves will be used to drain this area prior to stroking the inboard valve.
There are vents and drains between the isolation valves, but not on the piping within the drywell. Both isolation valves on each loop are outside the drywell. The spray headers are at an elevation higher than that of the piping where it enters the drywell, and as such, have not been directly wetted by the water entering the piping as a result of the stroke time testing of the inboard isolation valves. Additional piping configuration information is provided in the response to NRC Question 3.
Water potentially remaining in the spray piping as a result of the current method of stroke testing the isolation valves will be removed by normal evaporation within the pipe and/or by draining back into the piping between the isolation valves when the inboard valve is stroked under the new stroking process. In the future, if water entered the spray piping in the drywell (e.g., inadvertent actuation), it could be drained through the drain valve between the isolation valves during an outage.
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ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING DRYWELL SPRAY NOZZLE TESTING FREQUENCY NRC Ouestion 2 The request states that the drywell spray nozzle orifices have a 1.0156 inch diameter and are designed to pass up to a 1.0 inch diameter particle without clogging. Please provide a drawing or a sketch of a nozzle and a brief description of how spray is achieved by nozzles that are larger than 1.0 inch.
NMPNS Response 2 A representative figure of one ofthe spray nozzles is shown below.
The ramp bottom tangential hollow cone nozzles utilize a right angle supply of water. The inlet is off center, subjecting the incoming fluid to a centrifugal swirling action that is accelerated by a ramp designed swirl chamber and shaped by the outlet orifice. Swirl is achieved via a swirl chamber, without the need for a swirl insert, for maximum resistance to clogging.
NRC Ouestion 3 The request states that piping to the nozzles is Type SAl06 Grade B carbon steel. Please explain the extent of the carbon steel piping upstream of the nozzles in quantitative terms (e.g. size, length) and why the pipes are not expected to rust, significantly.
NMPNS Response 3 The piping to the nozzles inside the drywell consists ofthe following:
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ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING DRYWELL SPRAY NOZZLE TESTING FREQUENCY A Loop:
16 inch diameter -18.87 ft 12 inch diameter - 3.33 ft to the spray header 12 inch diameter octagon shape spray header - 27.25 ft radius or 177 ft circumference There is approximately 15 feet ofpiping from the inboard isolation valve to where the 16 inch pipe elbows up (the spray header is at a higher elevation than the piping penetration). This is the only portion ofthe A Loop piping in the drywell that is expected to have been previously wetted.
BLoop:
16 inch diameter - 17.86 ft 12 inch diameter 1.5 ft to the spray header 12 inch diameter spray header - 30.33 ft in radius or 189.53 ft circumference There is approximately 12 feet ofpiping from the inboard isolation valve to where the 16 inch pipe elbows up. This is the only portion of the B Loop piping in the drywell that is expected to have been previously wetted.
The reasons why the piping inside the drywell is not expected to rust significantly are addressed on page 2 ofAttachment (1) ofthe LAR.
NRC Question 4 The current TS SR 3.6.1.6.3 requires verification that each drywell spray nozzle is unobstructed every 10 years.
The request proposes to change the surveillance frequency from "10 years" to "following maintenance that could result in nozzle blockage." Please explain and justify the verification methods that will be employed to accomplish this SR.
NMPNS Response 4 As described in the LAR, the proposed frequency change takes credit for the Foreign Material Exclusion (FME) Program to prevent entry of foreign material into the drywell spray system. Should FME control be lost during maintenance, a condition report is initiated to determine the appropriate action to restore FME integrity. A visual inspection (e.g., boroscope) of the nozzles or piping could be utilized in lieu of an air test if a visual inspection is determined to provide an equivalent or more effective post-maintenance test. A visual inspection may be more effective if the potential for material intrusion is localized and the affected area is accessible. Should it be determined that an activity or event could have resulted in the potential for nozzle blockage, various methods could be utilized to perform the surveillance (e.g., an air flow test or visual inspections of nozzle and piping interiors).
The appropriate method utilized to complete the surveillance would be determined based on an analysis of the potential foreign material and its location.
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