ML20198L424
| ML20198L424 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 01/08/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198L411 | List: |
| References | |
| NUDOCS 9801160027 | |
| Download: ML20198L424 (4) | |
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UNITE] STATES
,j NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.c. 3006 0001 l
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO INSERVICE TESTING PROGRAM RELIEF REQUEST NUMBER VR-51-R2 DETROIT EDISON COMPANY FERMI UNIT 2 DOCKET NO. 50-341
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1.0 INTRODUCT. LOB The Code of Federal Regulations,10 CFR 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 pumps and p
valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel b
Code (B&PVC) and applicable addenda, except where relief has been requested and granted nr proposed attematives 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 attemative 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.
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 attematives to the Code requirements determined to be acceptable to the staff and authorized the use of the attematives in Positions 1,2,6,7,9, and 10 provided the licensee follows the guidance delineated in the applicable position. When an attemative is proposed that is in accordance with GL 89-04 guidance and is documented in the IST program, no further evaluation is required; however, implementation of the attemative is subject to NRC inspection.
Section 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed attematives upon making the necessary findings. The NRC staffs findings with respect to granting or not granting the relief requested or authorizing the proposed attemative as part of the licensee's IST program are contained in this safety evaluation (SE).
Relief Request VR-51 was previously granted on an interim basis in an SE cated May 2,1996, for a period of 1 year. During the interim period, the licensee was required to develop acceptance criteria to verify that these valves adequately stroke during the monthly diesel test which would satisfy the quarterly Code requirements. The licensee submitted a revised version of this relief request in a letter dated May 1,1997. The staffs evaluation is included in Section 3.0 of this SE.
9801160027 980100 PDR ADOCK 05000341 P
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' The first 10 year interval for Fermi Unit 2 began on' January 23,1988, and, because of a
- shutdown that lasted over one year, is currently scheduled to end on February _15,1999. The -
current IST program is based on the requirst tents of the 1W Edition through the Winter 1981 Addenda of ASME Section XI.
I 2.0 - RELIEF REQUEST VR-51
. The heensee has requested relief from the power-eperated valve stroke time test requirements of ASME Section XI. Subsection IWV 3413(b), for the eight emergency diesel generator (EDG)_
air start system solenoid valves listed below The licensee has proposed to verify the -
necessary valve movement by observing an appropriate indicator which signals the required -
change of disk position. The valves will not be stroke timed.
R30FA04AL R30FA04B R30FA04C R30FA04D R30FA05A R30FA05B R30FA05C R30FA05D 2.1-Licensee's Basis for Requesting Reimf The licensee states:-
- it is impractical to apply the requirements of IWV-3413(b) to these valves for [three]
reasons:
These are solenoid valves and have a very short stroke time, i.e. less than 2 seconds. Solenoid valves typically have full stroke times under one second. For these short stroke time valves, variances of 50 percent or more can occur in the measured times for reasons that are in no way related to valve performance; for example, operator reaction times. In this case verifying that the valve's stroke time satisfies system operating requirements is sufficient to evaluate valve performance.
There is no position indication, remote or local, on these valves to observe.
i Stroking of the valves in a i.st start causes excessive wear and tear on the EDGs.
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Since there is no direct indication of valve position, P 3 mates are 10 be used to indicate that the solenoids have stroked. During the six month fast start, the valves will use the time to achieve's speed of 900 rpm and 60 Hz, electrical, as the equivalent to stroke I
time. Since these tests are only required every six months per Technical Specifications, the slow start test, which is performed on a monthly basis, will be evaluated at least quarterly in such a maaner to assure that the valve has stroked as required. This venfication is achieved by visually verifying that the air start line vents after diesel startup.
A wiping cloth placwd over the solerio6d valve vent port will be rapidly moved as the line vents. Both tests provide positive indication that the solenoid has performed its safety
- function of providing adequate motive force to start the diesel.
f 3-2.2 Alternate Testing j
The licensee proposes:
There are two start tests that are performed on the EDGs, a fast start and load from I
ambient conditions and a manual slow start and load test. The fast start and load test venfies the capability of the EDGs to achieve rated speed and voltage within Technical Specifications ti.ue limits and the capability of the EDGs to be loaded. The manual start and load test verifies the capability of the EDGs to be manually started and loaded. The fast start is accomplished on a 6 month (184 day) test frequency. The slow start is accomplisW on a monthly (31 day) test frequency. Attemate testing of the air start solenoids will be accomplished differently for each test as follows:
1.
Fast Start and Load from Ambient Conditions For the subject valves, a successful start of the diesel generator within the required Technical Specifications requirement of achieving speed and voltage level (Ref.
Technical Specifications Paragraph 4.8.1.1.2.a.4) within 10 seconds, shall be sufficient to demonttrate that the 3-wcy solenoid valves have opened in the required time. The actual start times are measured with a Visicorder and are extremely consistent. Slow response time of the solenoids will be reflected by increased start times.
The test frequency shall be once every 6 months (184 days).
2.
Manual Slow Start and Load For the subject valves, visible evidence that each air start header was pressurized and then vented would show that the valve opened on start demand and then shut when the start signal was removed. Each EDG has two air start headers and each i
header has its own 3-way solenoid, in the closed position the air start headers ve vented to atmosphere. Upon receiving a start signal each valve lines up to the starting air supply and closes off the vent, thus supplying starting air pressure to c
the headers. When the diesel reaches a set speed, the solenoid valves are de-energized and the starting air supply is isolated from the headers and the headers vented as the vent ports open. As the header is vented, its pressure is reduced to
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atmospheric pressure through the vent port. A wiping cloth placed loosely over the vent port will be propelled away from the valve as the header vents. Movement of the cloth is sufficient to show that the valves cycled open and then retumed to the de-energized position. During the manual slow start, the diesel is only allowed to accelerated to 500 to 700 rpm, after which speed is manually increased to achieve the desired spe3d of 900 rpm (60 Hz). Therefore, time to rated condition is meaningless.
The test fr quency shall be at least once every calender quarter (92 days).
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3.0 EVALUATION _
- The Code requires that the desel air start solenoid valves be stroke timed to the nearest -
accond every 3 months. These valves have _a safety function to open in ooriunction with the -
_ operation of their aaa~w desel generators. These valves have a stroke time less than 2 seconds and are fully enclosed with no means to observe the position of the valve stem.
Since these valves cannot be stroke timed by observation of valve position, either remotely or L
locally, it is impractical to measure the valve stroke times by conventional means. it would be an undue burden for the licensee to meet the Code requirements because the valves would L
have to be either modified or replaced. Thus,' direct measurement of valve stroke times is impractical.-
As stated in NUREG-1482, Guidelines for Inservice Testing at Nuclear Power Plants, Section 4.2.8, if the licensee cannot time the stroke of a solenoid-operated valve by the -
conventional method using position indication, the Code would require that it propose a method to time the stroke of the valve or otherwise monitor for degrading conditions to give adequate _
assurance of operational readiness. The licensee has proposed to verify that air start line vents after the diesel starts which verifies the valve has moved to its safety position. This will be 1
performed at least quarterly _during the monthly diesel manual slow start and load test. During the diesel fast start test every 6 months, the licensee states that a successful start of the EDG emergency within the 10-second time limit specified by the Technical Specifications vill verify
. that the valves are stroking within their 2-second time limit (Note The 2-second time limit is provided as guidance in GL 8g-04, Guidance on Developing Acceptable Inservice Testing _
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_ Programs, Position 6). The quarterly verification, while not measuring stroke time or monitoring for degradation, does provide an indication that each solenoid valve is moving to its safety position by verifying actual disk movement. The diesel fast start test every 6 months provides i
definitive acceptance criteria that all associated diesel air start solenoid valves are stroking
' within their required time limit. On this basis, the staff finds the licensee's proposed attemative
. to be acceptable.
4.0 CONCLUSIOT l
C a the basis of the above evaluation, the staff concludes that relief may be granted from the pc wor-o erated valve stroke time test requirements of ASME Section XI, Subsection IV. W413(b), for the eight EDG air start system solenoid valves pursuant to 10 CFR 50.55a(f)(6)(i) based on the impracticality of performing testing in accordance with the Code requirements. In addition, the licensee will perform attemative testing as described in Section 3.0 above. Granting this relief is authorized by law and will not endanger life or prope@ or the common defense and security and is otherwise in the public interest, giving due F
consiooration to the burden upon the licensee that would result if the requirements were imposed on tt.e facility.
Principal Contnbutor: Joseph Coleccino h
Date: January 8,1998 l'
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