ML20151X065
| ML20151X065 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 09/11/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20151X052 | List: |
| References | |
| GL-89-04, GL-89-4, NUDOCS 9809160242 | |
| Download: ML20151X065 (5) | |
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UNITED STATES v
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION I
RELATED TO THE INSERVICE TESTING PROGRAM RELIEF REQUEST VR-63 DETROIT EDISON COMPANY FERMI 2 NUCLEAR PLANT DOCKET NUMBER 50-341
1.0 INTRODUCTION
The Code of Federal Regulations,10 CFR 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the 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 difficulty without a compensating increase in the level of quality and safety. For requirements that the licensee has indicated are impractical, the Commission may grant relief and may impose such alternative requirements as it determines are authorized by law and will not 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 if tha requirements were imposed on the facility.
As stated in 10 CFR 50.55a(f)(4)(iv), 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. 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. Guidance related to the development and implementation of IST programs is given in Generic Letter 89-04, " Guidance on Developing Acceptable inservice Testing Programs,"
issued April 3,1989, and its Supplement 1 issued April 4,1995. Also see NUREG-1482,
" Guidelines for Inservice Testing at Nuclear Power Plants," and NUREG/CR-6396, " Examples, Clarifications, and Guidance on Preparing Requests for Relief from Pump and Valve Inservice Testing Requirements."
The current IST program for the Fermi 2 nuclear plant was developed to the requirements of the 1980 Edition of the ASME Code,Section XI, up to and including the Winter 1981 addenda.
9809160242 980911 PDR ADOCK 05000341 P
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' Detroit Edison (DECO or the licensee) submitted relief requests VR 63 and VR-64 in a letter dated February 14,1997. The staff reviewed the submittal and sent a request for additional information (RAl) to DECO in a letter dated August 27,1997. DECO responded to the staff 's RAI in a letter dated April 30,1998, withdrawing relief request VR-64 and providing additional justification for relief request VR-63. The staff has evaluated relief request VR-63 as discussed in the following evaluation.
2.0 REllEF REQUEST VR-63 The licensee requests relief from the quarterly stroke time test requirements of ASME Code Section XI for those valves (listed below) in the residual heat removal service water (RHRSW),
emergency diesel generator service water (EDGSW), and emergency equipment service water (EESW) systems.
The subject valves are minimum flow va ves that are required to maintain minimum flow requirements for the RHRSW, EDGSW and EESW pumps. These valves are air-to-open and spring-to-close valves that fail closed on loss of air. These valves are normally closed and their safety function is to assure primary safety system flow is not diverted through the minimum flow lines. All three systems start against open flow paths so that the minimum flow valve function to l
open is not required when the pumps are started from their normal valve lineup positions.
These valves do not have remote position indication. They are equipped with a local pointer on the stem, permitting only a gross measure of valve position and making it very difficult to obtain repeatable test results without extensive modification to the valve and its control logic. The i
affected valves are listed in Table 1.
TABLE 1 - VALVES AFFECTED BY VR-63 Valve System E11F400A RHRSW E11F400B RHRSW E11F400C RHRSW E11F400D RHRSW R3OF400 EDGSW R3OF401 EDGSW R3OF402 EDGSW R3OF403 EDGSW P45F400 EESW l
P45F401 EESW i
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\\ 2.1 Licensee's Basis for Relief Reauest The licensee states:
All 10 minimum flow valves have a control logic that does not provide the capability for stroke t;me testing. These valves automatically open when pump discharge pressure is high and close when pressure decreases. There are no manual override switches or controls. High discharge pressure indicates that the normal pump flow path is either closed or severely restricted. Normal pressure indicates a viable flow path is available.
l Current fail-safe testing of the subject valves is accomplished by actually restricting flow with the appropriate pump running such that the minimum flow valve opens. As flow is restored, the minimum flow valve closes as discharge pressure decreases below the set point pressure and control air pressure is l
reduced to zero psi. The valve closes as the control air supply decreases opening pressure on the diaphragm. The spring pressure force then becomes dominant l
and closes the valve. This testing is accomplished on a quarterly basis.
l These valves have no remote position indicating devices and are only equipped j
with a local pointer on the stem which is, at best, a gross measure of position.
i From this indicator there is no way of knowing the exact starting open position of l
the valve or the exact travel distance from open to close. Also, the exact open l
starting position would vary from test to test as the exact position would be a result of varying pressure within the system. This would make test repeatability difficult without significant modification to the valve and its conirol logic.
In order to accurately and precisely stroke time these valves, it would be necessary to modify the control circuitry to allow for manual override operation.
However, the installation of such controls would not improve system operation or contribute to protecting the health and safety of the public. In fact, it would make operation more complicated by adding additional hardware whose only function is to allow stroke time testing of the valves.
It is not, however, impractical to stroke time thesa valves on a less frequent basis using a temporary control air source to full stroke the valves. This has been demonstrated to be effective in full stroking these valves. Using a manual three way valve connected to the valves operator with two altemate positions to either supply the operator air or vent the air from the operator, the minimum flow valves are full stroke closed and timed. Results have been repeatable and accurate. The primary drawback is that it requires the breaking of control air connections and thus, causes the system to be inoperable. Because of the time ilmitations placed on the unavailability of safety systems and the potential damage to the connections after frequent disconnections and reconnections, conformance to the l
quarterly requirements would result in unusual hardship and difficulty without a l
compensating increase in the level of safety and quality. The proposed timed l
stroking is to be performed only during refueling outages.
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The alternatives presented in NUREG-1482, Paragraph 4.2.9, were evaluated for J
implementation at Fermi for these 10 valves. Fermi intends to stroke time these valves on a refueling outage basis while continuing the untimed strokes on a quarterly basis. This option is discussed in paragraph 4.2.9 as the option of
" stroke timing and fail-safe testing during cold shutdowns or refueling outages that involve bypassing control signals." In this situation, the Fail Safe Test (FST) will continue to be performed on a quarterly basis as well as at the completion of the stroke time test. Both stroke time testing using temporary control air signals and quarterly fail safe testing have been successfully demonstrated on the service water minimum flow valves.
2.2 Altemative Testina The licensee states:
Stroke time testing in lieu of Paragraphs IWV-3413(b) and IWV-3411 of Section XI of the ASME B&PV Code is to be implemented as follows:-
1.
Stroke timing will be performed on a refueling outage frequency.
2.
A fail-safe full stroke test during system operation will be performed on a quarterly basis and upon completion of each stroke time test.
3.0 EVALUATION Paragraphs IWV-3411 and IWV-3413(b) of ASME Code Section XI require full stroke exercise and timing of all power-operated valves at least once every 3 months. In lieu of the Code required tests, the licensee proposes to stroke-time test these valves on a refueling outage frequency and, in addition, to exercise these valves without timing by performing a fail-safe full-stroke test on a quarterly basis.
All 10 minimum flow valves have a control logic that does not provide the capability for-stroke-time testing. These valves automatically open when pump discharge pressure is high and close when pressure decreases. These valves do not have remote position indication, nor manual override switches or controls. They are equipped with a local pointer on the stem, permitting only a gross measure of valve position and making it very difficult to obtain repeatable test results. In order to accurately and precisely stroke-time these valves, the licensee would have to redesign the control circuitry to allow for manual override operation, which requires extensive modification to the valve and its controllogic. The staff finds that this extensive design modification would result in a hardship without a compensating increase in the level of quality or safety.
The licensee's preposed attemative to stroke-time test these valves on a refueling outage frequency would provide the Code-required information, but at a reduced frequency. To 4
supplement the refueling outage test, the licensee proposes to verify the full stroke of these valves during quarterly fail-safe tests. The quarterly full-stroke fail-safe test assures that these valves are operable and would move to their required safety position. As such, the proposal
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a provides reasonable assurance of valve operability. Furthermore, the staff finds that the l
licensee's proposed alternative meets the guidance of NUREG-1482 (paragraph 4.2.9), which i
recommends stroke-timing and fail-safe testing during cold shutdowns or refueling outages when testing involves bypassing control signals.
4.0 CONCLUSION
The staff concludes that the licensee's proposed alternative to stroke time these valves on a refueling outage frequency and to exercise these valves without timing by performing a fail-safe, full-stroke test on a quarterly basis is authorized pursuant to 10 CFR 50.55a(a)(3)(ii), based on the determination that the proposed alternative provides reasonable assurance of operational readiness for the affected valves and compliance with the specified Code requirements results in a hardship without a compensating increase in the level of quality and safety.
Principal Contributor: J. Huang Date: September 11, 1998 l
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