L-MT-18-006, Application to Revise Technical Specifications to Adopt TSTF-551, Revision 3, Revise Secondary Containment Surveillance Requirements

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Application to Revise Technical Specifications to Adopt TSTF-551, Revision 3, Revise Secondary Containment Surveillance Requirements
ML18187A400
Person / Time
Site: Monticello Xcel Energy icon.png
Issue date: 07/03/2018
From: Church C
Northern States Power Company, Minnesota, Xcel Energy
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-18-006, TSTF-551, Rev 3
Download: ML18187A400 (18)
v • d • e


Text

2807 West County Road 75 Monticello, MN 55362 (l Xcel Energy*

RES PO N S I BL E BY NAT U RE 800.895.4999 xcelenergy.com July 3, 2018 L-MT-18-006 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 Application to Revise Technical Specifications to Adopt TSTF-551, Revision 3, "Revise Secondary Containment Surveillance Requirements" Pursuant to 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," the Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), requests an amendment to the Technical Specifications (TS) for the Monticello Nuclear Generating Plant (MNGP). The proposed change revises MNGP Specification 3.6.4.1, "Secondary Containment," Surveillance Requirement (SR) 3.6.4.1.1.

The SR is revised to address conditions during which the secondary containment pressure may not meet the SR pressure requirements. In addition, SR 3.6.4.1.3 is modified to acknowledge that secondary containment access openings may be open for entry and exit.

Enclosed is a description and assessment of the proposed TS changes. The enclosure also provides the no significant hazards consideration evaluation in accordance with 10 CFR 50.92, "Issuance of Amendment," and the Environmental Assessment. These provide the bases for the conclusion that the license amendment request involves no significant hazards consideration and meets the eligibility criterion for a categorical exclusion as set forth in 10 CFR 51.22, "Criteria for categorical exclusion; identification of licensing and regulatory actions eligible for categorical exclusion or otherwise not requiring environmental review,"

specifically paragraph (c)(9). to the enclosure provides the existing TS pages marked up to show the proposed changes. Attachment 2 to the enclosure provides the revised (clean) TS pages. to the enclosure provides TS Bases pages marked up to show the associated TS Bases changes and is provided for information only.

Document Control Desk Page 2 NSPM requests approval of this proposed amendment by August 6, 2019. Once approved, the amendment will be implemented within 90 days.

In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"

paragraph (b), NSPM is notifying the State of Minnesota by providing a copy of this application, with the enclosure and attachments, to the designated State Official.

If additional information is needed, please contact Mr. Richard Loeffler at (612) 342-8981.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

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

Executed on July fi, 2018.

hristopher R. Church Site Vice President - Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc: Administrator, Region Ill, US NRC Project Manager, Monticello Nuclear Generating Plant, US NRC Resident Inspector, Monticello Nuclear Generating Plant, US NRC State of Minnesota

ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT Evaluation of the Proposed Change LAR: Application to Revise Technical Specifications to Adopt TSTF-551, Revision 3, "Revise Secondary Containment Surveillance Requirements"

1.0 DESCRIPTION

2.0 ASSESSMENT 2.1 Applicability of Published Safety Evaluation 2.2 Variations 2.3 Facility Description 2.4 Appendix A General Design Criteria Versus MNGP Principal Design Criteria

3.0 REGULATORY ANALYSIS

3.1 No Significant Hazards Consideration Analysis 3.2 Conclusions 4.0 ENVIRONMENTAL EVALUATION ATTACHMENTS:

1. Technical Specification Pages (Markup)
2. Technical Specification Pages (Retyped)
3. Technical Specification Bases Pages (Markup - for information only)

L-MT-18-006 NSPM Enclosure Application to Revise Technical Specifications to Adopt TSTF-551, Revision 3, "Revise Secondary Containment Surveillance Requirements"

1.0 DESCRIPTION

The proposed change revises Monticello Nuclear Generating Plant (MNGP) Specification 3.6.4.1, "Secondary Containment," SuNeillance Requirement (SR) 3.6.4.1.1. The SR is revised to address conditions during which the secondary containment pressure may not meet the SR pressure requirements. In addition, SR 3.6.4.1.3 is modified to acknowledge that secondary containment access openings may be open for entry and exit.

2.0 ASSESSMENT 2.1 Applicability of Published Safety Evaluation Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), has reviewed the final model safety evaluation provided to the Technical Specifications Task Force (TSTF) in a letter dated September 21, 2017 (ADAMS Package Accession No. ML17236A365). This review included a review of the NRC staff's evaluation, as well as the information provided in TSTF-551. NSPM has concluded that the justifications presented in TSTF-551 and the safety evaluation prepared by the NRC staff is applicable to MNGP and justify this amendment for incorporation of the proposed changes to the MNGP Technical Specifications (TS).

The most recent radiological consequence analysis for the MNGP was for the AREVA fuel transition approved by the NRC as Amendment 188 on June 5, 2015 (Accession No. ML15072A141), and is documented in the MNGP Updated Safety Analysis Report (USAR)

Subsection 14.7.2.4. NSPM has confirmed that the brief, inadvertent, simultaneous opening of both an inner and outer personnel access door during normal entry and exit conditions, and their prompt closure by normal means, is bounded by the radiological dose consequence analysis. In the unlikely event that an accident would occur when both personnel access doors are open for entry or exit, the brief time required to close one of the doors is small compared to the 5 minute (300 seconds) positive pressure period assumed in the accident analysis for reducing the post-accident secondary containment pressure to 0.25 inch of vacuum water gauge and will not result in an increase in any onsite or offsite dose.

2.2 Variations NSPM is proposing the following variations from the TS changes described in the TSTF-551 or the applicable parts of the NRC staff's safety evaluation. These variations do not affect the applicability of TSTF-551 or the NRC staff's model safety evaluation to the proposed license amendment.

Page 1 of 6

L-MT-18-006 NSPM Enclosure

[GDC] for Nuclear Power Plants." The MNGP was designed and constructed to comply with NSPM's understanding of the intent of the Atomic Energy Commission (AEC) 70 proposed GDCs for Nuclear Power Plant Construction Permits, proposed for public comment in July 1967. The equivalent MNGP specific Principal Design Criteria to the referenced GDCs are discussed in Subsection 2.4 below. These differences do not alter the conclusion that the proposed change is applicable to the MNGP.

  • The final model safety evaluation for TSTF-551 discusses that the NRC staff review determined that there are two design basis accidents that take credit for the secondary containment and are possibly impacted by the brief, inadvertent, and simultaneous opening of both an inner and outer access door during normal entry and exit conditions:

the loss of coolant accident (LOCA) and the fuel handling accident (FHA) in secondary containment. The MNGP FHA does not credit the secondary containment for the mitigation of FHAs occurring beyond 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following reactor shutdown. However, the ability to use these systems to mitigate a FHA beyond this time period has been retained as a defense in depth measure. This difference does not alter the conclusion that the proposed change is applicable to the MNGP.

2.3 Facility Description MNGP is a single unit plant located on the south bank of the Mississippi River in the city of Monticello, Minnesota. The facility is owned and operated by NSPM. The plant is a single cycle, forced circulation, low power density boiling water reactor, designed and supplied by the General Electric Corporation. Construction of the MNGP started on June 19, 1967, with initial fuel loading completed during the fall of 1970. Full power commercial operation began on June 30, 1971 under Provisional Operating License No. DPR-22. The Full Term Operating License was issued on January 9, 1981. The MNGP Renewed Facility Operating License expires at midnight September 8, 2030.

2.4 Appendix A General Design Criteria Versus MNGP Principal Design Criteria The MNGP was not licensed to the 10 CFR 50, Appendix A, GDC. The MNGP was designed and constructed to comply with NSPM's understanding of the intent of the AEC 70 proposed GDCs for Nuclear Power Plant Construction Permits. Also, the MNGPs design predates NUREG-0800, "Standard Review Plan" (SRP). The 10 CFR 50, Appendix A, GDC criterion is presented first below followed by the corresponding criteria from the 70 draft AEC GDCs provided for comparison. The applicable Principal Design Criteria (PDC) from the MNGP USAR Subsection 1.2.4, "Plant Containment", are then presented for comparison.

Page 2 of 6

L-MT-18-006 NSPM Enclosure 10 CFR 50, Appendix A, GDC Criterion 16, "Containment design," states:

Reactor containment and associated systems shall be provided to establish an essentially leak-tight barrier against the uncontrolled release of radioactivity to the environment and to assure that the containment design conditions important to safety are not exceeded for as long as postulated accident conditions require.

The corresponding AEC draft GDC Criterion 10, "Containment (Category A)," states:

Containment shall be provided. The containment structure shall be designed to sustain the initial effects of gross equipment failures, such as a large coolant boundary area, without loss of required integrity and, together with other engineered safety features as may be necessary to retain for as long as the situation requires the functional capability to protect the public.

10 CFR 50, Appendix A, GDC Criterion 19, "Control room," states:

A control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including loss-of-coolant accidents. Adequate radiation protection shall be provided to permit access and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 5 rem whole body, or its equivalent to any part of the body, for the duration of the accident.

The corresponding AEC draft GDC Criterion 11, "Control Room (Category B)," states:

The facility shall be provided with a control room from which action to maintain safe operational status of the plant can be controlled. Adequate radiation protection shall be provided to permit access, even under accident conditions, to equipment in the control room or other areas as necessary to shut down and maintain safe control to the facility without radiation exposures of personnel in excess of 10 CFR 20 limits. It shall be possible to shut the reactor down and maintain it in a safe condition if access the control room is lost due to fire or other causes.

Meeting the intent of the 10 CFR 50, Appendix A GDCs is supported by the design of the plant to the General Electric PDC stated below from MNGP USAR Subsection 1.2.4, "Plant Containment".

c. The reactor building, encompassing the primary containment system, provides the secondary containment when the primary containment is closed and in service, and provides primary containment when the primary containment system is open and the containment function is required.
d. . .. Provision is also made for demonstrating the functional integrity of the secondary containment system.

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L-MT-18-006 NSPM Enclosure

e. The integrity of the complete plant containment system and such other associated engineered safeguards as may be necessary are designed and maintained so that offsite and Control Room operator doses resulting from postulated design basis accidents are below the values stated in 10 CFR 50.67.

The 10 CFR 50, Appendix A GDCs, the AEC 70 draft GDCs, and the MNGP PDCs, while worded differently, are equivalent in that the reactor (primary and secondary) containment and associated systems are required to provide an essentially leak-tight barrier against the uncontrolled release of radioactivity to the environment, and the doses resulting from postulated design basis accidents are not to exceed regulatory limits, i.e., currently 10 CFR 50.67, "Accident source term," for the MNGP. These differences in presentation do not alter the conclusion that the proposed change is applicable to the MNGP.

3.0 REGULATORY ANALYSIS

3.1 No Significant Hazards Consideration Analysis Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), requests adoption of Technical Specification Task Force (TSTF) traveler TSTF-551, "Revise Secondary Containment Surveillance Requirements," which is an approved change to the Standard Technical Specifications (STS), into the Monticello Nuclear Generating Plant (MNGP) Technical Specifications (TS). The proposed change revises TS Surveillance Requirement (SR) 3.6.4.1.1. The SR is revised to permit conditions during which the secondary containment may not meet the SR acceptance criterion for a period of up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> if an analysis demonstrates that one Standby Gas Treatment (SGT) subsystem remains capable of establishing the required secondary containment vacuum. In addition, SR 3.6.4.1.3 is modified to acknowledge that secondary containment access openings may be open for entry and exit.

NSPM has evaluated the proposed change against the criteria of 10 CFR 50.92, "Issuance of amendment," to determine if the proposed change results in any significant hazards. The following is the evaluation of each of the 10 CFR 50.92(c) criteria:

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

Response: No The proposed change addresses conditions during which the secondary containment SRs are not met. The secondary containment is not an initiator of any accident previously evaluated. As a result, the probability of any accident previously evaluated is not increased. The consequences of an accident previously evaluated while utilizing the proposed changes are no different than the consequences of an accident while utilizing the existing four hour Completion Time for an inoperable secondary Page 4 of 6

L-MT-18-006 NSPM Enclosure containment. In addition, the proposed Note for SR 3.6.4.1.1 provides an alternative means to ensure the secondary containment safety function is met. As a result, the consequences of an accident previously evaluated are not significantly increased.

Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

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 change does not alter the protection system design, create new failure modes, or change any modes of operation. The proposed change does not involve a physical alteration of the plant and no new or different kind of equipment will be installed. Consequently, there are no new initiators that could result in a new or different kind of accident.

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 addresses conditions during which the secondary containment SR is not met. Conditions in which the secondary containment vacuum is less than the required vacuum are acceptable provided the conditions do not affect the ability of the SGT System to establish the required secondary containment vacuum under post-accident conditions within the time assumed in the accident analysis. This condition is incorporated in the proposed change by requiring an analysis of actual environmental and secondary containment pressure conditions to confirm the capability of the SGT System is maintained within the assumptions of the accident analysis.

Therefore, the safety function of the secondary containment is not affected. The allowance for both an inner and outer secondary containment door to be open simultaneously for entry and exit does not affect the safety function of the secondary containment as the doors are promptly closed after entry or exit, thereby restoring the secondary containment boundary.

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

Based on the above evaluation, NSPM 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.

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L-MT-18-006 NSPM Enclosure 3.2 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.

4.0 ENVIRONMENTAL EVALUATION The proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, "Standards for Protection Against Radiation," or would change an inspection or surveillance requirement.

However, 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 amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22, "Criteria for categorical exclusion; identification of licensing and regulatory actions eligible for categorical exclusion or otherwise not requiring environmental review," specifically paragraph (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.

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L-MT-18-006 NSPM ATTACHMENT 1 MONTICELLO NUCLEAR GENERATING PLANT APPLICATION TO REVISE TECHNICAL SPECIFICATIONS TO ADOPT TSTF-551, REVISION 3, "REVISE SECONDARY CONTAINMENT SURVEILLANCE REQUIREMENTS" TECHNICAL SPECIFICATION PAGE (Markup) 1 page follows

Secondary Containment 3.6.4.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.6.4.1.1 ------------------------------NOTE-------------------------------

Not required to be met for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> if analysis demonstrates one standby gas treatment (SGT) subsystem is capable of establishing the required secondary containment vacuum.

Verify secondary containment vacuum is::: 0.25 inch 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of vacuum water gauge.

SR 3.6.4.1.2 Verify all secondary containment equipment hatches 31 days are closed and sealed.

31 days SR 3.6.4.1.3 Verify one secondary containment access door in each access opening is closed, except when the access opening is being used for entry and exit.

SR 3.6.4.1.4 Verify the secondary containment can be maintained 24 months on a

0.25 inch of vacuum water gauge for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> using STAGGERED one SGT subsystem at a flow rate~ 4000 cfm. TEST BASIS for each SGT subsystem Monticello 3.6.4.1-2 Amendment No. 44e.,__ I

L-MT-18-006 NSPM ATTACHMENT 2 MONTICELLO NUCLEAR GENERATING PLANT APPLICATION TO REVISE TECHNICAL SPECIFICATIONS TO ADOPT TSTF-551, REVISION 3, "REVISE SECONDARY CONTAINMENT SURVEILLANCE REQUIREMENTS" TECHNICAL SPECIFICATION PAGE (Retyped) 1 page follows

Secondary Containment 3.6.4.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.6.4.1.1 ------------------------------NOTE-------------------------------

Not required to be met for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> if analysis demonstrates one standby gas treatment (SGT) subsystem is capable of establishing the required secondary containment vacuum.

Verify secondary containment vacuum is ::c: 0.25 inch 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of vacuum water gauge.

SR 3.6.4.1.2 Verify all secondary containment equipment hatches 31 days are closed and sealed.

31 days SR 3.6.4.1.3 Verify one secondary containment access door in each access opening is closed, except when the access opening is being used for entry and exit.

SR 3.6.4.1.4 Verify the secondary containment can be maintained 24 months on a

c: 0.25 inch of vacuum water gauge for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> using STAGGERED one SGT subsystem at a flow rates 4000 cfm. TEST BASIS for each SGT subsystem Monticello 3.6.4.1-2 Amendment No. 4-4e, _ I

L-MT-18-006 NSPM ATTACHMENT 3 MONTICELLO NUCLEAR GENERATING PLANT APPLICATION TO REVISE TECHNICAL SPECIFICATIONS TO ADOPT TSTF-551, REVISION 3, "REVISE SECONDARY CONTAINMENT SURVEILLANCE REQUIREMENTS" TECHNICAL SPECIFICATION BASES PAGES (Markup)

(Provided for Information Only) 4 pages follow

Secondary Containment B 3.6.4.1 BASES ACTIONS (continued)

C.1 and C.2 Movement of recently irradiated fuel assemblies in the secondary containment and OPDRVs can be postulated to cause significant fission product release to the secondary containment. In such cases, the secondary containment is the only barrier to release of fission products to the environment. Therefore, movement of recently irradiated fuel assemblies must be immediately suspended if the secondary containment is inoperable.

Suspension of these activities shall not preclude completing an action that involves moving a component to a safe position. Also, action must be immediately initiated to suspend OPDRVs to minimize the probability of a vessel draindown and subsequent potential for fission product release.

Actions must continue until OPDRVs are suspended.

Required Action C.1 has been modified by a Note stating that LCO 3.0.3 is not applicable. If moving recently irradiated fuel assemblies while in MODE 4 or 5, LCO 3.0.3 would not specify any action. If moving recently irradiated fuel assemblies while in MODE 1, 2, or 3, the fuel movement is independent of reactor operations. Therefore, in either case, inability to suspend movement of recently irradiated fuel assemblies would not be a sufficient reason to require a reactor shutdown.

SURVEILLANCE SR 3.6.4.1.1 INSERT A REQUIREMENTS This SR ensures that the secondary containment boundary is suffi leak tight to preclude exfiltration under expected wind conditions.

24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Frequency of this SR was developed based on operating experience related to secondary containment vacuum variations during the applicable MODES and the low probability of a DBA occurring.

Furthermore, the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Frequency is considered adequate in view of other indications available in the control room, including alarms, to alert the operator to an abnormal secondary containment vacuum condition.

SR 3.6.4.1.2 and SR a.6.4 .1.a Verifying that secondary containment equipment hatches and one access door in each access opening 3re closed ensures that the infiltration of outside air of such a magnitude as to prevent maintaining the desired negative pressure does not occur Verifying that all such openings are eleseG provides adequate assura e that exfiltration from the secondary and Monticello B 3.6.4.1-3 Revision No. ~

Secondary Containment B 3.6.4.1 BASES SURVEILLANCE REQUIREMENTS (continued) containment will not occur. In this application, the term "sealed" has no connotation of leak tightness. Maintaining secondary containment OPERABILITY requires verifying one door in the access opening is closed. An access opening contains one inner and one outer door. In some oases, secondary containment access openings are shared such that a secondary containment barrier may have multiple inner or multiple outer doors. The intent is to not breach the secondary containment at any time *uhen seoondarf containment is required. This is achieved by maintaining tho inner or outer portion of tho barrier closed at all times.

Ho*.ve','er, all secondary containment access doors are normally kept closed, except when tho access opening is being used for entry and e:x:it or when maintenance is being performed on an access opening. The 31 day Frequency for tAese Rs has been shown to be adequate, based on operating experience, an *s considered adequate in view of the other SR 3.6.4.1.3 hi.ndications of door and hatch s tus that are available to the operator.

IL..:,._(I_N_S_E_R_T_B-'--)_ ___.I ~ this SR 3.6.4.1.4 The SGT System exhausts the secondary containment atmosphere to the environment through appropriate treatment equipment. To ensure that all fission products released to the secondary containment are treated, SR 3.6.4.1.4 verifies that a pressure in the secondary containment that is less than the lowest postulated pressure external to the secondary containment boundary can be maintained. When the SGT System is operating as designed, the maintenance of secondary containment pressure cannot be accomplished if the secondary containment boundary is not intact. SR 3.6.4.1.4 demonstrates that the pressure in the secondary containment can be maintained ~ 0.25 inches of vacuum water gauge for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> using one SGT subsystem at a flow rate :5 4000 cfm.

The 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> test period allows secondary containment to be in thermal equilibrium at steady state conditions. The primary purpose of this SR is to ensure secondary containment boundary integrity. The test is normally performed under calm wind (< 5 mph) conditions. If calm wind conditions do not exist during this testing, the test data is to be corrected to calm wind conditions. The secondary purpose of this SR is to ensure that the SGT subsystem being tested functions as designed. There is a separate LCO with Surveillance Requirements which serves the primary purpose of ensuring OPERABILITY of the SGT System. This SR need not be performed with each SGT subsystem. The SGT subsystem used for this Surveillance is staggered to ensure that in addition to the requirements of LCO 3.6.4.3, either SGT subsystem will perform this test. The in operability of the SGT System does not necessarily constitute a failure Monticello B 3.6.4.1-4 Revision No. ~

Secondary Containment B 3.6.4.1 BASES SURVEILLANCE REQUIREMENTS (continued) of this Surveillance relative to the secondary containment OPERABILITY.

Operating experience has shown the secondary containment boundary usually passes this Surveillance when performed at the 24 month Frequency. Therefore, the Frequency was concluded to be acceptable from a reliability standpoint.

REFERENCES 1. USAR, Section 14.7.2.

2. USAR, Section 14.7.6.

j3. Procedure 0151-01.

j4. Calculation 04-043.

Monticello B 3.6.4.1-5 -bast Revision No. ~

L-MT-18-006 -TSTF-551 LAR TS BASES INSERTS SR 3.6.4.1.1 --- INSERT A The SR is modified by a Note which states the SR is not required to be met for up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> if an analysis demonstrates that one SGT subsystem remains capable of establishing the required secondary containment vacuum. The ability of one SGT subsystem to maintain secondary containment vacuum is demonstrated by the capability test (Reference 3). Reference 4 provides the analysis that the SGT System can restore secondary containment vacuum within the five minute Positive Pressure Period assumed in the LOCA dose analysis. Use of the Note is expected to be infrequent but may be necessitated by situations in which secondary containment vacuum may be less than the required containment vacuum, such as, but not limited to, wind gusts or failure or change of operating normal ventilation subsystems. These conditions do not indicate any change in the leak tightness of the secondary containment boundary. The analysis should consider the actual conditions (equipment configuration, temperature, atmospheric pressure, wind conditions, measured secondary containment vacuum, etc.) to determine whether, if an accident requiring secondary containment to be OPERABLE were to occur, one subsystem of SGT could establish the assumed secondary containment vacuum within the time assumed in the accident analysis. If so, the SR may be considered met for a period of up to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> limit is based on the expected short duration of the situations when the Note would be applied.

SR 3.6.4.1.3 --- INSERT 8 Verifying that one secondary containment access door in each access opening is closed provides adequate assurance that exfiltration from the secondary containment will not occur. An access opening contains at least one inner and one outer door. In some cases, secondary containment access openings are shared such that there are multiple inner or outer doors. The intent is to not breach the secondary containment, which is achieved by maintaining the inner or outer portion of the barrier closed except when the access opening is being used for entry and exit.

The 31 day Frequency for this SR has been shown to be adequate, based on operating experience, and is considered adequate in view of the other indications of door status that are available to the operator.

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