ML17164A932
| ML17164A932 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 12/16/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17164A931 | List: |
| References | |
| NUDOCS 9812280138 | |
| Download: ML17164A932 (5) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&4001 UCLEA C 0 GULA 0 S
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-388 The Code ofFederal Regulations, 10CFR50.55a, requires that'inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section Xl of the ASME Boilerand Pressure'Vessel Code (the Code) and applicable addenda, except where alternatives have been authorized or relief has been requested by the licensee and granted by the Commission pursuant to Sections (a)(3)(i),
(a)(3)(ii), or (f)(6)(i) of 10CFR50.55a.
In proposing alternatives or requesting relief, the licensee must demonstrate that: (1) the proposed alternatives provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficultywithout a compensating increase in the level of quality and safety; or (3). conformance is impractical'for its facility.
Section 50.55a authorizes the Commission to approve alternatives and to grant relief from ASME Code requirements upon making the necessary findings. Additionally, 50.55a(f)(4)(iv) provides that IST of pumps and valves may meet the requirements set forth in subsequent editions and addenda of the Code that are incorporated by reference in paragraph (b) of Section 50.55a, subject to the limitations and modifications listed therein, and subject to Commission approval.
Portions of editions and addenda may be used provided that all related requirements of-the-respective editions or addenda are met. Guidance related to the development and implementation of IST programs is given in Generic Letter (GL) 89-04, "Guidance on Developing Acceptable lnservice Testing Programs," issued April 3, 1989, and its Supplement 1 issued April4, 1995. Also see NUREG-1482, "Guidelines for Inservice Testing at Nuclear Power Plants."
The 1989 Edition of the ASME Code is the latest edition incorporated by reference in paragraph (b) of Section 50.55a.
Subsection IWVof the 1989 Edition, which gives the requirements for IST of valves, references Part 10 of the American National Standards Institute/ASME Operations and Mainfenance Standards (OM-10) as the rules for IST of valves.
OM-10 replaces specific requirements in previous editions of Section XI, Subsection IWV, of the ASME Code.
By letter dated August 3, 1998, PP8L, lnc. (the licensee), submitted a request for relief from certain ASME Code IST requirements pertaining to tests of the Susquehanna Steam Electric Station, Unit 2 (Susquehanna 2), main steam safetylrelief valves (SIRVs). This request was superseded in its entirety by letter dated October 19, 1998, which revised the request for the same relief. The plant IST program requires that the testing of the subject valves meet the requirements of ASME Code OM-1987, Part 1 (herein referred to as the Code).
Specifically, 98i2280i38 9'8i2i6 PDR ADQCK 05000388 P
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this request seeks relief from performing as-found set pressure tests on all S/RVs within a 5-year period. There are 16 S/RVs installed on the Susquehanna 2 main steam piping and are identified as valves PSV-241F013A, B, C, D, E, F, G, H, J, K, L, M, N, P, R, andS.
Forthese16 valves, the licensee is requesting relief from the following test requirement:
OM-1987, Part 1, paragraph 1.3.3.1(b), 'Subsequent 5 Year Periods
. AIIvalves of each type and manufacture shall be tested within each subsequent 5-year period with a minimum of 20% of the valves tested within any 24 months. This 20% shall be previously untested valves, ifthey exist.
3.0 REVISED RELIEF REQUEST The licensee states that Susquehanna 2 has implemented a 24-month fuel cycle, and that continuing to meet the above Code testing requirement, as has been done for previous 18-month fuel cycles, would be impractical and without a compensating increase in the level of quality and safety. The licensee states that the plant history forthe S/RVs indicates that several leaking valves are required to be replaced, in addition to those selected for testing, and that a total of 8 of the 16 valves are typically removed and tested (i.e, 5 or 6 valves for the test sample plus 2 or 3 additional leaking valves) during each outage.
Because the Code requires that the test valve sample be previously untested valves, the licensee projects that more than 8 valves would be required to be removed and tested following a 24-month cycle since all 16 valves (plus any leaking valves) would be required to be tested within two cycles. When the facilitywas operating under an 18-month cycle, all valves were required to be tested within three cycles. The licensee states that the purchase of additional spare valves would be required since a larger number of valves would potentially need to be removed each outage.
Furthermore, the licensee states that the setpoint history of the S/RVs has been good such that there has been infrequent need for testing additional valves when test valve setpoints are found greater than 3% above the nominal values.
4.0 PROPOSED ALTERNATIVETESTING As an alternative to the above Code test requirement, the licensee proposes that the S/RVs be tested such that all valves would be tested within three 24-month fuel cycles (or 6 years) with a minimum of 20% of previously untested valves tested within any outage.
With the projected number of additional leaking valves which would also require refurbishing, the licensee could then continue to remove and test 8 valves per outage.
5.0 EVALUATION The staff has reviewed the licensee's S/RVs test results to determine ifthe licensee's proposed alternative testing provides an acceptable level of safety. This included setpoint test results for the time period from initial operation to the present, which comprises 207 data points. The average of the setpoint drift percentages is -0.705 %, which indicates that, in general, the S/RVs tend to drift slightly downward, not upward. The licensee also calculated the standard deviation from the average for the data set and determinedit to be 1.44%. The data indicates that a significant number of the as-found setpoints are outside the+/-1% tolerance allowed by the plant Technical Specifications (TS). However, most of the points outside the TS tolerance were below
- 1%, not above + 1%, which results in a slightly downward setpoint drifttrend over time. This indicates that, for the longer test interval proposed, there is not expected to be a reduced capability of the S/RVs to provide adequate system overpressure protection. Also, there were only 2 data points above the+ 3% tolerance allowed by the Code. Another consideration is that with the licensee's proposed alternative testing, if setpoints are found above the Code+ 3%
tolerance, at. least two additional valves are required to be tested for each valve found above+
3%, which would significantly increase the rate of testing as a corrective measure.
It should also be noted that the Susquehanna 2 TS S/RV (SR 3.4.3.1) setpoint tolerance is+I-1% and is a more stringent criterion than a TS tolerance of+I-3%, as provided in licensing topical report NEDC-31753P (The NEDC-31753P topical report was approved by the NRC in a letter to the BWR Owners Group dated March 8, 1993). However, this topical report provides that, for an increase in the S/RV TS tolerance to+/- 3%, all S/RVs must be tested within 40 months.
Therefore, the staff finds that, given that the TS S/RV tolerance is+I-1%, allowing the testing to be extended to three 24-month cycles with a minimu'm of 20% of previously untested valves tested during any one outage provides an acceptable level of quality and safety because it provides assurance that the S/RVs willbe capable of performing their function. The staff notes that the acceptance is based on the safety/ relief valve setpoint tolerance being +I-1% and if, in the future, this tolerance is revised, the licensee willneed to resubmit the request for this relief because the basis for the staff acceptance willhave been changed.
6.0 CONCLUSION
Based on the above evaluation, the staff has determined that, pursuant to 10CFR50.55a(a)(3)(i), the proposed alternative may be authorized on the basis that the alternative testing provides an acceptable level of quality and safety.
Principal Contributors:
D. Collins G. Hammer Date:
December 16, 1998
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