ML20212K990

Proposed Tech Spec Change 130,reflecting Revised LOCA Limits

ML20212K990
Person / Time
Site:	Maine Yankee
Issue date:	02/24/1987
From:	Maine Yankee
To:
Shared Package
ML20212K987	List: ML20212K983 ML20212K990
References
NUDOCS 8703100029
Download: ML20212K990 (11)

Text

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MAIN 2 YANK 3E ATOMIC POWEQ COMPANY

4. If the CEA deviation alarms from both the computer pulse counting system and the reed switch indication system are not available, individual CEA positions shall be logged and misalignment checked every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

5. Operation of the CEA's in the automatic mode is not permitted.

B. Shutdown Margin Limits

1. When the reactor is critical, the shutdown margin will not be less than that shown in Figure 3.10-7, except during low power physics tests when the shutdown margin will not be less than 2% in reactivity.

2. A trippable CEA is considered inoperable if it cannot be tripped.

A CEA that cannot be driven shall be assumed not able to be tripped until it is proven that it can be tripped. Operation with an inoperable CEA is permitted provided:

a. The shutdown margin specified in 3.10.B.1 is satisfied without the reactivity associated with the inoperable CEA within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> of identification of the inoperable CEA.

b. Except for low power physics tests and CEA exercises, only one CEA is inoperable.

3. A trippable CEA is considered to be a slow CEA if the drop time from de-energizing its holding coil to reaching 90% of its full insertion exceeds 2.7 seconds at operating temperature and 3 pump flow.

Operation with a slow CEA is permitted provided:

a. The shutdown margin specified in 3.10.B.1 is satisfied without 1.5 times the reactivity associated with the slow CEA after 2.5 seconds of drop time.

C. Power Distribution Limits

1. The peak linear heat rate with appropriate consideration of normal flux peaking, measurement-calculational uncertainty (8%), engineering factor (3%), increase in linear heat rate due to axial fuel densification and thermal expansion (0.3% for Type E only) and power measurement uncertainty (2%) shall not exceed the limits shown in ]

Figure 3.10-12 as a function of core height. ]

]

Should any of these limits be exceeded, immediate action will be taken to restore the linear heat rate to within the appropriate limit specified in Figure 3.10-12. ]

8463L-LM0 3.10-2 02/23/87 0703100029 070224 PDH ADOCK 05000309 p PDR

MAINE YANM",E ATOMIC POWEQ COMPANY

. .s 2. The total radial peaking factor, defined as T -P F R = FR ' (1 + Tq )

shall be evaluated at least once a month during power operation above 50% of rated full power.

2.1 FR is the latest available unrodded radial peak determined from the incore monitoring system for a condition where all CEAs  !

are at or above the 100% power insertion limit. Tq is given by the following expression:

t Tq= 2 (Pa-Pc)2 , (ph_pd)2 N (Pa+Pb + Pc+Pd)2 where Pi is the relative quadrant power determined from the incore system for quadrant 1, when the incore system is operable. If the incore system is not operable, the P1 are the  !

signals from excore detector channels 1.

T 2.2 If the measured value of FR exceeds the value given in Figure 3.10-4, perform one.of the following within 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s:

1. Reduce symmetric offset LCO (Figures 3.10-9 and 3.10-10) and trip band (Figure 2.1-2), thermal margin / low pressure -

trip limit (Figures 2.1-1 a and b and Technical Specification 2.1), and excore LOCA monitoring limits  ;

(Figures 3.10-2 and 3.10-3) by a factor greater than or  ;

equal to:

i T T (FR measured] / (FR Figure 3.10-4) 08:

l

2. Reduce thermal power at a rate of at least 1%/ hour to bring thecombinationofthermalpowerand%increaseinFdto 4 within the Ilmits of Figure 3.10-5, while maintaining CEAs at or above the 100% power insertion limit. If incores are not operable and Fig. 3.10-2 is in use, then also reduce excore LC0A monitoring limit (Figure 3.10-2) by a factor greater than or equal to T T (FR measured] / [FR Figure 3.10-4)  !

0H:

3. Be in at least HOT SHUTDOHN.

8463L-LHO 3.10-3 02/19/07 .

i

MAIN 3 YANKEE ATOMIC POWED COMPANY

3. Incore detector alarms shall be set at least weekly. Alarms will be based on the latest power distribution obtained, so that the linear ,

heat rate does not exceed the linear heat reat limit defined in I Specification 3.10.C.1. If four or more coincident alarms are l received, the validity of the alarms shall be immediately determined and, if valid, power shall be immediately decreased below the alarm l setpoint.

3.1 If the incore monitoring system becomes inoperable, perform one of the following within 4 EFPH:

1. Initiate a power reduction to less than er equal to P at a rate of at leat 1%/ hour where P (% of rated Power) is given by:

P = 0.85 x R, where R is the minimum ratio ]

of (Linear helt rate oermitted by Sggelfication 3.10.C.1 x 100)_ )

(Latest measured peak linear heat rate corrected to 100% Power) at any core height, while maintaining CEAs above the 100% ) l power insertion limit and monitor symmetric offset once a shift to insure that it remains within 1 0.05 of the value measured at the time when the above equation is evaluated.

This procedure may be employed for up to 2 effective full power weeks; or

2. Comply with the LCO given in Figure 3.10-2 while I maintaining the CEAs above the 100% power insertion limit.

If a power reduction is required, reduce power at a rate of at least 1%/ hour; or ]  :

3. Comply with the LCO in Figure 3.10-3. If a power reduction is required, reduce power at a rate of at least 1%/ hour.

4. The azimuthal power tilt Tg, shall be determined prior to i operation above 50% of full rated power after each refueling and at least once per day during operation above 50% of full rated power.

Tq is given by the following expression:

T q= 2 (Da-Dc)2 + (Ob-D d2

% (Da+0b + Oc+0d}2 where D1 is the signal from excore detector channel 1. If an excore channel is inoperable, Di are the relative quadrant powers determined from the incore system for all quadrants, l.

Tg shall not exceed 0.03.

4.1 If the measured value of To is greater than 0.03 but less than or equal to 0.10, or an excore channel is inoperably,assurethatthetotalradialpeaking factor (FR) is within the provisions of Specification 3.10.C.2 once por shift.

8463L-LHO 3.10-4 02/19/87 l

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MAINE YANKEE ATOMIC POWEO COMf'ANY ATTACHMENT D HN-87-18 Maine Yankee Atomic Power Company Cycle 10 Loss of Coolant Accident Evaluation l

I

MAINE YANMEC ATOMIC POWER COMPANY MAINE YANKEE LOSS OF COOLANT ACCIDENT EVALUATION

1. Introduction and Summary Large break Loss of Coolant Accident (LOCA) calculations for Maine Yankee were performed for Cycle 5 through Cycle 9 using the Yankee Atomic Electric Company (YAEC) HREM-based generic PWR ECCS' Evaluation Model (Reference 1). The Cycle 5 calculation consisted of a complete break spectrum analysis and the calculation of cycle specific limits. Cycle 6 through Cycle 9 evaluations demonstrated that the Cycle 5 break spectrum analysis was applicable and the results of this analysis were then used in calculating the LOCA limits for each cycle.

For Cycle 10 and subsequent analyses, the YAEC LOCA methodology has been modified to include (1) an improved ECCS water-steam interaction model and (2) a more complete spectrum of possible axial power shapes than that previously analyzed. These model improvements required a complete re-examination of the previous break spectrum analysis for large breaks. The small break licensing basis analysis results were evaluated and determined to remain valid and non11miting for Cycle 10 operation.

Axially-dependent LOCA limits were determined for Cycle 10 fuel types based upon beginning-of-life (BOL) analyses where initial fuel stored energy is calculated to be at a maximum value. Burnup-dependent evaluations performed for past cycles to evaluate the LOCA limits at lower values of calculated initial fuel stored energy have not been performed for Cycle 10 operation.

Based on the results of these analyses, it is concluded that Appendix K criteria are met for Cycle 10 fuel types operating within the linear heat generation rate limits specified in Figure 1.

2. Luge _flr_eak LOCA Analysis 2.1 ti0deling_ Chang 21 The changes in modeling approach for the large break LOCA analysis were submitted for NRC review in Reference 2. The NRC staff has completed the review of these changes. A Safety Evaluation Report has been issued in which these modifications were judged acceptable and in compliance with Appendix K of 10CFR50 (Reference 3).

2.1.1 Adalfoyer__Shapet In the analyses for Cycle 5 through Cycle 9, two axial power shapes were considered: a top skew design shape with its peak at 68 percent of the core height (68 percent shape) and a chopped cosine shape (50 percent shape).

The derived LOCA limit curve was represented by a peak linear heat generation rate (PLHGR) of 16 kH/f t between 0 percent and 50 percent core height and a PLHGR of 14 kH/ft at axial locations above 50 percent core height. In a recent review of the YAEC LOCA methodology, this curve was found to be nonconservative at higher elevations (greater than approximately 75 percent core height). For the Cycle 10 analysis, a now LOCA limit curve is derived using a more complete spectrum of possible axial power shapes than that previously analyzed.

MAINE YANNEE OTOMIC POWEQ COMPONV This' curve is generated by determining the LOCA limit at four axial locations (52 percent, 65 percent 73 percent, and 85 percent). The axial power shapes used in these calculations are determined according to the methodology outlined in Reference 2. The LOCA limit is assumed to be constant l between 0 percent and 52 percent core height and linear between the analyzed points, and is determined assuming a conservative fall off rate between 85 percent and 100 percent core height. These assumptions are discussed in detail in Reference 2.

2.1.2 ECCS Hater - Steam Interaction Model l In the YAEC reflood model, the interaction of ECCS water with steam is l evaluated by means of a frictional pressure loss penalty (delta P penalty).

The magnitude of this parameter in Cycle 5 through Cycle 9 analyses was overly conservative. A more realistic value of this parameter was developed from the EPRI data base for the Cycle 10 and subsequent analyses. The improved delta P penalty is applied in the reflood model; therefore, the reflood and T000EE calculations of the previous (Cycle 5) break spectrum analysis have been reanalyzed.

2.2 Break _Soectrum Analysis j

The purpose of the break spectrum analysis is to identify the limiting break for each axial power shape. The analysis was performed for each of the l four axial locations. The features of the analysis have been discussed with the NRC staff and have been described in Reference 4. The limiting break for the axial locations at 52 percent and 65 percent of core height is a guillotine break with flow area 80 percent of twice the cold leg flow area r (0.8G). The limiting break for the axial locations at 73 percent and 85 percent of core height is a pipe crack with flow area of twice the cold leg flow area (1.0S).

2.3 LQCA Limits Analysis To determine the LOCA limit at an axial location in the core, the limiting axial power shape with its peak at the specified location is used in the LOCA analysis. If the results of the analysis meet the LOCA design critoria, the Peak Linear Heat Generation Rate (PLHGR) is the derived limit at the specified location. The process is repeated for the four axial locations, and the curve through these established PLHGR values forms the axially-dependent LOCA limit curve.

The PLHGR calculation is performed in a manner consistent with previous analyses (Reference 5). Changes to the reactor physics parameters associated with the core loading modification for Cycle 10 (Reference 6) are addressed in i

r

MAIN 3 YANKEE ATOMIC POWECJ COMPANY the analysis. The system configuration and thermal-hydraulic parameters remain unchanged from the previous analysis.

The results of the analysis for each axial power shape are provided in Table 1. The calculated peak cladding temperatures, cladding oxidation values, and hydrogen generation results demonstrate compliance with Appendix K criteria. In the determination of axial power shapes (Reference 2), two types of shapes (" symmetric" and "nonsymmetric") are generated at each axial location. The results shown in Table I are those for the limiting axial power shape type. Higher PCT values were calculated consistently for the "nonsymmetric" shape.

The PLHGR values are plotted as a function of core height in Figure 1.

In the region above 85 percent core height, a conservative fall off rate is assumed. The intermediate point at 93 percent core height is the value of LHGR at this location for the limiting axial power shape with its peak at 85 percent of core height.

3. Small Break LOCA Analyses The small break LOCA analysis performed by Combustion Engineering for Cycle 4 considered a spectrum of cold leg breaks varying in size from 0.1 to

, 0.5 ft (Reference 7). Results showed that the limiting break size is the 0.5 ft break with a peak clad temperature of 13480F, well below the acceptance criteria of 10CFR50.46. A demonstration analysis of the limiting

, break performed for Cycle 5 (Reference 8) utilizing YAEC methodology yielded a peak clad temperature of 12300F, well below the 10CFR50.46 acceptance criteria and Maine Yankee large break results. In that analysis, a 68 percent peak top skew design shape and a PLHGR of 16 kH/ft were used. The analysis predicted a short period of core uncovery and resultant cladding heatup.

Thus, small break LOCAs for Maine Yankee were shown to be nonlimiting.

l The results of previous analyses are applicable to Cycle 10 because they are determined primarily by the decay heat values which are insensitive to fuel type. Additionally, slight differences in Cycle 10 and Cycle 5 system configuration would have minor effects on the PCT which was predicted to be well below the 10CFR50.46 criteria. Hence, the minor system changes will not

, make the small break a limiting scenario.

i

MAINE YANKEE ATOMIC POWER COMPANY

- REFERENCES

1. YAEC-1160, " Application of Yankee HREM Based Generic PHR ECCS Evaluation Model to Maine Yankee," July 1978.

2. Letter from G. D. Whittler (MYAPCo) to A. C. Thadani (USNRC), MN-86-141, dated November 10, 1986.

3. Memorandum for P. M. Sears (USNRC) from D. M. Crutchfield (USN!!C);

" Safety Evaluation of Maine Yankee Large Break ECCS Evaluaticn Model Modification Related to Axial Power Shape Issue, Phase I;" dated December 31, 1986.

4. Letter from G. D. Whittier (MYAPCo) to A. C. Thadant (USNRC), " Maine Yankee LOCA Analysis," MN-87-15, dated February 23, 1987.

5. YAEC-1479, " Maine Yankee Cycle 9 Core Performance Analysis," April 1985.

l 6. YAEC-1573, " Maine Yankee Cycle 10 Core Performance Analysis," Attachment i

to MYAPCo Letter to USNRC, MN-87-04, dated January 12, 1987.

7. Maine Yankee Letter to USNRC, HMY 77-87, dated September 22, 1977.

8. YAEC-1202, " Maine Yankee Cycle 5 Core Performance Analysis," Attachment l

to MYAPCo Letter to USNRC, HMY 79-143, dated Decembcr 5, 1979.

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. y MAINE YANNEE ATOMIC POWEQ COMPANY TABLE 1 Maine Yankee Cycle 10' Larae Break LOCA Analysis Results A'xial Limiting Peak Claddin Claddina Power. Break PLHGR(1) Temperature Z(g) Oxidation (2,3)

Shapt Tvoe (kW/ft) ._

(OF) (% Thickness) 52% 0.8G 16.0 1960 2.9 65% 0.8G 15.0 2157 5.6 I 73% 1.0S 14.4 2106 4.7 85% 1.0S 13.0 2009 4.7 NOTES

1. All analyses are performed at beginning-of-life conditions.

2. Results shown are those for the limiting axial power shape type.

3. Less than one percent hydrogen generation is predicted in all analyses.

i 8463L-LM0

_ _ . _ _ _ - _ _ _ - _ _ -