NL-24-0217, License Amendment Request: Source Range Neutron Flux Doubling Function Applicability

License Amendment Request: Source Range Neutron Flux Doubling Function Applicability

ML24306A131
Person / Time
Site:	Vogtle
Issue date:	11/01/2024
From:	Coleman J Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
NL-24-0217
Download: ML24306A131 (1)

Text

A Southern Nuclear November 1, 2024 Docket Nos.52-025 52-026 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Regulatory Affairs Vogtle Electric Generating Plant Units 3 and 4 License Amendment Request:

3535 Colonnade Parkway Birmingham, AL 35243 Tel 205.992.5000 NL-24-0217 10 CFR 50.90 Source Range Neutron Flux Doubling Function Applicability Pursuant to 10 CFR 52.98(c) and in accordance with 10 CFR 50.90, Southern Nuclear Operating Company (SNC) requests an amendment to the combined license (COL) for Vogtle Electric Generating Plant (VEGP) Units 3 and 4 (License Numbers NPF-91 and NPF-92, respectively) to remove the Mode 2 applicability for the Source Range Neutron Flux Doubling instrumentation as required by Technical Specification 3.3.8, Engineered Safety Feature Actuation System (ESFAS) Instrumentation, Table 3.3.8-1, Function 17, and administratively, adds a missing dash in the name of Function 22.

These changes were previously discussed with the NRC Staff during a public conference call on June 17, 2024 (ADAMS Accession Number ML24165A192). SNC has incorporated information into the request to address topics discussed during the above call.

The Enclosure to this letter provides the description, technical evaluation, regulatory evaluation (including the significant hazards consideration) and environmental considerations for the proposed licensing basis changes.

SNC requests NRC staff review and approval of this license amendment request no later than twelve months from acceptance. Delayed approval of this license amendment subjects the plant personnel and the NRC Staff to additional regulatory burden. SNC expects to implement the proposed amendment within sixty days of issuance.

This letter contains no regulatory commitments. This letter has been reviewed and determined not to contain security-related information.

In accordance with 10 CFR 50.91, SNC is notifying the State of Georgia by transmitting a copy of this letter and its enclosures to the designated State Official.

If you have any questions, please contact Mr. Ryan Joyce at (205) 992-6468.

U. S. Nuclear Regulatory Commission NL-24-0217 Page 2 I declare under penalty of perjury that the foregoing is true and correct.

Executed on the 1st of November 2024.

Respectfully submitted,

~MWIAM Jamie M. Coleman Director, Regulatory Affairs Southern Nuclear Operating Company

Enclosure:

Evaluation of Proposed Changes cc:

NRC Regional Administrator, Region II NRR Project Manager - Vogtle 3&4 Senior Resident Inspector - Vogtle 3&4 Director, Environmental Protection Division - State of Georgia Document Services RTYPE: VND.LI.L00

ENCLOSURE TO NL-24-0217 Evaluation of Proposed Changes License Amendment Request:

Source Range Neutron Flux Doubling Function Applicability

1.

SUMMARY

DESCRIPTION

2.

DETAILED DESCRIPTION 2.1 System Design and Operation 2.2 Current Technical Specification Requirements 2.3 Reason for Proposed Change 2.4 Description of Proposed Change

3.

TECHNICAL EVALUATION

4.

REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 Significant Hazards Consideration 4.4 Conclusions

5.

ENVIRONMENTAL CONSIDERATION Attachments: 1 :

2:

3:

Technical Specification Marked-up Pages Revised Technical Specification Pages Technical Specification Bases Markups (for information only)

Enclosure to NL-24-0217 Evaluation of Proposed Changes

1.

SUMMARY

DESCRIPTION Southern Nuclear Operating Company (SNC) requests an amendment to the combined license (COL) for Vogtle Electric Generating Plant (VEGP) Units 3 and 4 (License Numbers NPF-91 and NPF-92, respectively). The proposed license change removes the Mode 2 applicability for the Source Range Neutron Flux Doubling instrumentation as required by Technical Specification (TS) 3.3.8, Engineered Safety Feature Actuation System (ESFAS)

Instrumentation, Table 3.3.8-1, Function 17, and administratively, adds a missing dash in the name of Function 22.

2. DETAILED DESCRIPTION 2.1 System Design and Operation As discussed in Updated Final Safety Analysis Report (UFSAR) Subsection 7.3.1.2.14, Boron Dilution Block, an excessive increasing rate of source range neutron flux doubling signal accomplishes a block of the boron dilution by closing the chemical and volume control system (CVS) makeup isolation valves and closing the makeup pump suction valves to the demineralized water storage tanks. This signal also provides a non-safety trip of the makeup pumps. These actions terminate the supply of potentially unborated water to the reactor coolant system as quickly as possible.

In the event of a loss of ac power sources (identified as low input voltage in UFSAR Subsection 15.4.6.2.5) or a reactor trip (as indicated by the P-4 interlock), the block of boron dilution is accomplished by closing the makeup pump suction valves to the demineralized water storage tanks and aligning the boric acid tank to the suction of the makeup pumps. This permits makeup as needed from a borated source that will not reduce the available shutdown margin in the reactor core.

The flux doubling condition is an average of the source range count rate, compared to a similar average taken at an earlier time. If the ratio of the current average count rate to the earlier average count rate is greater than a preset value, a partial trip is generated in the division. On a coincidence of excessively increasing source range neutron flux in two of the four divisions, boron dilution is blocked. The flux doubling function is also delayed from actuating each time the source range detector's high voltage power is energized to prevent a spurious dilution block due to the short-term instability of the processed source range values. This source range neutron flux doubling signal may be manually blocked to permit plant startup and normal power operation when reactor coolant average temperature is above the P-8 interlock setpoint. It is automatically reinstated when reactor power is decreased below the P-6 interlock power level during shutdown or reactor coolant average temperature decreases below the P-8 interlock setpoint.

Below the P-6 setpoint, the source range neutron flux detectors are automatically energized and the source range neutron flux doubling actuation of the boron dilution block and CVS isolation function is automatically reinstated. Above the P-10 setpoint, the source range neutron flux doubling actuation of the boron dilution block and CVS isolation is automatically blocked and the source range neutron flux detectors are de-energized. Above the P-6 setpoint and below the P-10 setpoint, automatic source range E-2

Enclosure to NL-24-0217 Evaluation of Proposed Changes neutron flux doubling actuation of the boron dilution block and CVS isolation functions can be manually blocked or manually unblocked.

The source range neutron flux doubling function can also be manually blocked during shutdown conditions when below the P-8 setpoint. Prior to manually blocking the source range neutron flux doubling function, the operator isolates unborated water source flow paths, thereby exiting the Applicability as required by Table 3.3.8-1, Function 17 Footnote U) applied to Modes 4 and 5 and Footnote (i) applied to Mode 3. When blocked during shutdown conditions, an automatic close signal is also sent to the CVS demineralized water system isolation valves to prevent boron dilution.

2.2 Current Requirements Technical Specification 3.3.8, Engineered Safety Feature Actuation System (ESFAS)

Instrumentation, Table 3.3.8-1, Function 17, Source Range Neutron Flux Doubling instrumentation, is required to be operable in Modes 2 and 3 with the unborated water source flow paths not isolated except when critical or except during intentional approach to criticality, and in Modes 4 and 5 with the unborated water source flow paths not isolated.

2.3 Reason for the Proposed Change For VEGP Unit 3 and Unit 4, the Source Range Neutron Flux Doubling instrumentation is not credited for accident mitigation in Mode 2 (see UFSAR Subsection 15.4.6.2.5) nor does it meet any of the other criteria of 10 CFR 50.36 for inclusion in the Technical Specifications. Furthermore, the Source Range Neutron Flux Doubling is blocked in accordance with operating procedures prior to entering Mode 2 on startup and not reenergized until exiting Mode 2 during a shutdown. Additionally, Function 22, Steam Generator Narrow Range Water Level High is missing a dash before the "High" designation.

2.4 Description of Proposed Change Technical Specification 3.3.8, Engineered Safety Feature Actuation System (ESFAS)

Instrumentation, Table 3.3.8-1, Engineered Safeguards Actuation System Instrumentation, is proposed to be revised to remove Mode 2, as modified by Footnote (i), from the Applicability column for Function 17, Source Range Neutron Flux Doubling. Related to this change, Footnote (i) is proposed to be modified by removing the phrase "except when critical or" from the foot note which currently reads "with unborated water source flow paths not isolated except when critical or except during intentional approach to criticality."

No changes are proposed for the Source Range Neutron Flux Doubling Function for Mode 3, 4 or 5, or for any other Source Range Functions. No hardware or logic changes are proposed.

Additionally, in Table 3.3.8-1, Function 22, is edited to include a missing dash in the name to read: "SG Narrow Range Water Level - High" consistent with its use in the Bases and other Function names.

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Enclosure to NL-24-0217 Evaluation of Proposed Changes A markup showing the proposed licensing basis document revision is provided in. Attachment 3 markup also shows related changes to the Technical Specification Bases document which will be implemented along with the proposed amendment to the Technical Specifications. The Bases changes are provided for information only.

3. TECHNICAL EVALUATION The UFSAR Subsection 15.4.6 describes the boron dilution event analysis. In particular, Subsection 15.4.6.2.5 describes the boron dilution considerations during startup (Mode 2) as follows "This mode of operation is a transitory operational mode in which the operator intentionally dilutes and withdraws control rods to take the plant critical. During this mode, the plant is in manual control. For a normal approach to criticality, the operator manually withdraws control rods and dilutes the reactor coolant with unborated water at controlled rates until criticality is achieved. Once critical, the power escalation is slow enough to allow the operator to manually block the source range reactor trip after receiving the P-6 permissive signal from the intermediate range detectors (nominally at 105 cps). Too fast a power escalation (due to an unknown dilution) would result in reaching P-6 unexpectedly, leaving insufficient time to manually block the source range reactor trip. Failure to perform this manual action results in a reactor trip and immediate shutdown of the reactor."

This UFSAR (Section 15.0, Table 15.0-6) identifies several reactor trips available to mitigate a Mode 2 boron dilution event. These reactor trips continue to be required in Mode 2 below the P-6 interlock by TS 3.3.1, Reactor Trip System (RTS) Instrumentation, and TS 3.3.2, Reactor Trip System Source Range Instrumentation, and by TS 3.3.3, Reactor Trip System (RTS) Intermediate Range Instrumentation, above the P-6 interlock. The flux doubling function to isolate the boron dilution is not modeled in the Mode 2 safety analysis specifically to determine the time before the loss of shutdown margin would occur, i.e., approximately 205 minutes as noted in UFSAR Subsection 15.4.6.2.5 and Table 15.4-1. This time frame is based on the power range high neutron flux-low setpoint reactor trip (TS 3.3.1 ).

Further, the current TS for Function 17 in Modes 2 and 3 are modified by a footnote that allows bypass of the flux doubling function during an intentional approach to criticality and when critical. As noted in TS 3.3.8, Table 3.3.8-1, footnote "i", the signal to block boron dilution on source range neutron flux doubling is not required in Mode 2 or Mode 3 when the reactor is critical or when an intentional approach to criticality is in progress." In practice, the bypass occurs above the P-8 and P-6 interlocks while in Mode 3 and prior to pulling rods or dilution for the purpose of initiating the intentional approach to criticality. Thus, Function 17 is bypassed during Mode 2 operation and requiring Function 17 to be operable in Mode 2 serves no purpose.

In the Westinghouse Standard Technical Specification (STS), NUREG-1431 (revision 5),

TS 3.3.9 addresses the Boron Dilution Protection System (BOPS) and requires operability of the source range neutron flux doubling instrumentation. The STS includes optional Mode 2 applicability for the BOPS and includes the following statement in the associated Bases Applicability discussion.

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Enclosure to NL-24-0217 Evaluation of Proposed Changes The BOPS OPERABILITY requirements are not applicable in MODE[S] 1 [and 2]

because an inadvertent boron dilution would be terminated by a source range trip, a trip on the Power Range Neutron Flux - High (low setpoint nominally 25% RTP),

or Overtemperature b. T.

For example, for Vogtle Units 1 and 2, the boron dilution event protection is provided by TS 3.3.8, "High Flux at Shutdown Alarm (HFASA)," which is applicable only in Modes 3, 4 and 5. As indicated in the Vogtle Units 1 and 2 TS Bases, "In MODES 1 and 2, operators are alerted to an unplanned dilution event by a reactor trip on overtemperature delta-Tor power range neutron flux high, low setpoint, respectively. "

For Vogtle Units 3 and 4, these same RTS Functions are discussed in, and required in Mode 2 by, TS 3.3.1, RTS Instrumentation," (for a reactor trip on the Power Range Neutron Flux - High or Overtemperature b. T functions) and TS 3.3.2, "Reactor Trip System (RTS)

Source Range Instrumentation," (for a reactor trip on the source range monitors).

The Vogtle Units 3 and 4 TS Bases do not address each individual Function or Mode but generally indicate only that the ESFAS instrumentation (including Function 17) satisfies Criterion 3 of 10 CFR 50.36(c)(2)(ii). The instrumentation does not meet Criterion 1, 2 or 4 in that it: 1) is not used to detect and indicate a significant abnormal degradation of the reactor coolant pressure boundary; 2) is not an initial condition of a design basis accident or transient analysis in Mode 2, and 3) neither operating experience or probabilistic risk assessment has shown the instrumentation to be significant to public health and safety in Mode 2. The proposed change does not change the function of the related systems, and no design change or revisions to plant operating procedures are required to support this change.

10 CFR 50.36(c)(2)(ii)(C) Criterion 3 indicates that an LCO is required for a structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier. As discussed above, the source range neutron flux doubling function (Function 17) is not part of the primary success path for a Mode 2 boron dilution event (as discussed in UFSAR Subsection 15.4.6.2.5), nor does it function or actuate to mitigate a design basis accident or transient in Mode 2. Thus, the Mode 2 Applicability for Function 17 does not meet Criterion 3 of 10 CFR 50.36 and can be removed from the Technical Specifications.

With Mode 2 removed, and because the plant is not critical in Mode 3, the footnote associated with Mode 3 need not discuss an exception for "when critical." Thus, the footnote is proposed to be revised to omit the exception for "when critical."

The additional change to Table 3.3.8-1, Function 22, is an administrative change to edit the Function name to read: "SG Narrow Range Water Level - High" (i.e., add hyphen) so that it is consistent with its use in the Bases and other Function names.

E-5

Enclosure to NL-24-0217 Evaluation of Proposed Changes 4

REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria General Design Criterion 13-Instrumentation and control of 10 CFR Part 50, Appendix A, requires "Instrumentation shall be provided to monitor variables and systems over their anticipated ranges for normal operation, for anticipated operational occurrences, and for accident conditions as appropriate to assure adequate safety, including those variables and systems that can affect the fission process, the integrity of the reactor core, the reactor coolant pressure boundary, and the containment and its associated systems. Appropriate controls shall be provided to maintain these variables and systems within prescribed operating ranges." The source range neutron flux doubling function is not required in Mode 2 to provide adequate safety for anticipated operational occurrences or accident conditions. The source range neutron flux doubling function continues to be required to provide the necessary protection in other Modes to maintain these variables and systems within prescribed operating ranges.

General Design Criterion 20-Protection system functions of 10 CFR Part 50, Appendix A, requires "The protection system shall be designed (1) to initiate automatically the operation of appropriate systems including the reactivity control systems, to assure that specified acceptable fuel design limits are not exceeded as a result of anticipated operational occurrences and (2) to sense accident conditions and to initiate the operation of systems and components important to safety." The source range neutron flux doubling function is not required to be operable in Mode 2 for the PMS protection function to satisfy GDC 20. The source range neutron flux doubling function continues to be required to provide the necessary protection in other Modes to satisfy GDC 20.

10 CFR 50.36(c)(2)(ii)(C) Criterion 3 indicates that an LCO is required for a structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier. As discussed above, the source range neutron flux doubling function (TS Table 3.3.8-1, Function 17) for Mode 2 is not part of the primary success path for a boron dilution event (as discussed in UFSAR Subsection 15.4.6.2.5), nor does it function or actuate to mitigate a design basis accident or transient.

Thus, General Design Criteria 13 and 20, and 10 CFR 50.36 continue to be met without requiring operability of the source range neutron flux doubling function in Mode 2.

4.2 Precedent None.

4.3 Significant Hazards Consideration Southern Nuclear Operating Company (SNC) is requesting an amendment to Combined License (COL) Nos. NPF-91 and NPF-92 for Vogtle Electric Generating Plant (VEGP)

Unit 3 and Unit 4. The proposed license change would remove the Mode 2 applicability for the Source Range Neutron Flux Doubling instrumentation as required by Technical E-6

Enclosure to NL-24-0217 Evaluation of Proposed Changes Specification 3.3.8, Engineered Safety Feature Actuation System (ESFAS)

Instrumentation, Table 3.3.8-1, Function 17.

An evaluation to determine whether or not a significant hazards consideration is involved with the proposed amendment was completed by focusing on the three standards set forth in 10 CFR 50.92(c), "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 change involves removal of a requirement which is not considered in the initiation or mitigation of an accident evaluated in the safety analysis. Therefore, the proposed change does not result in any increase in probability of an analyzed accident occurring. The proposed change does not involve a change to any mitigation systems or features or the predicted radiological releases due to postulated accident conditions. Thus, the consequences of the accidents previously evaluated are not adversely affected.

Therefore, the proposed reporting schedule 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 involve a change to any structure, system or component and does not change the function of the related systems, and thus, the change does not introduce a new or different kind of accident from any previously evaluated.

Therefore, the proposed reporting schedule change will 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 continues to provide the required functional capability of the safety systems for previously evaluated accidents and anticipated operational occurrences. The proposed change does not change the function of the related systems nor significantly affect the margins provided by the systems. No safety analysis or design basis acceptance limit/criterion is challenged or exceeded by the requested reporting schedule change.

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

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Enclosure to NL-24-0217 Evaluation of Proposed Changes Based on the above, it is concluded 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.

4.4 Conclusions 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. Therefore, it is concluded that the requested 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.

5 ENVIRONMENTAL CONSIDERATION A review has determined that the proposed changes require an amendment to the COL. A review of the anticipated operational effects of the requested amendment has determined that the requested amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9), in that 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.

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NL-24-0217 ATTACHMENT 1 Technical Specification Marked-up Pages Insertions denoted by underlined Blue text and deletions by Red strikethrough Omitted text is identified by three asterisks ( * * * )

(This enclosure consists of 3 pages, including this cover page)

Technical Specification Table 3.3.8-1 (page 2 of 2)

ESFAS Instrumentation 3.3.8 Engineered Safeguards Actuation System Instrumentation APPLICABLE MODES OR OTHER SPECIFIED FUNCTION CONDITIONS

15. Core Makeup Tank (CMT) Level - Low 3 1,2,3,4(b) 4(d),5(h)

16. CMT Level - Low 6 1,2,3,4(b) 4(d),5(h)(n)

17. Source Range Neutron Flux Doubling

~14,3(il,4ul

50)

18. I RWST Lower Narrow Range - Low 3 1,2,3,4(b) 4(d),5(n) 5(g)(n)

19. Reactor Coolant Pump Bearing Water 1,2,3,4 Temperature - High 2

20. SG Narrow Range Water Level - Low 2 1,2,3,4(b)

21. SG Wide Range Water Level - Low 2 1,2,3,4(b)

22. SG Narrow Range Water Level = High 1,2,3,4

23. SG Narrow Range Water Level - High 3 1,2 3,4

24. Steam Line Pressure - Low 2 1,2,3(c)(l)(m)

25. Steam Line Pressure - Negative Rate - High 3(k)

(b) With the RCS not being cooled by the Normal Residual Heat Removal System (RNS).

(c) Above the P-11 (Pressurizer Pressure) interlock.

(d) With the RCS being cooled by the RNS.

(g) With upper internals in place.

(h) With RCS not VENTED.

REQUIRED CHANNELS CONDITIONS 4 per tank F

4 per OPERABLE J

tank 4 per tank F

4 per OPERABLE J

tank 4

4 4

F 4

M 4

N 4 per RCP 0

4 per SG F

4 per SG F

4 per SG 4 per SG D

4 per SG 4 per steam line G

4 per steam line (i) With unborated water source flow paths not isolated e*ee13t wi'len eFitieal OF except during intentional approach to criticality U) With unborated water source flow paths not isolated (k) Below the P-11 (Pressurizer Pressure) interlock when Steam Line Pressure - Low 2 is blocked.

(I) Below the P-11 (Pressurizer Pressure) interlock and RCS boron concentration is less than that necessary to meet the SOM requirements at an RCS temperature of 200°F.

(m) Below the P-11 (Pressurizer Pressure) interlock when Steam Line Pressure - Low 2 is not blocked.

(n) For Unit 3 only, not required to be OPERABLE prior to initial criticality.

VEGP Units 3 and 4 3.3.8 - 8 Amendment No. 4W (Unit 3)

Amendment No. 447 (Unit 4)

NL-24-0217 ATTACHMENT 2 Revised Technical Specification Pages (This enclosure consists of 2 pages, including this cover page)

Technical Specifications ESFAS Instrumentation 3.3.8 Table 3.3.8-1 (page 2 of 2)

Engineered Safeguards Actuation System Instrumentation APPLICABLE MODES OR OTHER SPECIFIED REQUIRED FUNCTION CONDITIONS CHANNELS CONDITIONS

15.

Core Makeup Tank (CMT) Level - Low 3 1,2,3,4(b) 4 per tank 4(d), 5(h) 4 per OPERABLE tank

16.

CMT Level - Low 6 1,2,3,4(b) 4 per tank 4(dl, 5(h)(n) 4 per OPERABLE tank

17.

Source Range Neutron Flux Doubling 3(i),40) 4 50l 4

18.

IRWST Lower Narrow Range Level - Low 3 1,2,3,4(b) 4 4(d), 5(n) 4 5(g)(n) 4

19.

Reactor Coolant Pump Bearing Water 1,2,3,4 4 per RCP Temperature - High 2

20.

SG Narrow Range Water Level - Low 2 1,2,3,4(b) 4 per SG

21.

SG Wide Range Water Level - Low 2 1,2,3,4(b) 4 per SG

22.

SG Narrow Range Water Level - High 1,2,3,4 4 per SG

23.

SG Narrow Range Water Level - High 3 1,2 4 per SG 3,4 4 per SG

24.

Steam Line Pressure - Low 2 1,2,3(c)(l)(m) 4 per steam line

25.

Steam Line Pressure - Negative Rate - High 3(k) 4 per steam line (b) With the RCS not being cooled by the Normal Residual Heat Removal System (RNS).

(c) Above the P-11 (Pressurizer Pressure) interlock.

(d) With the RCS being cooled by the RNS.

(g) With upper internals in place.

(h) With RCS not VENTED.

(i) With unborated water source flow paths not isolated except during intentional approach to criticality.

U) With unborated water source flow paths not isolated.

(k) Below the P-11 (Pressurizer Pressure) interlock when Steam Line Pressure - Low 2 is blocked.

F J

F J

F M

N 0

F F

D G

(I) Below the P-11 (Pressurizer Pressure) interlock and RCS boron concentration is less than that necessary to meet the SOM requirements at an RCS temperature of 200°F.

(m) Below the P-11 (Pressurizer Pressure) interlock when Steam Line Pressure - Low 2 is not blocked.

(n) For Unit 3 only, not required to be OPERABLE prior to initial criticality.

VEGP Units 3 and 4 3.3.8 - 8 Amendment No.

Amendment No.

(Unit 3)

(Unit 4)

NL-24-0217 ATTACHMENT 3 Technical Specification Bases Markups (for information only)

Insertions denoted by underlined Blue text and deletions by Red strikethrough Omitted text is identified by three asterisks ( * * * )

(This enclosure consists of 2 pages, including this cover page) to NL-24-0217 Technical Specification Bases Markups (for information only)

VEGP Units 3 and 4 Technical Specification BASES Markups (for information only):

Technical Specifications Bases B 3.3.8, Engineered Safeguards Actuation System Instrumentation APPLICABLE SAFETY ANALYSES, LCOs, and APPLICABILITY

17. Source Range Neutron Flux Doubling The source range neutron detectors are used for this Function. A signal to block boron dilution is derived from source range neutron flux increasing at an excessive rate (source range neutron flux doubling). The LCO requires four divisions to be OPERABLE. There are four divisions and two-out-of-four logic is used. On a coincidence of excessively increasing source range neutron flux in two of the four divisions, demineralized water is isolated (CVS demineralized water system isolation valves closed) from the makeup pumps and reactor coolant makeup is isolated (CVS makeup line isolation valves closed) from the reactor coolant system to preclude a boron dilution event.

The Boron Dilution Block ESFAS protective function is actuated by Source Range Neutron Flux Doubling.

The signal to block boron dilution on source range neutron flux increasing at an excessive rate (source range neutron flux doubling) must be OPERABLE in MODE 2 and MODE 3 if unborated water source flow paths are not isolated except. However, the signal to block boron dilution on source range flux doubling is not required in MODE 2 or MODE 3 when the reactor is critical or when an intentional approach to criticality is in progress. It must also be OPERABLE in MODES 4 and 5 if unborated water flow paths are not isolated. In MODE 6, a dilution event is precluded by the requirement in LCO 3.9.2 to close, lock and secure at least one valve in each unborated water source flow path.

Above the P-6 setpoint the source range detectors can be manually deenergized and above the P-10 setpoint they are automatically deenergized. OPERABILITY of the Source Range Neutron Flux Doubling Function requires the source range neutron flux detectors to be energized.

When the Source Range Neutron Flux Doubling feature is blocked below P-8, an automatic close signal is sent to both valves in the CVS demineralized water flow path to ensure a single failure does not reestablish this potential dilution flow path.