CP-201301199, Relief Request No. C-3 for the Unit 2 Reactor Pressure Vessel leak-off Flange (Second ISI Interval Start Date: August 3, 2004; Second ISI Interval End Date: August 2, 2014

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Relief Request No. C-3 for the Unit 2 Reactor Pressure Vessel leak-off Flange (Second ISI Interval Start Date: August 3, 2004; Second ISI Interval End Date: August 2, 2014
ML13312A121
Person / Time
Site: Comanche Peak Luminant icon.png
Issue date: 10/31/2013
From: Flores R, Thomas McCool
Luminant Generation Co, Luminant Power
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
CP-201301199, TXX-13145
Download: ML13312A121 (17)
v • d • e


Text

Rafael Flores Luminant Power Senior Vice President P 0 Box 1002 0_____ & Chief Nuclear Officer 6322 North FM 56 Rafael.Flores@Luminant.com Glen Rose, TX 76043 Lum inant 2548975590 C 817 559 0403 F 254 897 6652 CP-201301199 Ref. # 10CFR50.55a(a)(3)(ii)

TXX-13145 October 31, 2013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT DOCKET NO. 50-446 RELIEF REQUEST NO. C-3 FOR THE UNIT 2 REACTOR PRESSURE VESSEL LEAK-OFF FLANGE (SECOND ISI INTERVAL START DATE: AUGUST 3,2004; SECOND ISI INTERVAL END DATE: AUGUST 2,2014)

REFERENCES:

1. Letter logged TXX-12129 dated August 23, 2012, from Rafael Flores to the NRC submitting Relief Request No. C-2 for the Unit 1 Third 10 Year ISI Interval From 10CFR50.55a Inspection Requirements Due to Hardship (Third Interval Start Date:

August 13, 2012)(ML12250A670) as supplemented by letter dated January 9, 2013 (ML130250339)

2. NRC Letter dated March 19, 2013, from Michael T. Markley to Rafael Flores concerning Comanche Peak Nuclear Power Plant, Unit I - Approval of Relief Request No. C-2 for the Third 10-Year Inservice Inspection Interval (TAC No. ME9409)

(ML13046A385)

Dear Sir or Madam:

Pursuant to 10 CFR 50.55a(a)(3)(ii), Luminant Generation Company LLC (Luminant Power) is submitting Relief Request C-3 for Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 for the second ten year inservice inspection interval. Luminant Power has determined that compliance with certain inspection requirements of ASME Section XI would result in an unnecessary hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The Reactor Pressure Vessel flange leak-off piping configuration precludes system pressure testing when the reactor vessel head is removed. The configuration also precludes pressurizing the line externally when the head is installed. A visual examination of the accessible areas was performed during the second interval on the unpressurized subject piping as part of the Class 2 leakage test. No evidence of leakage has been identified for the subject component. No undue risk to the public health and safety is presented by this request.

A similar relief request was previously submitted to the NRC for Unit 1 via Reference 1, and reviewed and approved via Reference 2.

A member of the STARS Alliance Callaway

  • Comanche Peak
  • Diablo Canyon
  • Palo Verde - South Texas Project - Wolf Creek 00 00

U. S. Nuclear Regulatory Commission TXX-13145 Page 2 of 2 10/31/2013 Luminant Power requests approval of this relief request by March 29, 2014, to support the upcoming CPNPP Unit 2 refueling outage.

This communication contains no new commitments regarding CPNPP Unit 2.

Should you have any questions, please contact Mr. Jack Hicks at (254) 897-6725.

Sincerely, Luminant Generation Company LLC Rafael Flores By: 7 7 Thomas P. McCool Vice President, Station Support Attachments: (1) Relief Request Number - C-3 For the Reactor Pressure Vessel Leak-Off Piping (Second 10-Year ISI Interval Start Date: August 3, 2004)

(2) Reactor Pressure Vessel Seal Leak-off Details (3) Piping and Instrumentation Diagram and Piping Isometric Drawings c- Marc L. Dapas, Region IV Balwant K. Singal, NRR Resident Inspectors, Comanche Peak Jack Ballard, ANII, Comanche Peak Robert Free Environmental Monitoring & Emergency Response Manager Texas Department of State Health Services Mail Code 1986 P.O. Box 149347 Austin, TX 78714-9347 to TXX-13145 Page 1 of 3 COMANCHE PEAK NUCLEAR POWER PLANT UNIT 2 RELIEF REQUEST NUMBER - C-3 FOR THE REACTOR PRESSURE VESSEL LEAK-OFF PIPING (SECOND 10-YEAR ISI INTERVAL START DATE: AUGUST 3,2004)

1. ASME Code Component Affected:

ASME Code Class: Code Class 2

References:

ASME Section XI, Table IWC-2500-1 and IWC-5220 Examination Category: C-H (All Pressure Retaining Components)

Item Number: C7.10

Description:

Alternative Pressure Testing Requirements for the RPV Flange Leak-Off Piping Component: NPS 33/44"RPV Flange Seal Leak-Off Piping Material: SA376 type 304 or 316 Stainless Steel Line Numbers: RC-2-080, RC-2-081, RC-2-082 Plant Drawings: BRP-RC-2-RB-005, BRP-RC-2-RB-006, BRP-RC-2-RB-007, BRP-RC-2-RB-013, BRP-RC-2-RB-014, BRP-RC-1-RB-042, BRP-RC RB-043, M2-0250

2. Applicable Code Edition and Addenda:

The applicable ASME Boiler and Pressure Vessel Code edition and addenda is ASME Section XI, "Rules for Inservice of Nuclear Power Plant Components," 1998 Edition through 2000 Addenda.

Hereafter referred to as the "Code."

3. Applicable Code Requirement:

IWC-2500, Table IWC-2500-1, Code Category C-H, Item Number C7.10 requires that all Class 2 pressure retaining components be subject to a system leakage test with a Visual, VT-2 examination each inspection period. The system leakage test is performed at the pressure obtained while the subject portion of the system is performing its normal operating function or during a comparable test.

4. Reason for Request: Impracticality of Compliance (10CFR50.55a(a)(3)(ii))

As discussed in 3, "Applicable Code Requirements," ASME Section XI, 1998 Edition through 2000 Addenda requires that Class 2 pressure boundary piping shall be pressure tested once each inspection period. The Reactor Pressure Vessel (RPV) head flange seal leak detection piping is separated from the reactor coolant pressure boundary by one passive membrane, which is an 0-ring located on the inner vessel flange as shown in Attachment 2 to TXX-13145. A second O-ring is located on the outside of the tap in the vessel flange. Failure of the inner O-ring is the only condition under which this line is pressurized. Therefore, the line is not expected to be pressurized during the system pressure test following a refueling outage.

The configuration of this piping precludes system pressure testing while the vessel head is removed because the time required by personnel for the installation and removal of a threaded plug in the flange face to act as a pressure boundary for the test would incur significant dose (estimated 20 - 40 mRem/min), which would be an ALARA concern. This activity would also present a Foreign Material Exclusion issue for the 1/8" plug that would be required to be installed to complete a leakage test at pressure.

Attachment i to TXX-13145 Page 2 of 3 COMANCHE PEAK NUCLEAR POWER PLANT UNIT 2 RELIEF REQUEST NUMBER - C-3 FOR THE REACTOR PRESSURE VESSEL LEAK-OFF PIPING (SECOND 10-YEAR ISI INTERVAL START DATE: AUGUST 3,2004)

The configuration also precludes pressurizing the line externally with the head installed. The top head of the vessel contains two grooves that hold the O-rings. The O-rings are held in place by a series of retainer clips that are housed in recessed cavities in the flange face. If a pressure test were to be performed with the head on, the inner O-ring would be pressurized in a direction opposite to its design function. This test pressure would result in a net inward force on the inner O-ring that would tend to push it into the recessed cavity that houses the retainer clips. The thin O-ring material would likely be damaged by the inward force.

Attachment 3 contains the piping and instrumentation diagram (P&ID) and the piping isometric drawings showing the subject flange leak-off line.

5. Burden Caused by Compliance:

Purposely failing or not installing the inner O-ring in order to perform a pressure test would require purchasing a new O-ring set and the time and radiation exposure associated with removing and reinstalling the RPV head to replace the O-rings would be an undue hardship.

Therefore, compliance with the IWC-5220 system leakage test requirements results in an unnecessary hardship without a sufficient compensating increase in the level of quality and safety.

6. Proposed Alternative and Basis for Use:

In lieu of the requirements of IWC-5220, a VT-2 visual examination of the accessible areas will be performed each period on the piping subjected to the static pressure head when the reactor cavity is filled. This test will be part of the reactor coolant Class 2 leakage test.

If the inner O-ring should leak during the operating cycle it will be identified by an increase in temperature of the leak-off line above ambient temperature. This high temperature would actuate an alarm in the Control Room, which would be closely monitored by procedurally controlled operator actions allowing identification of any further compensatory actions required.

This leakage would be collected in the Reactor Coolant Drain Tank.

Additionally, the flange seal leak-off line is essentially a leakage collection/detection system and the line would only function as a Class 2 pressure boundary if the inner O-ring fails, thereby pressurizing the line. If any significant leakage does occur in the leak-off line piping itself during this time of pressurization then it would clearly exhibit boric acid accumulation and be discernable during the proposed VT-2 visual examination that will be performed unpressurized as proposed in this request. The elevation of the Reactor Vessel flange is 834' 11/2". The elevation for the water level when the cavity is flooded is 858" 6". Therefore, the minimum pressure at the opening of the flange leak-off line when the exam is performed is 24' 5 11/2"" of static pressure head or 10.6 psi.

There has been no known evidence of corrosion, stress corrosion cracking, fatigue, etc. in the subject flange leak-off piping at Comanche Peak.

7. Duration of Proposed Alternative:

This alternative is requested for the Second Inservice Inspection Interval, which began on August 3, 2004 and ends on August 2, 2014.

to TXX-13145 Page 3 of 3 COMANCHE PEAK NUCLEAR POWER PLANT UNIT 2 RELIEF REQUEST NUMBER - C-3 FOR THE REACTOR PRESSURE VESSEL LEAK-OFF PIPING (SECOND 10-YEAR ISI INTERVAL START DATE: AUGUST 3,2004)

8. Precedents:

(1) Comanche Peak Nuclear Power Plant, Unit 1 Third Inspection Interval Relief Request C-2 "Alternative Pressure Testing Requirements for the RPV Flange Leak-Off Piping", as approved by the NRC on March 19, 2013 (ML13046A385).

(2) LaSalle County Station Third Inspection Interval Relief Request I3R-08.

"Pressure Testing of the Reactor Vessel Head Flange Leak Detection System", as approved by the NRC in a letter dated January 30, 2008 (ADAMS Accession No. ML073610587)

(3) Susquehanna Steam Electric Station Third 10-Year Inservice Inspection (ISI) Interval Program Plan Request for Relief 3RR-07 "Exemption for Pressure Testing Reactor Pressure Vessel Head Flange Seal Leak Detection System", approved by the NRC in a letter dated September 24, 2004 (ADAMS Accession No. ML042680078)

9.

Reference:

Code Case N-805, "Alternative to Class 1 Extended Boundary End of Interval or Class 2 System Leakage Testing of Reactor Vessel Head Flange O-ring Leak Detection System," was issued to the 2010 Edition of the ASME Section XI Code and is listed in Supplement 6 for Code Cases.

However, Code Case N-805 has not been approved by the NRC and is not identified in Regulatory Guide 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1."

to TXX- 13145 Page 1 of3 Reactor Pressure Vessel Seal Leak-Off Details Luminant Power Comanche Peak Nuclear Power Plant to TXX- 13145 Page 2 of 3 Figure 1:

REACTOR PRESSURE VESSEL HEAD FLANGE LEAK-OFF LINE CONFIGURATION to TXX- 13145 Page 3 of 3

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Reactor Pressure Vessel Head Flange Leak-Off Line Details

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