ML111881029

Issuance of Relief Request RR-04-04 Regarding Use of Alternative Pressure Testing Requirements

ML111881029
Person / Time
Site:	Millstone
Issue date:	07/27/2011
From:	Chernoff H Plant Licensing Branch 1
To:	Heacock D Dominion Nuclear Connecticut
Sandeers, Carleen, NRR/DORL, 415-1603
References
RR-04-04, TAC ME4473
Download: ML111881029 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 July 27, 2011 Mr. David A. Heacock President and Chief Nuclear Officer Dominion Nuclear Connecticut, Inc.

Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 203060-6711

SUBJECT:

MILLSTONE POWER STATION, UNIT NO.2-ISSUANCE OF RELIEF REQUEST RR-04-04 REGARDING USE OF ALTERNATIVE SYSTEM LEAKAGE TESTING REQUIREMENTS (TAC. NO. ME4473)

Dear Mr. Heacock:

By letter dated July 29,2010, as supplemented by letter dated August 5,2010 (Agencywide Document Access and Management System (ADAMS) Accession Nos. ML102580204 and ML102220527, respectively), Dominion Nuclear Connecticut, Inc. (DNC or the licensee) submitted relief requests for the fourth 10-year inservice inspection (lSI) interval program at Millstone Power Station, Unit No.2 (MPS2). DNC requested use of alternatives to certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

Section XI requirements. Included in this submittal was Relief Request RR-04-04 which prepossessed to use alternative system leakage testing pressure criteria for certain Class 1 piping at or near the end of the inspection interval. RR-04-04 was supplemented by letter dated May 5, 2011 (ADAMS Accession No. ML111250103). Each Relief Request contained in the July 29,2010, submittal will be addressed separately.

The Class 1 piping covered in RR-04-04 is divided into three component groups (Le. component Groups 1, 2, and 3). The May 5, 2011, letter included DNC's withdrawal of Component Group

2. This letter and enclosed Safety Evaluation (SE) address the remaining two component groups.

The Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed SE, that performance of an ASME Code system leakage test at or near the end of the inspection interval would result in a hardship without a compensating increase in the level of quality and safety. The NRC staff's review also concludes that the alternative pressure testing criteria as described in RR-04-04 is acceptable because it provides reasonable assurance of structural integrity of the subject Class 1 piping.

Therefore, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(a)(3)(ii), the NRC authorizes the use of alternative pressure testing criteria as an alternative to the ASME Code,Section XI, required system leakage test of certain Class 1 piping at or near the end of the interval for the remainder of the fourth 10-year lSI interval for MPS2. The fourth 10-year lSI interval at MPS2 began on April 1, 2010, and is scheduled to be completed on March 31, 2020.

D. Heacock -2 All other ASME Code,Section XI, requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

If you have any question, please contact the Project Manager, Carleen Sanders, at 301-415-1603.

Sincerely,

t;;c Harold K. Chernoff, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-336

Enclosure:

As stated cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INSERVICE INSPECTION INTERVAL REQUEST FOR RELIEF NO. RR-04-04 MILLSTONE POWER STATION, UNIT NO.2 DOMINON NUCLEAR CONNECTICUT, INC.

DOCKET NO. 50-336

1.0 INTRODUCTION

By letter dated July 29,2010, as supplemented by letter dated August 5,2010 (Agencywide Document Access and Management System (ADAMS) Accession Nos. IVIL 102580204 and ML102220527, respectively), Dominion Nuclear Connecticut, Inc. (DNC or the licensee) submitted relief requests for the fourth 10-year inservice inspection (lSI) interval program at Millstone Power Station, Unit No.2 (MPS2). DNC requested use of alternatives to certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),

Section XI requirements. Included in this submittal was Relief Request RR-04-04 which prepossessed to use alternative system leakage testing pressure criteria for certain Class 1 piping at or near the end of the inspection interval. RR-04-04 was supplemented by letter dated May 5, 2011 (ADAMS Accession No. ML111250103).

The Class 1 piping covered in RR-04-04 is divided into three component groups (Le. component Groups 1, 2, and 3). The May 5, 2011, letter included DNC's withdrawal of Component Group 2.

This letter and enclosed Safety Evaluation (SE) address the remaining two component groups.

The licensee requests relief from the ASME Code,Section XI, IWB-5222(b) requirement to extend the reactor coolant pressure boundary (RCPB) for the system leakage test to be conducted at or near the end of the lSI interval on certain Class 1 piping segments.

2.0 REGULATORY EVALUATION

The lSI of ASME Code Class 1, 2, and 3 components is performed in accordance with Section XI of the ASME Code and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(g), except where specific relief has been granted by the Nuclear Regulatory Commission (NRC) pursuant to 10 CFR 50.55a(g)(6)(i).

10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the licensee demonstrates that: (i) the proposed alternatives Enclosure

-2 when authorized by the NRC, if the licensee demonstrates that: (i) the proposed alternatives would provide an acceptable level of quality and safety; or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the pre service examination requirements, set forth in the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.

The ASME Code of Record for the fourth 1O-year lSI interval at IVIPS2 is the 2004 Edition with no Addenda.

3.0 TECHNICAL EVALUATION

3.1 System/Component(s) For Which Relief Is Requested Twenty eight RCPB piping segments, primarily consisting of small bore (S 2 inch) Nominal Pipe Size (NPS) piping vents, drains and branch (VTDB) lines and connections, and an additional segment of the shutdown cooling (SOC) system of 3/4-, 1- and 12-inch NPS piping. The piping segments are broken into two groups (i.e. Group 1 and Group 3) based on configuration of the segments. Identification of these piping segments is provided in Tables 1 and 2, below:

Table 1: Affected Piping Segments of Component Group 1  !

Segment Description Segment BoundaryllJ Dia. Length i (in.) (ft)

M2-1 PZR [pressurizerJ Spray Line 2-RC-036A to 2-RC-037A 3/4 <1 Drain M2-2 PZR Spray Line Drain 2-RC-036B to 2-RC-037B 3/4 <1 M2-3 RX [reactor] Head Vent to 2-RC-039 to 2-RC-413 3/4 <1 Enclosure Building Filtration System Refuel Level Indication 2-RC-214 to 2-RC-433 3/4 <1 Loop 1A Hot Leg Drain 2-RC-215 to 2-RC-040 2 2 Loop 2B RCP [reactor coolant 2-RC-232 to 2-RC-035D 2 2 pump] Suction Drain M2-7 Loop 2A RCP Suction Drain 2-RC-233 to 2-RC-035C . 2  ! 4 M2-8 Loop 1A Drain to Primary Drain 2-RC-234 to 2-RC-035A 2 12 Tank (PDT)

W M2-9 Loop 'I B Drain to PDT. 2-RC-235 to 2-RC-035B 2 M2-10 RX Head Vent 2-RC-414 to 2-RC-415 1 M2-11 RX Head Vent 2-RC-416 to 2-RC-417 1

-3 M2-12 RX Head Vent Header Drain, 2-RC-426 to 2-RC-427 3/4 2 M2-13 PZR Spray Line Vent 2-RC-015 to 2-RC-014 1 030 3/4 2 M2-14 PZR Relief Line Vent 2-RC-050 to 2-RC-051 3/4 2 I M2-15 Loop 1A Charging Header Vent 2-CH-679 to 2-CH-680 3/4 8

! M2-16 Loop 1A Charging Header Drain 2-CH-681 to 2-CH-682 1 1 M2-17 Loop 2A Charging Header Vent 2-CH-684 to 2-CH-683 3/4 <1 i M2-18 Loop 2A Charging Header Drain 2-CH-685 to 2-CH-686 1 1 M2-19 Aux [auxiliary] Spray Line 2-CH-699 to 2-CH-700 3/4 1 Charging Header Drain M2-20 Aux Spray Line 2-CH-431 to 2-CH-697, 517 2, 1 61 and 752 M2-21 Letdown Line Inlet Header Drain 2-CH-656 to 2-CH-657 1 <1 M2-22 M2-23 Letdown Line Inlet Header Drain Letdown Line Inlet Header Drain 2-CH-652 to 2-CH-653 2-CH-654 to 2-CH-655 q <1

<1 M2-25 Loop 1A LPSI [low pressure 2-SI-024A to 2-SI-0248 1 <1 safety injection] Header Drain M2-27 Loop 18 LPSI Header Drain 2-SI-013A to 2-SI-0138 1 <1 M2-29 Loop 2A LPSI Header Drain 2-SI-713A to 2-SI-7138 1 <1 M2-31 Loop 28 LPSI Header Drain 2-SI-712A to 2-SI-7128 1 <1 M2-33 SOC Return Line Drain 2-SI-1008 to 2-SI-100A 1 2 Note: 1: These segment boundaries are described in terms of valve-to-valve.

Table 2: Affected Piping Segments of Component Group 3 Dia. Length Segment Description Segment Boundary(1)

(in.) (tt) i M2-32 SOC Return Line to LPSI Suction 2-SI-651 to 2-SI-652, 12 36 8ypass Line and SOC Return 2-SI-1008 and RO-3664(2) 3/4 9 Line Relief 1 14 Note 1: Segment boundary is described in terms of valve-to-valve unless otherwise annotated.

Note 2: Segment boundary is described in terms of valve-to-orifice 3.2 ASME Code Requirements ASME Code,Section XI, Table IW8-2500-1, Examination Category 8-P, Item 815.10 requires that all Class 1 pressure retaining components be visually examined (VT-2) each refueling outage, and a system leakage test be conducted per IW8-5220. IW8-5221 requires that the system leakage test be conducted at a pressure not less than the pressure corresponding to 100% rated reactor power. IW8-5222(a) requires that the pressure retaining boundary during the system leakage test correspond to the RCP8, with all valves in the position required for normal reactor operation startup, with the visual examination extending to and including the second closed valve at the boundary extremity. IW8-5222(b) requires that the pressure retaining boundary during the system leakage test conducted at or near the end of each inspection interval extend to all Class 1 pressure retaining components within the system boundary.

-4 3.3 Licensee's Basis for Requesting Relief 3.3.1 Component Group 1 Each of the Category Group 1 piping segments (Table 1) is equipped with at least one manual valve which provides an isolation point to obtain double isolation of the RCPB. These valves are generally maintained in the closed position during normal operation, and the piping outboard of the first isolation valve is not normally pressurized. The licensee states that U[u]nder normal operating conditions, these VTOB lines and connections, except for the LPSI [low pressure safety injection] VTOB lines and connections, are subject to RCS pressures and temperatures only if leakage through the inboard valves occurs. For the LPSI VTOB lines and connections, leakage at inboard valves will only result in pressures associated with the pressure of the safety injection tanks." Because these VTOB lines and connections typically do not have test connections that allow them to be individually pressure tested without design modifications, it would be necessary to open the inboard valves to pressurize these VTOB lines and connections to perform the system leakage test in accordance with IWB-5222(b), defeating the double isolation feature and presenting significant safety concerns for the personnel performing the test on the valves that are at normal RCS pressure and temperature.

Performing the system leakage test with the inboard isolation valves open requires several man-hours to position or cycle these valves for the test and restore the valves after the test is complete. Most of these valves are located in close proximity to the RCS loop piping and thus require personnel entry into high radiation areas within containment; 0.404 roentgen equivalent man (rem) of additional radiation exposure is expected from cycling the valves for testing.

Based on the significant safety concerns for the personnel performing the test, as well as As Low As Reasonably Achievable (ALARA) radiological dose considerations, performing the required tests would present a hardship.

3.3.2 Component Group 3 Piping segment M2-32 is part of the SOC system that cannot be pressurized to full RCPB pressure because the pressure interlock and alarm that is associated with the SOC isolation valve 2-SI-652 prevents opening this valve when the RCS pressure exceeds 280 psig.

Additional protection is provided by a relief valve with a setpoint of 300 psig within the piping segment. To attempt to pressurize this segment to RCS pressure would require defeating the SOC system over-pressure protection, potentially endangering the plant, thus presenting a hardship.

3.4 Licensee's Proposed Alternatives 3.4.1 Component Group 1 The Component Group 1 piping segments (Table 1) are VTOB lines and connections that are equipped with manual valves which provide double isolation of the RCPB. As an alternative to the IWB-5222(b) system leakage test requirements for these RCPB pipe segments, the licensee proposes to perform an ASME Code,Section XI, IWB-5221 (a) system leakage test with the isolation valves in the normally closed position. The July 29, 2010, letter states the "[t]his

- 5 examination will be performed at the nominal operating pressure associated with 100% reactor power after satisfying the ASME Code required hold time."

3.4.2 Component Group 3 The Category Group 3 piping segment (Table 2) is part of the SDC system and is prevented from exceeding 280 psig by a pressure interlock on valve 2-SI-652 and pressure is further limited by a relief valve with a setpoint of 300 psig within the piping segment. The proposed alternative to the IWB-5220(b) system leakage test is to examine this pipe segment at its normal operating pressure.

4.0 NRC STAFF EVALUATION ASME Code,Section XI, Table IWB-2500-1, Examination Category B-P, requires that pressure retaining components be tested in accordance with IWB-5220. IWB-5222(b) requires that the pressure retaining boundary during the system leakage test conducted at or near the end of each inspection interval extend to all Class 1 pressure retaining components within the system boundary. The licensee has proposed an alternative to the system leakage test requirements of the ASME Code for the line segments detailed in Section 3.1 of this SE (Tables 1 and 2). The request and the review are separated into two component groups based on the configuration of the segments.

4.1 Component Group 1 The licensee states that a typical VTDB line includes at least one manual valve which provides an isolation point to obtain double isolation of the RCPB, and these valves are generally maintained closed during normal operation. In order to perform the ASME Code-required test on the subject VTDB lines, it would be necessary to manually open the inboard valves to pressurize the line segments. Pressurization by this method would defeat the reactor coolant system (RCS) double isolation, resulting in potential safety concerns, and would expose the personnel performing the examination to an estimated radiation exposure of 0.404 rem. Based on the review of the information provided by the licensee, the NRC staff concludes that the ASME Code requirement to perform the system leakage test per IWB-5222(b) presents a hardship for the licensee on basis of radiological dose accumulation and safety concerns.

The licensee states that the subject RCS vent and drain piping are heavy-walled ASTM A-376, Type 316 stainless steel that have a design pressure of 2485 psig, with a design temperature of between 600 OF and 700 OF, and are not subject to high or cyclic loads. Under normal plant operating conditions, segments 1 through 22 would be exposed to RCS pressures and temperatures only if leakage through the inboard valve occurs, and segments 25,27,29, and 31 would only be subjected to a maximum pressure equal to that of the safety injection tanks. In addition, these segments are visually examined, as required by the ASME Code, during each refueling outage with the isolation valves in the normally closed position. Based on the material of construction, low usage service conditions, and the ASME Code-compliant VT-2 examination of the segments performed each outage, the NRC staff finds that there is reasonable assurance of structural integrity. The NRC staff concludes that imposition of the ASME Code requirement to extend pressure retaining boundary to all Class 1 components within the system boundary for the system leakage test at the end of the lSI interval would result in hardship without a compensating increase in the level of quality and safety.

-6 4.2 Component Group 3 The licensee states that Component Group 3 piping segment M2-32 is part of the SDC system and is prevented from exceeding 280 psig by a pressure interlock and alarm associated with SDC isolation valve 2-SI-652. In addition, protection of the piping segment is provided by a relief valve with a setpoint of 300 psig. The NRC staff finds that defeating the SDC system over-pressure protections to perform the ASME Code-required examination could endanger the plant and personnel, thus would present a hardship for the licensee.

The licensee states the 1V12-32 piping segment is heavy-walled ASTM A-376, Type 316 stainless steel with a design pressure for the 2485 pSig, a design temperature of 650 of and an operating pressure of approximately 190 psig. This segment is visually examined during each refueling outage while isolated from the RCS, as required by the ASME Code. Based on the material of construction, low usage service conditions, and the ASME Code-compliant VT-2 examination of the segment performed each outage, the NRC staff finds that there is reasonable assurance of structural integrity. The NRC staff concludes that pressurizing the M2-32 segment to the RCS test pressure to perform the ASME Code-required examination for the system leakage test at the end of the lSI interval, would result in a hardship without a compensating increase in the level of quality and safety.

5.0 CONCLUSION

Based on review presented above, the NRC staff concludes that complying with the specified ASIVIE Code requirement to extend the pressure retaining boundary to all Class 1 components within the system boundary for system leakage tests at or near the end of the interval for the Class 1 piping segments described in Tables 1 and 2 would result in hardship to the licensee without a compensating increase in the level of quality and safety. The NRC staff also concludes the proposed alternatives provide a reasonable assurance of structural integrity.

Therefore, pursuant to 10 CFR 50.55a(a)(3(ii), the NRC authorizes the use of Relief Request RR-04-04 for the remainder of the fourth 10-year lSI interval for MPS2. The fourth 10-year lSI interval for MPS2 began on April 1, 2010, and is scheduled to be completed on March 31, 2020.

All other requirements of the ASME Code,Section XI for which relief has not been specifically requested and approved remain applicable, including a third party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: Jay Wallace Date: July 27, 2011

ML111881029

• via email OFFICE LPL 1-2/PM LPL 1-2/LA DCI/CPNB LPL 1-2/BC NAME CSanders ABaxter TLupold* HChernoff (changes only)

DATE 07/27/2011 07/27/2011 05/24/2011 07/27/2011