ML092740662

Alternative Request RR-89-68 for Use of Code Case N-722-1 for Bare Metal Visual Examination of the RPV Flange Seal Leak-off Line Welds Made of Alloy 600/82/182 Materials

ML092740662
Person / Time
Site:	Millstone
Issue date:	10/01/2009
From:	Price A Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
09-622, RR-89-68, FOIA/PA-2011-0115
Download: ML092740662 (12)

Text

i >orninion Nuclear Connecticut, Inc.

'110(1 [)ominion Boulevard, Glen Allen, Virgini I

' '1160

\\,h \\ddress: www.dom.com October 1, 2009 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.

NLOSIWDC Docket No.

License No.09-622 RO 50-336 OPR-65 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2 ALTERNATIVE REQUEST RR-89-68 FOR USE OF CODE CASE N-722-1 FOR BARE METAL VISUAL EXAMINATION OF THE RPV FLANGE SEAL LEAK-OFF LINE WELDS MADE OF ALLOY 600/82/182 MATERIALS The Reactor Pressure Vessel (RPV) Flange Seal Leak-Off Line at Millstone Power Station Unit 2 (MPS2) contains welds of Alloy 600/82/182 materials that currently require bare metal visual examination in accordance with 10 CFR 50.55a(g)(6)(ii)(E)(1) through (4) using the American Society of Mechanical Engineers (ASME) Code Case N-722.

The welds in this line are inaccessible for direct visual examination and ASME has revised this Code Case to no longer require the examination of these welds.

Dominion Nuclear Connecticut, Inc. (DNC) is requesting to use the revised Code Case N-722-1 based on the information contained in Attachment 1.

Specifically, ONC submits alternative request RR-89-68 to use Code Case N-722-1 in lieu of Code Case N-722 under the provisions of 10 CFR 50.55a(a)(3)(i). This proposed request provides an acceptable level of quality and safety.

DNC requests approval of the alternative by March 31, 2010.

If you have any questions regarding this submittal, please contact Ms. Wanda D. Craft at (804) 273-4687.

Sincerely, J. A.

rice (vic President - Nuclear Engineering

\\....

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 2 of 2 Attachments: (1)

1. Alternative Request RR-89-68 for the use of Code Case N-722-1 for the Bare Metal Visual Examination of the RPV Flange Seal Leak-Off Line Welds Made of Alloy 600/82/182 Materials Commitments made in this letter:

None cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Ms. C. J. Sanders Project Manager - Millstone Power Station U.S. Nuc:lear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 0-8B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No.09-622 Alternative Request RR-89-68 Docket No. 50-336 ATTACHMENT 1 ALTERNATIVE REQUEST RR-89-68 FOR USE OF CODE CASE N-722-1 FOR BARE METAL VISUAL EXAMINATION OF THE RPV FLANGE SEAL LEAK-OFF LINE WELDS MADE OF ALLOY 600/82/182 MATERIALS DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 1 of 9 ALTERNATIVE REQUEST RR-89-68 FOR USE OF CODE CASE N-722-1 FOR BARE METAL VISUAL EXAMINATION OF THE RPV FLANGE SEAL LEAK-OFF LINE WELDS MADE OF ALLOY 600/82/182 MATERIALS CONTENTS 1.0 ASME CODE COMPONENT(S) AFFECTED 2

2.0 APPLICABLE CODE EDITION AND ADDENDA 3

3.0 APPLICABLE CODE REQUiREMENT 3

4.0 REASON FOR THE REQUEST 3

5.0 PROPOSED ALTERNATIVE AND BASIS FOR USE 4

6.0 DURATION OF PROPOSED ALTERNATIVE 5

7.0 PRECEDENTS 5

8.0 REFERENCES

5 FIGURES Figure 1 - Typical Sketch of RPV Flange Seal Leak-Off Line 2

SUPPLEMENT TO ATTACHMENT 1 Code Case 1\\1-722-1, "Additional Examinations for PWR Pressure Retaining Welds In Class 1 Components Fabricated With Alloy 600/82/182 Section XI, Division 1," Approval Date:

January 26, ~W09

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 2 of 9 ALTERNATIVE REQUEST RR-89-68 FOR USE OF CODE CASE N-722-1 FOR BARE METAL VISUAL EXAMINATION OF THE RPV FLANGE SEAL LEAK-OFF LINE WELDS MADE OF ALLOY 600/82/182 MATERIALS Proposed Alternative in Accordance with 10 CFR 50. 55a(a)(3)(i)

-- Alternative Provides Acceptable Level of Quality And Safety --

1.0 ASME CODE COMPONENT(S) AFFECTED Code Class:

1 Category:

Class 1 PWR Components Containing Alloy 600/82/182 Materials Reactor Vessel Item No.:

815.100 Instrument connections

==

Description:==

Millstone Power Station Unit 2 (MPS2) - % inch schedule 80 piping made of S8-167 material inside the Reactor Pressure Vessel (RPV) flange.

At MPS2, three welds are located on the RPV Flange Seal Leak-Off Line monitor tube, which is made of Alloy 600/82/182 materials. The location of the three welds, using the typical sketch in Figure 1 below are:

1) the weld at the top of the flange described in (b),

2) a butt weld between the upper manufactured % inch S8-166 Alloy 600 tube and lower S8-167 Alloy 600 pipe (e), (the weld is not shown in the Figure 1), and 3) the socket welded S8-167 Alloy 600 pipe to the 316 stainless steel elbow weld made of Alloy 82 material (c).

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St..aT}..,.)l6 Figure 1 - Typical Sketch of RPV Flange Seal Leak-Off Line

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 3 of 9 2.0 APPLICABLE CODE EDITION AND ADDENDA MPS2 is in the third 10-year inservice inspection (lSI) interval and the lSI program is in accordance with the 1989 Edition of Section XI with No Addenda (Reference 1). However, the requirement to perform the examination of the Alloy 600/82/182 welds in the RPV Flange Seal Leak-Off Line is in accordance with 10 CFR 50.55a(g)(6)(ii)(E)(1) through (4).

This provision of the regulation requires implementation of the augmented inspections required by Code Case N-722 (Reference 2). Code Case N-722 requires bare metal visual examinations of Class 1 welds in Alloy 600/82/182 materials.

3.0 APPLICABLE CODE REQUIREMENT The subject of this request involves requirements of 10 CFR 50.55a(g)(6)(ii)(E)(1) through (4), which require examinations of the Class 1 welds made of Alloy 600/82/182 materials.

The requirements also have criteria for when these examinations need to be performed in Footnote 1 to the regulation.

Footnote 1:

"For inspections to be conducted every refueling outage and inspections conducted every other refueling outage, the initial inspection shall be performed at the next refueling outage after January 1, 2009. For inspections to be conducted once per interval, the inspections shall begin in the interval in effect on January 1, 2009, and shall be prorated over the remaining periods and refueling outages in this interval."

Examinations are required to be performed once per interval for the Class 1 welds associated with Code Case N-722, Table 1, and Item No. 815.100, Instrument connections. With the second sentence in Footnote 1, MPS2 is required to perform the bare metal visual examination of the Class 1 welds in the RPV Flange Seal Leak-Off line that are made of Alloy 600/82/182 materials by the end of the current 10 year interval. Thus, the only opportunity to meet this requirement is during the MPS2 fall 2009 (2R19) refueling outage, which will take place in October 2009.

4.0 REASON FOR THE REQUEST The RPV head and flange leakage detection system has elements with Alloy 600/82/182 materials, but they are not accessible for visual examination, and the welds are not normally subject to continuous contact with reactor coolant. Consequently, the welds are not subject to Primary Water Stress Corrosion Cracking (PWSCC) concerns. ASME revised Code Case N-722 to N-722-1 (Reference 3) and added a Footnote (8) in Table 1 related to Item No. 815.100, Instrument connections, in the revised Code Case N-722-1 that states, "This Case does not require visual examination of Alloy 600/82/182 materials in flange seal leak-off lines. "

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 4 of 9 5.0 PROPOSED ALTERNATIVE AND BASIS FOR USE 5.1 AL.TERNATIVE:

The alternative proposed in this request is to use the ASME approved Code Case N-722-1 in lieu of Code Case N-722 for the requirements associated with the Class 1 welds made of Alloy 600/82/182 materials in the RPV Flange Seal Leak-Off Line at MPS2.

5.2 BASIS

A typical section of piping in the RPV head and flange leakage detection system (Le., the monitor tube) is shown in Figure 1. This system is used to support the identification of inner O-ring seal leakage. This system is essentially a drain system and reasonably does not belong in the same scope of piping and components that are included in Code Case N-722.

The RPV head and flange leakage detection system operates in the following manner.

During operation, an increase in temperature above ambient temperature indicates inner a-ring seal leakage. High temperature actuates an alarm in the control room. The seal leakage would be identified by temperature alarm or by reactor coolant system (ReS) inventory balance calculations and addressed by procedures. On the indication of inner O-ring leakage, the isolation valve in the leak-off line can be closed to place the outer a-ring into the pressure retention mode, and the inner a-ring leak detection system piping would then be pressurized to RCS pressure, up to the closed isolation valve. This would be a temporary condition until the next outage when the head a-rings are replaced. Seal leakage would be closely monitored and procedurally controlled by operator actions allowing identification of any further compensatory actions required. If an inner a-ring seal leak occurs and the isolation valve is not closed, the inner a-ring seal leakage would be directed to the primary system drains tank. If an inner a-ring seal leak occurs and the isolation valve was not closed, full rupture is not credible because the primary drains tank has a relief valve system that would relieve the pressure in the line. If an inner a-ring seal leak were to occur and the isolation valve was closed, given the short exposure time to RCS water, leakage at welds in the monitoring tube from PWSCC would be highly unlikely.

The alternative to use Code Case N-722-1 does not require visual examinations of the welds in the RPV flange seal leak-off line. The welds are not accessible for direct bare metal visual examination. This alternative has an acceptable level of quality and safety because the welds in the RPV flange seal leak-off line are; 1)1 not normally subject to continuous contact with reactor coolant during normal operation, and 2) not subject to PWSCC concerns.

Although the welds of the RPV flange seal leak-off line are made of Alloy 600/82/182 materials, the required examination of the welds cannot be achieved to the intended purpose of the Code Case N-722. The ASME approved Code Case N-722-1 eliminates the requirement. This alternative provides an acceptable level of quality and safety equal to what can be gained by performing examinations of these welds to the current Code Case N-722 requirements. Therefore, it is requested that the NRC approve this alternative request under the provisions of 10 CFR 50.55a(a)(3)(i).

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 5 of 9 6.0 DURATION OF PROPOSED ALTERNATIVE This proposed alternative in this request if approved will be applicable to the end of the current 10 year lSI interval which is scheduled for March 31, 2010.

7.0 PRECEDENTS No precedent similar to this alternative request is known.

8.0 REFERENCES

1.

ASME Code Section XI, 1989 Edition with No Addenda.

2.

ASME Code Case N-722, "Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated With Alloy 600/82/182 MaterialsSection XI, Division 1, Approval Date: July 5, 2005.

3.

ASME Code Case N-722-1, " Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated With Alloy 600/82/182 MaterialsSection XI, Division 1, Approval Date: January 26, 2009.

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 6 of 9 SUPPLEMENT TO ATTACHMENT 1 CODE CASE N-722-1, "ADDITIONAL EXAMINATIONS FOR PWR PRESSURE RETAINING WELDS IN CLASS 1 COMPONENTS FABRICATED WITH ALLOY 600/82/182 MATERIALS SECTION XI, DIVISION 1" "Reprinted from ASME 2007 BPVC, Code Cases, Nuclear Components, by permission of The American Society of Mechanical Engineers.

All rights reserved. "

Serial No.09-622 Docket No. 50-336 Alternative Request RR-89-68 Page 7 of 9 CASES OF ASME BOILER AND PRESSURE VESSEL CODE Approval Date: January 26. 2009 The ASME Boiler and Pressure Vessel Standards Committee took action to eliminate Code Case expiration dates effective March 11. 2005. This means that aI/ Code Cases listed in this Supplement and beyond will remain available for use until annul/ed by the ASME Boiler and Pressure Vessel Standards Committee.

CASE N-722-1 Case N*722*1 Additional Examinations for PWR Pressure Retaining Welds in Class 1 Components Fabricated With Alloy 600/82/182 MaterialsSection XI, Division 1 inquiry: What examinations, in addition to those of Table IWB-2500-1. may be performed to provide addi-tional detection capability for pressure boundary leakagein pressurized water reactor plants having pressure retaining partial or full penetration welds ill Class 1 compo>>ents fabricated with Alloy 600/821182 material?

Reply: Itis the opinion ofthe Committee that in addition to the examination requirements of Table IWB-25QO-1 the additional examinations of Table 1 shall be performed for pressurized water reactor plants having partial or full penetration welds in Class 1 components fabricated with Alloy 600/821182 material.

The Committee'. function is to establish rules of safety, relating only to pressure Integrity, governing the construction of bollars. prossure vosse1sf transport tanks and nucl&ar components, end inservice inspection for pressure integrity of nuclear components and transport tanks, and to interpret tnese rutes when questions arise regarding lhelr Inlent. This Code doeonotaddress other safelY 1....08 relating wthe construclion ofboilers, pressors v_ols.transporttanks end nuc1eercomponents, and the inservice inspection of nuclear components and transport tanks. The user of the Code should refer to other pertinent codes. standards, lawa, regUlations or othor rslovant documentll.

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II 011 TABLE I EXAMINATION CATEGORIES CLASS 1 PWR COMPONENTS CONTAINING ALLOY 600/82/1821 Extent and Frequency of Examination Deferral of Item Examination Examination Acceptance Successive Inspection to No.

Parts Examinedz Requirements Method 3,4,5 Standard First Inspection Interval Inspection Intervals End of Interval Reactor Vessel2 B15.80 RPV bottom-mounted instrument penetrations All penetrations Visual, VE IWB-3522 Every other refueling outage Same as for 1st interval Not permissible B15.90 Hot leg nozzle-to-pipe connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st Interval Not permiSSible B15.95 Cold leg nozzle-to-pipe connections All connections Visual, VE IWB-3522 Once per interval b, I Same as for 1st interval Not permissible B15.100 Instrument connections8 All connections Visual, VE IWB-3522 Once per interval"' 7 Same as for 1st interval Not permissible l-:I Steam Generators

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BI5.110 Hot leg nozzle-te-pipe connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Not permissible

j B15.115 Cold leg nozzle-to-pipe connections All connections Visual, VE IWB-3522 Once per Interval"' 7 Same as for 1st interval Not permissible

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B15.120 Bottom channel head drain tube penetration All penetrations Visual, VE IWB-3522 Once per Interval"' 7 Same as for 1st interval Not pet'misslble B15.130 Primary side hot leg instrument connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Not permissible BI5.135 Primary side cold leg Instrument connections All connections Visual, VE IWB-3522 Once per intervalb, 7 Same as for 1st interval Not permissible Pressurizer 815.140 Heater penetrations All penetrations Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Nat permissible 815.150 Spray nozzle-to-pipe connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Not permissible 815.160 Safety and relief nozzle-to-plpe connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Not permissible 815.170 Surge nozzle-to-pipe connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Nat permissible 615.180 Instrument connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st Interval Not permiSSible B15.190 Drain nozzle-to-plpe connections All connect!ons Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Not permissible Piping 815.200 Hot leg Instrument connections All connections Visual, VE IWB-3522 Each refueling outage Same as for 1st interval Not permissible 815.205 Cold leg instrument connections All connections Visual, VE IWB-3522 Once per interval"' 7 Same as for 1st interval Not permissible B15.210 Hot leg full penetration welds All welds Visual, VE IWB-3522 Each refueling outage Same as for 1st Interval Not permissible B15.215 Cold leg fUll penetration welds Ail welds Visual, VE IWB-3522 Once per interval6, 7 Same as for 1st interval Not permissible z~

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NOTES:

(l) Alloy 600/821182 are equivalent to UNS N06600 (S6-163,56-166, 58-167,56-168 and S6-564l, UNS N06082 (SFA 5.14 ERNiCr-3l and UNS WB6182 (SFA 5.11 ENiCrFe-:3).

(2) The reactor vessel closure head Is not addressed in this Case.

(:3) The Vis'ual Examination (VE) performed on Alloy 600/821182 components for evidence of pressure boundary leakage and corrosion on adjacent ferritic steel components shall consist of the foHowing:

(a) A direct VE of the bare-metal surface performed with the insulation removed. Alternatively, the VE may be performed with insulation in place using remote visual inspection equipment that provides resolution of the component metal surface equivalent to a bare-metal direct VE.

(b) The VE may be performed when the system or component is depressurized.

(c) The direct VE shall be performed at a distance not greater than 4 ft 1l.2 m) from the component and with a demonstrated illumination level sufficient to allow resolution of lower case characters having a height of not greater than 0.105 in (2.7 mm).

(4) Personnel performing the VE shall be qualified as VT-2 Visual examiners and shall have completed a minimum of four (4) hours of additional training in detection of borated water leakage from Alloy 600/82/182 components and the resulting boric acid corrosion of adjacent ferritic steel components.

(5) An ultrasonic examination, performed from the component Inside or outside surface in accordance with the requirements of Table IW8-2500-1 and Appendix VllI (1995 Edition with the 1996 Addenda or later) shall be acceptable in lieu of the VE requirement of this table.

(oJ VEshall be performed in accordance with the schedule in IWB-2400.

(7) The detection of evidence of pressure leakage at a VE location shall require the VE of all components within the Examination Item No. prior to reactor startup. These additional VEs shall not affect the original VE schedule of the components within the Examination Item No.

(8) This Case does not require visual examination of Alloy 600/821182 materials in flange seal leak-off lines.

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