NOC-AE-04001747, Request for Authorization to Use an Alternative to the ASME Boiler and Pressure Vessel Code, Section XI Requirements (Relief Request VRR-05)
| ML042860041 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 09/30/2004 |
| From: | Crenshaw J South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| G25, NOC-AE-04001747, VRR-05 | |
| Download: ML042860041 (5) | |
Text
Nuclear Operating Company South roas Prn/ct
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September 30, 2004 NOC-AE-04001747 File No.: G25 10CFR50.55a U.S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 208952 South Texas Project Unit 2 Docket No. STN 50-499 Request for Authorization to Use an Alternative to the ASME Boiler and Pressure Vessel Code Section Xl Requirements (Relief Request VRR-05)
In accordance with the provisions of 10C.FR50.55a(a)(3)(i), the South Texas Project requests authorization to use an alternative to the requirements of ASME Section Xl 1989 Edition (OM Code 1987 Edition with 1988 addenda). The ASME Code requires stroke-time testing of motor-operated valves on a quarterly basis and after maintenance. However, surveillance testing on one Unit 2 motor-operated valve as specified by the Code is not appropriate at this time.
The subject valve has been identified as a source of leakage inside containment. The leakage rate when discovered was approximately 5 gallons per day. A flaw on the stem has been identified as the probable cause of damage to the valve packing when the valve is stroked, resulting in a packing leak. Tightening the packing reduced the leak rate to an acceptable level.
However, until the flaw is repaired, further surveillance tests by stroking the valve may cause additional damage to the valve packing and contribute to more leakage. The valve can not be repaired without plant shutdown, fuel removal, and draindown of the reactor vessel below the nozzle line. Consequently, the South Texas Project proposes an alternative to stroke time testing the valve quarterly and after maintenance until the valve is repaired.
There are no commitments included with this letter.
The attached relief request includes a discussion of the basis and justification for the relief request as well as an implementation schedule. NRC approval is requested by December 1, 2004.
If there are any questions, please contact either Mr. Philip L. Walker at (361) 972-8392 or me at (361) 972-7074.
John W. Crenshaw Manager, Plant Engineering PLW
Attachment:
Request for Authorization to Use an Alternative to the ASME Boiler and Pressure Vessel Code Section Xl Requirements (Relief Request VRR-05)
STI: 31758121 7
NOC-AE-04001747 Page 2 of 2 cc:
(paper copy) (electronic copy)
Bruce S. MalleKt A. H. Gutterman, Esquire Regional Administrator, Region IV Morgan, Lewis & Bockius LLP U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 L. D. Blaylock Arlington, Texas 76011-8064 City Public Service U. S. Nuclear Regulatory Commission David H. Jaffe Attention: Document Control Desk U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike R. L. Balcom Rockville, MD 20852 Texas Genco, LP Richard A. Ratliff C. A. Johnson Bureau of Radiation Control AEP Texas Central Company Texas Department of State Health Services 1100 West 49th Street Jon C. Wood Austin, TX 78756-3189 Matthews & Branscomb Jeffrey Cruz U. S. Nuclear Regulatory Commission P. O. Box 289, Mail Code: MNI16 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 STI: 31758121
NOC-AE-04001 747 Page 1 of 3 SOUTH TEXAS PROJECT UNIT 2 REQUEST FOR AUTHORIZATION TO USE AN ALTERNATIVE TO THE ASME BOILER AND PRESSURE VESSEL CODE, SECTION Xl REQUIREMENTS (RELIEF REQUEST VRR-05)
- 1. ASME Code Component Affected Systems: Residual Heat Removal (RHR) System and Safety Injection (SI) system Valve ID: 2-RH-0031A Function: This valve is normally open to provide low head safety injection flow to the cold leg of the Reactor Coolant System under accident conditions.
The valve is closed during switchover of recirculation flow from the cold leg to the hot leg of the RCS.
Under normal cooldown procedures, this valve is closed during initiation of residual heat removal operation. The valve is opened to provide RHR flow to the RCS.
Class: ASME Code Class 2
2. Applicable Code Edition and Addenda
ASME Boiler and Pressure Vessel Code, Section Xl, 1989 Edition (OM Code 1987 Edition and 1988 addenda)
3.4 Effect of Valve or Actuator Replacement, Repair, and Maintenance on Reference Values When a valve or its control system has been replaced, repaired, or has undergone maintenance that could affect the valve's performance, a new reference value shall be determined or the previous value reconfirmed by an inservice test run prior to the time it is returned to service or immediately if not removed from service, to demonstrate that performance parameters which could be affected by the replacement, repair, or maintenance are within acceptable limits.
4.2.1.1 Exercising Test Frequency:
Active Category A and B valves shall be tested nominally every 3 months....
4.2.1.4 Power-Operated Valve Stroke Testing:
The limiting value(s) of full-stroke time of each power-operated valve shall be specified by the Owner.
The stroke time of all power-operated valves shall be measured to at least the nearest second.
4.2.1.8 Stroke Time Acceptance Criteria 4.2.1.9 Corrective Action
NOC-AE-04001 747 Page 2 of 3 (a) If a valve fails to exhibit the required change of obturator position or exceeds the limiting values of full-stroke time, the valve shall be immediately declared inoperable.
(b) Valves with measured stroke times which do not meet the acceptance criteria of para. 4.2.1.8 shall be immediately retested or declared inoperable....
- 4. Reason for Request Currently, the valve is subject to stroke time testing quarterly and prior to return to service after maintenance, as described in section 3. In addition, following valve or actuator maintenance, post-maintenance testing is applied which consists of the following:
- MOV Diagnostic testing - MOV is stroked, with diagnostic test equipment installed, to obtain data for analysis to verify the condition of the MOV.
Diagnostic testing requirements are based on the maintenance performed.
Data collection may require removal of the actuator's limit switch compartment cover, in which case a valve stroke is performed following restoration of the actuator to verify that restoring the limit switch compartment cover did not damage any wires.
- Other post-maintenance testing as required for the maintenance performed.
The valve has a blemish on the stem in the packing area, which is postulated to be the source of damage to the valve packing and causing leakage of borated water at this location. Although the valve is not currently leaking, surveillance testing and post-maintenance testing with full valve strokes increase the potential for damage to the valve packing.
In normal plant configuration, the only pressure on the valve is static head pressure from the Refueling Water Storage Tank. However, quarterly inservice testing of the associated Residual Heat Removal pump and Low Head Safety Injection pump pressurizes the line incorporating the valve, which could exacerbate the leakage rate if the packing has been damaged by stroke time testing.
Valve 2-RH-0031A is in a line connected directly to the Reactor Coolant System. To separate the high-pressure RCS from the low-pressure components of the Residual Heat Removal System, two check valves are located in series downstream of the motor-operated valve. While they meet their design intent, the check valves are not appropriate for use as isolation valves. Without isolation from the Reactor Coolant System, repairing the flaw in the valve stem will require shutdown of Unit 2, removal of the fuel, and draining the reactor pressure vessel below the nozzle line. The next scheduled drain down of Unit 2 does not occur until 2RE12 in March 2007.
Consequently, the South Texas Project proposes an alternative to full stroke time testing of this valve.
- 5. Proposed Alternative The ASME Operations and Maintenance Code Committee has developed a method to verify MOV design-basis capability through periodic testing. Non-mandatory code case OMN-1, "Alternative Rules for Preservice and Inservice Testing of Certain Electric Motor Operated Valve Assemblies in LWR Power Plants, OM Code 1995 Edition; Subsection ISTC," allows frequent stroke-time testing to be replaced with periodic exercising of all
NOC-AE-04001 747 Page 3 of 3 safety-related MOVs once per cycle. Diagnostic testing may be performed under static or dynamic conditions, as appropriate.
The South Texas Project proposes to apply the MOV diagnostic testing program in lieu of the Code requirements listed in section 3. The alternative test is in accordance with the South Texas Project periodic verification program developed in response to Generic Letters 89-10 and 96-05.
- 6. Basis for Use The South Texas Project has established a program to periodically verify the design-basis capability of safety-related motor-operated valves. This program has been reviewed and found to be acceptable by the NRC (Safety Evaluation: South Texas Project, Units 1 and 2 - Completion of Generic Letter 96-05, "Periodic Verification of Design Basis Capability Of Safety-Related Motor-Operated Valves" (TAC Nos. M97102 and M97103, dated February 14, 2000). The program has been determined to provide an acceptable level of quality and safety as an alternative to the existing OM Code requirements.
Safety analyses do not assume a specific closure time for the valve.
The potential benefits (such as identification of decreased force output and increased force requirements) and potential adverse effects (such as accelerated degradation due to aging or valve damage) are considered when determining the appropriate testing for each MOV.
- 7. Duration of Proposed Alternative The South Texas Project requests NRC approval to use this alternative approach for testing this valve for the remainder of the current Unit 2 refueling cycle and the duration of the subsequent refueling cycle. The valve is expected to be repaired during the refueling outage in March 2007 when the reactor pressure vessel is drained down below the nozzle line.
- 8. Implementation The South Texas Project requests permission to implement the alternate examinations described above immediately following approval of this relief request. Approval by December 1, 2004 is requested in order to minimize the number of times the valve is stroked for surveillance testing and post-maintenance testing until the repair is completed. The next surveillance test of this valve is currently scheduled for no later than December 23, 2004.