ML17313A691
| ML17313A691 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/25/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17313A690 | List: |
| References | |
| NUDOCS 9811300122 | |
| Download: ML17313A691 (4) | |
Text
Section 1.0 - Less Restrictive The CTS does not include a provision equivalent to the ISTS that combines the definition of channel functional test for both analog and bistable channel, providing requirements for such tests.
Combining the definitions for both analog and bistable channels in the ITS allows the bistable channel test signal to be injected "as close to the sensor as practicable" in lieu of "into the sensor" as required by the CTS definition. Injecting a signal at the sensor increases the probability of actuating related circuits that are not being tested in those cases where several logic channels are associated with one sensor.
Therefore, performing the test by injecting a signal at the sensor may require (1) jumpering associated logic channels to prevent their initiation during the test or (2) increasing the scope of the test to include the other logic channels.
Allowing initiation of the signal close to the sensor provides a complete test of the desired logic channel while reducing the probability of an undesired initiation. This change is a less restrictive requirement for unit operations and is consistent with the ISTS, and is acceptable.
The definition of core alterations in the CTS does not specify the specific components (i.e., the movement of fuel, source, or reactivity control components) that comprise a core alteration.
Including the ISTS definition in the ITS relaxes the requirement for core alteration by limiting the definition of core alterations to the movement of the following specific components:
fuel, source, or reactivity control components.
The ITS definition willexclude movement of control element assemblies (CEAs) when withdrawn into the upper guide structure as a core alteration. The ITS definition willexclude the movement of components other than fuel, sources, or reactivity control components as core alterations.
The movement or manipulation of other components have a negligible (if any) effect on core reactivity; therefore, there is no need for a restriction on the movement of components other than fuel, sources, or reactivity control components.
This change is consistent with the ISTS and is acceptable.
The ITS definition of channel functional test does not include the following statement in the CTS definition that: "The CHANNELFUNCTIONALTEST shall include adjustment, as necessary, of the alarm, interlock and/or trip setpoints such that the setpoints are within the required range and accuracy."
The intent of the channel functional test is to verify channel operability not to verify setpoints.
The ITS deletes the CTS requirement to check setpoints during the test and this change is a less restrictive requirement for unit operations.
This change is acceptable because, by definition, setpoints are verified and, ifrequired, adjusted during the performance of a channel calibration. A channel calibration is inclusive of a channel functional test.
This change will afford PVNGS the opportunity to remove setpoint verification from the channel functional test and to rely on the channel calibration for this function. The licensee stated that (1) this willbe made on an individual basis as analysis shows that setpoint verification performance is not adversely affected when extended out to channel calibration frequencies, and (2) the setpoint verification frequency changes are controlled under the 10 CFR 50.59 98'fi300l22 98ii25 PDR ADOCK 05000528 P
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~f" that the licensee actions to ensure that all pre-1990 P8 B MDR dc relays and all pre-1992 P8 B MDR ac relays have been removed from PVNGS ESFAS applications are acceptable.
This condition has been met.
On this basis, the staff finds that the proposed TS changes for extending the ESFAS subgroup relay functional test interval from 62 days to 9 months on a staggered test interval are in conformance with the NRC-approved Topical Report CEN-403, Revision 1-A, and are, therefore, acceptable.
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The proposed TS change would increase the minimum required nitrogen cover pressure for the safety injection tanks (SITs) from 254 psig to 260 psig, and would change the related Bases.
The change resulted from new instrument uncertainty values associated with the pressure transmitters in the SIT pressure indication loops. The 235-psig minimum SIT cover pressure used in the analysis (i.e., the analytical limit)was not changed.
The licensee's reanalysis noted that the uncertainty associated with the instruments used to measure the minimum nitrogen cover pressure could be as high as 22.6 psig. Previously, only 19 psig was allocated for the instrument uncertainty.
Therefore, the minimum nitrogen cover pressure needs to be revised to specify 260 psig to ensure that the analytical limitwas not compromised.
This change is only applicable to Modes 3 and 4 when the pressurizer pressure is less than 1837 psia.
Each unit has four SITs which supply water to the reactor vessel during the blowdown phase of a large-break LOCA, provide inventory to help accomplish the refill phase that follows thereafter, and provide RCS makeup for a small-break LOCA. The SITs are pressure vessels partially filled with borated water and pressurized with nitrogen gas and are passive components because no operator or control action is required for them to perform their function. The internal tank pressure is sufficient to discharge the tank contents to the RCS, ifRCS pressure decreases below the SIT pressure.
In Modes 3 and 4, with pressurizer pressure less than 1837 psia, CTS 3/4.5.1 requires either (a) four SITs, each with minimum and maximum borated water volumes of 962 cubic feet (39 percent wide range indication) and 1914 cubic feet (83 percent wide range indication),
respectively or (b) three SITs, each with minimum and maximum borated water volumes of 1415 cubic feet (60 percent wide range indication) and 1914 cubic feet (83 percent wide range indication), respectively.
The SIT gas and water volumes, gas pressure, and outlet pipe size are selected to allow one less than the number of required-operable SITs to partially recover the core before significant cladding melt or zirconium-water reaction can occur following a LOCA.
The need to ensure that one less than the required SITs is adequate for this function is consistent with the LOCA assumption that the entire contents of one SIT will be lost through the break during the blowdown phase of a LOCA. This is to meet single failure criteria.
A minimum nitrogen cover pressure requirement (the subject of this evaluation) ensures that the SIT gas volume willgenerate discharge flow rates during injection that are consistent with
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