CNL-15-008, Response to Request for Additional Information Related to ISPT-03

Response to Request for Additional Information Related to ISPT-03

ML15048A203
Person / Time
Site:	Watts Bar
Issue date:	02/13/2015
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-15-008
Download: ML15048A203 (6)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-15-008 February 13, 2015 10 CFR 50.55a U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001

Subject:

Watts Bar Nuclear Plant, Unit 1 Facility Operating License NPF-90 NRC Docket No. 50-390 Watts Bar Nuclear Plant Unit 1 - Response to Request for Additional Information Related to ISPT-03

References:

1.

TVA Letter to NRC, "Watts Bar Nuclear Plant (WBN) Unit 1 -

Request for Alternative ISPT-03," dated September 12, 2014 (ML14267A368)

2.

NRC Electronic Mail to TVA, RAI Related to Request for Alternative ISPT-03," dated December 4, 2014 In Reference 1, the Tennessee Valley Authority (TVA) submitted a request for alternative to the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," as applicable to Watts Bar Nuclear Plant (WBN), Unit 1. The code of record for the second 1 0-year interval for WBN, Unit 1, is the ASME Section XI B&PV code, 2001 Edition with Addenda through 2003. In Reference 2, the Nuclear Regulatory Commission (NRC) submitted a request for additional information (RAI) related to TV A's submittal.

The enclosure to this letter provides a response to NRC's request for information.

There is one new regulatory commitment associated with this submittal.

L44 150213 002

U.S. Nuclear Regulatory Commission CNL-15-008 Page 2 February 13, 2015 If you have any questions or comments, please contact Gordon Arent at (423) 365-2004.

Respectfully, L J.W.She//~

Vice President, Nuclear Licensing

Enclosures:

1.

Request for Additional Information-Relief Request ISPT-03 Regarding System Leakage Test of Class 1 Piping Isolated Between Normally Closed Valves

2.

List of Commitments cc (Enclosure):

U. S. Nuclear Regulatory Commission, Region II NRC Resident Inspector-Watts Bar Nuclear Plant Unit 1 NRC Resident Inspector-Watts Bar Nuclear Plant Unit 2 NRR Project Manager-Watts Bar Nuclear Plant

ENCLOSURE 1 Request for Additional Information Relief Request ISPT -03 Regarding System Leakage Test of Class 1 Piping Isolated Between Normally Closed Valves Watts Bar Nuclear Plant, Unit 1 NRC Request By Jetter dated September 12, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML14267A368), Tennessee Valley Authority (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PV Code),Section XI. The relief request (RR)

/SPT-03 pertains to the IWB-5222(b) requirement for system leakage testing of the ASME Code Class 1 piping conducted at or near the end of the second 1 0-year in service inspection (IS/)

interval at the Watts Bar Nuclear Plant (Watts Bar), Unit 1.

The NRC staff requests the following additional information for its detailed safety evaluation.

1. For the chemical volume and control system (CVCS) piping segments listed in Table 1 of Enclosure to /SPT-03, the NRC staff notes that the licensee did not provide any discussions about these lines in Sections titled "Proposed Alternative and Basis for Use" and "Reason for Request" of /SPT-03. For the above piping segments, provide the proposed alternative, basis for use, and reason for request.

2. For those piping segments that are equipped with isolation and check valves, or two check valves, provide discussions regarding the radiation dose incurred by personnel including the safety hazards associated with performing activities such as opening the valve, bypassing the valve, using external hoses and pump, or modifying existing configurations of piping to accommodate pressurization of these lines in order to conduct the IWB-5222(b) required system leakage test. Provide an estimate for person-roentgen equivalent man (rem) exposure with consideration of an as low as reasonably achievable.

3. (a) Discuss whether there are any welded (e.g., full penetration butt weld or fillet weld) connections in the piping segments listed in Table 1 of Enclosure to ISPT-03. (b)

Discuss whether these welds have been subjected to any nondestructive examinations (NDE) during previous inservice inspection or are included in the future inservice inspection program. (c) Discuss inspection results. (d) If these welds have not been inspected, provide justification.

4.

The NRC staff notes that NRC Information Notice (IN) 2011-04, "Contaminants and Stagnant Conditions Affecting Stress Corrosion Cracking in Stainless Steel Piping in Pressurized water Reactors," discusses potential stress corrosion cracking (SCC) in the stainless steel piping. Discuss any operating experience regarding sec of the welds in the subject piping segments.

5. Discuss any operating experience regarding thermal fatigue in the subject piping segments.

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6. (a) For the segments of piping for which relief is being requested, identify any pressure boundary leakage regardless of how it was identified (e.g., from the ASME Code,Section XI, Table IWB-2500-1, Category B-P pressure testing requirements, boric acid corrosion control program walkdowns, or reactor restart walkdowns) during the current 1 0-year in service inspection interval. (b) If leakage occurred in the subject piping, discuss the extent of condition assessment and any compensatory measure(s) taken.

TV A Response

1. The three identified CVCS piping segments described are the charging flow path to Reactor Coolant System (RCS) cold leg loop 1, the charging flow path to RCS cold leg loop 4, and the auxiliary spray line to the pressurizer (Reference 1, enclosure pages 11 and 12).

Normal operating procedures would not have more than one of the charging flowpaths in service, and the pressurizer auxiliary spray line normally is not used. For this reason, it cannot be assured that check valve bounded segments will necessarily be at full pressure.

With a charging pump inservice, and by alternating placing the loop 1 charging flowpath, the loop 4 charging flowpath, and the auxiliary spray flowpath momentarily into service, it is expected that the section of piping between the associated check valves for these paths would be at or near normal RCS pressure (2235 psig) during the inservice leak test. The associated procedure for performing this inservice leak test will be revised to require these valves to be cycled prior to commencement of the test to provide a high level of confidence that these pipe segments are being tested at or very near to RCS pressure.

2. The inservice leak test of the RCS is normally performed after a refueling outage, and is therefore performed with fuel in the core with the plant in Mode 3. The use of external hoses and pumps is impractical, as this equipment would be required to comply with all requirements of the_ RCS based on plant operating mode (ASME Section Ill, Class I, Seismic Category I). Alterations to the RCS permanent configuration would be a very significant task to undertake, with the potential to create other problems. Since alterations to the RCS configuration were deemed impractical, no radiation exposure estimates were performed. The RCS piping design at WBN Unit 1 is consistent with other Westinghouse plants of this vintage.

3. Each portion of this question is discussed individually.

a. All of the piping described in Reference 1 is welded piping, primarily butt welded.

b. A portion of RCS piping welds are required to be examined every 1 0-year lnservice Interval as required by ASME Section XI. The welds on these sections of pipe are mostly risk informed welds. Therefore only a sample population of the welds are inspected in accordance with the WBN Unit 1 Risk-Informed lnservice Inspection (RI-ISI) Program. The welds selected for inspection receive volumetric examination.

c.

No relevant indications have been found on any welds in either the first or second 1 0-year inspection interval at WBN Unit 1.

d. Only a sample of welds are inspected based on risk. The same welds inspected during the first 1 0-year inspection interval were also inspected during the second 1 0-year inspection interval, to allow for trending.

All welds and associated piping have received a VT -2 examination for leakage during the ASME Class 1 pressure test performed each refueling outage.

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Additionally, as-found containment walkdowns that look for RCS leaks are conducted prior to each refueling outage upon entry into MODE 3 to complete the discovery effort and document any potential findings that would be required to be addressed. These walkdowns are conducted per plant procedures. These discovery walkdowns are also conducted to the extent practical during any plant forced shutdowns/forced outages.

4. No indications of stress corrosion cracking have been identified in any reactor coolant system pressure boundary welds at WBN Unit 1.

5. No indications of thermal fatigue have been identified in any portions of the reactor coolant system piping at WBN Unit 1.

6. Each portion of this question is discussed individually.

a. For the piping segments identified in reference 1, no pressure boundary leakage has been identified during the life of the plant.

b. As stated above, no pressure boundary leakage has been identified for the piping segments in question, thus no compensatory measures have been required.

References

1. TVA Letter to NRC, "Watts Bar Nuclear Plant (WBN) Unit 1 -Request for Alternative ISPT-03," dated September 12, 2014 (ML14267A368)

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ENCLOSURE 2 LIST OF COMMITMENTS

1.

Revise the Reactor Coolant System Leakage test procedure to require the pressurizer auxiliary spray inlet valve (1-FCV-62-84), the loop 1 charging inlet valve (1-FCV-62-85),

and the loop 4 charging inlet valve (1-FCV-62-86) to be cycled prior to commencement of the leakage test.

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