The specifications of this section provide assurance of fuel integrity during Condition I (Normal Operation) and Condition II (Incidents of Moderate Frequency) events by:

• (a) Meeting the DNB Design Criteria during normal operation and short-term transients
• (b) Limiting fission gas release, fuel pellet temperature, and cladding mechanical properties to within assumed design criteria

In addition, limiting the peak linear power density during Condition I events provides assurance that the initial conditions assumed for the LOCA analyses are met and the ECCS acceptance criteria limit of 2200°F is not exceeded.

Hot channel factor definitions:

• FQ(Z) — Heat Flux Hot Channel Factor: the maximum local heat flux on the surface of a fuel rod at core elevation Z divided by the average fuel rod heat flux, allowing for manufacturing tolerances on fuel pellets and rods
• F^N_ΔH — Nuclear Enthalpy Hot Channel Factor: the ratio of the integral of linear power along the rod with the highest integrated power to the average rod power
• Fxy(Z) — Radial Peaking Factor: the ratio of peak power density to average power density in the horizontal plane at core elevation Z

(Amendment No. 197)

AFD limits assure that the FQ(Z) upper bound envelope specified in the COLR times the normalized axial peaking factor is not exceeded during either normal operation or xenon redistribution following power changes.

Target flux difference is defined at equilibrium xenon conditions with part-length control rods withdrawn from the core. Full-length rods may be positioned within the core in accordance with their respective insertion limits and should be inserted near their normal position for steady-state operation at high power. The value obtained under these conditions divided by the fraction of RTP is the target flux difference at RTP for the associated burnup conditions. The target flux difference varies slowly with core burnup and is periodically updated to reflect burnup considerations.

Penalty deviation system: During rapid power reductions, control rod motion causes AFD to deviate outside the target band at reduced power levels. This deviation will not affect xenon redistribution sufficiently to change the peaking factor envelope on a subsequent return to RTP provided the time duration is limited:

• 50–90% RTP: 1-hour penalty deviation limit cumulative during the previous 24 hours for operation outside the target band but within COLR limits
• 15–50% RTP: 2-hour actual time penalty — deviations at these lower power levels are less significant

Monitoring: Provisions for monitoring AFD are derived from the plant nuclear instrumentation system through the AFD Monitor Alarm. A control room recorder continuously displays the auctioneered high flux difference and the target band limits as a function of power level. An alarm is received any time the auctioneered high flux difference exceeds the target band limits. Time outside the target band is graphically presented on the strip chart.

Target flux difference measurement: Accomplished by measuring the power distribution when the core is at equilibrium xenon conditions, preferably at high power levels with the control banks nearly withdrawn. This measurement provides the equilibrium xenon axial power distribution from which the target value can be determined. Alternatively, linear interpolation between the most recent measurement and a predicted end-of-cycle value provides a reasonable update because AFD changes due to burnup tend toward 0% AFD.

(Amendment No. 289)

The limits on heat flux hot channel factor and RCS flow rate ensure that: (1) design limits on peak local power density and minimum DNBR are not exceeded, and (2) in the event of a LOCA the peak fuel clad temperature will not exceed the 2200°F ECCS acceptance criteria limit.

FQ(Z) is measurable but will normally only be determined periodically as specified in SR 4.2.2. This periodic surveillance is sufficient to insure that limits are maintained provided:

• (a) Control rods in a single group move together with no individual rod insertion differing from the group demand position by more than the allowed rod misalignment
• (b) Control rod groups are sequenced with overlapping groups as described in Spec 3.1.3.5
• (c) The control rod insertion limits of Specs 3.1.3.4 and 3.1.3.5 are maintained
• (d) The axial power distribution, expressed in terms of AFD, is maintained within the limits

FQ measurement uncertainties: When an FQ measurement is taken, both experimental error and manufacturing tolerance must be allowed for:

• 5% allowance for a full core map taken with the incore detector flux mapping system
• 3% allowance for manufacturing tolerance
• For measurements obtained using the Power Distribution Monitoring System (PDMS), the appropriate measurement uncertainty is determined using the methodology contained in WCAP-12472-P-A. The cycle and plant uncertainty calculation information needed to support the PDMS calculation is contained in the COLR. The PDMS will automatically calculate and apply the correct measurement uncertainty, and apply a 3% allowance for manufacturing tolerance.

Fxy(Z) evaluation: The radial peaking factor Fxy(Z) is measured periodically to provide assurance that FQ(Z) remains within its limit. The Fxy limit for RTP (F^RTP_xy) is provided in the COLR per Spec 6.9.1.9 and was determined from expected power control maneuvers over the full range of burnup conditions. Core plane regions applicable to an Fxy evaluation exclude the following (measured in percent of core height from bottom of fuel):

• (a) Lower core region: 0% to 8% inclusive
• (b) Upper core region: 92% to 100% inclusive
• (c) Grid plane regions: ±2% inclusive
• (d) Core plane regions within ±2% of core height (±2.88 inches) about the bank demand position of bank D control rods

(Amendment No. 218, TSBC S2015-072)

The limits on nuclear enthalpy hot channel factor ensure that design limits on minimum DNBR are not exceeded. Like FQ, F^N_ΔH is measurable but normally only determined periodically per SR 4.2.3, subject to the same four periodic surveillance conditions (rod alignment, group sequencing, insertion limits, and AFD limits).

Power-dependent relaxation: The relaxation in F^N_ΔH as a function of THERMAL POWER allows changes in the radial power shape for all permissible rod insertion limits. F^N_ΔH will be maintained within its limits provided the four surveillance conditions are maintained.

F^N_ΔH measurement uncertainty: The specified limit contains an 8% allowance for uncertainties, which means normal operation will result in F^M_ΔH ≤ F^RTP_ΔH, where F^RTP_ΔH is the limit at RTP specified in the COLR. The 8% allowance is based on:

• (a) Abnormal perturbations in the radial power shape (e.g., rod misalignment) affect F^N_ΔH more directly than FQ
• (b) Although rod movement has a direct influence upon limiting FQ to within its limit, such control is not readily available to limit F^N_ΔH
• (c) Errors in prediction for control power shape detected during startup physics testing can be compensated for in FQ by restricting axial flux distributions; this compensation for F^N_ΔH is less rapidly available

For measurements obtained using PDMS, the appropriate measurement uncertainty is determined using the methodology contained in WCAP-12472-P-A. The cycle and plant specific uncertainty information is contained in the COLR. The PDMS will automatically calculate and apply the correct measurement uncertainty to the measured F^N_ΔH. When using the incore detection system, the experimental error is obtained from the COLR.

(Amendment No. 218)

The QPTR limit assures that the radial power distribution satisfies the design values used in the power capability analysis. Radial power distribution measurements are made during startup testing and periodically during power operation.

The limit of 1.02 at which corrective action is required provides DNB and linear heat generation rate protection with x-y plane power tilts. A limiting tilt of 1.025 can be tolerated before the margin for uncertainty in FQ is depleted. The limit of 1.02 was selected to provide an allowance for the uncertainty associated with the indicated power tilt.

The 2-hour time allowance for operation with a tilt condition >1.02 but <1.09 is provided to allow identification and correction of a dropped or misaligned rod. In the event such action does not correct the tilt, the margin for uncertainty on FQ is reinstated by reducing the power by 3% from RTP for each percent of tilt in excess of 1.0.

(TSBC S2015-072)

The limits on DNB related parameters assure that each parameter is maintained within the normal steady-state envelope of operation assumed in the transient and accident analyses. The limits are consistent with the initial FSAR assumptions and have been analytically demonstrated adequate to maintain a minimum DNBR of the design DNBR value throughout each analyzed transient.

The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

(Amendment No. 282)