ML20085N094
| ML20085N094 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/06/1991 |
| From: | NIAGARA MOHAWK POWER CORP. |
| To: | |
| Shared Package | |
| ML20085N088 | List: |
| References | |
| NUDOCS 9111140072 | |
| Download: ML20085N094 (3) | |
Text
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o EMERGENCY CORE COOLING SYSTEti,3-
' ECCS - OPERATING SURVEILLg CE REQUIREMENTS 4.5.1 (Continued) e.
For the ADS by:
1.
At least once per 31 days, performing a CHANNEL FUNCTIONAL TEST of the accumulator backup compressed gas system, lov-pressure alarm system.
2.
At least once per 18 months:
a)
Performing-a system functional test which includes simulated automatic _ actuation of the system throughout its emergency operating sequence, excluding actual valve' actuation, b)
Hanually opening each ADS valve whan the reactor steam dome pressure is greater than or equal to 950 psig* and observing that either:
1)
The SRV discharge acoustic monitoring system responds accordingly, or 2)
The control valve or bypass valve responds accordingly, or 3)
There is a corresponding change in the measured steam flow, or 4)
The SRV discharge ~line temperature monitoring system responds accordingly.
l c)
Performing a CHANNEL CALIBRATION of the accumulator backup compressed gas system, low-pressure alarm system, and verifying an alarm setpoint of 163.5 +3.2,
-3.2 psig on decreasing pressure, d)
Performing a leak rate-test for ADS SRV pneumatic operators by pressurizing each' ADS accumulator at 178 psig (supply header high pressure alarm) up to its supply header isolation' check valve with the SRV in the open position.
Total leakage rate for each SRV shall not exceed 0.5 SCFH l
for the SFV actuated by either of the ADS solenoids.
o
- a 0,0 M
The provisions of Specification 4.0.4 are not applicable provided the gg surveillance is performed within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after reactor steam pressure is 3c adequate to perform the test.
NINE MILE POINT - UNIT 2 3/4 5-5 l9a.a 1
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4 ATTACENENT 4 NIAGARA MORAVK POWER CORPORATION LICENSE NO. NPF-69 DOCKET No. 50-410 SyyDorting InformAtlon and No Stanificant Hazardji Discussion Technical Specification 4.5.1.e.2(b) specifies that each ADS valve shall be manually opened for surveillance testing within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after from the time reactor steam dome pressure is greater than or equal to 100 psig.
- However, the design of an Automatic Depressurization (ADS) valve is such that damage to the valve can occur when-the valve is subject to low pressure testing below its nominal operating range.- Therefore, Niagara Mohawk is proposing a. change to:this specification to specify 950 vice 100 psig. This would conform the Technical' Specifications to the present practice.
The ADS valve design utilizes system pressure to assure proper-valve operation. The valve seats have a mirror finish to make the valves leak-tight.
System pressure acts to protect this finish and prevent seat leakage.
After a relief valve actuation, a higher system pressure is more efficient in counteracting the-spring-assisted closing force, thereby reducing _the resultant impact force on the valve seat.
A higher pressure also assists in aligning the valve disk seat with the nozzle seat.- If system pressure is lov, the resultant-impact force is much higher, the alignment is less accurate, and the potential-for seat damage is therefore greater._ Since the mirror finish maintains leak tightness, relatively small L;ounts of' seat deformation' vill cause the valve to leak.
Leakage vill ultimately require valve refurbishment or replacement.
Furthermore, testing-the ADS valves at a minimum of 950 psig serves to enhance safety by assuring _that the valves can operate at normal operating conditions..
Changing the_ test pressure to 950 psig vill not affect the operability of the ADS valves. The valves vill continue to be tested within the required 18 month surveillance-interval. The ADS surveillance verifies that the valves vill function properly and that no blockage exists in the SRV discharge lines.
The proposed change vill not affect this verification in any manner.
Valve operability and setpoint are_ verified prior to valve installation.
It is reasonable to conclude, therefore, that-the operability of the ADS valvea vill be unaffected by this proposed change.
ADS is not required to be operable when reactor steam dome pressure is less than or equal to 100-psig.
Only three ADS valves are required to be operable for all analyzed events.
In the extremely unlikely event that at least five of the seven ADS valves are inoperable prior to reaching test pressure during a startup, adequate redundant systems (e.g. the High Pressure Core Spray system) are provided to prevent the reduction of safety margin.
-The proposed change vill not affect the operation of the reactor.
During the test, tha_ Electro-Hydraulic:(EHC) system is controlling reactor pressure at 950 psig which is within the normal EHC control band.
The test vill result in a mild transient as the EHC system vill automatically restore pressure and reactor power vill stabilize at or near the initial power level.
The test is currently performed in accordance with N2-OSP-ADS-R001 (ADS Valve and Position Indication Operability Test). This procedure requires that reactor pressure is between 950 psig and 976 psig prior to opening any ADS valve.
Conducting the ADS surveillance test in this manner has not adversely affected reactor operation in any way.
Moreover, the proposed change vill prevent hastening operations from 100 psig to 950 psig in order to perform this surveillance within the allotted 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> time frame.
The consequences of a stuck open relief valve have been previously analyzed in the Updated Safety Analysis Report (USAR) Section 15.1.4, Inadvertent Safety / Relief-Valve Opening. The results indicate that the increase in steam flow causes a mild depressurization transient, and the MCPR safety limit is unaffected. The dynamic loads and suppression pool heatups associated with safety-relief valve actuation have been shown to be acceptable in USAR-Appendix 6A, Design Assessment for Hydrodynamic Loads.
Based on the above analysis, Niagara Mohawk concludes that the proposed change vill not affect the public health and safety or involve a significant safety hazards condition.
Nine Mile Point Unit 2 can be safely operated wit.h the incorporation of the
-changes in the_ proposed amendment.
10CFR50.91. requires that at the time a licensee requests an amendment, it must provide the Commission its analysis using the standards in 10CFR50.92 concerning the issue of no significant hazards consideration. Therefore, in accordance with 10CFR50.91, the following analysis has been performed:
The operation of Nine Mile Point Unit 2, in accordance with the proposed amendment, vill not involve a'significant increase in the probability or consequences of an accident previously evaluated.
-The proposed-change-vill not affect the operability or reliability of the ADS
. vah'es.
In. addition, the-probability or consequences of a stuck open relief valve analyzed in USAR Section 15.1.4 or any other accident previously analyzed vill not be increased.
The operation of Nine Mile Point Unit 2, in accordance with the proposed-
-amendment, vill not create the. possibility of a new or different kind of accident from any previously evaluated.
No new operational modes vill result from the proposed change.
The valves have been routinely tested at the proposed minimum pressure in the past with no adverse effects. The safety function of the ADS valves vill be unaffected such that the proposed change vill not create the possibility of a new or different accident from any previously analyzed.
The operation of Nine Mile Point Unit 2, in acecrdance with the proposed amendment, vill not involve a significant reduction in a margin of safety.
Testing at 950 psig enhances safety by assuring that the ADS valves can operate under normal operating conditions and also by preventing damage to the
_