ML063190323

Supplement to Application for Technical Specification Change Regarding Main Steam Isolation Valves

ML063190323
Person / Time
Site:	Palo Verde
Issue date:	11/03/2006
From:	Mauldin D Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-05590-CDM/SAB/RJR
Download: ML063190323 (32)

Text

10 CFR 50.90 David Mauldin Mail Station 7605 Palo Verde Nuclear Vice President Tel: 623-393-5553 PO Box 52034 Generating Station Nuclear Engineering Fax: 623-393-6077 Phoenix, Arizona 85072-2034 102-05590-CDM/SAB/RJR November 03, 2006 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 Supplement to Application for Technical Specification Change Regarding Main Steam Isolation Valves (LCO 3.7.2)

By letter dated September 26, 2006 (letter no. 102-05574), Arizona Public Service Company (APS) submitted to the NRC an Operating License (OL) amendment request to modify the PVNGS technical specification (TS) requirements for the main steam isolation valves (MSIVs) Limiting Condition for Operation (LCO) 3.7.2 by adding Conditions, Required Actions and Completion Times for the MSIV actuator trains. The NRC published a Notice for the proposed amendment in the October 5, 2006, Federal Register (71 FR 58879).

Telephone discussions with the NRC regarding the September 26, 2006, submittal have identified the need for APS to modify the proposed actuator trains' Actions to remove the proposed Note that would have allowed a separate Condition entry for each MSIV, and to specify additional Actions for multiple inoperable actuator trains. Therefore, APS is submitting, in Enclosure 2, the proposed amendment requested in the September 26, 2006 submittal, but modified with changes to the proposed inoperable actuator trains' Actions. is the notarized affidavit for the proposed amendment.

The proposed amendment is being submitted in whole for ease of NRC review. The no significant hazards consideration determination in the enclosed proposed amendment has not changed from the no significant hazards consideration determination in the original September 26, 2006, application, and therefore is within the scope of the October 5, 2006, Federal Register notice.

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

• Comanche Peak 0 Diablo Canyon 0 Palo Verde

• South Texas Project 0 Wolf Creek

/T o

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Supplement to Application for Technical Specification Change Regarding LCO 3.7.2, Main Steam Isolation Valves Page 2 APS requests approval of the proposed amendment on an expedited basis, with an implementation period of 10 days after approval. The expedited approval date is requested due to the NRC interpretation that was issued on October 19, 2006, stating that a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> MSIV Action must be entered when one MSIV actuator train is inoperable.

Due to this position, if an MSIV actuator should become inoperable, failure to have the amendment would result in a shutdown of the facility without a commensurate safety benefit.

In accordance with the PVNGS Quality Assurance Program, the Plant Review Board and Offsite Safety Review Committee have reviewed and concurred with this proposed amendment. 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).

No commitments are being made to the NRC by this letter. Should you have any questions, please contact Thomas N. Weber at (623) 393-5764.

Sincerely, CDM/SAB/RJR/gt

Enclosures:

. 1. Notarized Affidavit

2. APS' Evaluation of Proposed Change to LCO 3.7.2, Main Steam Isolation Valves Attachments:

1. Proposed Technical Specification Changes (mark-up)

2. Proposed Technical Specification Pages (retyped)

3. Changes to TS Bases Pages cc:

B. S. Mallett NRC Region IV Regional Administrator M. B. Fields NRC NRR Project Manager G. G. Warnick NRC Senior Resident Inspector for PVNGS A. V. Godwin Arizona Radiation Regulatory Agency (ARRA)

T. Morales Arizona Radiation Regulatory Agency (ARRA)

ENCLOSURE 1 NOTARIZED AFFIDAVIT STATE OF ARIZONA

)) SS.

COUNTYOF MARICOPA

)

I, David Mauldin, represent that I am Vice President - Nuclear Engineering, Arizona Public Service Company (APS), that the foregoing document has been signed by me on behalf of APS with full authority to do so, and that to the best of my knowledge and belief, the statements made therein are true and correct.

-David Mauldin Sworn To Before Me This 5)

Day Of 1

, 2006.

OFFICIAL SEAL Christy L. Arter Commission #166400 NOTARY PUBLIC - STATE of ARIZONA MARICOPA COUNTY MY COMM. EXPIRES August 20, 2010 NotarVy blic Notary Commission Stamp E.1-1

ENCLOSURE2 Arizona Public Service Company's Evaluation

Subject:

Proposed Change to LCO 3.7.2, Main Steam Isolation Valves

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration Determination 5.2 Applicable Regulatory Requirements/Criteria 6.0 ENVIRONMENTAL EVALUATION

7.0 REFERENCES

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves

1.0 DESCRIPTION

Pursuant to 10 CFR 50.90, Arizona Public Service Company (APS) hereby requests to amend Operating Licenses 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 3.7.2, "Main Steam Isolation Valves (MSIVs)," to include specific requirements (Conditions, Required Actions, and Completion Times) for the MSIV actuator trains. Additionally, surveillance requirement (SR) 3.7.2.1 will be revised to clearly identify that each MSIV actuator train is required to be tested to support the operability of the associated MSIV.

2.0 PROPOSED CHANGE

Technical Specification 3.7.2 specifies operability and surveillance requirements (SR) for the MSIVs. Currently, these specifications do not address or provide specific requirements (Conditions, Required Actions, and Completion Times) for the MSIV actuator trains. These changes are considered to be necessary based on an NRC staff interpretation that results in declaring an MSIV inoperable with one actuator train inoperable. The completion time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for an inoperable MSIV is not commensurate with the safety significance of a single inoperable actuator train.

Declaring an MSIV inoperable and having to enter the Condition and Required Action for an inoperable valve due to a single inoperable actuator train is unnecessarily restrictive because inoperability of one of the two redundant actuator trains associated with each MSIV does not, by itself, make that valve incapable of closing since the remaining OPERABLE actuator train can effect valve closure on demand. Therefore, APS proposes the following changes to TS 3.7.2:

Limiting condition for operation (LCO) 3.7.2 is revised to include the actuator trains in the LCO and will now require "Four MSIVs and their associated actuator trains shall be OPERABLE."

Five new Conditions A through E are added to TS 3.7.2 to address various configurations of inoperable MSIV actuator trains and the existing Conditions that address inoperable MSIVs are relabeled such that those Conditions would become Conditions F through I. The proposed new Conditions related specifically to the actuator trains would address the various combinations of inoperable actuator trains as follows:

1. New Condition A would address the condition of one MSIV with a single actuator train inoperable. The proposed Required Action for this Condition would require restoring the inoperable actuator train to OPERABLE status within 7 days.

2. New Condition B would address the condition of having two MSIVs each with a single actuator train inoperable such that the inoperable actuator trains are not in the E.2-1

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves same instrumentation train (i.e., one Train A and one Train B). The proposed Required AMtion for this Condition would require restoring at least one actuator train to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

3. New Condition C would address the situation when two MSIVs each with a single actuator train inoperable and both inoperable actuator trains are in the same instrumentation train (i.e., either both actuators are in Train A, or both are in Train B). The proposed Required Action for this Condition would require restoring at least one actuator train to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

4. New Condition D would address the situation when two actuator trains for one MSIV are inoperable (i.e., Train A and Train B). The Required Action proposed for this Condition is to immediately declare the affected valve inoperable. This action requires entry into Condition F (previously Condition A).

5. New Condition E would address the condition of having three or more MSIV actuator trains inoperable or the condition when, after entering Conditions A, B, or C, it is determined that the Required Action and Completion Time of any of those Conditions cannot be met. The Required Action for this Condition is to immediately declare each of the affected valves inoperable. Declaring two or more MSIVs inoperable in MODE 1 requires entry into LCO 3.0.3.

A revision to SR 3.7.2.1, clearly identifies that, each MSIV actuator train is required to, be tested to verify that each actuates the MSIV to the isolation position on an actual or simulated actuation signal.

Proposed revisions to the TS Bases are also included in this application. The changes to the affected TS Bases pages will be incorporated in accordance with TS 5.5.14, Technical Specifications Bases Control Program, after NRC approval of the proposed amendment.

3.0 BACKGROUND

On August 21, 2006, the NRC Project Manager from the Wolf Creek Nuclear Plant communicated to the Wolf Creek licensee that the NRC interpretation of Wolf Creek's SR 3.7.2.2 requires the MSIV actuator trains to be surveillance tested. Since SR 3.0.1 requires SRs to be met, the failure to meet the surveillance, whether such failure is experienced during the performance of the surveillance or between performances of the surveillance, shall be a failure to meet the LCO. Therefore, the failure of an actuator train is a failure to meet the SR, which results in LCO 3.7.2 not being met. The result is an MSIV must be declared inoperable absent any specific Conditions associated with the MSIV actuator trains. This NRC interpretation would apply to Palo Verde due to a similar design.

E.2-2

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves At Palo Verde one MSIV is installed in each of the four main steam lines (2 per steam generator) outside the containment and downstream of the safety valves. The MSIVs prevent uncontrolled blowdown from more than one steam generator in the event of a postulated design basis accident. The MSIVs are 28-inch gate valves with redundant actuator trains (A and B). An actuator train consists of a pneumatic-hydraulic accumulator, an air reservoir, solenoid valves, shuttle valves and the main steam and feedwater isolation system (MSFIS) circuitry. The instrumentation and controls of the train A actuator train are physically and electrically separate and independent of the instrumentation and controls of the train B actuator train. Either actuator train can independently perform the safety function to fast-close the MSIV on demand.

The MSFIS is part of the Engineered Safety Features Actuation System (ESFAS). The MSFIS consists of two independent trains of equipment which provide for the operation of the MSIVs and the economizer Feedwater Isolation Valves (FWIVs). Each MSFIS train has a cabinet of logic which receives handswitch, valve position, and protection system inputs, and which in turn controls solenoid valves. These solenoid valves control MSIV operation.

Each MSFIS train logic cabinet contains the controls for six valve actuator trains: one of the two that is on each of the four MSIVs, and the single actuator train on each of two FWIVs. The MSIVs each have two actuator trains, one driven by Train A MSFIS and one driven by Train B MSFIS. Either actuator train on an MSIV can close the valve independent of the other actuator train. The FWIVs have only one actuator train and are not part of this request.

The MSFIS control logic has one safety function and several auxiliary functions for the valves it controls. The auxiliary functions are manually initiated and are primarily used for testing e.g. fast close, slow close, slow open etc. The safety function is to propagate the Main Steam Isolation Signal (MSIS) from the Auxiliary Relay Cabinets during postulated plant events. The MSIS is generated by either low steam generator pressure, high steam generator level, or high containment pressure. An MSIS in either MSFIS train will cause an unrestricted fast-close of the MSIVs and FWIVs controlled by that train. This will also happen on a loss of 125v DC vital bus power to either MSFIS logic cabinet or on loss of control power from either cabinet to the solenoid valves.

4.0 TECHNICAL ANALYSIS

Consistent with other Technical Specifications, the proposed Completion Times for inoperable MSIV actuator trains are based on a hierarchy of Conditions such that shorter Completion Times are specified for increasingly degraded conditions.

Conditions addressing inoperable actuator trains are specified first in TS 3.7.2, i.e.,

before the Conditions that are currently in place for addressing inoperability of the MSIVs themselves. The intent is that when only an actuator train is declared inoperable, the applicable Condition for the inoperable actuator train would be entered first. Then, as an example, if Condition C is entered and the Required Action and Completion Time cannot be met, the MSIV associated with the inoperable actuator E.2-3

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves trains would be declared inoperable so that the condition addressing inoperability of the MSIV (Condition F, previously Condition A) would be entered.

Justification for the Completion Times to be specified for Required Actions A.1, B.1, and C.1 are provided below:

1. Condition A - For one MSIV with a single actuator train inoperable (i.e., one Train A or Train B), a Completion Time of 7 days for Required Action A.1 is reasonable because of the redundant actuator train design. The affected valves are still capable of closing on demand (assuming no additional failures) using the remaining OPERABLE actuator train. The proposed 7-day Completion Time takes into account the design redundancy, the accident analysis assumption that only 3 of 4 MSIVs close in the accident, a reasonable time for repairs, and the low probability of a design basis accident occurring during this period. Additionally, this Completion Time is consistent with Required Action A.1 of TS 3.7.5, "Auxiliary Feedwater (AFW)

System," which provides a 7-day Completion Time to restore one inoperable steam supply to the turbine driven AFW pump (the turbine driven AFW pump has redundant steam supplies).

2. Condition B - For two MSIVs each with a single actuator train inoperable such that the inoperable actuator trains are not in the same instrumentation train (i.e., one Train A and one Train B), a Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for Required Action B.1 is reasonable. Because of the redundant actuator train design, the affected valve is still capable of closing on demand. The proposed 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 design redundancy and the accident analysis assumption that only 3 of 4 MSIVs close in the accident. Compared to Condition A however, it is appropriate to have a shorter Completion Time for Condition B since, with an actuator train inoperable on each of two MSIVs, there is an increased likelihood that an additional failure (such as the failure of an actuation logic train) would cause an MSIV to fail to close.

3. Condition C - For two MSIVs each with a single inoperable actuator train such that both inoperable actuator trains are in the same instrumentation train (i.e., either both Train A or both Train B), a Completion Time of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> for Required Action C.1 is reasonable. As in the above cases, the redundant actuator train design for each MSIV ensures that a single inoperable actuator train for a valve would not prevent the affected valve from closing on demand. In this regard, 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is reasonable and conservative since only one actuator train per valve is permitted to be inoperable (for two MSIVs), so that the remaining OPERABLE actuator train on each affected MSIV remains capable of effecting valve closure on demand (assuming no additional failures). A Completion Time of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is also considered conservative since only 3 of 4 MSIVs are assumed to close in the accident analyses and the low probability of an event occurring during such an interval that would demand MSIV closure.

E.2-4

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves Additionally, this Completion Time is consistent with Condition D of TS 3.3.6, "Engineered Safety Feature Actuation System (ESFAS) Logic and Manual Trip,"

which provides a 48-hour Completion Time for restoring the inoperable channel to OPERABLE status. Condition D is applicable to Function 5.c of TS 3.3.6, Table 3.3.6-1 (Steam Line lsomation - Automatic Actuation Logic) which provides the actuation logic from the Solid State Protection System through the ESFAS cabinets to the actuator trains. A loss of one actuation logic train would be equivalent to a loss of four actuator trains in the same train.

When compared to the Required Action for Condition B above, a shorter Completion Time for Condition C is appropriate since, with two actuator trains inoperable in the same train, an additional failure such as the failure of an actuation logic train in the other train could cause both affected MSIVs to fail to close on demand.

For Conditions D and E, the Completion Time of "immediately" is conservative and appropriate.

4. Condition D - When two actuator trains for one MSIV are inoperable (i.e., Train A and Train B), it is appropriate to immediately declare the valve inoperable since having both actuator trains inoperable would constitute a condition that renders the affected MSIV incapable of closing on demand.

5. Condition E - When three or more actuator trains are inoperable; it is conservative and appropriate as well to immediately declare the affected MSIVs inoperable for this condition. For the situation of having three actuator trains inoperable, for example, such a condition could involve two inoperable actuator trains on one valve and one inoperable actuator train on another valve, or an inoperable actuator train on each of three valves. In each case, the inoperable actuator trains could all be in the same train or be staggered among the two trains. In the former case, a single assumed failure such as an instrument logic train failure could cause one or two valves to fail to close on demand. In the latter case, such a single failure could cause either none of the valves to fail to close on demand, or all three to fail to close on demand. Thus, immediately declaring the affected MSIVs inoperable is appropriate and conservative. In any case, the conditions addressed by Condition E would constitute an inoperability that exceeds the scope of any of the conditions addressed by Conditions A, B, or C, and it is conservative in this case to simply require declaring all of the affected MSIVs inoperable.

Condition E - When required Action and associated Completion Time of Condition A, B, or C are not met, it follows that the affected MSIV(s) should immediately be declared inoperable since the assumption is that the Completion Time(s) of Condition A, B, or C has expired or cannot be met. This "default" Condition is in keeping with the intent that when only the actuator trains for affected MSIVs are inoperable (and not the valves themselves), the Conditions and Required Actions for the inoperable valve actuator trains should be entered first, and then if those Required Actions cannot be met, the affected MSIVs should be declared inoperable E.2-5

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves so that "he Conditions and Required Actions for the inoperable valves are then entered. This format or approach is consistent with other TSs and the format of the Improved Standard TSs (NUREG-1432).

Required Action E.1 ensures the affected MSIV(s) are promptly declared inoperable.

Also, declaring two or more MSIVs inoperable in MODE 1 requires entry into LCO 3.0.3.

A revision to SR 3.7.2.1 is added to clearly identify that each MSIV actuator train is required to be tested to support the operability of the associated MSIVs.

A probabilistic risk assessment (PRA) was performed to determine the risk associated with Completion Times for single and concurrent inoperable MSIV actuator trains. This evaluation was not used to establish the proposed Completion Times (for proposed Conditions A, B and C), but was used to gauge the acceptability of the Completion Times being proposed, which were based on engineering judgment and consistency with other TSs, as described above. The PRA evaluation used the Regulatory Guide 1.174 and Regulatory Guide 1.177 metrics to determine acceptability of the proposed Completion Times. The following three configurations were modeled:

1. A single actuator train on a single MSIV (associated with Condition A);

2. A single actuator train on two MSIVs on the same steam generator (associated with Conditions B and C);

3. A single actuator train on two MSIVs on opposite steam generators (also associated with Conditions B and C).

In cases 2 and 3 above, the inoperable actuator trains were assumed to be on the same train. This is more limiting than opposite trains, since it makes the train with no inoperable actuator trains more important. Case 2 is associated with mitigation of Steam Generator Tube Rupture. Case 3 is associated with steam line or feedwater line breaks, where one MSIV failing to close on each SG would result in blowing down both SGs. Other success paths are available for all three of the above accidents, so MSIV failures do not necessarily lead to core damage. This is one reason for their very low risk significance. A Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is used in the calculations for each case, even though only 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is being requested for the condition of actuator trains on the same train. This, of course, bounds the results for a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Completion Time.

The risk metrics used to determine the acceptability of this change are those presented in Regulatory Guides 1.174 and 1.177. Regulatory Guide 1.174 provides guidelines for average increase in CDF and LERF from the change. These are 1 E-6/yr for CDF and 1E-7/yr for LERF. Regulatory Guide 1.177 provides guidelines for incremental conditional core damage probability (ICCDP) and incremental conditional large early release probability (ICLERP) for the entire duration of the proposed completion time.

These are 5E-7 for ICCDP and 5E-8 for ICLERP.

E.2-6

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves The following table summarizes the risk values determined for each case modeled:

Risk Metric Case 1 Case 2 Case 3 Delta-CDF 4.0E-8/yr 8.0E-8/yr 8.OE-8/yr ICCDP 7.7E-10 (7 days) 6.6E-10 (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) 6.6E-10 (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />)

Delta-LERF 4.OE-10/yr 8.OE-10/yr 8.OE-10/yr ICLERP 7.7E-12 (7 days) 6.6E-12 (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) 6.6E-12 (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />)

The following conclusions can be drawn:

1. There is no measurable difference between having inoperable accumulators associated with MSIVs on the same SG vs. opposite SGs. This is because the likelihood of failing two MSIVs is still so remote that no MSIV cutsets appear with the steam or feed line break initiators (truncation levels are 1E-11 for CDF and 9E-13 for LERF).

2. The ICCDP and ICLERP values are orders of magnitude below the guidelines in RG 1.177.

3. Since the delta-CDF and delta-LERF values are below the RG 1.174 guidelines, any of these conditions could exist permanently. Thus, any Completion Time imposed is conservative.

There is no additional risk impact from internal flooding or external events. The MSIVs are not involved in mitigation of flooding, fire or earthquakes.

5.0 REGULATORY ANALYSIS

This section addresses the standards of 10 CFR 50.92 as well as the applicable regulatory requirements and acceptance criteria.

5.1 No Significant Hazards Consideration Determination This license amendment request proposes to revise Technical Specification (TS) 3.7.2, "Main Steam Isolation Valves (MSIVs)" to incorporate the MSIV actuator trains into the Limiting Condition for Operation (LCO) and provide associated Conditions and Required Actions. Additionally, Surveillance Requirement (SR) 3.7.2.1 is being revised to clearly identify that each MSIV actuator train is required to be tested to verify that each actuator train actuates the MSIV to the isolation position on an actual or simulated actuation signal. In providing this revised application, Arizona Public Power Company (APS) has determined pursuant to 10 CFR 50.92 that the revised license amendment request does E.2-7

-APS' Evaluation of the Proposed Changes to L.CO 3.7.2, Main Steam Isolation Valves not involve a significant hazards consideration and that the basis for that determination remains unchanged as discussed below:

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

Response

No The proposed changes to incorporate requirements for the MSIV actuator trains do not involve any design or physical changes to the facility, including the MSIVs and actuator trains themselves. The design and functional performance requirements, operational characteristics, and reliability of the MSIVs and actuator trains remain unchanged. Therefore, there is no impact on the design safety function of the MSIVs to close (as an accident mitigator), nor is there any change with respect to inadvertent closure of an MSIV (as a potential transient initiator). Since no failure mode or initiating condition that could cause an accident (including any plant transient) evaluated in the Palo Verde Nuclear Generating Station (PVNGS)

Updated Final Safety Analysis Report (UFSAR) described safety analyses is created or affected, the change cannot involve a significant increase in the probability of an accident previously evaluated.

With regard to the consequences of an accident and the equipment required for mitigation of the accident, the proposed changes involve no design or physical changes to the MSIVs or any other equipment required for accident mitigation. With respect to MSIV actuator train Completion Times, the consequences of an accident are independent of equipment Completion Times as long as adequate equipment availability is maintained. The proposed MSIV actuator train Completion Times take into account the redundancy of the actuator trains, the accident analysis assumption that only 3 of 4 MSIVs close in the accident, and are limited to be consistent with other Completion Times specified in the Technical Specifications. Adequate equipment availability would therefore continue to be required by the Technical

• Specifications. On this basis, the consequences of applicable analyzed accidents (such as a main steam line break) are not significantly impacted by the proposed changes.

Therefore, the proposed changes do 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 changes to incorporate requirements for the MSIV actuator trains do not involve any design or physical changes to the facility, including the MSIVs and actuator trains themselves. No physical alteration of the plant is involved, as no new E.2-8

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves or different type of equipment is to be installed. The proposed changes do not alter any assumptions made in the safety analyses, nor do they involve any changes to plant procedures mechanisms that could cause a new or different kind of accident from any previously evaluated are being introduced.

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

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

Response

No.

The proposed change to incorporate requirements for the MSIV actuator trains does not alter the manner in which safety limits or limiting safety system settings are determined. No changes to instrument/system actuation setpoints are involved.

The safety 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.

==

Conclusion:==

Based on the above evaluation, APS concludes that the proposed amendment presents no 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.

5.2 Applicable Regulatory Requirements/Criteria The regulatory basis for TS 3.7.2, "Main Steam Isolation Valves (MSIVs)," is the isolation of main steam flow from the secondary side of the steam generators following a high energy line break (HELB). Closure of the MSIVs terminates flow from the unaffected (intact) steam generators. The MSIVs prevent uncontrolled blowdown from more than one steam generator. Closing the MSIVs isolates each steam generator from the others, and isolates the turbine, Condenser Steam Dump System, and other auxiliary steam supplies from the steam generators.

The MSIVs isolate nonsafety related portions of the main steam supply system from the safety related portions. In the event of a main steam line break inside containment, the MSIVs close automatically. Closure of the MSIVs ensures that no more than one steam generator can supply the postulated break. The steam line to the auxiliary feedwater pump turbine is connected to a cross-connecting header upstream of the MSIV to ensure a supply of steam to this turbine when the steam generators are isolated.

E.2-9

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves The safety related functions of the MSIV actuator trains are to close an MSIV within the specified time frame and to ensure that no more than one steam generator can supply a postulated break. A single failure of any active component cannot prevent the actuator trains from performing their safety functions. Adding requirements for the MSIV actuator trains provides appropriate limits on out-of-service times for an MSIV actuator train, with consideration given to the redundant actuator train design, while also assuring adequate availability. At the same time, it also provides operability requirements appropriate to the MSIV actuator trains without having to unnecessarily or prematurely declare an MSIV inoperable when an actuator train is inoperable and thus have to take action that is unnecessarily restrictive. This also avoids an unnecessary transient and plant shutdown minimizing potential safety consequences and operational risks.

The portion of the main steam supply system from the steam generators to the MSIVs is safety related and is required to function following a design basis accident (DBA), and to achieve and maintain the plant in a safe shutdown condition.

Applicable General Design Criterion (GDC):

GDC 2, "Design bases for protection against natural phenomena," requires that the safety related portion of the Main Steam Supply System and Condensate and Feedwater 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 Main Steam Supply System and Condensate and Feedwater System be designed to remain functional after a safe shutdown earthquake or to perform its intended function following postulated hazards such as internal missiles, or pipe break.

GDC 34, "Residual heat removal," requires that component redundancy be provided for the Main Steam Supply System and Condensate Feedwater System so that safety functions can be performed, assuming a single active component failure coincident with the loss of offsite power.

The proposed TS change does not affect the MSIVs or the associated actuator train design and compliance with the above regulatory requirements and criteria. Therefore, 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 approval of the proposed change will not be inimical to the common defense and security or to the health and safety of the public.

E.2-10

-APS' Evaluation of the Proposed Changes to LCO 3.7.2, Main Steam Isolation Valves 6.0 ENVIRONMENTAL EVALUATION APS has evaluated the proposed amendment and determined that the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or 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 change 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 change.

7.0 REFERENCES

On June 16, 2006, a similar change, Callaway Plant, - License Amendment to add the actuator trains to LCO 3.7.2 on MSIVs (TAC NO. MC7212) was approved. The differences between Callaway Amendment No. 172 and the APS request are:

APS is requesting a longer Completion Time for new Condition A.

APS has made a revision to Surveillance Requirement 3.7.2.1 to verify each actuator train actuates the MSIV to the isolation position on an actual or simulated signal.

" The Palo Verde MSIVs are designed to fail-closed.

The Palo Verde safety analysis assumes one MSIV fails to close.

On August 25, 2006, Wolf Creek Nuclear Operating Corporation submitted letter WM06-0033, "Docket No. 50-482: Revision to Technical Specification (TS) 3.7.2, 'Main Steam Isolation Valves (MSIVs),' and TS 3.7.3, 'Main Feedwater Isolation Valves (MFIVs),'"

requesting similar changes as proposed by APS. The differences between the Wolf Creek request and the APS request are:

E

• A longer Completion Time for new Condition C.

• The Palo Verde MSIVs are designed to fail-closed.

• APS' request is for the MSIVs only.

E.2-11 Proposed Technical Specification Changes (mark-up)

Pages:

3.7.2-1 3.7.2-2

MSIVs 3.7.2 3.7 PLANT SYSTEMS 3.7.2 Main Steam Isolation Valves (MSIVs)

LCO 3.7.2 Four MSIVs shall be OPERABLE.

APPLICABILITY:

MODE 1, MODES 2, 3, and 4 except when all MSIVs are closed and deactivated.

ACTIONS

__EURDACINCMLEINTM

=

COND=ITION REQUIRED ACTION COMPLETION TIME Restore MSIV to OPERABLE status.

4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 4

• 1 Required Action and Associated Completi Time of Condition A not met.

ýr Be in MODE 2.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> NOTE------

( Separate Condition entry is allowed for each MSIV.

AND Close MSIV.

Verify MSIV is closed.

4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Once per 7 days One or more MSIVs inoperable in MODE 2, 3, or 4.

Required Action and associated Completi Time of Condition" not met.

P Be in MODE 3.

Be in MODE 5.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 36 hours

)

AMENDMENT NO.(ý PALO VERDE UNITS 1,2,3 3.7.2-1

Insert fo, TS 3.7.2 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One MSIV with a single A.1 Restore MSIV actuator 7 days actuator train inoperable train to OPERABLE status B. Two MSIVs each with a B.1 Restore one MSIV 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> single actuator train actuator train to inoperable such that the OPERABLE status.

inoperable actuator trains are not in the same instrumentation train.

C. Two MSIVs each with a C.1 Restore one MSIV 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> single actuator train actuator train to inoperable and both OPERABLE status.

inoperable actuator trains are in the same instrumentation train.

D. Two actuator trains for D.1 Declare the affected Immediately one MSIV inoperable.

MSIV inoperable.

E. Three or more MSIV E. 1 Declare each affected Immediately actuator trains MSIV inoperable.

inoperable.

OR Required Action and associated Completion Time of Condition A, B, or C not met.

MSIVs 3.7.2 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.2.1 NOTE---------------

Not required to be performed prior to entry into MODE 3.

Verify closure time of each MSIV is In accordance

_< 4.6 seconds on an actual or simulated with the actuation signal.

Inservi ce Testing Program PALO VERDE UNITS 1,2,3 3.7.2-2 AMENDMENT NO.,+e-Proposed Technical Specification Changes (Re-typed))

Pages:

3.7.2-1 3.7.2-2 3.7.2-3

MSIVs 3.7.2 3.7 PLANT SYSTEMS 3.7.2 Main Steam Isolation Valves (MSIVs)

LCO

3.7.2 APPLICABILITY

Four MSIVs and their associated actuator trains shall be OPERABLE.

MODE 1, MODES 2, 3, and 4 except when all MSIVs are closed and deactivated.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One MSIV with a single A.1 Restore MSIV actuator 7 days actuator train train to OPERABLE status inoperable.

B. Two MSIVs each with a B.1 Restore one MSIV actuator 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> single actuator train train to OPERABLE status inoperable such that the inoperable trains are not in the same instrumentation train.

C. Two MSIVs each with a C.1 Restore one MSIV actuator 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> single actuator train train to OPERABLE status inoperable and both inoperable actuator trains are in the same instrumentation train.

D. Two actuator trains D.1 Declare the affected MSIV Immediately for one MSIV inoperable.

inoperable.

(continued)

PALO VERDE UNITS 1,2,3 3.7.2-1 AMENDMENT NO.4-5,9,

MSIVs 3.7.2 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME E.

Three or more MSIV E.1 Declare each affected Immediately actuator trains MSIV inoperable.

inoperable.

OR Required Action and associated Compl eti on Time of Condition A, B, or C not met.

F. One MSIV inoperable in F.1 Restore MSIV to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> MODE 1.

OPERABLE status.

G. Required Action and G.1 Be in MODE 2.

6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Associated Completion Time of Condition F not met.

H.--------NOTE--------

H.1 Close MSIV.

4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Separate Condition entry is allowed for AND each MSIV.

H.2 Verify MSIV is Once per 7 days closed.

One or more MSIVs inoperable in MODE 2, 3, or 4.

I.

Required Action and 1.1 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 of Condition H AND not met.

1.2 Be in MODE 5.

36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> PALO VERDE UNITS 1,2,3 3.7.2-2 AMENDMENT NO. ;4-ý,

MSIVs 3.7.2 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.7.2.1

---

NOTE----------------

Not required to be performed prior to entry into MODE 3.

Verify closure time of each MSIV is In accordance

! 4.6 seconds with each actuator train on with the an actual or simulated actuation signal.

Inservice Testing Program PALO VERDE UNITS 1,2,3 3.7.2-3 AMENDMENT NO.

Changes to Technical Specification Bases Pages Pages:

B 3.7.2-1 B 3.7.2-3 B 3.7.2-4 B 3.7.2-5 B 3.7.2-6

c~.Lx~(~

MSIVs B 3.7.2 B 3.7 PLANT SYSTEMS B 3.7.2 Main Steam Isolation Valves (MSIVs)

BASES BACKGROUND The MSIVs isolate steam flow steam generators following a MSIV closure terminates flow steam generator.

from High from the secondary side of the Energy Line Break (HELB).

the unaffected (intact)

One MSIV is located in each main steam line outside, but close to, containment.

The MSIVs are downstream from the Main Steam Safety Valves (MSSVs),

atmospheric dump valves, and auxiliary feedwater pump turbine steam supplies to prevent their being isolated from the steam generators by MSIV closure.

Closing the MSIVs isolates each steam generator from the other, and isolates the turbine, Steam Bypass Control System, and other auxiliary steam supplies from the steam generators.

The MSIVs close on a main steam isolation signal generated by either low steam generator pressure, high steam generator level or high containment pressure.

The MSIVs fail closed on loss of control or actuation power.

The MSIS also actuates the Main Feedwater Isolation Valves (MFIVs) to close.

The MSIVs may also be actuated manually.

A description of the MSIVs is found in the FSAR, Section 10.3 (Ref. 1).

APPLICABLE SAFETY ANALYSES The design basis of the MSIVs is established by the containment analysis for the large steam line break (SLB) inside containment, as discussed in the CESSAR, Section 6.2 (Ref. 2).

It is also influenced by the accident analysis of the SLB events presented in the UFSAR, Section 15.1.5 (Ref. 3).

The design precludes the blowdown of more than one steam generator, assuming a single active component failure (e.g., the failure of one MSIV to close on demand).

The limiting case for the containment analysis is the hot zero power SLB inside containment with a loss of offsite power following turbine trip, and failure of the MSIV on the affected steam line to close.

At zero power, the steam generator inventory and temperature are at their maximum, (continued)

PALO VERDE UNITS 1,2,3 B 3.7.2-1 REVISION,-4--"

MSIVs B 3.7.2 BASES APPLICABLE SAFETY ANALYSES (continued) main steam header downstream of the closed MSIVs in the intact loops.

b.

A break outside of containment and upstream from the MSIVs.

This scenario is not a containment pressurization concern.

The uncontrolled blowdown of more than one steam generator must be prevented to limit the potential for uncontrolled RCS cooldown and positive reactivity addition.

Closure of the MSIVs isolates the break, and limits the blowdown to a single steam generator.

c.

A break downstream of the MSIVs.

This type of break will be isolated by the closure of the MSIVs.

Events such as increased steam flow through the turbine or the steam bypass valves will also terminate on closure of the MSIVs.

d.

A steam generator tube rupture.

For this scenario, closure of the MSIVs isolates the affected steam generator from the intact steam generator.

In addition to minimizing radiological releases, this enables the operator to maintain the pressure of the steam generator with the ruptured tube high enough to allow flow isolation while remaining below the MSSV setpoints, a necessary step toward isolating the flow through the rupture.

e.

The MSIVs are also utilized during other events such as a feedwater line break.

These events are less limiting so far as MSIV OPERABILITY is concerned.

The MSIVs satisfy Criterion 3 of 10 CFR 50.36 (c)(2)(ii).

LCO This LCO requires that the MSIVkin each of the four steam lines be OPERABLE.

The MSIVs are considered OPERABLE when the isolation times are within limits, and they close on an isolation actuation signal m*V ay re-an]-,_

This LCO provides assurance that the MSIVs will perform their design safety function to mitigate the consequences of accidents that could result in offsite exposures comparable to the 10 CFR 100 (Ref. 4) limits.

(continued)

REVISION-4I--

PALO VERDE UNITS 1,2,3 B 3.7.2-3

MSIVs B 3.7.2 BASES (continued)

APPLICABILITY The MSIVs must be OPERABLE in MODE 1 and in MODES 2, 3 and 4 except when all MSIVs are closed and deactivated when there is significant mass and energy in the RCS and steam generators.

When the MSIVs are closed, they are already performing their safety function.

In MODES 5 and 6, the steam generators do not contain much energy because their temperature is below the boiling point of water; therefore, the MSIVs are not required for isolation of potential high energy secondary system pipe breaks in these MODES.

ACTIONS

/1 With one MSIV inoperable in MODE 1, time is allowed to restore the component to OPERABLE status.

Some repairs can jAAjey*--)

I be made to the MSIV with the unit hot.

The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Completion Time is reasonable, considering the probability of an accident occurring during the time period that would require closure of the MSIVs.

The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Completion Time is consistent with that normally Tallowed for containment isolation valves that isolate a closed system penetrating containment.

These valves differ from other containment isolation valves in that the closed system provides an additional means for containment isolation.

(continued)

PALO VERDE UNITS 1,2,3 B 3.7.2-4 REVISION-8-ýý

MSIVs B 3.7.2 BASES (continued)

ACTIONS (continued)

If the MSIV cannot be restored to OPERABLE within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, 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 MODE 2 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Condition(would be entered.

The Completion Time is reasonable, base, on operating experience, to reach MODE 2, and clhose the MSIVs in an orderly manner and without challenging unit systems.

H H

n

,r 1and Z.

Condition s modified by a Note indicating that separate Condition entry is allowed for each MSIV.

Since the MSIVs are required to be OPERABLE in MODES 2 and 3, the inoperable MSIVs may either be restored to OPERABLE status or closed.

When closed, the MSIVs are already in the position required by the assumptions in the safety analysis.

The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Completion Time is consistent with that allowed in Condi tion*ý' F Inoperable MSIVs that cannot be restored to OPERABLE status within the specified Completion Time, but are closed, must be verified on a periodic basis to be closed.

This is necessary to ensure that the assumptions in the safety analysis remain valid.

The 7 day Completion Time is reasonable, based on engineering judgment, MSIV status indications available in the control room, and other administrative controls, to ensure these valves are in the closed position.

I Lan4do If the MSIVs cannot be restored to OPERABLE status, or closed, 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 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

(continued)

PALO VERDE UNITS 1,2,3 B 3.7.2-5 REVISIONA"ý'

MSIVs B 3.7.2 BASES (continued)

ACTIONS 0.9i andU2* (continued)

The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from MODE 2 conditions in an orderly manner and without challenging unit systems.

SURVEILLANCE REOUIREMENTS SR 3.7.2.1 acd-h ecct C~~~AIc:;tY-10-v-.

This SR)rifies that the closure time of each MSIV is

• 4.6 seconds" on an actual or simulated actuation signal.

The MSIV closure time is assumed in the accident and containment analyses.

This SR is normally performed upon returning the unit to operation following a refueling outage.

The MSIVs should not be full stroke tested at power.

The Frequency for this SR is in accordance with the Inservice Testing Program.

This Frequency demonstrates the valve closure time at least once per refueling cycle.

This test is conducted in MODE 3, with the unit at operating temperature and pressure, as discussed in the Reference 5 exercising requirements.

This SR is modified by a Note that allows entry into and operation in MODE 3 prior to performing the SR.

This allows a delay of testing until MODE 3, in order to establish conditions consistent with those under which the acceptance criterion was generated.

REFERENCES

1.

UFSAR, Section 10.3.

2.

CESSAR, Section 6.2.

3.

UFSAR, Section 15.1.5.

4.

10 CFR 100.11.

5.

ASME, Boiler and Pressure Vessel Code,Section XI, Inservice Inspection, Article IWV-3400.

PALO VERDE UNITS 1,2,3 B 3.7.2-6 REVISION 0

TS Bases Insert "A" The MSIV is a 28-inch gate valve with redundant hydraulic actuator trains. The actuation system is composed of redundant trains A and B. The instrumentation and controls of the train A valve actuator trains are physically and electrically separate and independent of the instrumentation and control of the train B valve actuator trains.

Either actuator train can independently perform the safety function to fast-close the MSIV on demand. Each actuator train consists of a hydraulic accumulator controlled by solenoid valves on the associated MSIV.

Insert "B" An MSIV actuator train is considered OPERABLE when it is capable of fast-closing the associated MSIV on demand and within the required isolation time. This includes having adequate accumulator pressure to support fast-closure of the MSIV within the required isolation time and adequate air pressure available to fast close the MSIV.

Insert "C" The MSIV actuator trains must be OPERABLE in MODES 1, 2, 3 and 4 to support operation of the MSIV.

Insert "D" The LCO specifies OPERABILITY requirements for the MSIVs as well as for their associated actuator trains. The Conditions and Required Actions for TS 3.7.2 separately address inoperability of the MSIV actuator trains and inoperability of the MSIVs themselves.

A.1 With one MSIV with a single actuator train inoperable (i.e., one Train A or one Train B),

action must be taken to restore the inoperable actuator train to OPERABLE status within 7 days. The 7-day Completion Time is reasonable in light of the redundant actuator train design such that with one actuator train inoperable, the affected MSIV is still capable of closing on demand via the remaining OPERABLE actuator train. The 7-day Completion Time takes into account the redundant OPERABLE actuator train to the MSIV, reasonable time for repairs, and the low probability of an event occurring that requires the inoperable actuator train to the affected MSIV.

B.1 With two MSIVs each with a single actuator train inoperable such that the inoperable actuator trains are not in the same train (i.e., one Train A and one Train B), action must be taken to restore one of the inoperable actuator trains to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. With two actuator trains inoperable on two MSIVs, there is an increased likelihood that an additional failure (such as the failure of an actuation logic train) could cause one MSIV to fail to close. The 72-hour Completion Time is reasonable since the redundant actuator train design ensures that with only one actuator train on each of two affected MSIVs inoperable, each MSIV is still capable of closing on demand.

C.1 With two MSIVs each with a single actuator train inoperable and the inoperable actuator trains are both in the same train (i.e., both Train A, or both Train B), action must be taken to restore one of the inoperable actuator trains to OPERABLE status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The 48-hour Completion Time provides a reasonable amount of time for restoring at least one actuator train since the redundant actuator train design for each MSIV ensures that a single inoperable actuator train cannot prevent the affected MSIV(s) from closing on demand. With two actuator trains inoperable in the same separation group, an additional failure (such as the failure of an actuation logic train in the other separation group) could cause both affected MSIVs to fail to close on demand.

The 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Completion Time takes into the redundant OPERABLE actuator trains to the affected MSIVs and the low probability of an event occurring that requires the inoperable actuator trains to the affected MSIVs.

D.1 With two actuator trains for one MSIV are inoperable, Required Action D.1 provides assurance that the appropriate Action is entered for one MSIV inoperable. Failure of both actuator trains for a single MSIV results in the inability to fast close the affected MSIV on demand.

E. 1 With three or more MSIV actuator trains inoperable or when Required Action A.1, B.1, or C.1 cannot be completed within the required Completion Time; the affected MSIVs may be incapable of closing on demand and must be immediately declared inoperable.

Having three actuator trains inoperable could involve two inoperable actuator trains on one MSIV and one inoperable actuator train on another MSIV, or an inoperable actuator train on each of three MSIVs, for which the inoperable actuator trains could all be in the same separation group or be staggered among the two separation groups.

Depending on which of these conditions or combinations is in effect, the condition or combination could mean that all of the affected MSIVs remain capable of closing on demand (due to the redundant actuator train design), or that at least one MSIV is

inoperable, or that with an additional single failure up to three MSIVs could be incapable of closing on demand. Therefore, in some cases, immediately declaring the affected MSIVs inoperable is conservative (when some or all of the affected MSIVs may still be capable of closing on demand even with a single additional failure), while in other cases it is appropriate (when at least one of the MSIVs would be inoperable, or up to three could be rendered inoperable by an additional single failure). Required Action E.1 is conservatively based on the worst-case condition and therefore requires immediately declaring all the affected MSIVs inoperable. Declaring two or more MSIVs inoperable while in MODE 1 requires entry into LCO 3.0.3.

Insert "E" Condition F is entered when one MSIV is inoperable in MODE 1, including when both actuator trains for one MSIV are inoperable. When only one actuator train is inoperable on one MSIV, Condition A applies.