NOC-AE-20003701, Proposed Alternatives to ASME OM Code 2012 Edition for the Fourth Inservice Test Interval (Relief Request PRR-02)

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Proposed Alternatives to ASME OM Code 2012 Edition for the Fourth Inservice Test Interval (Relief Request PRR-02)
ML20022A319
Person / Time
Site: South Texas  STP Nuclear Operating Company icon.png
Issue date: 01/22/2020
From: Dunn R
South Texas
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-20003701, PRR-02
Download: ML20022A319 (5)
v • d • e


Text

Nuclear Operating Company South Texas Project Electric Generating Station P.O. Box 289 Wadsworth, Texas 77483 January 22,2020 NOC-AE-20003701 10CFR50.55a(z)

STI:34969724 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Proposed Alternatives to ASME OM Code 2012 Edition for the Fourth Inservice Test Interval (Relief Request PRR-02)

Pursuant to 10 CFR 50.55a(z), STP Nuclear Operating Company (STPNOC) hereby requests an alternative to the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) 2012 Edition for use during the fourth ten-year Inservice Test (1ST) interval at South Texas Project. The details of the request are attached.

STPNOC request approval of the alternatives by September 1, 2020 to support the fourth ten-year interval starting on September 25,2020.

There are no new commitments in this letter.

If there are any questions regarding this request, please contact N, Boehmisch at 361-972-8172 or me at 361-972-7743.

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Roland Dunn General Manager, Engineering

Attachment:

Relief Request PRR-02, Use of Code Case OMN-16 ec:

Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 East Lamar Boulevard Arlington, TX 76011-4511

Attachment NOC-AE-20003701 Page 1 of 4 Attachment Relief Request PRR-02, Use of Code Case OMN-16

1. ASME Code Component(s) Affected 3R281(2)NPA1(2)01A, Essential Cooling Water [ECW] Pump A (Class 3) 3R281(2)NPA1(2)01B, Essential Cooling Water [ECW] Pump B (Class 3) 3R281(2)NPA1(2)01C, Essential Cooling Water [ECW] Pump C (Class 3) 2R171(2)NPA1(2)01A, Centrifugal Charging Pump [CCP] A (Class 2) 2R171(2)NPA1(2)01B, Centrifugal Charging Pump [CCP] B (Class 2)

Function:

The ECW pumps take suction from the Essential Cooling Pond (ECP) and deliver cooling water to Emergency Diesel Generator heat exchangers, Essential Chillers, and Component Cooling Water heat exchangers during normal operating, shutdown, and accident conditions. The ECW pumps receive an automatic start signal on receipt of an Safety Injection (81) initiation signal.

The Chemical Volume Control System (CVCS) CCPs provide a safety-grade means of delivering boric acid solution to the reactor coolant system (RCS) for boration. Their normal function is to provide reactor makeup for diluting or borating the RCS and to provide sufficient flow to maintaining coolant inventory in the RCS.

2. Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) 2012 Edition.

3. Applicable Code Requirements ISTB-5221, "Group A Test Procedure", states: Group A tests shall be conducted with the pump operating at a specific reference point.

ISTB-5221(b) states: The resistance of the system shall be varied until the flow rate equals the reference value. The pressure shall then be determined and compared to its reference value.

Alternatively, the flow rate can be varied until the pressure equals the reference value and the flow rate shall be determined and compared to the reference flow rate value.

ISTB-5221 (c) states: Where system resistance cannot be varied, flow rate and pressure shall be determined and compared to their respective reference values.

ISTB-5223, "Comprehensive Test Procedure", states: Comprehensive tests shall be conducted with the pump operating at a specific reference point.

ISTB-5223(b) states: The resistance of the system shall be varied until the flow rate equals the reference value. The pressure shall then be determined and compared to its reference value.

Alternatively, the flow rate can be varied until the pressure equals the reference value and the flow rate shall be determined and compared to the reference flow rate value.

ISTB-5223(c) states: Where system resistance cannot be varied, flow rate and pressure shall be determined and compared to their respective reference values.

Attachment NOC-AE-20003701 Page 2 of 4

4. Reason for Request

The ECW System and CVCS are designed so that total pump flow cannot be readily adjusted to one reference value for testing without adversely affecting the operating system flow balance or utilizing excessive operator resources which would be better utilized to monitor the safe operation of the plant. These pumps must be tested in a manner that does not adversely affect the flow balance and system operability.

System resistance is not fixed since each flow path and load have an acceptable flow range.

Adjusting system total flow to meet a specific reference value may change the individual load flow rates and may cause one or more of the loads to move outside its respective operating range, possibly requiring an entry into a Technical Specification Limiting Condition for Operation (LCO)

Action Statement. Additionally, for the ECW pumps, the Essential Chillers loads have specific "Cold" and "Warm" weather lineups for operation which vary system resistance. Consequently, adjusting flow to one specific value on a quarterly basis to perform pump testing conflicts with system design and challenges system operability.

For the CCPs, establishing a fixed flow different from the normal operating flow for a given plant condition will result in transient increases or decreases in volume control tank and pressurizer levels as charging and seal injection flow are unmatched to CVCS letdown flow. This condition would require additional operator attention to maintain proper inventories while providing no corresponding increase in safety.

Guidelines set forth in Code Case OMN-16 Revision 1, "Use of a Pump Curve for Testing," will be followed. This Code Case has been approved for use per Regulatory Guide (RG) 1.192 Revision 2 for the ASME OM Code, 2012 Edition, however the associated Code Case applicability statement included in that edition reflects 1998 and subsequent editions and addenda through the OMa-2011 Addenda only, necessitating a relief request for its use.

5. Proposed Alternative and Basis for Use Compliance with the Code requirements to return to a specific value of flow rate or discharge pressure to test these pumps presents a hardship or unusual difficulty without a compensating increase in the level of quality or safety. As stated in NUREG-1482, Revision 2, Section 5.2, some system designs do not allow for testing at a single reference point or a set of reference points. In such cases, it may be necessary to plot pump curves to use as the basis for variable reference points.

Code Case OMN-16, "Use of Pump Curves for Testing," was included in the issuance ofASME OMb-2006. This Code Case was approved for use by the NRC staff in Revision 2 of USNRC Regulatory Guide (RG) 1.192; "Operation and Maintenance Code Case Acceptability, ASME OM Code"; however, OMN-16 is listed in Table 2 with a condition requiring the use of Figure 1 from the OMN-16 Code Case published with ASME OMb-2006. The condition imposed on OMN-16 will be met by STP by use of Figure 1 from the ASME OMb-2006 published version of OMN-16.

As an alternative to the testing requirements of ISTB-5221 and ISTB-5223, STPNOC will assess pump performance and operational readiness through the use of reference pump curves per the guidelines provided in Code Case OMN-16. Flow rate and pump differential pressure will be measured during inservice testing in the as-found condition of the system and compared to an established reference curve. The following elements will be used in the development of the reference pump curves:

Attachment NOC-AE-20003701 Page 3 of 4

1. A reference pump curve (flow rate versus discharge pressure) has been established for each of the pumps from the data taken when these pumps are known to be operating acceptably.
2. Pump curves will be established from measurements taken with instrumentation meeting or exceeding the accuracy requirements of Table ISTB-3510-1.
3. Each pump curve will be based on at least five points beyond the flat portion of the pump curve in the normal operating range of the pumps. This range is sufficient to bound the points of operation expected during testing and is within +/-20% of rated capacity (design) flow at any given point.

For the ECW pumps, rated capacity is 19,280 gpm. Use of a 15,700 - 20,500 gpm point flow curve is well within +/-20% of rated capacity flow (15424-23136 gpm).

For the CVCS CCPs, rated capacity is 160 gpm. Use of a 142-178 gpm 5-point flow curve is well within +/-20% of rated capacity flow (128-192 gpm).

4. The reference pump curves will be based on flow rate versus discharge pressure. The acceptance criteria (acceptable, alert and required action ranges) curves will be based on the differential pressure limits of Table ISTB-5221-1, as appropriate for the type of test being performed.
5. Vibration levels for the Group A and Comprehensive tests will be measured at each of the reference points ISTB-5221(d) or ISTB-5223(d). If negligible variation readings are observed over the range of pump conditions, a single reference value may be assigned to each vibration measurement location. If vibration levels change over the range of pump conditions, appropriate acceptance criteria will be assigned to regions of the pump curve.

After any maintenance or repair that may affect the existing reference pump curve, a new reference curve shall be determined or the existing pump curve revalidated by an inservice test. A new pump cun/e shall be established based on at least five points beyond the flat portion of the pump curve. The proposed alternative to establish a reference curve is consistent with the NRC staff guidance provided in NUREG-1482, Rev.2, Section 5.2 and Code Case OMN-16 and it will provide reasonable assurance of pump operational readiness. Note: Code Case OMN-16, "Use of a Pump Curve for Testing" is listed in Table 2, Conditionally Acceptable Code Cases of Regulatory Guide 1.192, Revision 2, issued March 2017. The Condition indicates Figure 1 of 2006 Addendum of the OM Code should be used with the OMN-16 Code Case published in the 2012 Edition of the OM Code, since Figure 1 was inadvertently omitted when the 2012 Edition was published.

==

Conclusion:==

In summary, STPNOC proposes to test the ECW and CCPs by implementing the requirements of ASME OM Code Case OMN-16, using Figure 1 from the 2006 Addendum, in lieu of subparagraphs ISTB-5121(b) and ISTB-5223(b) of the 2012 Edition of the OM Code.

Using the provisions of this request would provide adequate detection of component degradation and, would continue to provide reasonable assurance of the operational readiness of affected components. Therefore, compliance with the requirements ofASME OM 2012 ISTB would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety pursuant to 10 CFR 50.55a(z)(2).

Attachment NOC-AE-20003701 Page 4 of 4

6. Duration of Proposed Alternative The proposed alternative, if approved, would be implemented from the end of the Third Interval (September 25, 2020) and the end of the Fourth Interval (September 25, 2030).
7. Precedent NRC Safety Evaluation approving STPNOC relief request PRR-01 for the second 10-year interval of the 1ST program for relief from Code requirements for the ECW pumps (Reference 3).

NRC Safety Evaluation approving STPNOC relief request PRR-02 for the third 10-year interval of the 1ST program for relief from Code requirements for the ECW pumps (Reference 4).

8. References
1. ASME 0Mb Code-2006, Code Case OMN-16, "Use of a Pump Curve for Testing", Figure 1
2. Regulatory Guide 1.192, Revision 2, "Operation and Maintenance Code Case Acceptability, ASME OM Code", March 2017, ML16321A337
3. Letter from R.A. Gramm, NRC, to J.J. Sheppard, STPNOC, "South Texas Project (STP), Units 1 and 2 - Evaluation of Relief Requests Related to the Second 10-year Inservice Testing Program (TAG Nos. MB2136 and MB 2137)," May 2, 2003, ML031220730
4. Letter from M.T. Markley, NRC, to E.D. Halpin, STPNOC, "South Texas Project (STP), Units 1 and 2 - Relief Request Nos. VRR-01, PRR-01, PRR-02, and PRR-03 for the Third 10-Year Inservice Testing Program Interval (TAG Nos. ME3515, ME3516, ME3517, ME3518, ME3519, ME3520, ME3521, and ME3522)," September 2, 2010, ML102150077
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