ML113220171
| ML113220171 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 11/30/2011 |
| From: | NRC/NRR/DPR/PSPB |
| To: | |
| References | |
| TSTF-523 | |
| Download: ML113220171 (4) | |
Text
SURVEILLANCE REQUIREMENTS Draft ECCS - Operating 3.5.2 SURVEILLANCE FREQUENCY SR 3.5.2.1 [ Verify the following valves are in the listed position [ 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> with power to the valve operator removed.
OR Number Position Function
[ ] [ ] [ ] In accordance
[ ] [ ] [ ] with the
[ ] [ ] [ ] Surveillance Frequency Control Program ]
SR 3.5.2.2 Verify each ECCS manual, power operated, and [ 31 days automatic valve in the flow path, that is not locked, sealed, or otherwise secured in position, is in the OR correct position.
In accordance with the Surveillance Frequency Control Program ]
SR 3.5.2.3 Verify ECCS locations susceptible to gas [ [31] days accumulation are sufficiently filled with water.
OR In accordance with the Surveillance Frequency Control Program ]
SR 3.5.2.4 Verify each ECCS pump's developed head at the In accordance test flow point is greater than or equal to the with the Inservice required developed head. Testing Program Westinghouse STS 3.5.2-2 Rev. 4.0
BASES Draft ECCS - Operating B 3.5.2 LCO (continued)
In MODES 1, 2, and 3, an ECCS train consists of a centrifugal charging subsystem, an SI subsystem, and an RHR subsystem. Each train includes the piping, instruments, and controls to ensure an OPERABLE flow path capable of taking suction from the RWST upon an SI signal and automatically transferring suction to the containment sump.
During an event requiring ECCS actuation, a flow path is required to provide an abundant supply of water from the RWST to the RCS via the ECCS pumps and their respective supply headers to each of the four cold leg injection nozzles. In the long term, this flow path may be switched to take its supply from the containment sump and to supply its flow to the RCS hot and cold legs. Management of gas voids is important to ECCS OPERABILITY.
The flow path for each train must maintain its designed independence to ensure that no single failure can disable both ECCS trains.
As indicated in Note 1, the SI flow paths may be isolated for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> in MODE 3, under controlled conditions, to perform pressure isolation valve testing per SR 3.4.14.1. The flow path is readily restorable from the control room.
As indicated in Note 2, operation in MODE 3 with ECCS trains made incapable of injecting in order to facilitate entry into or exit from the Applicability of LCO 3.4.12, "Low Temperature Overpressure Protection (LTOP) System," is necessary for plants with an LTOP arming temperature at or near the MODE 3 boundary temperature of 350°F.
LCO 3.4.12 requires that certain pumps be rendered incapable of injecting at and below the LTOP arming temperature. When this temperature is at or near the MODE 3 boundary temperature, time is needed to make pumps incapable of injecting prior to entering the LTOP Applicability, and provide time to restore the inoperable pumps to OPERABLE status on exiting the LTOP Applicability.
APPLICABILITY In MODES 1, 2, and 3, the ECCS OPERABILITY requirements for the limiting Design Basis Accident, a large break LOCA, are based on full power operation. Although reduced power would not require the same level of performance, the accident analysis does not provide for reduced cooling requirements in the lower MODES. The centrifugal charging pump performance is based on a small break LOCA, which establishes the pump performance curve and has less dependence on power. The SI pump performance requirements are based on a small break LOCA.
MODE 2 and MODE 3 requirements are bounded by the MODE 1 analysis.
Westinghouse STS B 3.5.2-5 Rev. 4.0
BASES Draft ECCS - Operating B 3.5.2 SURVEILLANCE REQUIREMENTS (continued)
SR 3.5.2.3 ECCS piping and components have the potential to develop voids and pockets of entrained gases. Preventing and managing gas intrusion and accumulation is necessary for proper operation of the ECCS and may also prevent water hammer, pump cavitation, and pumping of noncondensible gas (e.g., air, nitrogen, or hydrogen) into the reactor vessel.
Selection of ECCS locations susceptible to gas accumulation is based on a review of system design information, including piping and instrumentation drawings, isometric drawings, plan and elevation drawings, and calculations. The design review is supplemented by system walk downs to validate the system high points and to confirm the location and orientation of important components that can become sources of gas or could otherwise cause gas to be trapped or difficult to remove during system maintenance or restoration.
The ECCS must be sufficiently filled with water in order to be OPERABLE. Acceptance criteria are established for the volume of accumulated gas at susceptible locations. If accumulated gas is discovered that exceeds the acceptance criteria for the susceptible location (or the volume of accumulated gas at one or more susceptible locations exceeds an acceptance criteria for gas volume at the suction or discharge of a pump), the Surveillance is not met. If it is determined by subsequent evaluation that the ECCS is not rendered inoperable by the accumulated gas (i.e., the system is sufficiently full of water), the Surveillance may be declared met. Accumulated gas should be eliminated or brought within the acceptance criteria limits.
ECCS locations susceptible to gas accumulation are monitored and, if gas is found, the gas volume is compared to the acceptance criteria for the location. Susceptible locations in the same system flow path which are subject to the same gas intrusion mechanisms may be verified by monitoring a representative sub-set of susceptible locations. Monitoring may not be practical for locations that are inaccessible due to radiological or environmental conditions, the plant configuration, or personnel safety.
For these locations alternative methods (e.g., operating parameters, remote monitoring) may be used to monitor the susceptible location.
Monitoring is not required for susceptible locations where the maximum potential accumulated gas void volume has been evaluated and determined to not challenge system OPERABILITY. The accuracy of the method used for monitoring the susceptible locations and trending of the results should be sufficient to assure system OPERABILITY during the Surveillance interval.
Westinghouse STS B 3.5.2-9 Rev. 4.0
Draft
[ The [31] day Frequency takes into consideration the gradual nature of gas accumulation in the ECCS piping and the procedural controls ECCS - Operating B 3.5.2 governing system operation.
OR The Surveillance Frequency is controlled under the Surveillance Frequency Control Program. The Surveillance Frequency may vary by location susceptible to gas accumulation.
REVIEWERS NOTE-----------------------------------
Plants controlling Surveillance Frequencies under a Surveillance Frequency Control Program should utilize the appropriate Frequency description, given above, and the appropriate choice of Frequency in the Surveillance Requirement.
]
Westinghouse STS B 3.5.2-10 Rev. 4.0