ML16342E003
| ML16342E003 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 02/25/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML16342E002 | List: |
| References | |
| NUDOCS 9803030323 | |
| Download: ML16342E003 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055$ 4001 LI F 1.0 The Code of Federal Regulations, 10 CFR 50.55a, requires that inservice testing (IST) of certain ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda, except where relief has been requested and granted or proposed alternatives have been authorized by the Commission pursuant to 10 CFR 50.55a (f)(6)(i), (a)(3)(i), or (a)(3)(ii). In order to obtain authorization or relief, the licensee must demonstrate that (1) conformance is impractical for its facility; (2) the proposed alternative provides an acceptable level of quality and safety; or (3) compliance would result in a hardship or unusual difficultywithout a compensating increase in the level of quality and safety.
Section 50.55a (f)(4)(iv)provides that inservice tests of pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b), subject to the limitations and modifications listed, and subject to Commission approval.
NRC guidance contained in Generic Letter (GL) 89-04, "Guidance on Developing Acceptable Inservice Testing Programs," provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives in Positions 1, 2, 6, 7, 9, and 10 provided the licensees followthe guidance delineated in the applicable position. When an alternative is proposed which is in accordance with GL 89-04 guidance and is documented in the IST program, no further evaluation is required; however, implementation of the alternative is subject to NRC inspection.
Section 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The NRC staffs findings with respect to granting or not granting the relief requested or authorizing the proposed alternative as part of the licensee's IST program are contained in this Safety Evaluation (SE).
The licensee submitted Relief Request P-RR4 ln a letter dated September 12, 1997, to allow the use of reference curves to satisfy the Code-required hydraulic acceptance criteria. A similar version of Relief Request P-RR4, was granted in the Diablo Canyon Supplemental Safety Evaluation Report Number 31. Appendix A, for the first ten-year interval. However, the licensee 9803030323 9B0225 PDR ADQCK 05000275 P
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'incorrectly assumed that NRC staff approval of this relief request would not to be necessary for the second ten-year IST interval as noted in LER 1-97-012-00.
The licensee's second ten-year interval relief requests had previously been approved in a SE dated June 24, 1997. The staffs evaluation of Relief Request P-RR4 is included in Section 2.0 of this SE.
The second ten-year interval for Diablo Canyon Power Plant Unit 1 began on January 1,,1996, and ends on December 31, 2006. The second ten-year interval for Diablo Canyon Power Plant Unit 2 began on June 1, 1996, and ends on May 31, 2006. The current IST programs for Units 1 and 2 are based on the requirements of the 1989 Edition of ASME Section XI which references the OMa-1988, Part 6 for pumps and Part 10 for valves.
2.0 The licensee has requested relief from the pump test procedure requirements of OMa-1988, Part 6, Paragraph 5.2(b), for the component cooling water pumps (CCWP) 1-1, 1-2, 1-3, 2-1, 2-2, and 2-3. The licensee has proposed to verify each pump's hydraulic performance by the use of pump reference curves in accordance with the guidance provided in Section 5.2 of NUREG-1482, "Guidance for Insewice Testing at Nuclear Power Plants."
i lif The licensee states:
A variable flow measurement for the CCWP test is required because it is impractical to establish a fixed reference value(s).
Relief is requested per 10 CFR 50.55a(f)(5)(iii). Diablo Canyon Power Plant (DCPP) had previously received relief for these pumps iri the first 10 year plan.
The CCW system has varying heat loads, and therefore, varying flow requirements.
A full flowtest line with a single throttle valve for the purpose of testing was not incorporated in the initial design of the system.
For some plant conditions, a reference flow condition cannot be established without adversely affecting the system flow balance and Technical Specification (TS) operability requirements.
Thus, these pumps must be tested in a manner that the CCW system remains properly flowbalanced during and after the testing and each supplied load remains fullyoperable per TS to maintain the required level of plant safety during power operation.
During refueling outages, CCW flow demand varies greatly due to reactor coolant system cooldown, clearing of components for maintenance and spent fuel pool heat exchanger cooling water demand.
Past experience at DCPP has shown that CCW flowduring refueling outages is usually greater than flowduring power operations and it is not practical to reduce flow in order to perform the CCWP IST. At a minimum, perturbation of multiple systems is required to establish a flow point due to the multiple flow paths of the CCW system.
This abnormal configuration would have to be maintained for the length of time required to take vibration data and pump hydraulic data.
In addition, the requirements for the operators to manipulate valves required to adjust CCW flowto the reference point is adverse to ALARA.
The licensee proposes:
Perform inservice tests on CCWP using guidance from NUREG-1482, paragraph 5.2. A reference pump curve (flow rate vs. pump head) has.been developed for each of the six CCWPs. The following elements willbe performed in developing the pump curves for testing the CCWPs.
Existing data may be used in developing the curves provided it meets the criteria below.
Pump reference curves willbe developed when the pumps are known to be operating satisfactorily.
instrumentation used to develop pump curves is at least as accurate (accuracy and range) as required by OM Part 6, Table 1.
3.
Pump curves willbe constructed using a minimum of five points.
Points used to construct the curves are beyond the flat portion (low flow rates) of the pump curves in a range which includes the design basis flow rate.
Acceptance criteria for flow rate and differential pressure willbe established by taking the more conservative of curves based on the limits of OM Part 6, Table 3b, or the operability criteria in TS or Safety Analysis Report.
Vibration levels willbe measured over the range of pump conditions, and appropriate vibration acceptance criteria based on OM Part 6, Table 3a, willbe assigned for regions of the pump curves.
7.
A new reference curve willbe prepared, or the previous curve willbe validated, ifthe pump curve is affected by replacement, repair, or routine service.
3.0 The Code requires that either the resistance of the system be varied until the flow rate equals the reference value or the flow rate be varied until the pressure equals the reference value; then either pressure or flow is recorded and compared with the Code pump acceptance criteria.
The licensee has stated that it is impractical to establish repeatable reference values.
Section 5.2 of NUREG-1482, "Guidelines for Inservice Testing at Nuclear Power Plants," states that the use of reference curves is not currently addressed by the Code and relief is required.
Section 5.2 provides guidance for the use of variable reference values for flow rate and differential pressure during pump testing (i.e., reference curves).
NUREG-1482 states that if the licensee implements this guidance, it must demonstrate the impracticality of a'chieving reference conditions for IST. The licensee states in its basis for requesting relief that the initial design of the system did not incorporate throttle valves to facilitate Code testing.
In addition, performing the test in accordance with the Code requirements may affect TS operability r
requirements. Therefore, the testing appears impractical to perform with the current plant
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design.
It would be a burden on the licensee ifthe Code requirements were imposed because the system would have to be redesigned to meet the Code requirements.
The licensee has proposed to use pump reference curves to determine compliance with the Code requirements.
NUREG-1482 states that to obtain approval to use pump reference curves, the licensee must demonstrate that the acceptance criteria are equivalent to the Code requirements in Table 3b of Part 6 for allowable ranges using reference values.
The guidance
- provides a list of seven elements that the licensee must perform in preparing pump curves for the IST pump relief request.
The licensee has committed to these seven elements in their proposed alternative testing. Adherence to this guidance provides assurance that the proposed reference curves satisfy the Code requirements and willdetect degradation in the pump over the range of the curve bounded by reference points. Therefore, the proposed alternative provides reasonable assurance of operational readiness of the pump.
- 4. 0 ttlQUlstss The staff concludes that relief may be granted from the pump test procedure requirements of OMa-1988, Part 6, Paragraph 5.2(b), for the six CCW pumps pursuant to 10 CFR
.50.55a(f)(6)(i). The relief is authorized by law and willnot endanger life or property or the common defense and security and is otherwise in the public interest, giving due consideration to the burden upon the licensee that could result ifthe requirements were imposed on the facility.
Principal Contributor: Joseph Colaccino Date:
February 25, 1998
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