ML102450051

Request for Amendment to Technical Specification 3.7.4, Atmospheric Dump Valves (Advs).

ML102450051
Person / Time
Site:	Palo Verde
Issue date:	08/25/2010
From:	Mims D Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-06241-DCM/DFS
Download: ML102450051 (30)

Text

10 CFR 50.90 LA M A subsidiaryof Pinnacle West CapitalCorporation Dwight C. Mims Mail Station 7605 Palo Verde Nuclear Vice President Tel. 623-393-5403 P.O. Box 52034 Generating Station Regulatory Affairs and Plant Improvement Fax 623-393-6077 Phoenix, Arizona 85072-2034 102-06241-DCM/DFS August 25, 2010 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 Request for Amendment to Technical Specification 3.7.4, "Atmospheric Dump Valves (ADVs)"

Pursuant to 10 CFR 50.90,'Arizona Public Service Company (APS) hereby requests to amend PVNGS Operating License Nos. NPF-41, NPF-51, and NPF-74 for Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3, respectively. The proposed amendment will revise Technical Specification (TS) 3.7.4, "Atmospheric Dump Valves (ADVs)," to require two ADV lines per Steam Generator (SG) be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4 when a SG is relied upon for heat removal. This proposed amendment will also make corresponding revisions to the Conditions, Required Actions, and Completion Times associated with one or more inoperable ADV lines. This proposed amendment maintains consistency between the TS and the PVNGS licensing and design bases. Consistent with the guidance in Nuclear Regulatory Commission (NRC) Administrative Letter 98-10, "Dispositioning of Technical Specifications that are Insufficient to Assure Plant Safety," the requirement for two ADV lines per SG is currently being administratively implemented to ensure that appropriate protective actions are in place while this license amendment is pursued.

Approval of the proposed amendment is requested by August 30, 2011- Once approved, the amendment shall be implemented within 90 days.

No commitments are being made to the NRC by this letter.

In accordance with the PVNGS Quality Assurance Program, the Plant Review Board and the Offsite Safety Review Committee have reviewed and concurred with the amendment proposed. By copy of this letter, this submittal is being forwarded to the Arizona Radiation Regulatory Agency (ARRA) pursuant to 10 CFR 50.91 (b)(1).

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde 0 San Onofre

• South Texas 0 Wolf Creek

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission

Subject:

Request for Amendment to Technical Specification 3.7.4 Page 2 Should you need further information regarding this amendment request, please contact Russell A. Stroud, Licensing Section Leader, at (623) 393-5111.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on (Date)

Sincerely, DCM/SAB/SWC/gat

Enclosure:

Evaluation of the Proposed Change cc: E. E. Collins Jr. NRC Region IV Regional Administrator J. R. Hall NRC NRR Senior Project Manager L. K. Gibson NRC NRR Project Manager J. H. Bashore NRC Senior Resident Inspector for PVNGS A. V. Godwin Arizona Radiation Regulatory Agency (ARRA)

T. Morales Arizona Radiation Regulatory Agency (ARRA)

ENCLOSURE Evaluation of the Proposed Change

Subject:

Request for Amendment to Technical Specification 3.7.4, Atmospheric Dump Valves (ADVs) 1.0

SUMMARY

DESCRIPTION 2.0 DETAILED DESCRIPTION

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration Determination 4.4 Conclusions

6.0 REFERENCES

ATTACHMENTS:

1. Technical Specification Page Markups

2. Retyped Technical Specification Pages

3. Technical Specification Bases Page Markups

Enclosure Evaluation of the Proposed Change 1.0

SUMMARY

DESCRIPTION This evaluation supports an Arizona Public Service Company (APS) request to amend Operating License Nos. NPF-41, NPF-51, and NPF-74 for Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3, respectively.

The proposed amendment will revise Technical Specification (TS) 3.7.4, "Atmospheric Dump Valves (ADVs)," to require two ADV lines per Steam Generator (SG) be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4 when a SG is relied upon for heat removal. This proposed amendment will also make corresponding revisions to the Conditions, Required Actions, and Completion Times associated with one or more inoperable ADV lines. This proposed amendment maintains consistency between the TS and the PVNGS licensing and design bases. Consistent with the guidance in Nuclear Regulatory Commission (NRC) Administrative Letter 98-10, "Dispositioning of Technical Specifications that are Insufficient to Assure Plant Safety," the requirement for two ADV lines per SG is being administratively implemented to ensure that appropriate protective actions are in place while this license amendment is pursued.

2.0 DETAILED DESCRIPTION The proposed license amendment revises the Limiting Condition for Operation (LCO) for TS 3.7.4 as follows:

From: "One ADV line per steam generator (SG) shall be OPERABLE."

To: "Two ADV lines per steam generator (SG) shall be OPERABLE."

The ACTIONS table associated with TS 3.7.4 is revised as follows:

1. New Condition A states: "One ADV line inoperable," with a Required Action of "Restore ADV line to OPERABLE status," within a Completion Time of "7 days."

2. Condition A is clarified by "NOTE - Separate Condition entry is allowed for each SG."

3. Condition B states: "Two ADV lines inoperable on one SG with one or two OPERABLE ADV lines on second SG," with a Required Action of "Restore ADV line to OPERABLE status so one ADV line is OPERABLE on each SG", with a Completion Time of "72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />."

4. Condition C states: "No OPERABLE ADV lines on either SG," with a Required Action of "Restore one ADV line to OPERABLE status on either SG," with a Completion Time of "24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />."

5. Condition D states: "Required Action and associated Completion Time not met."

6. The Condition D Required Actions D.1 and D.2 were previously C.1 and C.2, respectively, and remain the same along with the associated Completion Times.

2

Enclosure Evaluation of the Proposed Change No changes are proposed to the associated Surveillance Requirement provided in SR 3.7.4.1.

These changes to TS 3.7.4 are proposed to ensure that the number of ADV lines maintained in an operable condition will allow each unit to be safely shut down after any design basis event concurrent with a loss of offsite power and the most limiting single failure. These changes are required to ensure single failure requirements are satisfied for mitigation of design basis accidents.,

3.0 TECHNICAL EVALUATION

TS 3.7.4 specifies operability and surveillance requirements for SG ADV lines. Each PVNGS unit is designed with two SGs, each of which discharges into two Main Steam lines. Each Main Steam line has five Main Steam Safety Valves (MSSVs) and one ADV connected to it. As a result, each unit has the availability of up to twenty safety valves and four ADVs.

In the event the turbine is unavailable, steam can normally be directed to the preferred heat sink through the Steam Bypass Control System (SBCS) which can route steam directly to the main condenser or to the atmosphere. The SBCS is not safety-related and is not available if the Main Steam Isolation Valves (MSIVs) are closed or if there is a loss of power to the SBCS. There are four ADV lines, two per SG, each of which has the capacity to cool the Reactor Coolant System (RCS) to the Shutdown Cooling (SDC) system entry conditions should the SBCS be unavailable. Each ADV line consists of a normally closed ADV and a normally open block valve. TS 3.7.4 currently requires that one ADV line per SG be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4 when a SG is relied upon for heat removal. The block valves are not credited to isolate a stuck-open ADV and do not have a credible failure mode that would result in their inadvertent closure:

UFSAR Design Descriptions The PVNGS UFSAR describes the ADVs and their functions for removing heat from the reactor coolant system and mitigating the consequences of accidents including the following:

UFSAR Section 10.3.2.2, "Component Description [Main Steam Supply System],"

provides the following component description of the Main Steam lines:

The main steam lines deliver the requiredsteam flow from the secondary side of the two steam generatorsto the high-pressure turbine; while branch lines deliver steam to the moisture separator/reheater,feedwater pump turbines, steam seal system, and the auxiliary steam system....

Each main steam line contains five spring-loadedsafety valves, one atmospheric dump valve, and one isolation valve. All of these valves are located outside the containment and are installed as close as possible to the containment wall....

3

Enclosure Evaluation of the Proposed Change UFSAR Section 10.3.2.2.4, "Atmospheric Dump Valves," provides the following description of the ADVs:

Atmospheric dump valves, one per main steam line, are provided to allow cooldown of the steam generatorswhen the main steam isolation valves are closed, or when the main condenseris not available as a heat sink.

Each atmospheric dump valve is sized to hold the plant at hot standby while dissipatingcore decay heat or to allow a flow of sufficient steam to maintain a controlled reactorcooldown rate. No automatic control capability is required or provided.

UFSAR Section 5.1.5, "CESSAR Interface Evaluation," provides the following description of the ADVs:

G. Thermal Limitations

4. One atmospheric dump valve is provided in each of the main steam lines to allow cooldown of the steam generatorswhen the main steam line isolation valves are closed, or when the main condenser is not available as a heat sink. Each ADV is sized to hold the plant at hot standby dissipatingcore decay and reactorcoolant pump heat, and to allow controlled cooldown from hot standby to shutdown cooling initiation temperatures. To meet this requirement, each atmospheric dump valve has a capacity of 1.47 x 106 pounds per hour at 1000 psia.

USFAR Accident, Design Bases Analyses The safety analyses in the PVNGS UFSAR credit the ADVs as dual use components that fulfill both heat removal and containment isolation design basis safety functions, in accordance with 10 CFR Part 50, Appendix A, General Design Criteria 34 and 57, respectively. As containment isolation valves, the ADV function is to close; however, the ADV function for heat removal is to open. Therefore, the control features of the ADVs have these valves fail closed, while they can be opened remotely from the control room via instrument air or a local nitrogen system. A manual, non-safety-related handwheel is also provided for local actuation.

The UFSAR safety analyses also account for credible limiting single failures that may result in a loss of capability of ADVs to perform their intended safety functions. These single failures include a failure of remote operation of one ADV to open; a failure of remote operation of one ADV to close after it has been opened by plant operators; or an electrical failure that renders two-ADVs, one on each steam generator, unavailable to open via remote operation, depending upon the safety analysis under consideration.

Failure of two ADVs in the opened position is not postulated as the ADVs are "powered components" which fail close on loss of control or power. Therefore, no single failure exists that could fail multiple ADVs in an open position.

Steam Generator Tube Rupture (SGTR) with a Coincident Loss of Offsite Power and a Single Failure (SGTRLOPSF) Analysis In the SGTRLOPSF analysis in UFSAR Section 15.6.3.3, the radiological consequences are maximized by assuming a coincident loss of offsite power which results in the closure of the MSIVs, a coincident iodine spike, and a single failure that results in one 4

Enclosure Evaluation of the Proposed Change ADV on the affected SG being in a failed open position. In this event scenario, after reactor trip, the operator opens one ADV on each SG to initiate unit cooldown; however, the ADV on the affected SG fails open. The operator then closes the ADV on the unaffected SG to prevent an excessive cooldown rate. In this scenario, as required, the operator reopens ADVs on the unaffected SG to continue the cooldown of the unit to SDC entry conditions. The SGTRLOPSF analysis is considered the bounding licensing basis for a SGTR event, and the maximum radiological consequences from that event remain within the Nuclear Regulatory Commission (NRC) 10 CFR 100 limits.

• SGTR with a Coincident Loss of Offsite Power (SGTRLOP) Analysis The SGTRLOP scenario is described in UFSAR Section 15.6.3.2 and states that its dose consequences are bounded by the SGTRLOPSF. As discussed in the UFSAR, this SGTRLOP analysis was specifically provided to validate the adequacy of Emergency Operating Procedures (EOPs), by demonstrating that the affected SG would not overfill if plant operators isolated it from the external environment. This analysis is not considered a bounding license basis analysis.

This analysis credits opening of one ADV on each SG for control of the RCS cooldown rate. Later in this event, the operator is assumed to close the ADV on the affected SG and to use the ADVs on the unaffected SG for heat removal. Consequently, this scenario increases the potential for overfill of the affected SG, but reduces the radiological consequences relative to the SGTRLOPSF analysis. As a result, the assumptions used in the SGTRLOP analysis do not result in the maximum radiological consequences for a SGTR event.

• Forced Shutdown as Result of Loss of Off Site Power and Seismic Event Analysis - Branch Technical Position (BTP) Reactor Systems Branch (RSB) 5-1 (Reference 6.1)

The BTP. RSB 5-1 scenario is described in UFSAR Appendix 5C. The functional requirements of BTP RSB 5-1 ensure that the cooldown can be accomplished within a reasonable time after reactor shutdown using only safety-grade systems (described in NRC guidance provided by Table 1 of the BTP RSB 5-1 for Class 2 plants). Following a reactor trip, the plant must have the capability to maintain Hot Standby conditions for at least four hours prior to commencement of a cooldown. The credited systems must function using either onsite electrical power system operation (assuming offsite power is not available) or offsite electrical power system operation (assuming onsite power is not available) and assuming a single failure. Systems must be capable of remote operation from the control room although limited operator action outside of the control room is acceptable to mitigate the effects of postulated single failures.

Identification of a Non-Conservative TS In July 2006, an APS review of the UFSAR Chapter 15 SGTRLOP analysis identified that this analysis credited the opening of a second ADV on the unaffected SG for cooldown, whereas the current TS 3.7.4 required only one OPERABLE ADV on each SG. The crediting of the second ADV in the SGTRLOP analysis was entered'into the PVNGS Corrective Action Program (CAP) because the SGTRLOP analysis assumptions did not conform to the TS 3.7.4 requirements.

5

Enclosure Evaluation of the Proposed Change APS took immediate corrective actions by issuing a Standing Order for licensed operators to supplement the current TS requirements with administrative controls.

These administrative controls prevented indefinite operation of the PVNGS units with inoperable ADV lines, which was otherwise allowed by the current TS 3.7.4.

APS formed an interdisciplinary team to evaluate and identify other corrective actions.

The team reviewed the applicable design and licensing bases and obtained additional information from the Nuclear Steam Supply System (NSSS) vendor and industry peers.

As a result, the team confirmed that the SGTRLOPSF analysis was the bounding licensing analysis and that one ADV was credited for mitigating any design basis event, which would meet the current TS 3.7.4. However, the review team identified that although PVNGS safety analyses had traditionally accounted for single failure of one ADV to either open or close, there was a potential single failure that was not previously identified or considered. Specifically, a potential single failure involving the ADV control circuits could potentially render two ADVs (i.e., one on each SG) incapable of being opened remotely. This type of single failure could occur because one pair of ADVs (i.e.,

one on each SG) is provided with control circuit power from "A" and "C" channels, whereas the other pair of ADVs receives power from "B" and "D" channels. Although the control circuits for the ADVs are redundant, each of the control channels within an associated control set are not separated. As a result, a fault (i.e., short, ground, or open circuit) within a single channel may affect both ADVs in the associated pair and render them incapable of being opened remotely. Each of these failed ADVs may still be operated manually using local hand wheels; however, use of that manual capability is not assumed in the PVNGS UFSAR Chapter 15 design basis accident analyses.

To address this single failure vulnerability, APS revised the PVNGS Technical Requirements Manual (TRM) T3.7.200, "Atmospheric Dump Valves (ADVs)", on July 12, 2007. The revised TRM requires two OPERABLE ADV lines per SG and provides associated Conditions, Required Actions, and Completion Times should one or more ADV lines be inoperable. Operability requirements for the ADVs are currently being controlled under that TRM change. The interim Standing Order was cancelled upon issuance of the revised TRM.

Approval of this license amendment request (LAR) by the NRC will effectively.

supersede the current TRM requirements for the number of operable ADVs, and the TRM will be modified as part of the implementation of the proposed TS change.

BTP RSB 5-1 Scenario Review In February 2009, APS reviewed the BTP RSB 5-1 scenario analysis to further clarify the design and licensing bases of the ADVs and their support systems. The BTP RSB 5-1 natural circulation cooldown analysis credits the opening of two ADVs, one on each SG, to ensure cold shutdown in the analyzed duration. As a result, considering the single failure that renders one ADV on each SG inoperable, two ADVs on each SG would be required operable to meet TS 3.7.4. This configuration is not supported by the current TS 3.7.4 which requires only one OPERABLE ADV on each SG. This issue was also entered into the PVNGS Corrective Action Program (CAP). The current control of the required ADV configuration is provided by TRM T3.7.200, "Atmospheric Dump Valves (ADVs)." The TRM ADV operability requirements are adequate, in the interim, to 6

Enclosure Evaluation of the Proposed Change ensure that the design basis requirements continue to be met and the identified TS inconsistencies are mitigated. Approval and implementation of the proposed amendment request will resolve this issue.

Proposed Chanqes to LCO 3.7.4 LCO 3.7.4 is revised to require that two ADV lines per SG shall be OPERABLE. The current PVNGS TS LCO requires one OPERABLE ADV line per SG; however, considering the single control system failure that may affect one ADV line on each SG, it is possible that no OPERABLE ADV lines would be available on any SG. This configuration is mitigated by the proposed change to the TS LCO requirement.

In addition to the modification of the TS LCO, all of the Conditions, Required Actions and Completion Times are proposed to be modified as discussed below:

Proposed New Condition A The current Condition A is being replaced by a proposed new Condition A. The current Condition A will become the proposed Condition B with some modifications as discussed below. The proposed new Condition A specifically allows one of the two required ADV lines per SG to be inoperable. This allowed configuration is the equivalent of the configuration allowed by Condition A of the standard Combustion Engineering (CE) TS in NUREG-1432. Required Action A.1 for the proposed Condition A requires that the inoperable ADV line be restored to OPERABLE status within the 7-day Completion Time to meet LCO 3.7.4.

In support of the change in the TS LCO, a Note is added to Condition A allowing separate entry for each SG with an inoperable ADV line. This Note will allow up to one ADV line to be inoperable on each SG, concurrently. Under the current TS LCO this same configuration is allowed with no restriction on remaining in that configuration. The proposed Condition A limits the amount of time that this configuration can exist to 7 days, which is more restrictive than the current TS LCO. The Note allows separate entry to Condition A for each SG, and exiting this Condition for each SG requires the inoperable ADV on the associated SG to be restored to OPERABLE status.

Condition A 7-Day Completion Time The proposed 7-day Completion Time for Condition A is considered reasonable and appropriate for completing corrective maintenance on ADV components. The 7-day Completion Time is in accordance with NUREG 1432, Revision 3 (Reference 6.2), and is based on the redundancy in heat removal options available to operators, on the relatively low contribution to overall facility risk contributed by the ADVs, and by a low probability of occurrence of a design basis event that would require ADV line operation occurring during this Completion Time.

The proposed Condition A, and its Completion Time, are reasonable because:

Each SG has two main steam lines, each of which has an ADV line, MSIV, and five safety grade MSSVs. There are no cross-tie vulnerabilities and no common failure points between the two main steam lines associated with each SG. The redundancy and reliability provided by this configuration supports a 7-day Completion Time.

7

Enclosure Evaluation of the Proposed Change When one ADV line is inoperable, the other ADV line on the associated SG is still available for design basis event mitigation, and any one ADV line has the capacity to safely remove heat from the RCS. In addition, the operable ADV lines on the other SG are also available for design basis event mitigation.

When MSIVs are open and offsite power is available, the SBCS, although not safety grade, is available as the preferred method of heat removal, to direct steam to the condenser, the atmosphere or both.

The safety grade MSSVs, located upstream of the MSIVs, would automatically open to provide SG overpressure protection and would remain available for RCS heat removal regardless of the availability of offsite power.

Although not credited in the UFSAR Chapter 15 accident analyses, operators may utilize a non-safety related local manual hand wheel on the ADV to open and close an inoperable ADV line ifthe area is habitable. PVNGS' Emergency Operating Procedures provide guidance to operate the ADV manually.

There is a low probability of any accident considered in the licensing basis which would require ADV line operation to occur during the proposed 7-day Completion Time.

Operating experience indicates that the proposed 7-day Completion Time is sufficient to restore inoperable ADV lines to OPERABLE status.

The proposed change does not allow continued operation with inoperable ADVs beyond the Completion Time.

Proposed Condition B Proposed Condition B would be entered when two required ADV lines are inoperable on one SG and there are either one or two OPERABLE ADV lines on the other SG.. Inthis Condition, Required Action B.1 would require that one of the inoperable ADV lines, on the SG with the two inoperable ADV lines, be restored to OPERABLE status so that there is at least one OPERABLE ADV line on each SG within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

This proposed Condition B represents a loss of ADV redundancy, but not a loss of design basis function because at least one ADV is still functional on one SG-. The proposed Condition B is similar to the current TS Condition A. The current TS LCO requires one OPERABLE ADV line per SG and the current Condition A allows for one required ADV line to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This could result in one SG having no OPERABLE ADV lines and the second SG having just one OPERABLE ADV line for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The proposed Condition B allows this same configuration to exist with the same Required Action and Completion Time. An inoperable ADV line must be returned to OPERABLE status so that at least one ADV line is OPERABLE on each SG to exit from this Condition.

The proposed Condition B does not correlate directly to the CE standard TS in NUREG-1432, Revision 3. The Condition B in the CE standard TS provides that two or more required-ADVs may be inoperable for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. As a result, Condition B of the CE standard TS could allow continued operation with three or four inoperable ADVs.

8

Enclosure Evaluation of the Proposed Change To increase operational flexibility, APS has divided the potential configurations controlled under the CE standard TS Condition B into proposed Condition B which allows up to three inoperable ADVs and Condition C which allows for all four ADVs to be inoperable. As discussed above, the Required Action for the proposed Condition B will return one ADV line to OPERABLE status on the SG with the two inoperable ADV lines. This action will ensure that there is at least one OPERABLE ADV line on each SG, which is the configuration allowed in proposed Condition A. In addition, although the CE TS Condition B does not provide a separate Completion Time for three versus four inoperable ADVs, APS has provided a Completion Time for Condition B of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This Completion Time is based on a reasonable time to perform maintenance on a single ADV line and the reduced risk from having at least one OPERABLE ADV over having no OPERABLE ADVs which is allowed by the CE TS Condition B. This Completion Time is supported by the current PVNGS TS discussed above and the following:

The 72-hour Completion Time provided in Condition B is consistent with that already afforded by Condition A of the current PVNGS TS 3.7.4 (i.e., wherein both ADV lines on one SG may be inoperable) as well as with similar PVNGS TS (e.g., Condition B of TS 3.7.5, "Auxiliary Feedwater System," which includes a 72-hour Completion Time for a loss of diversity in operable AFW pumps).

• Condition B reflects a loss of redundancy, but not a loss of function.

• A minimum of one of the ADV lines associated with one of the SGs would remain available for design basis event mitigation.

• When MSIVs are open and offsite power is available, the preferred method of RCS heat removal would be through the non-safety grade SBCS to the condenser, the atmosphere, or both.

The safety grade MSSVs, located upstream of the MSIVs, would automatically open to provide SG overpressure protection and would remain available for RCS heat removal regardless of the availability of offsite power.

There is a low probability of an accident considered in the licensing basis which would require ADV line operation to occur during this 72-hour Completion Time.

Although not credited in the UFSAR Chapter 15 accident analyses, and with the exception of a seismic event which has a very low probability of occurrence, operators could utilize a non-safety related local manual hand wheel on the ADV to open and close an inoperable ADV line if the area is habitable. PVNGS EOPs provide guidance to' operate the ADV manually.

• Some repairs may be possible with an associated unit at power because block valves can be closed to isolate inoperable ADVs.

Proposed Condition C The proposed Condition C would be entered if all four ADV lines were inoperable. The Completion Time, requires, that at least one ADVline on either SG be restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This Condition reflects the loss of ADV function and is 9

Enclosure Evaluation of the Proposed Change consistent with current TS Condition B, which would apply if all four ADV lines were inoperable and also requires that one required ADV line be returned to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. One ADV line on either SG must be restored to operable status to exit this Condition.

The proposed Condition C does not correlate directly to the CE standard TS in NUREG-1432, Revision 3. However, Condition B in NUREG-1432 would allow the same configuration of having no OPERABLE ADV lines for up to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The Required Action to this CE TS Condition is to return all but one ADV line to OPERABLE status, which would result in only one inoperable ADV line on one SG. In this amendment, APS has provided a Required Action for the proposed Condition C that returns one ADV to OPERABLE status on either SG Returning one ADV to OPERABLE status will allow exit from Condition C, however Condition B will apply, as discussed above. Though this proposed Required Action is different from the CE TS Condition B, it is justified by the reduction in risk by re-establishing the one OPERABLE ADV onone SG required for design basis accident mitigation. The CE TS allows a 24-hour Completion Time for its Condition B configurations and the proposed Condition C provides the same 24-hour Completion Time..

The proposed Condition C is reasonable because:

0 This Completion Time is consistent with that already afforded by Condition B of the current PVNGS TS 3.7.4 wherein'all four ADV lines are inoperable.

There is a low probability of an accident considered in the licensing basis which would require ADV operation to occur during this time frame.

• RCS'heat removal may still be accomplished via the safety grade MSSVs, the non-safety grade SBCS, or both.

• Although not credited in the UFSAR Chapter 15 accident analyses, and with the exception of a seismic event which has a very low probability of occurrence, operators could utilize a non-safety-related local manual hand wheel on the ADV to open and close an inoperable ADV line in a reasonable time if the area is habitable. PVNGS' Emergency Operating Procedures provide guidance to operate the ADV manually.

• Some repairs may be possible with the unit at power because block valves can be closed to isolate inoperable ADVs.

Proposed Condition D Changes Proposed Condition D requires being in Mode 3 within six hours and being in Mode 4within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if the Required Actions and Completion Times are not met, and is exactly the same as the current TS Condition C. The only proposed change to this Condition is the letter designations for the Condition and Required Actions under this Condition.

All of the proposed changes to TS 3.7.4 support the current design basis of PVNGS Units 1,2, and 3.

10

Enclosure Evaluation of the Proposed Change Technical Specification Bases Changes The Bases for TS 3.7.4 will also be changed to reflect the proposed changes, and a proposed markup is included "For Information Only" in Attachment 3.

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria In accordance with 10 CFR Part 50, Appendix A, the PVNGS design basis and accident analyses account for credible single failures of active components. With respect to the ADV lines, this includes failure of as many as two ADVs (i.e., one per SG) to open on demand, and failure of one ADV to close on demand after it has been opened by plant operators. The first of these single failure mechanisms may adversely affect the capability of the SGs to provide RCS heat removal, whereas the failure of a single ADV to close is postulated to maximize the potential for design basis accident radiological consequences. Failure of two ADVs in the opened position is not postulated as the ADVs are "powered components" which fail close on loss of control or power.

Therefore, no single failure exists that could fail multiple ADVs in an open position.

Four ADV lines (i.e., two per SG) are provided to ensure that at least one ADV line on at least one SG will remain available for heat removal following all potential design basis events and limiting single failures, including those accidents that may render one SG unavailable for heat removal. This is consistent with the PVNGS design and licensing bases, and BTP-RSB 5.1 scenarios. Additionally, for postulated SGTR accidents, at least one ADV line would remain available for heat removal on each SG, thereby assuring that plant operators may prevent SG overfill conditions by selectively delivering auxiliary feedwater to, and selectively steaming from, the affected SG. BTP RSB 5-1 scenarios, including seismic events, can also be mitigated with two ADVs, one per SG.

The applicable General Design Criteria (GDC) are:

GDC 2, "Design Bases for Protection Against Natural Phenomena," requires that the safety-related portion of the Main Steam Supply System be protected from the effects of natural phenomena, such as earthquakes, tornadoes, hurricanes, floods, and external missiles.

• GDC 4, "Environmental and Dynamic Effects Design Bases," requires that the safety-related portion of the Main Steam Supply System be designed to remain functional after a safe shutdown earthquake and to perform its intended functions following postulated hazards such as internal missiles or pipe breaks.

• GDC 34, "Residual Heat Removal," requires that suitable redundancy be provided to assure that for onsite electrical power system operation (assuming offsite power is not available), and for offsite electrical power system operation (assuming onsite power is not available), Main Steam Supply System safety functions can be performed, assuming a single failure.

GDC 57, "Closed System Isolation Valves," requires that ADVs be located as close to the containment as practical and be capable of remote manual operation.

11

Enclosure Evaluation of the Proposed Change The proposed changes to TS 3.7.4 do not alter the SG ADV line design, nor do they affect compliance with the applicable regulatory requirements and criteria.

4.2 Precedent The Combustion Engineering (CE) Improved Technical Specifications (ITS) in NUREG 1432, Revision 3 (Reference 6.2), provides comparable LCO and Action requirements, along with their associated TS Bases discussions.

4.3 No Significant Hazards Consideration Determination The proposed change would revise technical specification (TS) 3.7.4, "Atmospheric Dump Valves (ADVs)," to require that two ADV lines per steam generator (SG) be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4 when a SG is relied upon for heat removal. This proposed change also makes corresponding revisions to the TS Conditions, Required Actions, and Completion Times associated with one or more inoperable ADV lines. This proposed amendment will ensure that the Palo Verde Nuclear Generating Station (PVNGS) licensing and design bases are maintained.

Arizona Public Service Company (APS) has evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of Amendment," as discussed below:

1. Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No.

The proposed amendment will revise TS 3.7.4, to require two ADV lines per SG be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4, when a SG is relied upon for heat removal. The proposed change to TS 3.7.4 is consistent with the PVNGS UFSAR Chapter 15 analyses. The proposed change does not involve any design or physical changes to the facility, including the ADV lines and their associated ADVs, block valves, pneumatic controllers, instrument power circuits, or control circuits. The design and functional performance requirements, operational characteristics, and reliability of the ADV lines remain unchanged.

Therefore, there is no impact on the design safety function of the ADVs to open (which mitigates certain postulated accidents by providing Reactor Coolant System heat removal) nor on the design safety function of the ADVs to close (which mitigates certain postulated accidents by providing containment isolation).

Furthermore, there is no change with respect to an inadvertent opening of an ADV (as a potential transient initiator).

With regard to the consequences of postulated design basis accidents and the equipment required for mitigation of those accidents, the proposed TS changes involve no design or physical changes to the ADV lines or any other equipment required for accident mitigation. The proposed ADV TS change does not affect any design basis analysis or the results of those analyses. The change provides additional assurance that ADVs will be available as required.

12

Enclosure Evaluation of the Proposed Change Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously analyzed.

2 Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No The proposed amendment will revise TS 3.7.4, to require two ADV lines per SG be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4, when a SG is relied upon for heat removal. The proposed change to TS 3.7.4 is consistent with the PVNGS UFSAR Chapter 15 analyses. The proposed change does not involve any design or physical changes to the facility, including the ADV lines and their associated ADVs, block valves, pneumatic controllers, instrument power circuits, or control circuits. No physical alteration of the plant is involved. The proposed change does not involve or introduce any changes to plant procedures that could cause a new or different kind of accident from any previously evaluated. The proposed change ensures that the ADVs perform their intended functions during all design basis accidents for which they are credited. The proposed change does not involve the creation of any new or different kind of accident initiator. The proposed change does not create any new failure modes for the ADVs and does not affect the interaction between the ADVs and any other system.

Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.

3. Does the proposed amendment involve a significant reduction in a margin of safety?

Response: No.

The proposed amendment will reviseTS 3.7.4, to require two ADV lines per SG be OPERABLE in MODES 1, 2, and 3, as well as in MODE 4, when a SG is relied upon for heat removal. The proposed change to TS 3.7.4 is consistent with the PVNGS UFSAR Chapter 15:analyses. The proposed change does not alter the manner in which safety limits or limiting safety system settings are determined. No changes to instrument and/or system actuation setpoints are involved. Safety and .Branch Technical Position (BTP) RSB 5-1 analysis acceptance criteria are not impacted by this change and the proposed change will not permit plant operation in a configuration outside the design basis.

Therefore, the proposed change does not involve a significant reduction in the margin of safety.

Based on the above, APS concludes that the proposed amendment does not involve a significant. hazards consideration under the standards set forth in 10 CFR 50.92(c) and, accordingly, a finding of "no significant hazards consideration" is justified.

13

Enclosure Evaluation of the Proposed Change 4.4 Conclusions In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

5.0 ENVIRONMENTAL CONSIDERATION

A review has determined the proposed amendment would change a requirement with respect to use of a facility component located within the restricted area, as defined in 10 CFR 20. The proposed amendment revises TS 3.7.4 to require two ADVs operable per SG, which is more restrictive than the current TS requirements, and ensures that the PVNGS Units 1, 2, and 3, design and licensing bases continue to be met. The proposed amendment does not modify any physical barriers or any accident dose consequences, and ensures the current accident analyzed dose consequences remain bounding.

The proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or a significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

6.0 REFERENCES

6.1. NUREG-0800, Standard Review Plan, Branch Technical Position (BTP) Reactor Systems Branch (RSB) 5-1.,

6.2. NUREG-1432, "Standard Technical Specifications Combustion Engineering Plants," Volume 1, Revision 3.0, June 2004.

14

ATTACHMENT 1 Technical Specification Page Markups Pages:

3.7.4-1

ADVs 3.7.4 3.7 PLANT SYSTEMS 3.7.4 Atmospheric Dump Valves (ADVs)

LCO 3.7.4 9ne-Two ADV lines per steam generator (SG) shall be OPERABLE.

APPLICABILITY: MODES 1, 2, and 3, MODE 4 when steam generator is being relied upon for heat removal.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. - ----- NOTE ---------

Separate Condition A.1 Restore ADV line to 7 days entry is allowed for OPERABLE status each SG One ADV line inoperable.

AB. POe i-eq.u-4d-Two ADV lines inoperable on AB.1 Restore ADV line to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> one SG with one or two OPERABLE status so OPERABLE ADV lines one ADV line is on second SG. OPERABLE on each SG.

4C. Two requred AV !in B9C.1 Restore one ADV line 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />

~pe.ab-b-*No to OPERABLE status on OPERABLE ADV lines either SG.

on either SG.

CED. Required Action and CED.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time not met. AND CD.2 Be in MODE 4 without 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> reliance on steam generator for heat removal.

PALO VERDE UNITS 1,2,3 3.7.4-1 AMENDMENT NO. 4-1;, ;4&

ATTACHMENT 2 Retyped Technical Specification Pages Pages:

3.7.4-1

ADVs 3.7.4 3.7 PLANT SYSTEMS 3.7.4 Atmospheric Dump Valves (ADVs)

LCO 3.7.4 Two ADV lines per steam generator shall be OPERABLE.

APPLICABILITY: MODES 1, 2, and 3, MODE 4 when steam generator is being relied upon for heat removal.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. -------- NOTE -------- A.1 Restore ADV line to 7 days Separate Condition OPERABLE status.

entry is allowed for each SG One ADV line inoperable.

B. Two ADV lines B.1 Restore ADV line to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> inoperable on one SG OPERABLE status so one with one or two ADV line is OPERABLE OPERABLE ADV lines on on each SG.

second SG.

C. No OPERABLE ADV lines C.1 Restore one ADV line to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> on either SG. OPERABLE status on either SG.

D. Required Action and D.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion time not met. AND D.2 Be in MODE 4 without 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> reliance on steam generator for heat removal.

PALO VERDE UNITS 1,2,3 3.7.4-1 AMENDMENT NO. 4-6-5,

ATTACHMENT 3 Technical Specification Bases Page Markups (For Information Only)

Pages:

B 3.7.4-1 B 3.7.4-2 B 3.7.4-3 B 3.7.4-4 B 3.7.4-5 B 3.7.4-6 B 3.7.4-7 B 3.7.4-8 B 3.7.4-9

ADVs B 3.7.4 B 3.7 PLANT SYSTEMS B 3.7.4 Atmospheric Dump Valves (ADVs)

BASES BACKGROUND The ADVs provide a safety grade method for cooling the unit to Shutdown Cooling (SDC) System entry conditions, should the preferred heat sink via the Steam Bypass Control System (SBCS) to the condenser and/or atmosphere not be available, as discussed in the UFSAR, Section 10.3 (Ref.

1). The ADVs have the capacity to achieve and maintain safe shutdown conditions following design basis accidents involving a loss of offsite power and/or closure of the Main Steam Isolation Valves (MSIVs) following receipt of a Main Steam Isolation Signal (MSIS). This is done in conjunction with the Auxiliary Feedwater System providing cooling water from the Condensate Storage Tank (CST). The ADVs may also be required to meet the design cooldown rate during a normal cooldown.

Four ADV lines are provided. Each ADV line consists of one normally closed ADV and an associated,'normally open block valve. OqeTwo ADV lines per steam generator 4-+/-are required to meet the single failure assumptions following a design basis accident that may render one steam generator (SG) unavailable for heat removal. The ADV block valves permit testing of the ADVs while a unit is at power. The safety analyses, however, do not credit block valve operation as a means of isolation of a failed open AnV as,,mt o I n thc Safety anal..SE.S. The ADV bloc va!veS are not required to be cloSed in the evenAt ofý q stuck open AD.

The ADVs are equipped with pneumatic controllers to permit control of the cooldown rate.

The ADVs are provided with a pressurized gas supply of bottled nitrogen that, on a loss of pressure in the normal instrument air supply, automatically supplies nitrogen to operate the ADVs. The nitrogen supply is sized to provide sufficient pressurized gas to operate the ADVs for the time required for Reactor Coolant System (RCS1 cooldown to the Shutdown Cooling (SDCJ System-entr-y-conditions, as described in UFSAR Appendix 5C, "Natural Circulation Cooldown Analysis." The Appendix 5C analysis is based on the assumptions and conditions in the NRC's Branch Technical Position (BTP) RSB 5-1, "Design Requirements of the Residual Heat Removal System." RSB 5-1 is an attachment (continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-1 REVISION 50

ADVs B 3.7.4 to Standard Review Plan (SRP) 5.4.7, "Residual Heat Removal (RHR) System," and identifies RHR System requirements that ensure conformance with General Design Criteria (GDC) 34, "Residual Heat Removal."

The PVNGS RSB 5-1 cooldown scenario described in UFSAR Appendix 5C is based on a natural circulation cooldown with both steam generators (SGs) available, using safety-grade equipment, assuming a loss of offsite power, a limiting single failure (assumed to be a diesel generator failure),

and with minimal operator actions outside the control room.

as approved by the NRC. The RSB 5-1 cooldown duration was 1'

(continued)

PALO VERDE UNITS 1,2,3 REVISION 50

ADVs B 3.7.4 BASES BACKGROUND (continued) established during actual testing performed in January 1986, and was confirmed through subsequent analyses to address steam generator replacement and power uprates.

A description of the ADVs is found in Reference 1. The ADVs require both Direct Current (DC) sources and class Alternating Current(ACI instrument power to be considered OPERABLE. In addition, non-safety related hand wheels are provided for local manual operation, although hand wheels are not required for AD/

OPERABILITY or credited in the accident analyses.

APPLICABLE The design basis of the ADVs is established by the SAFETY ANALYSES capability to cool the unit to SDC System entry conditions.

The design must also accommodate credible single failures that may render as many as two ADVs (i.e., one on each steam generator) incapable of opening on demand. A coo! down rate of 75°F per hour is obtainable by o or bothgl -em.

.. ,,ptp. This design is adequate to cool the unit to SDC System entry conditions with only one ADV and one SGt gen r utilizing the cooling water supply available in the CST. Cooldown scenarios using a single ADV may require a combination of the available nitrogen supply and local manual operation or other actions.

Alternatives for cooldown and for ADV operation beyond the RSB 5-1 scenario have been evaluated using probabilistic

.risk analysis (PRA) as part of the resolution of Unresolved Safety Issue (USI) A-45, "Shutdown Decay Heat Removal Requirements." USI A-45 was subsumed into the Individual Plant Examination (IPE)which used PRA techniques and was submitted to the NRC in response to Generic Letter 88-20.

The IPE considered various operator actions and the use of non-safety related equipment, and concluded that there are no significant heat removal vulnerabilities at PVNGS.

Operator actions to locally operate the ADVs are not credited in the UFSAR Chapter 15 accident analyses but are described in the EOPs; non-safety related equipment such as the supplemental nitrogen supply could also be used during extended cooldown situations.

In the accident analysis p-reseted in the UFSAR, the ADVs are assu.med t be used by he operator to cool doWn the unit to SDC System entr cn i acidents accompanied by a loss o offsite power. Prior to the operator acýtG, the Main Steam Safety Va!ves (MSSVS)a.e (continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-3 REVISION 50

ADVs B 3.7.4 BASES used to MSanHtan Steam gerator preSSUre and temperature at thc.SSV setpoint. Th.s is typically 0 m.in!tes fqollowiR the initiation of an event. (This is less for Steam Gecreator Tube Rupture (SGTR) events as detailed below). The limit4Rg events ape those that r-e*der He ctpAm c,*nrrfnr fnr RCQ, hpAft 4n=.,i..h!. rpmnv!.. 0 it h A (continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-4 REVISION 50

ADVs B 3.7.4 BASES APPLICABLE SAFETY ANALYSES GnHn et !. .÷ ,

pewe* hs .... ts f a,,Hnb (continued) trp Tpical ini t 4ng ..... fall

• 4HtG th# Gte ,,-re events, ADV's are assumed to be op.ncd tGo mnut4e post trip ý ope util the affected SG isisoated. FromH then on, remai the ADVs' on th affected SG is used till shutdown cooling entr.y -onditIns apc reached.

The design basis accident analyses also account for a single failure that may render one ADV incapable of being closed remotely, after it is opened by control room operators. This typ of postulated failure yields more adverse radiological consequences for certain analyses, because it creates a pathway for radioisotope discharges to the environment. For accident mitigation the safety analyses do not credit isolation of a failed open ADV by either local manual hand wheel operation or closure of its associated block valve.

The safety analyses in the UFSAR assume that plant operators will use the ADVs to cool down an affected unit to SDC System entry conditions, following accidents accompanied by a loss of offsite power and/or closure of the MSIVs. Initiation of operator action is typically assumed to occur 30 minutes following the initiation of an event; however, for Steam Generator Tube Rupture (SGTR) events, initiation of this operator action is assumed to occur 2 minutes following reactor trip. Prior to the operator action, the Main Steam Safety Valves (MSSVs) are credited in the analyses to maintain SG pressure and temperature near the MSSV setpoints.

The limiting design basis event for nitrogen supply capacity is the RSB 5-1 natural circulation cooldown scenario described above. This scenario includes an initial period of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> at hot standby conditions followed by natural circulation cooldown for 9.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> until SDC entry conditions are achieved. Each ADV is required to have a nitrogen supply that supports ADV operation for a total of 13.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.

Limiting design basis accidents with respect to RCS heat removal and ADV steam flow capacity include those that may render one SG unavailable, with a coincident loss of offsite power and a single active component failure (i.e., main steam li e breaks upstream of the MSIVs, and feedwaterline breaks).

(continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-5 REVISION 50

ADVs B 3.7.4 BASES The limiting design basis event with respect to offsite radiological consequences is a SGTR with a coincident loss of offsite power, a coincident RCS iodine spike, and a single failed open ADV on the affected SG (SGTRLOPSF). To determine boundina radioloaical conseauences. an ADV is assumed to stick oeen durina ooerator action that occurs 2 minutes after triiJV" and remains open for the duration of the cooldown. For this SGTRLOPSF case, plant operators will direct auxiliary feedwatei flow to the affected SG after the accident has occurred. The steam released through the ADVs is contaminated, however, because of primary-to-secondary leakage that transports radioisotopes from the RCS to the SG.

The Fai!,,e Ge*ep.....

Steam(ST-LPT F) .....ith a Sri ,aLqsG

...... Of 0fs#t an .... affcte Anvo DPthe

• ia qd affcc ,ADS! - G The ADVs satisfy Criterion 3 of 10 CFR 50.36 (c)(2)(ii).

LCO Two ADV lines are required to be OPERABLE on each SG, to ensure a design basis accident that renders one SG unavailable for heat removal (in combination with a coincident loss of offsite power and a single active component failure) would not prevent control room operators from remotely opening an ADV on the unaffected SG. Failure to meet the LCO can result in an inability to cool the affected unit to SDC System entry conditions when the SBCS is unavailable.ne ADPV line i# required to be OPERABLE on each steam generator to conduct a unit cooldo'n following an event in which one ste gener ......... unavilable.

r becomes a e t meet the LCO cAn -'reslt in the in bilit9, to coo the unit toGnC S;t'em eRntry *cndRitin following an event 4n which the cndenrser iS u6Ravaila-h for uSe w1iththe Steam Bypass Control System.

(continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-6 REVISION 50

ADVs B 3.7.4 BASES LOC An ADV is considered OPERABLE when it is capable of (continued) providing a controlled 'relief of the main steam flow, and is capable of fully opening and closing on demand.

APPLICABILITY In MODES 1, 2, and 3, and in MODE 4, when steam generator a SG is being relied upon for heat removal, the ADVs are required .to be OPERABLE.

In MODES 5 and 6, there is insufficient heat available to produce steam that could be released through the ADVs, and design basis accidents such as main steam line breaks, Feedwater line breaks, and SGTRs are not credible events4-4 SGTR is ,not a credHible envnt.

ACTIONS A.1 The condition for this ACTION is modified by a Note that states separate Condition entry is allowed for each SG. This is acceptable because only one SG is required for RCS heat removal after a design basis accident, and because this Condition provides the appropriate Required Action and Completion Time for one inoperable ADV line on each SG.

When one ADV line on a SG is inoperable, action must be taken to restore that ADV line to OPERABLE status within 7 days to meet the LCO for each SG that has entered this Condition. The 7-day Completion Time takes into consideration the availabilitV of the other ADV line on the same SG, the availability of othe ADV lines on the other SG, the availability of safety grade MSSVs to remove heat; the capability to remove heat via the non-safety grade SBCS to the condenser and/or atmosphere, the low probability of a design basis accident that would require ADV line operation during this time frame, and the ability to use a local manual hand wheel to open and close an ADV that is incapable of being operated remotely. Furthermore, operating experience indicates the 7-day Completion Time is sufficient to restore an inoperable ADV line to OPERABLE status.

The 7-day Completion Time for each SG that has entered this Condition prevents indefinite continued operation while a unit is not in full compliance with the LCO. To meet the LCO, all inoperable ADV lines must be returned to OPERABLE status (continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-7 REVISION 50

ADVs B 3.7.4 BASES for both SGs. Furthermore, operating experience indicates the 7-day Completion Time is sufficient to complete planned inservice testing and maintenance activities that may render one ADV line inoperable on eachSG.Wi-thoe re*. red A*DV line ýinprpable, action must be taken to res the OPERABLE status with-i 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time takes into account the availability of a nonsafety grade backup in the Steam Bypass Ctrol System and MSSVs.

B.1 When both of the ADV lines on one SG are inoperable and there are either one or two OPERABLE ADVs on the second SG, action must be taken to restore one of the two ADV lines on the SG with two inoperable ADV lines to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The 72-hour Completion Time takes into consideration the availability of the ADV lines on the other SG, the availability of safety grade MSSVs to remove heat, the capability to remove heat via the non-safety grade SBCS to the condenser and/or atmosphere, the low probability of a design basis accident that would require ADV operation during this time frame, and the ability to use local manual hand wheels to open and close a ADVs that are incapable of being operated remotely.With two r.equr*ed ADV lines inoperable (one in each steam generator), action must be taken to restore one of the ADV lines to OPERABLE status.

As the block Valve can be clsed to isolate an A\V, some repas may be Possile .* ý 4the unit at power. The 24 hourComleton imeis easonable to repair- inoPpeable APV lies bsed on the avail1abili4ty of the Steam Bypas Conrol1 System and MSSVs, anld the low proGbability of an even~t occurring9 duPrig this period that requires the ADV lines.

C.1 When all four ADV lines (i.e., two on each SG) are inoperable, action must be taken to restore at least one ADV line to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The 24-hour Completion Time takes into consideration the low probability of a design basis accident that would require ADV operation during this time frame, the capability afforded by safety grade MSSVs and the non-safety grade SBSC o remove heat, and the availability of local manual hand wheels that may be used to open and close ADVs that are incapable of being operated remotely.

Some repairs may be possible with a unit at power, because block valves may be closed to operate inoperable ADVs.

(continued)

PALO VERDE UNITS 1,2,3 B 3.7.4-8 REVISION 50

ADVs B 3.7.4 BASES ACTIONS GD.1 and-GD.2 If the ADV lines cannot be restored to OPERABLE status within the associated Completion Time, the unit must be placed in a MODE in which the LCO does not apply. To achieve this status, the unit must be placed in at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and in MODE 4, without reliance on the steam generatorSG for heat removal, within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.

SURVEILLANCE SR 3.7.4.1 REQUIREMENTS To perform a controlled cooldown of the RCS, the ADVs must be able to be opened and throttled through their full range.

This SR ensures the ADVs are tested through a full control cycle at least once per fuel cycle. Performance of inservice testing or use of an ADV during a unit cooldown may satisfy this requirement. Operating experience has shown that these components usually pass the SR when performed at the 18 month Frequency. Therefore, the Frequency is acceptable from a reliability standpoint.

REFERENCES 1. UFSAR, Section 10.3.

PALO VERDE UNITS 1,2,3 B 3.7.4-9 REVISION 50