ML20247E751
| ML20247E751 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 09/07/1989 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20247E758 | List: |
| References | |
| CON-NRC-89-107 VPNPD-89-484, NUDOCS 8909150369 | |
| Download: ML20247E751 (5) | |
Text
., _
'Y 7*
r:
Wisconsin Electnc POWER COMPANY 231 W Michigon, Po. Box 2046, Milwaukee. WI S3201 (414)221-2345 VPNPD-89-4 84 NRC 107 September 7, 1989 10 CFR 50.90
' Document Control Desk
'U.S.
NUCLEAR REGULATORY COMMISSION Mail Station F1-137
. Washington, D.C.
20555 Gentlemen:
DOCKETS 50-266 AND 50-301 TECHNICAL SPECIFICATION CHANGE REQUEST 131 TURBINE VALVE TEST FREQUENCY POINT BEACH. NUCLEAR PLANT, UNITS 1 AND 2 In accordance with the requirements of 10 CFR 50.59(c), 50.90, and 50.4, Wisconsin Electric Power Company (Licensee) hereby requests amendments to Facility Operating Licenses DPR-24 and DPR-27 for Point Beach Nuclear Plant Units 1 and 2, respectively, to incorporate changes in the plant Technical Specifications.
These proposed changes, as described.below, modify the turbine stop and governor valve test frequencies and update the meteorological data record-keeping requirements.
We have attached modified Technical Spec-ification pages with the proposed changes identified by margin bars.
Technical Specification Table 15.4.1-2, Item 18 requires that turbine stopLand governor valves be functionally tested monthly except during periods of refueling shutdown and during end-of-cycle operations when the. primary coolant boron concentration is less than 100 ppm.
The functional test of the valves is conducted by cycling each valve to the full closed position and returning it to-the original pocition.
To conduct the test, reactor power must be reduced to about 60-70 percent.
This power is the maximum steam-flow which one set of 1 stop and~2 governor valves can provide, thereby allowing a functional test of the other set of stop and governor valves.
The reactor. power level reduction is achieved by adding boron to the reactor coolant system and by inserting control rods.
When both sets of stop and governor valves have been tested, reactor power is returned to pretest conditions, normally 100% power, by withdrawing control rods and by removing the added boron by processing the reactor coolant in the chemical and volume control system.
40CY]
8909150369 890907 r
g PDR ADOCK 05000266 P
PDC ilsubskth.7ofliionk Ency Oe;wathw
U.S. NRC Document Control Desk September 7, 1989 Page 2 The Point Beach turbine stop and governor valves have been very reliable, especially since early 1975 after both units switched to all volatile secondary chemistry control.
Prior to 1975 these valves demonstrated some sticking during testing; this was attributed to chemical deposit on the valve stems resulting from steam generator chemical carryover.
Since January 1975, Unit 1 has undergone 174 surveillance tests and the Unit 2 valves have been tested 182 times.
During the Unit 1 tests there have been three instances where a turbine valve did not fully close.
Each time the right hand stop valve failed to fully close.
In April 1977, a plugged orifice in the test solenoid valve prevented the valve from shutting completely on two of six closing attempts.
In December 1977, the top of the valve plunger and housing required cleaning and lubrication.
Finally, in March 1978, an air leak in the pilot valve for opening prevented the stop valve from closing more than 95%.
In each instance, the appropriate governor valves fully closed and no threat of turbine overspeed existed.
Since March 1978, Unit 1 stop and governor valves have experienced no failures to close fully upon demand.
Since January 1975, Unit 2 has experienced no turbine stop valve failures and two instances of a governor valve to fully shut.
In December 1975, the #4 governor valve did not fully close.
Testing and maintenance on the valve did not reveal the cause of the failure and the valve functioned properly in subsequent testing prior to returning to service.
In June 1988, the #1 governor valve failed to fully close.
Once again, the cause could not be determined and the valve functioned properly during further testing.
In each of these cases the appropriate turbine stop valve closed as required and there was no threat of a turbine overspeed.
i
'l Each-of these tests and the prerequisite power swings places an i
additional thermal and pressure cycle on plant equipment, increases the amount of radioactive waste from reactor coolant processing to remove the added boron, and places the plant in a condition more vulnerable to an inadvertent reactor trip.
Additionally, later in core life, these power swings cause axial power fluctuations and divergent xenon oscillations during which core power stabilization becomes more difficult.
Because of the demonstrated excellent reliability of the PBNP turbine valves and because of the increased risk of reactor trip, the additional cycling of plant equipment and additional cost associated with monthly turbine valve testing, we joined the Westinghouse Owners' Group subcommittee on Turbine Valve Testing Frequency.
The purpose of this subcommittee was to evaluate and possibly justify a reduction in l
turbine valve testing frequency.
]
l I
1 1
.-_______--_____-_______-________:-___J
a U.S. NRC Document Control Desk September 7, 1989 Page 3 In support of the subcommittee, Westinghouse Electric Corporation performed an evaluation of turbine valve testing frequency, the results of which are contained in a topical report, WCAP-ll525, "Probabilistic Evaluation of Reduction in Turbine Valve Test Frequency."
This report provides a detailed probabilistic basis for extending the turbine valve' test intervals.
This report was submitted to the NRC by Northern States Power Company in support of a license amendment request to reduce turbine valve testing frequency at the Prairie Island Nuclear Generating Plant, Units 1 and 2.
Prairie Island was the designated lead plant for this WOG subcommittee.
The NRC approved the use of WCAP-11525 as well as the Prairie Island amendment request in Safety Evaluations dated February 7, 1989.
WCAP-11525 demonstrates that the mean annual probabilities of turbine missile ejection for PBNP Units 1 and 2 for turbine valve test intervals of up to one year remain well below the NRC criterion for turbine valve missile generation probability.
The acceptance criterion for_an unfavorably oriented turbine (applicable to PBNP) was established in an NRC staff letter to Westinghouse Electric Corporation, dated February 2, 1987.
In light of this report and the demonstrated reliability of the turbine. valves, we hereby request that Technical Specification table 15.4.1-2, Item 18, " Turbine Governor and Stop Valves," be modified to require an annual test, that footnote (10) be deleted, since it would no longer be necessary, and that footnotes (11) and (12) be renumbered as (10) and (11) respectively.
We recognize that the turbine missile generation probabilities calculated in WCAP-ll525 for Point Beach are based on turbine valve failure rates available at the time the report was prepared.
Since changes in failure rates would affect these probabilities, and thus the periodicity at which turbine valve testing is required, Wisconsin Electric will review,at least once every three years, turbine valve failure-rate data to determine if the testing frequency requires modification.
Additionally, any time that major changes to the turbine system are made or a significant upward trend in turbine valve failure rate is' identified, we will review the turbine valve test frequency.
The commitment to perform these reviews will be placed in the Point Beach Final Safety Analysis Report with i
the first FSAR annual update following approval of this amendment.
l Westinghouse currently maintains a turbine valve failure data base and is developing a method to assist licensees in the review of failure-rate data and turbine valve test frequency changes, when required.
The second change we are proposing with this amendment application will update the meteorological data requirements as found in l
Specification 15.7.8.4.A.5.
This specification requires that precipitation data be maintained if measured.
Since we do not measure precipitation, this may be removed.
Additionally, the third sentence in this specification provides three different options for maintaining i
c t
U S. NRC Document Control Desk September 7, 1989 Page 4 meteorological data:
strip charts, hour-by-hour averages, or joint frequency distributions of each parameter.
We propose to specify that
. the data be stored on strip charts or in electronic form as hour-by-hour averages.
This would begin by January 1, J.990, when in addition to the strip charts currently used, data will be stored as hour-by-hour averages on magnetic media.
Specifying electronic rather than magnetic form would provide greater flexibility to convert, if appropriate, to other equivalent media in the future.
Finally, we propose to delete the last sentence regarding magnetic tape and joint frequency distribution availability.
With the implementation of the preceding change proposed for this section, the statement regarding magnetic tape availability will not be necessary.
As to the recording of joint frequency distributions, we believe it to be unnecessary and propose that this not be required.
We are aware of only one possible use of joint frequency distributions at Point Beach.
That would be to conduct offsite dose assessments for members of the general public.
At Point Beach, in accordance with Technical Specification 15.7.5,' general public dose calculations are required only if the actual equivalent curies released exceed either the quarterly or annual equivalent curie release limits by a factor of two.
These calculations, if required, would be done in accordance with the Point Beach Offsite Dose Calculation Manual (ODCM).
Since the ODCM method does not use joint frequency distributions we have no use for the data.
If further refinement of these general public dose calculations were subsequently required, the distributions could be calculated at that time from the stored data.
As required by 10 CFR 50.91(a), we have evaluated these proposed changes in accordance with the standards specified in 10 CFR 50.92 to determine if the proposed changes constitute a significant hazards consideration.
A proposed license amendment involves no significant hazards consideration if operation of the facility in accordance with the proposed amendments'would not (1) involve a significant increase in the probability or consequence of an accident previously evaluated, (2) create the possibility of a new or different kind of accident from any accident previously evaluated, or (3) involve a significant reduction in a margin of safety.
Regarding the change in turbine governor and stop valve testing frequency, the three criteria are. met as follows:
1.
WCAP-11525 calculates the probability of generating a turbine missile based on different turbine valve test frequencies.
This WCAP demonstrates that with a test frequency of once per year, the probability of generating a turbine missile remains well below the NRC-established acceptance criteria.
Therefore, this is not a significant increase in the probability or consequences of an accident previously evaluated.
I 1
b
fR..
s.
e l-U.S. NRC' Document Control Desk September 7, 1989 Page 5 2.
Changing the frequency of turbine valve testing does not create the possibility of a new-or different kind of accident since turbine missile accidents have been previously evaluated and since WCAP-11525 demonstrates that Point Beach remains well below the NRC-acceptance criteria for turbine missile generation for frequencies as low as once per year.
3.
For the same reasons as noted in 1 above, this proposed amendment does not involve a significant reduction in the margin of safety.
Since none of the three criteria are violated, we have determined that this proposed change will not result in a significant hazards consideration.
Regarding the proposed changes in meteorological data record keeping requirements, these changes are strictly administrative in nature and do not involve or impact-any accidents or safety margins.
These changes fall within the scope of actions not likely to involve a significant hazards consideration as provided at 51 FR 7751, specifically a " purely administrative change to Technical Specifications..."
Therefore, we have determined that these proposed changes will not result in a significant hazards consideration.
Please contact us if you have any questions concerning this request.
Very trulg ours, LYltbIp/
C. W. F y/
Vice President Nuclear Power Enclosures Copies to NRC Regional Administrator, Region III NRC Resident Inspector Subscribed and sworn to before me this 9 t!L day of Cct;Lv,1989.
0 0
nn <5 e.
n
. Notary Public, State %ot Wisconsin 1
My Commission expires 6-27 9o i
l J