ML13331A525
| ML13331A525 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/21/1990 |
| From: | Ray H Southern California Edison Co |
| To: | |
| Shared Package | |
| ML13331A524 | List: |
| References | |
| NUDOCS 9012270159 | |
| Download: ML13331A525 (12) | |
Text
BEFORE THE UNITED STATES NUCLEAR REGULATORY COMMISSION Application of SOUTHERN CALIFORNIA EDISON
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COMPANY and SAN DIEGO GAS & ELECTRIC
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COMPANY for a Class 104(b) License to
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DOCKET NO. 50-206 Acquire, Possess, and Use a Utilization
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Facility as Part of Unit No. 1 of the San
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Amendment Application Onofre Nuclear Generating Station
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No. 191 SOUTHERN CALIFORNIA EDISON COMPANY and SAN DIEGO GAS & ELECTRIC COMPANY, pursuant to 10 CFR 50.90, hereby submit Amendment Application No. 191.
This amendment application consists of Proposed Change Number (PCN) 235 to Provisional Operating License No. DPR-13.
PCN 235 modifies the Technical Specifications incorporated in Provisional Operating License No. DPR-13 as Appendix A to reflect modifications of the Volume Control and Charging System (VCCS) that will be completed prior to restart from the current Cycle 11 refueling outage, and to correct an editorial error.
The VCCS modifications are necessary to satisfy single failure requirements.
The VCCS modifications consist of installation of a redundant Volume Control Tank (VCT) outlet isolation valve, MOV-1100E in series with the existing isolation valve MOV-LCV-1100C (MOV-1100C). MOV-1100C and MOV-1100E will be powered separately from MCC-2A and MCC-1, respectively. The existing MCC transfer switch for MOV-1100C, as well as the existing circuit from MOV-1100C to MCC-1 will be removed since they will no longer be required.
9012270159 901221 PDR ADOCK 05000206 P
Based on the significant hazards analysis provided in the Description and Significant Hazards Consideration Analysis of PCN 235, it is concluded that (1) the proposed change does not involve a significant hazards consideration as defined in 10 CFR 50.92, and (2) there is reasonable assurance that the health and safety of the public will not be endangered by the proposed change.
Subscribed on this )fSday of 1990 Respectfully submitted, SOUTHERN CALIFORNIA EDISON COMPANY By:
Harold B. Ray Senior Vice Presid t Subscribed and sworn to before me this bd (&fr day of Pe0tf)P I
OFFICIAL SEAL MAIRANE SANCHEZ No taryPublic.Calffomio ORANGE COUNTY MY Commason Notary Public in toh-State of California James A. Beoletto Attorney for Southern alifor ia Edison Company By:
iJ es A. Be 81ettd
DESCRIPTION AND SIGNIFICANT HAZARDS CONSIDERATION ANALYSIS OF PROPOSED CHANGE NUMBER 235 TO PROVISIONAL OPERATING LICENSE NUMBER DPR-13 INTRODUCTION This is a request for NRC approval to change Technical Specification Section 3.3.1.B, and Table 4.1.2, entitled "Minimum Equipment Check and Sample Frequency", for San Onofre Nuclear Generating Station, Unit 1 (SONGS 1).
The Technical Specification changes are necessary to reflect certain modifications to the Volume Control and Charging System (VCCS) that are being implemented during the current Cycle 11 refueling outage. The modifications include the addition of a redundant Volume Control Tank (VCT) outlet isolation valve MOV 1100E, in series with the existing MOV-LCV-1100C (MOV-1100C). Associated control and power supply circuit changes are also being made to provide separate and redundant actuation signals, and power sources to the valves.
The changes will ensure isolation of the VCT and establishment of the charging pump suction flow path from the Refueling Water Storage Tank (RWST) in the event of a Safety Injection Signal (SIS), Safety Injection Signal with Loss of Power (SISLOP), or VCT low-low level signal.
Technical Specification Section 3.3.1.B allows maintenance of certain redundant subsystem components in the Emergency Core Cooling System (ECCS).
With the addition of MOV-1100E, redundant valves will be provided for isolating the charging pump suction from the VCT. Therefore, an additional paragraph is proposed in Section 3.3.1.B of the Technical Specifications to allow maintenance of these redundant VCT outlet isolation valves.
In the modified configuration, MOV-1100C and MOV-1100E will be powered separately from MCC-2A and MCC-1, respectively. The existing MOV-1100C transfer switch previously used to switch the MOV-1100C power supply from MCC-2A to MCC-1 will be removed since it will no longer be required. This switch currently appears in Technical Specification Table 4.1.2 (Item 11).
Therefore, it is proposed to delete the associated surveillance requirements for the MOV-1100C transfer switch from the Technical Specifications, and to correct an editorial error in Table 4.1.2.
These modifications are being implemented to satisfy single failure requirements discovered as a result of the Emergency Core Cooling System (ECCS) Single Failure Analysis. An interim report on the results of that analysis was submitted to the NRC on July 31, 1990. These proposed changes to the Technical Specifications are part of the resolution to the topic identified as Issue No. 2, "Loss of Suction to the Charging Pumps Prior to Safety Injection Signal," in Enclosure 2 of that report.
Additional changes to Technical Specifications proposed by Proposed Change Number (PCN) 151 in Amendment Application 188 will be required by these modifications. However, in as much as the changes proposed in Amendment Application 188 are not yet part of SONGS 1 Provisional Operating License, these Technical Specification changes will be addressed in a separate revision to PCN 151/Amendment Application 188 to be submitted after return-to-service of SONGS 1 from cycle 11 refueling outage.
-2 EXISTING TECHNICAL SPECIFICATIONS See Attachment 1.
PROPOSED TECHNICAL SPECIFICATIONS See Attachment 2 DESCRIPTION OF TECHNICAL SPECIFICATION CHANGES This proposed change requests NRC approval to revise Technical Specification Section 3.3.1.B and Table 4.1.2, entitled "Minimum Equipment Check and Sample Frequency", to reflect modifications that are being implemented on the VCCS prior to restart from the Cycle 11 refueling outage. The modifications are described in detail in the "DISCUSSION" section below. In addition, an editorial error in Table 4.1.2 is corrected.
The new design change will provide redundant VCT outlet isolation valves similar to the redundant RWST outlet isolation valves (MOV-1100B and MOV-1100D) in the existing design. Paragraph 3.3.1.B(1) of the Technical Specifications allows maintenance of one of the two safety related RWST valves for a period not longer than 72 consecutive hours.
It is herein proposed to add a similar paragraph to the Technical Specifications for the redundant VCT outlet valves. The proposed new paragraph, 3.3.1.B.(8), will allow maintenance of one of the two redundant VCT outlet isolation valves for a period of time not longer than 72 consecutive hours.
This proposed change will be applicable during critical operation of SONGS 1 or when the Reactor Coolant System (RCS) temperature is above 200 *F. The proposed 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> requirement is consistent with the guidelines provided in the Westinghouse Standard Technical Specifications for ECCS subsystems.
The proposed technical change to Technical Specification Table 4.1.2 is to delete Item 11, entitled "MOV-LCV-1100C Transfer Switch."
Item 11 requires verification that the fuse block for either breaker 8-1198 to MCC-1 or breaker 42-12A76 to MCC-2A is removed. The modifications to the VCCS that accompany this proposed change delete the MOV-1100C transfer switch from the plant design. The intent of this transfer switch was to provide redundant power train supplies from MCC-2A (Train B) and MCC-1 (Train A) to MOV-1100C. With the new design change, a redundant VCT isolation valve (MOV-1100E) will be installed. MOV-1100C and MOV-1100E will be powered separately from MCC-2A and MCC-1, respectively. Therefore the existing MOV-1100C transfer switch as well as the circuit from the transfer switch to MCC-1 will be removed since they will no longer be required.
It is also proposed to correct an inadvertent editorial error in Technical Specification Table 4.1.2 regarding the surveillance frequency for verifying that fuse blocks are removed for Item 12, "Emergency Siren Transfer Switch" and Item 13, "Communication Power Panel Transfer Switch."
The frequency is presently stated to be the "Same as Item 10 above," however Item 10 states "Not Used."
Item 10 was modified in Amendment 134, thus deleting the
-3 frequency requirement referred to by Items 12 and 13. The frequency for Items 12 and 13 should be stated as "monthly, when the reactor is critical, and prior to returning reactor to critical, when period of subcriticality extended the test interval beyond one month," which is how it was previously stated in Item 10.
DISCUSSION An interim report on the methodology and results of the ECCS Single Failure Analysis.was submitted to the NRC on July 31, 1990. The report identified eight issues related to satisfying single failure requirements that need resolution. SCE committed to implement corrective actions for all eight of these open issues prior to restart from the current Cycle 11 outage.
The proposed Technical Specification changes address the issue that concerns a potential loss of charging pump suction. The issue involves two postulated single failure scenarios which could potentially result in failure of both charging pumps due to loss of suction caused by gas entrainment from the VCT hydrogen cover gas.
Existing VCCS Configuration and Operation The existing design configuration for the charging pump water supply is shown on Figure 1. The VCCS is designed such that the charging pumps can take suction from either the VCT or the RWST. The charging pumps are isolated from the RWST by means of safety related valves, MOV-LCV-1100B (MOV-1100B) and MOV-LCV-1100D (MOV-11000), and non-safety related fire protection valve FCV-5051. FCV-5051 is being upgraded to safety related during the current Cycle 11 outage. The VCT is isolated by safety-related valve MOV-1100C. The RWST and VCT isolation valves MOV-1100B, MOV-1100C, and MOV-1100D are interlocked so that only one tank is aligned to the charging pumps at a time.
FCV-5051 opens automatically on low charging pump suction pressure to prevent loss of charging flow, and does not have an interlock.
During normal operation, one of the charging pumps operates continuously while taking suction from the VCT. The redundant charging pump normally remains on standby and will start automatically upon low header discharge pressure.
However, a SIS or SISLOP signal will lock out the second pump from starting automatically. Each charging pump is provided with a switch which allows the operator to select which pump will be locked out and which pump will automatically start during the SIS/SISLOP.
The design for VCT isolation valve MOV-1100C currently includes a transfer switch which allows the operator to select the preferred power supply train (either MCC-1 or MCC-2A) corresponding to the Train A or B charging pump that is selected to start on a SIS/SISLOP. The transfer switch is provided to ensure that an alternate power supply is available to MOV-1100C in the event of a power failure in one electrical train. MOV-1100B and MOV-1100D are powered from Train A (MCC-1) and Train B (MCC-2), respectively.
-4 On receipt of a VCT low-low signal from level transmitter LT-1100 (powered from vital bus 4) or a SIS/SISLOP signal, MOV-1100B and MOV-1100D both automatically open and MOV-1100C automatically closes.
Closure of MOV-1100C prevents hydrogen gas entrainment in the charging pump suction. A hydrogen gas blanket is maintained in the VCT for chemistry control and to provide net positive suction pressure to the charging pumps.
VCT level transmitter LT-2550 (powered from vital bus 3A) is provided to trip charging pump G-8B in the event of a low-low-low VCT level.
This interlock is designed to protect pump G-8B during a design basis fire scenario.
Potential for Single Failure Decreasing pressurizer level results in automatically increased charging flow, and eventual isolation of letdown flow. In certain cases the charging pump, which is providing RCS makeup, could empty the VCT. Failure of the running charging pump could occur due to hydrogen gas entrainment, if: a) the VCT level instrument loop for LT-1100 fails to initiate a low-low level signal to transfer the charging pump suction from the VCT to the RWST, or b) VCT isolation valve MOV-1100C fails to close upon receipt of a low-low level signal from LT-1100 or a SIS/SISLOP.
The SIS/SISLOP or VCT low-low-low level pump trip signal from LT-2550 would lock-out the second pump from starting. However, hydrogen gas would potentially be trapped in the common charging pump suction line. Unless the operator notices this condition and vents the hydrogen, the second pump could also fail due to gas binding when required to start.
VCCS Modifications To preclude the above postulated failure scenarios, SCE is implementing a system design change to install a redundant VCT outlet isolation valve MOV-1100E in series with, and upstream of, the existing valve MOV-1100C.
This new valve will ensure positive isolation of the VCT from the charging pump suction, even in the event of a single active failure resulting in failure of MOV-1100C to close.
Figure 2 illustrates the modified charging pump suction design configuration.
The VCCS control and power supply circuits will be modified such that MOV-1100C and MOV-1100E are actuated from independent controls, power supplies and circuitry. MOV-1100C and MOV-1100E will be powered separately from MCC-2A and MCC-1, respectively. The existing transfer switch for MOV-1100C, as well as the circuit from MOV-1100C to MCC-1 will be removed since they will no longer be required. The VCT and RWST outlet isolation valves will be interlocked to close MOV-1100C and open MOV-1100D on either a SIS/SISLOP from Sequencer #2 or on a low-low VCT level signal from level transmitter LT-1100.
Likewise, MOV-1100E will close and MOV-1100B will open on either a SIS/SISLOP from Sequencer #1 or on a low-low VCT level signal from level transmitter LT-2550.
-5 As indicated above, each pair of valves and controls will be physically separate and redundant from a mechanical, electrical and controls design standpoint. This will ensure that no single active failure will prevent isolating the VCT outlet and aligning the RWST to the suction of the charging pumps on either a low-low VCT level or a SIS/SISLOP.
SIGNIFICANT HAZARDS CONSIDERATION ANALYSIS As required by 10 CFR 50.91(a)(1) this analysis is provided to demonstrate that the proposed license amendment to revise Technical Specification Section 3.3.1.B and Table 4.1.2 does not represent a significant hazards consideration. As demonstrated below, in accordance with the three factor test of 10 CFR 50.92(c), implementation of the proposed amendment was analyzed using the following standards and found not to: 1) involve a significant increase in the probability or consequences of an accident previously evaluated; or 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.
- 1.
Will operation of the facility in accordance with these proposed changes involve a significant increase in the probability or consequences of an accident previously evaluated?
Response
No The proposed changes involve revising the Technical Specifications to reflect modifications being made to the VCCS and to correct an editorial error. The modifications include addition of a redundant VCT outlet isolation valve and related circuit changes to resolve single failure susceptibilities. As explained below, with the new design, the plants ability to mitigate the consequences of an accident are improved. There is no significant increase in the probability or consequences of an accident previously evaluated resulting from these proposed changes.
The proposed changes to the Technical Specifications are to 1) add a paragraph to Section 3.3.1.B to allow maintenance of the VCT isolation valves, 2) revise Table 4.1.2 to delete surveillance requirements for a switch which is being removed from the system design, and 3) correct an editorial error in Table 4.1.2.
The applicable SONGS 1 Technical Specification bases do not address the VCT outlet isolation valve with the exception of the surveillance requirement of Table 4.1.2 Item 11 for the MOV-LCV-1100C (MOV-1100C) transfer switch. The previous design required manual transfer of the power sources for MOV-1100C via the transfer switch. With the installation of MOV-1100E as the Train A VCT outlet isolation valve, VCT outlet isolation valve MOV-I100C will remain aligned to Train B. Since each MOV will have independent power sources, it is no longer necessary for an operator to manually transfer MOV power sources. Consequently, the MOV-1100C transfer switch from Train B to Train A power is no longer
-6 required and is being removed by these modifications. Due to the deletion of the switch from the design, the corresponding surveillance requirement is not required. Removal of this surveillance requirement from Table 4.1.2 does not involve an increase in the probability or consequences of an accident.
In Section 3.3.1.B, the Technical Specifications currently allow maintenance of redundant equipment and components required to ensure ECCS functions. Maintenance of these system components is allowed for periods not longer than 72 consecutive hours. This is in accordance with the Westinghouse Standard Technical Specification (W-STS) requirements for ECCS subsystems. Similarly, paragraph 3.3.1.B (1) presently allows maintenance of the RWST redundant isolation valves MOV 1100B and MOV-1100D. It is proposed to add a new paragraph, 3.3.1.B (8), which allows maintenance of the redundant VCT outlet isolation valves. This addition is consistent with the current Technical Specification maintenance requirements for similar redundant ECCS subsystem components, and complies with the guidelines presented in W-STS. Therefore it is concluded that there is no significant increase in the probability or consequences of a previously evaluated accident.
Regarding the editorial change to Table 4.1.2, the proposed change is being made to properly reflect the correct information which was previously approved by the NRC for use at SONGS 1. The proposed change will improve the quality of the Technical Specifications. The proposed editorial change is administrative in nature and does not affect accident probabilities or consequences.
Failure of MOV-1100B, MOV-1100C, MOV-1OOD, MOV-1100E, LT-1100, LT-2550, or the VCT level instrument loops are not precursors to any of the accidents or events evaluated in UFSAR Chapter 15 with the exception of UFSAR Section 15.10, "VCCS Malfunction (Boron Dilution)", and 15.12, "Inadvertent Operation of SI System and VCCS Malfunction that Increase Reactor Coolant Inventory."
An inadvertent isolation of the VCT during normal plant operation could result due to a spurious closure of either MOV-1100C or MOV-1100E. Spurious closure of MOV-1100C is bounded by the analyses in UFSAR Sections 15.10 and 15.12 which relate to Volume Control and Charging System Malfunctions (Boron Dilution events and events resulting in an increase in RCS inventory).
If a spurious closure of MOV-1100C occurs without operator intervention, then the plant would subsequently shutdown due to an inadvertent boration of the RCS when FCV-5051 opens on low charging pump suction pressure. The probability of inadvertently isolating the VCT from the charging pumps is increased slightly by the existence of two VCT outlet isolation valves in series; however, this event is classified in UFSAR Section 15.0.1 as a "moderate frequency event" which may occur once per calendar year and is not a limiting design basis event. This classification is not changed by this design.
-7 The charging pumps, the VCT outlet valves, and portions of the VCT level instrument loops have functions that support the Safety Injection System for mitigating the consequences of LOCAs analyzed in UFSAR Sections 15.13, 15.14, and 15.16; Steam Generator Tube Ruptures (SGTR) analyzed in UFSAR Section 15.15; Main Steam Line Breaks (MSLB) analyzed in UFSAR Section 15.2; and the Main Feedwater Line Breaks (MFLB) analyzed in UFSAR Section 15.6. The charging system is assumed to provide Long Term Core Cooling for LOCAs and normal RCS makeup for MSLB/MFLB events and for other moderate frequency events such as VCCS malfunctions evaluated in UFSAR Section 15.10 (boron dilution events).
At least one charging pump must be available to support long term recirculation for core cooling following a Large or Small Break LOCA. When a SIS/SISLOP occurs, the VCT outlet valve closes and the RWST isolation valves to the suction of the charging pumps open to maintain a source of water to the charging pumps.
However, if VCT outlet valve MOV-1100C fails to close due to single failure, the charging pump suction line and the charging pumps could become gas bound due to the VCT hydrogen cover gas when the VCT empties.
The addition of a redundant VCT outlet valve MOV-1100E in series with, and upstream of, VCT outlet valve MOV-1100C will ensure positive isolation of the VCT under any postulated single active failure. The modifications will also ensure a flowpath from the RWST to the suction of the charging pumps is available when either SIS/SISLOP occurs or when a VCT low-low level is present and the valves are in "auto."
The requirements for mitigating a SGTR are similar to a Small Break LOCA with the exception that RCS Cold/Hot Leg Recirculation is not established. At least one charging pump must be available to support post-safety injection RCS cold leg injection from the RWST until the RCS can be cooled down to cold shutdown. With the present design configuration, only one VCT outlet valve, MOV-1100C, is available to isolate the VCT. If MOV-1100C fails to close (whether it be valve failure or power failure), an operator is required to manually close MOV-1100C and vent the charging pump suction prior to establishing RCS cold leg injection.
Installing the redundant VCT outlet valve MOV-1100E in series with, and upstream of, MOV-1100C provides added assurance of positive isolation of the VCT from the suction of the charging pumps on a SIS/SISLOP resulting from a SGTR. Mitigation of the SGTR is enhanced because local operator actions in the Reactor Auxiliary Building are no longer required. All required actions for establishing RCS cold leg injection can be performed from the Control Room, which maximizes core cooling capability.
-8 Therefore, this modification will enhance the mitigation of a postulated SGTR by ensuring charging pump availability Post-Safety Injection. The post-accident radiological consequences and offsite dose will remain bounded by the 10 CFR 100 Guidelines.
Following a MSLB or MFLB, it may be necessary to establish secondary recirculation because of a common-cause or single failure in the Residual Heat Removal (RHR) System. The charging pumps are required to be available for RCS boration control and makeup. When a SIS/SISLOP occurs, the VCT outlet valve is closed and the RWST isolation valves to the suction of the charging pumps open to maintain a source of water to the charging pumps. This design change installs a redundant VCT outlet valve, MOV-1100E, in series with and upstream of VCT outlet valve MOV-1100C. This change will ensure positive isolation of the VCT under any postulated single active failure and ensure a flowpath from the RWST to the suction of the charging pumps is available.
- Volume Control and Charging System Malfunction (UFSAR Section 15.10):
The boron dilution event evaluation in UFSAR Section 15.10.1 assumes that operator action will be taken to open MOV-1100B and/or MOV-1100D to provide borated water from the RWST to terminate the boron dilution event. In order to be successful, it is required that the VCT be isolated by closing MOV-1100C. The limiting single failure for this recovery mode would be a failure of MOV-1100C to close on demand. This proposed change installs a redundant VCT outlet isolation valve MOV-1100E in series with, and upstream of, MOV-1100C. Additionally, the control circuits are being modified so that the two VCT outlet valves are powered from independent electrical trains. The valves will also be actuated by independent level controllers which are powered by independent trains corresponding to the VCT outlet valve they actuate. The redundant VCT outlet valves, controls, and power supplies will ensure positive isolation of the VCT under any postulated single failure and ensures a flowpath from the RWST to the suction of the charging pumps is available.
Based on the above, it is concluded that operation of SONGS 1 in accordance with these proposed changes will not involve a significant increase in the probability or consequences of an accident previously evaluated.
- 2.
Will operation of the facility in accordance with these proposed changes create the possibility of a new or different kind of accident from any accident previously evaluated?
Response
No
-9 The only accidents or events related to the charging system are evaluated in UFSAR Section 15.2, 15.6, 15.10, 15.12, 15.13, 15.14, 15.15, and 15.16. These modifications do not involve new pressure boundary penetrations, interactions between the VCCS and other systems, or equipment failure modes different from those already analyzed.
The proposed addition of paragraph 3.3.1.B.(8) to the Technical Specifications to allow maintenance of the VCT outlet valves is consist with the maintenance requirements for other similar ECCS subsystem components and with the W-STS guidelines.
The Technical Specification surveillance requirement for the MOV-1100C transfer switch is no longer required since the switch is being deleted.
Removal of this surveillance requirement does not create the possibility of a new or different kind of accident.
The proposed editorial change to Table 4.1.2 is administrative in nature and does not create the possibility of a new or different kind of accident.
Based on the above, it is concluded that the proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.
- 3.
Will operation of the facility in accordance with this proposed change involve a significant reduction in a margin of safety?
Response
No The operability requirements for the VCCS are contained in Technical Specification 3.2. The basis for VCCS operability as defined in Technical Specification 3.2 is to provide Reactor reactivity control by controlling RCS Boron concentration and to provide the capability of emergency Reactor shutdown or the ability to maintain the Reactor subcritical by injection of Boric Acid from either the Boric Acid Makeup Tank or the RWST.
The basis for VCCS operability as defined in Technical Specification 3.3 is for the charging pumps to provide RCS cold/hot leg recirculation for Long-Term Core Cooling.
The modifications ensure that the charging pump suction can be switched from the VCT to the RWST without gas binding the charging pumps under any postulated single active failure. These modifications increase the margin to safety as defined by the applicable Technical Specification bases by improving the availability and reliability of the portions of the VCCS required for accident mitigation.
The applicable SONGS 1 Technical Specification bases do not address the VCT outlet isolation valve with the exception of the surveillance requirement of Table 4.1.2 Item 11 for the MOV-LCV-1100C (MOV-1100C) transfer switch. With the installation of MOV-1100E as the Train A VCT
-10 outlet isolation valve, VCT outlet isolation valve MOV-1100C will remain aligned to Train B. The MOV-1100C transfer switch from Train B to Train A power is no longer required and is being removed by these modifications. The modifications provide a more separate and redundant, hence safer, design. Therefore, removal of the surveillance requirement for this transfer switch from Table 4.1.2 (Item 11) of the Technical Specifications does not involve a reduction in any margin of safety.
Section 3.3.1.B of the Technical Specifications currently allows maintenance of redundant equipment and components required to ensure ECCS functions. Maintenance of these system components is allowed for periods not longer than 72 consecutive hours. This is in accordance with the W-STS requirements for ECCS subsystems. Similarly, paragraph 3.3.1.B (1) presently allows maintenance of the RWST redundant isolation valves MOV-1100B and MOV-1100D. Addition of a new paragraph, 3.3.1.B (8), which allows maintenance of the redundant VCT outlet isolation valves is consistent with the current Technical Specification maintenance requirements for similar redundant ECCS subsystem components. Therefore the proposed change to Section 3.3.1.B does not involve a significant reduction in the margin of safety.
As stated above, the proposed editorial change to Table 4.1.2 is administrative in nature and does not impact any margin of safety.
Based on the above, it is concluded that the proposed changes do not reduce the margin of safety as defined in the basis for any Technical Specification.
SAFETY AND SIGNIFICANT HAZARDS DETERMINATION Based on the preceding analysis, it is concluded that:
(1) PCN 235 does not constitute a significant hazards consideration as defined by 10 CFR 50.92; (2) there is reasonable assurance that the health and safety of the public will not be endangered by the propose change; and (3) this action will not result in a condition which significantly alters the impact of the Station or the environment as described in the NRC Final Environmental Statement. - Existing Technical Specifications - Proposed Technical Specifications Figure 1 - Existing Configuration for Charging Pumps Suction Figure 2 - Modified Configuration for Charging Pumps Suction