NRC-19-0002, Application to Revise Technical Specifications to Adopt TSTF-564, Safety Limit MCPR

Application to Revise Technical Specifications to Adopt TSTF-564, Safety Limit MCPR

ML19039A126
Person / Time
Site:	Fermi
Issue date:	02/08/2019
From:	Polson K DTE Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC-19-0002
Download: ML19039A126 (23)

Text

Keith J. Polson Senior Vice President and CNO DTE Energy Company 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.6515 Fax: 734.586.1431 Email: keith.polson@dteenergy.com February 8, 2019 10 CFR 50.90 NRC-19-0002 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Fermi 2 Power Plant NRC Docket No. 50-341 NRC License No. NPF-43

Subject:

Application to Revise Technical Specifications to Adopt TSTF-564, Safety Limit MCPR Pursuant to 10 CFR 50.90, DTE Electric Company (DTE) is submitting a request for an amendment to the Technical Specifications (TS) for Fermi Unit 2 (Fermi 2).

DTE requests adoption of TSTF-564, "Safety Limit MCPR," Revision 2, which is an approved change to the Improved Standard Technical Specifications (ISTS), into the Fermi 2 Technical Specifications (TS). The proposed amendment revises the Technical Specification (TS) safety limit (SL) on minimum critical power ratio (MCPR) to reduce the need for cycle-specific changes to the value while still meeting the regulatory requirement for an SL. provides a description and assessment of the proposed changes. provides the existing TS pages marked to show the proposed changes. provides revised (clean) TS pages. Enclosure 4 provides existing TS Bases pages marked to show the proposed changes for information only.

No regulatory commitments are made in this submittal.

Approval of the proposed amendment is requested by February 5, 2020. Once approved, the amendment shall be implemented within 45 days.

In accordance with 10 CFR 50.91, a copy of this application, with attachments, is being provided to the designated Michigan State Official.

Should you have any questions or require additional information, please contact Mr. Scott A. Maglio, Manager - Nuclear Licensing, at (734) 586-5076.

USNRC NRC-19-0002 Page 2 I declare under penalty of perjury that the foregoing is true and correct.

Executed on February 8, 2019 Keith J. Polson Senior Vice President and CNO

Enclosures:

1. Description and Assessment

2. Proposed Technical Specification Changes (Mark-Up)

3. Revised Technical Specification Pages

4. Proposed Technical Specification Bases Changes (Mark-Up) For Information Only cc: NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 5, Region III Regional Administrator, Region III Michigan Public Service Commission Regulated Energy Division (kindschl@michigan.gov)

Enclosure 1 to NRC-19-0002 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Description and Assessment to NRC-19-0002 Page 1

1.0 DESCRIPTION

DTE Electric Company (DTE) requests adoption of TSTF-564, "Safety Limit MCPR," Revision 2, which is an approved change to the Improved Standard Technical Specifications (ISTS), into the Fermi, Unit 2 (Fermi 2) Technical Specifications (TS). The proposed amendment revises the Technical Specification (TS) safety limit (SL) on minimum critical power ratio (MCPR) to reduce the need for cycle-specific changes to the value while still meeting the regulatory requirement for an SL.

2.0 ASSESSMENT 2.1 Applicability of Safety Evaluation DTE has reviewed the safety evaluation for TSTF-564 provided to the Technical Specifications Task Force in a letter dated November 16, 2018. This review included a review of the NRC staffs evaluation, as well as the information provided in TSTF-564. DTE has concluded that the justifications presented in TSTF-564 and the safety evaluation prepared by the NRC staff are applicable to Fermi 2 and justify this amendment for the incorporation of the changes to the Fermi 2 TS.

The Fermi, Unit 2, reactor is currently fueled with GE14 fuel bundles and will be fueled with GNF3 fuel bundles starting in the spring of 2020. The proposed Safety Limit in SL 2.1.1.2 is 1.07, consistent with Table 1 of TSTF-564 for Global Nuclear Fuel GNF3 fuel bundles. The larger (i.e., most limiting) safety limit of 1.07 for GNF3 was selected, consistent with TSTF-564 guidance for cores loaded with a mix of fuel types and to eliminate the need for a future license amendment request when Fermi 2 loads fresh GNF3 fuel into the reactor in 2020.

The MCPR value calculated as the point at which 99.9% of the fuel rods would not be susceptible to boiling transition (i.e., reduced heat transfer) during normal operation and anticipated operational occurrences is referred to as MCPR99.9%. Technical Specification 5.6.5, "Core Operating Limits Report (COLR)," is revised to require the MCPR99.9% value to be included in the cycle-specific COLR.

2.2 Variations DTE is proposing the following variations from the TS changes described in TSTF-564 or the applicable parts of the NRC staffs safety evaluation:

The Fermi 2 TS utilize different numbering than the Standard Technical Specifications on which TSTF-564 was based. Specifically, Fermi 2 TS 5.6.5 Core Operating Limits Report (COLR) corresponds to STS 5.6.3 Core Operating Limits Report. These differences are administrative and do not affect the applicability of TSTF-564 to the Fermi 2 TS.

to NRC-19-0002 Page 2

3.0 REGULATORY ANALYSIS

3.1 No Significant Hazards Consideration Analysis DTE requests adoption of TSTF-564, "Safety Limit MCPR," which is an approved change to the Improved Standard Technical Specifications (ISTS), into the Fermi 2 Technical Specifications (TS). The proposed change revises the Technical Specifications (TS) safety limit on minimum critical power ratio (SLMCPR). The revised limit calculation method is based on using the Critical Power Ratio (CPR) data statistics and is revised from ensuring that 99.9% of the rods would not be susceptible to boiling transition to ensuring that there is a 95% probability at a 95%

confidence level that no rods will be susceptible to transition boiling. A single SLMCPR value will be used instead of two values applicable when one or two recirculation loops are in operation. TS 5.6.5, "Core Operating Limits Report (COLR)," is revised to require the current SLMCPR value to be included in the COLR.

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

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

Response: No The proposed amendment revises the TS SLMCPR and the list of core operating limits to be included in the Core Operating Limits Report (COLR). The SLMCPR is not an initiator of any accident previously evaluated. The revised safety limit values continue to ensure for all accidents previously evaluated that the fuel cladding will be protected from failure due to transition boiling. The proposed change does not affect plant operation or any procedural or administrative controls on plant operation that affect the functions of preventing or mitigating any accidents previously evaluated.

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

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

Response: No to NRC-19-0002 Page 3 The proposed amendment revises the TS SLMCPR and the list of core operating limits to be included in the COLR. The proposed change will not affect the design function or operation of any structures, systems or components (SSCs). No new equipment will be installed. As a result, the proposed change will not create any credible new failure mechanisms, malfunctions, or accident initiators not considered in the design and licensing bases.

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

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

Response: No The proposed amendment revises the TS SLMCPR and the list of core operating limits to be included in the COLR. This will result in a change to a safety limit, but will not result in a significant reduction in the margin of safety provided by the safety limit. As discussed in the application, changing the SLMCPR methodology to one based on a 95% probability with 95% confidence that no fuel rods experience transition boiling during an anticipated transient instead of the current limit based on ensuring that 99.9% of the fuel rods are not susceptible to boiling transition does not have a significant effect on plant response to any analyzed accident. The SLMCPR and the TS Limiting Condition for Operation (LCO) on MCPR continue to provide the same level of assurance as the current limits and do not reduce a margin of safety.

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

Based on the above, DTE concludes that the proposed change 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.

3.2 Conclusion 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 Commissions 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.

to NRC-19-0002 Page 4 4.0 ENVIRONMENTAL EVALUATION The proposed change 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, or would change an inspection or surveillance requirement. However, the proposed change 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.

Enclosure 2 to NRC-19-0002 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Proposed Technical Specification Changes (Mark-Up)

SLs 2.0 2.0 SAFETY LIMITS (SLs) 2.1 SLs 2.1.1 Reactor Core SLs 2.1.1.1 With the reactor steam dome pressure < 785 psig or core flow < 10X rated core flow:

THERMAL POWER shall be 5 25X RTP.

2.1.1.2 With the reactor steam dome pressure 2 785 psig and core flow 2 10X rated core flow: 1.07.

MCPR shall be 2 1.08 for two recirculation loop operation or > 1.09 for single recirculation loop operation.

2.1.1.3 Reactor vessel water level shall be greater than the top of active irradiated fuel.

2.1.2 Reactor Coolant System Pressure SL Reactor steam dome pressure shall be s 1325 psig.

2.2 SL Violations With any SL violation, the following actions shall be completed within 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />s:

2.2.1 Restore compliance with all SLs: and 2.2.2 Insert all insertable control rods.

FERMI -UNIT 2 2.0-1 Amendment No. 1 A./4,~164

MCPR No Changes. Included for Reference 3.2.2 3.2 POWER DISTRIBUTION LIMITS 3.2.2 MINIMUM CRITICAL POWER RATIO (MCPR)

LCO 3.2.2 All MCPRs shall be greater than or equal to the MCPR operating limits specified in the COLR.

APPLICABILITY: THERMAL POWER 2 25X RTP.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. Any MCPR not within A.1 Restore MCPR(s) to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> limits. within limits.

B. Required Action and B.1 Reduce THERMAL POWER 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> associated Completion to < 25% RTP.

Time not met.

FERMI - UNIT 2 3.2-2 Amendment No. 134

No Changes. Included for Reference MCPR 3.2.2 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.2.2.1 Verify all MCPRs are greater than or equal Once within to the limits specified in the COLR. 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after a 25% RTP AND In accordance with the Surveillance Frequency Control Program SR 3.2.2.2 Determine the MCPR limits. Once within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after each completion of SR 3.1.4.1 AND Once within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after each completion of SR 3.1.4.2 AND Once within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after each completion of SR 3.1.4.4 FERMI - UNIT 2 3.2-3 Amendment No. 134, 201

Reporting Requirements 5.6

..5.6 Reporting Requirements (continued) 5.6.4 Deleted 5.6.5 CORE OPERATING LIMITS REPORT (COLR)

a. Core operating limits shall be established prior to each

• reload cycle, or prior to any remaining portion of a reload cycle, and shall be documented in the COLR fdr the following:

• LCO 3.2.1, "AVERAGE PLANAR LINEAR HEAT GENERATION RATE (APLHGR)":

LCO 3.2.2, "MINIMUM CRITICAL POWER RATIO (MCPR)';

LCO 3.2.3. "LINEAR HEAT GENERATION RATE (LHGR)": and LCO 3.3.2.1, "Control Rod Block Instrumentation."

b. The analytical methods used to determine the.core operating limits shall be those previously reviewed and approved by the NRC, specifically those described in the following documents:

1. NEDE-24011-P-A, "General Electric Standard Application for Reactor Fuel," (lalest approved version); and

2. NEDE-23785-1-PA, 'The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant-Accident - -

SAFER/GESTR, Application Methodology," (the approved version at the time the reload analyses are performed).

c. The core operating limits shall be determined such that all applicable limits (e.g., fuel thermal mechanical limits, core thermal hydraulic limits, Emergency Core Cooling Systems (ECCS) limits. nuclear limits such as SDM. transient analysis limits, and accident analysis limits) of the safety analysis are met.

d. The COLR,.including any midcycle revisions or supplements, shall be provided upon issuance for each reload cycle to the NRC.

The MCPR99.9% value used to calculate the LCO 3.2.2, "MCPR," limit shall be specified in the COLR.

(continued)

FERMI - UNIT 2 5.0 21 Amendment No. /W34. 166

Enclosure 3 to NRC-19-0002 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Revised Technical Specification Pages

SLs 2.0 2.0 SAFETY LIMITS (SLs) 2.1 SLs 2.1.1 Reactor Core SLs 2.1.1.1 With the reactor steam dome pressure < 785 psig or core flow < 10% rated core flow:

THERMAL POWER shall be 25% RTP.

2.1.1.2 With the reactor steam dome pressure 785 psig and core flow 10% rated core flow:

MCPR shall be 1.07.

2.1.1.3 Reactor vessel water level shall be greater than the top of active irradiated fuel.

2.1.2 Reactor Coolant System Pressure SL Reactor steam dome pressure shall be 1325 psig.

2.2 SL Violations With any SL violation, the following actions shall be completed within 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />s:

2.2.1 Restore compliance with all SLs; and 2.2.2 Insert all insertable control rods.

FERMI - UNIT 2 2.0-1 Amendment No. 134, 138, 164

Reporting Requirements 5.6 5.6 Reporting Requirements (continued) 5.6.4 Deleted 5.6.5 CORE OPERATING LIMITS REPORT (COLR)

a. Core operating limits shall be established prior to each reload cycle, or prior to any remaining portion of a reload cycle, and shall be documented in the COLR for the following; LCO 3.2.1, AVERAGE PLANAR LINEAR HEAT GENERATION RATE (APLHGR);

LCO 3.2.2, MINIMUM CRITICAL POWER RATIO (MCPR);

LCO 3.2.3, LINEAR HEAT GENERATION RATE (LHGR); and LCO 3.3.2.1, Control Rod Block Instrumentation.

The MCPR99.9% value used to calculate the LCO 3.2.2, MCPR, limit shall be specified in the COLR.

b. The analytical methods used to determine the core operating limits shall be those previously reviewed and approved by the NRC, specifically those described in the following documents:

1. NEDE-24011-P-A, General Electric Standard Application for Reactor Fuel, (latest approved version); and

2. NEDE-23785-1-PA, The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant-Accident -

SAFER/GESTR, Application Methodology, (the approved version at the time reload analyses are performed).

c. The core operating limits shall be determined such that all applicable limits (e.g., fuel thermal mechanical limits, core thermal hydraulic limits, Emergency Core Cooling Systems (ECCS) limits, nuclear limits such as SDM, transient analysis limits, and accident analysis limits) of the safety analysis are met.

d. The COLR, including any midcycle revisions or supplements, shall be provided upon issuance for each reload cycle to the NRC.

(continued)

FERMI - UNIT 2 5.0-21 Amendment No. 134, 166

Enclosure 4 to NRC-19-0002 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Proposed Technical Specification Bases Changes (Mark-Up)

For Information Only

Reactor Core SLs B 2.1.1 B 2.0 SAFETY LIMITS (SLs)

B 2.1.1 Reactor Core SLs BASES BACKGROUND GDC 10 (Ref. 1) requires, and SLs ensure, that specified acceptable fuel design limits are not exceeded during normal operation, including the effects of anticipated operational occurrences (AOOs).

The fuel cladding integrity SL is set such that no significant fuel damage is calculated to occur if the limit is not violated. Because fuel damage is not directly observable, a stepback approach is used to establish an SL, such that the MCPR is not less than the limit specified in Specification 2.1.1.2. MCPR greater than the specified limit represents a conservative margin relative to the conditions required to maintain fuel cladding integrity.

The fuel cladding is one of the physical barriers that separate the radioactive materials from the environs. The integrity of this cladding barrier is related to its relative freedom from perforations or cracking. Although some corrosion or use related cracking may occur during the life of the cladding, fission product migration from this source is incrementally cumulative and continuously This is accomplished by measurable. Fuel cladding perforations, however, can result having a Safety Limit from thermal stresses, which occur from reactor operation Minimum Critical Power Ratio significantly above design conditions.

(SLMCPR) design basis, referred to as SLMCPR95/95, While fission product migration from cladding perforation is which corresponds to a 95% just as measurable as that from use related cracking, the probability at a 95% thermally caused cladding perforations signal a threshold confidence level (the 95/95 beyond which still greater thermal stresses may cause gross, MCPR criterion) that transition rather than incremental, cladding deterioration. Therefore, boiling will not occur. the fuel cladding SL is defined with a margin to the conditions that would produce onset of transition boiling (i.e., MCPR = 1.00). These conditions represent a significant departure from the condition intended by design for planned operation. The MCPR fuel cladding integrity SL ensures that during normal operation and during AOOs, at least 99.9% of the fuel rods in the core do not experience transition boiling.

Operation above the boundary of the nucleate boiling regime could result in excessive cladding temperature because of the onset of transition boiling and the resultant sharp FERMI - UNIT 2 B 2.1.1-1 Revision 0

Reactor Core SLs B 2.1.1 BASES BACKGROUND (continued) The Technical Specification SL reduction in heat transfer coefficient. Inside the steam is set generically film, high cladding temperatures are reached, and a on a fuel product cladding-water (zirconium-water) reaction may take place. MCPR This chemical reaction results in oxidation of the fuel correlation basis cladding to a structurally weaker form. This weaker form as the MCPR may lose its integrity, resulting in an uncontrolled release which of activity to the reactor coolant. corresponds to a 95% probability at a 95%

confidence level The fuel cladding must not sustain damage as a result of that transition APPLICABLE boiling will not SAFETY ANALYSES normal operation and AOOs. The reactor core SLs are occur, referred to established to preclude violation of the fuel design criterion that an MCPR limit is to be established, such that as SLMCPR95/95.

at least 99.9% of the fuel rods in the core would not be expected to experience the onset of transition boiling.

The Reactor Protection System setpoints (LCO 3.3.1.1, "Reactor Protection System (RPS) Instrumentation"), in combination with the other LCOs, are designed to prevent any anticipated combination of transient conditions for Reactor Coolant System water level, pressure, and THERMAL POWER level that would result in reaching the MCPR safety limit.

2.1.1.1 Fuel Cladding Integrity General Electric Company (GE) critical power correlations are applicable for all critical power calculations at pressures Ž 785 psig and core flows Ž 10% of rated flow.

For operation at low pressures or low flows, another basis is used, as follows:

Since the pressure drop in the bypass region is essentially all elevation head, the core pressure drop at low power and flows will always be > 4.5 psi.

Analyses (Ref. 2) show that with a bundle flow of 28 x 10' Ib/hr, bundle pressure drop is nearly independent of bundle power and has a value of 3.5 psi.

Thus, the bundle flow with a 4.5 psi driving head will be > 28 x 103 Ib/hr. Full scale ATLAS test data taken at pressures from 14.7 psia to 800 psia indicate that the fuel assembly critical power at this flow is approximately 3.35 MWt. With the design peaking factors, this corresponds to a THERMAL POWER > 50% RTP.

Thus, a THERMAL POWER limit of 25% RTP for reactor pressure < 785 psig is conservative.

FERMI - UNIT 2 B 2.1.1-2 Revision 0

Reactor Core SLs B 2.1.1 BASES APPLICABLE SAFETY ANALYSES (continued) 2.1.1.2 MCPR The MCPR SL is set such that no significant fuel damage is calculated to occur if the limit is not violated. Since the parameters that result in fuel damage are not directly observable during reactor operation, the thermal and hydraulic conditions that result in the onset of transition boiling have been used to mark the beginning of the region in which fuel damage could occur. Although it is recognized that the onset of transition boiling would not result in damage to BWR fuel rods, the critical power at which boiling transition is calculated to occur has been adopted as a convenient limit. However, the uncertainties in monitoring the core operating state and in the procedures used to calculate the critical power result in an uncertainty in the See Insert 1 value of the critical power. Therefore, the MCPR SL is defined as the critical power ratio in the limiting fuel assembly for which more than 99.9% of the fuel rods in the core are expected to avoid boiling transition, considering the power distribution within the core and all uncertainties.

The MCPR SL is determined using a statistical model that combines all the uncertainties in operating parameters and the procedures used to calculate critical power. The probability of the occurrence of boiling transition is determined using the approved General Electric Critical Power correlations. Details of the fuel cladding integrity SL calculation are given in Reference 2. Reference 2 also includes a tabulation of the uncertainties used in the determination of the MCPR SL and of the nominal values of the parameters used in the MCPR SL statistical analysis.

2.1.1.3 Reactor Vessel Water Level During MODES 1 and 2 the reactor vessel water level is required to be above the top of the active fuel to provide core cooling capability. With fuel in the reactor vessel during periods when the reactor is shut down, consideration must be given to water level requirements due to the effect of decay heat. If the water level should drop below the top of the active irradiated fuel during this period, the ability to remove decay heat is reduced. This reduction in cooling capability could lead to elevated cladding temperatures and clad perforation in the event that the FERMI - UNIT 2 B 2.1.1-3 Revision 0

Insert 1 The Technical Specification SL value is dependent on the fuel product line and the corresponding MCPR correlation, which is cycle independent. The value is based on the Critical Power Ratio (CPR) data statistics and a 95% probability with 95% confidence that rods are not susceptible to boiling transition, referred to as MCPR95/95.

The SL is based on GNF3 fuel. For cores with a single fuel product line, the SLMCPR95/95 is the MCPR95/95 for the fuel type. For cores loaded with a mix of applicable fuel types, the SLMCPR95/95 is based on the largest (i.e., most limiting) of the MCPR values for the fuel product lines that are fresh or once-burnt at the start of the cycle.

MCPR B 3.2.2 B 3.2 POWER DISTRIBUTION LIMITS B 3.2.2 MINIMUM CRITICAL POWER RATIO (MCPR)

BASES BACKGROUND MCPR is a ratio of the fuel assembly power that would result in the onset of boiling transition to the actual fuel assembly power. The MCPR Safety Limit (SL) is set such that

, and that 99.9% of the fuel 99.9% of the fuel rods avoid boiling transition if the limit rods are not susceptible to is not violated (refer to the Bases for SL 2.1.1.2. The boiling transition if the limit operating limit MCPR is established to ensure that no fuel is not violated. damage results during anticipated operational occurrences (AOOs). Although fuel damage does not necessarily occur if a fuel rod actually experienced boiling transition (Ref. 1),

the critical power at which boiling transition is calculated to occur has been adopted as a fuel design criterion.

The onset of transition boiling is a phenomenon that is readily detected during the testing of various fuel bundle designs. Based on these experimental data, correlations have been developed to predict critical bundle power (i.e.,

the bundle power level at the onset of transition boiling) for a given set of plant parameters (e.g., reactor vessel pressure, flow, and subcooling). Because plant operating Safety Limit (SL) conditions and bundle power levels are monitored and determined relatively easily, monitoring the MCPR is a convenient way of ensuring that fuel failures due to inadequate cooling do not occur.

APPLICABLE The analytical methods and assumptions used in evaluating SAFETY ANALYSES the AOOs to establish the operating limit MCPR are presented in References 2, 3, 4, 5, 6, 7, and 8. To ensure that the MCPR SL is not exceeded during any transient event that occurs with moderate frequency, limiting transients have been analyzed to determine the largest reduction in critical power ratio (CPR). The types of transients evaluated are loss of flow, increase in pressure and power, positive reactivity insertion, and coolant temperature decrease. The limiting transient yields the largest change in CPR (ACPR).

When the largest ACPR is added to the MCPR SL, the required' See Insert 2 operating limit MCPR is obtained.

SLMPCR99.9%

combined with FERMI - UNIT 2 B 3.2.2-1 Revision 0

Insert 2 MCPR99.9% is determined to ensure more than 99.9% of the fuel rods in the core are not susceptible to boiling transition using a statistical model that combines all the uncertainties in operating parameters and the procedures used to calculate critical power. The probability of the occurrence of boiling transition is determined using the approved Critical Power correlations.

Details of the MCPR99.9% calculation are given in Reference 2. Reference 2 also includes a tabulation of the uncertainties and the nominal values of the parameters used in the MCPR99.9%

statistical analysis.

MCPR

, and B 3.2.2 BASES APPLICABLE SAFETY ANALYSES (continued) are the MCPR99.9% value and The MCPR operating limits derived from the transient analysis are dependent on the operating core flow and power state (MCPRf and MCPRp, respectively) to ensure adherence to fuel design limits during the worst transient that occurs with moderate frequency (Refs. 6, 7, and 8). Flow dependent MCPR limits are determined by steady state thermal hydraulic methods with key physics response inputs benchmarked using the three dimensional BWR simulator code (Ref. 9) to analyze slow flow runout transients. The operating limit is dependent on the maximum recirculation scoop tube mechanical stop setting in the Recirculation Flow Control System.

Power dependent MCPR limits (MCPRp) are determined mainly by the three~dimensional transient code (Refs. 10 and 11). Due to the sensitivity of the transient response to initial core flow levels at power levels below those at which the turbine stop valve closure and turbine control valve fast closure by approved scrams are bypassed, high and low flow MCPRp operating transient analysis limits are provided for operating between 25% RTP and the models previously mentioned bypass power level.

Transients involving increase in pressure and power are sensitive to the size of the steam volume and the availability of this steam volume to accommodate the reactor steam production. Larger steam volumes and longer or earlier availability result in less severe pressure transients. Thus operation of the turbine generator bypass valves and the availability of the moisture separator reheater have an effect on the transient results. For this reason the COLR contains MCPR limits for when the turbine bypass valves and/or moisture separator reheater are out-of-service (refer to LCO 3.7.6, "The Main Turbine Bypass System and Moisture Separator Reheater").

The MCPR satisfies Criterion 2 of 10 CFR 50.36(c)(2)(ii).

LCO The MCPR operating limits specified in the COLR are the result of the design basis transient analysis. The operating limit MCPR is determined by the larger of the MCPRf and MCPRp limits.

(MCPR99.9% value, MCPRf values, and MCPRp values)

, which are based on the MCPR99.9% limit specified in the COLR.

FERMI - UNIT 2 B 3.2.2-2 Revision 55