ML18150A161

Proposed Tech Specs Re Operation When Control Rod Declared Inoperable & Shutdown Margin Requirement of Tech Spec 3.12.A.3.c Satisfied

ML18150A161
Person / Time
Site:	Surry
Issue date:	06/08/1987
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18150A159	List: ML18150A157 ML18150A161
References
NUDOCS 8706150217
Download: ML18150A161 (6)

Text

ATTACHMENT 1 PROPOSED TECHNICAL SPECIFICATION CHANGE SURRY POWER STATION UNITS 1 AND 2

e TS 3.12-9

b. the rod is declared inoperable and the shutdown margin requirement of Specification 3.12.A.3.c is satisfied. Operation at power may then continue provided that:

1) either:

(a) power shall be reduced to less than 75% of rated power within one (1) hour, and the High Neutron Flux trip setpoint shall be reduced to less than or equal to 85% of rated power within the next four (4) hours, or (b) the remainder of the rods in the group with the inoperable rod are aligned to within 12 steps of the inoperable rod within one (1) hour while maintaining the rod sequence and insertion limits of Figure 3.12-1; the thermal power level shall be restricted pursuant to Specification 3.12.A during subsequent operation.

2) the shutdown margin requirement of Specification 3.12.A.3.c is determined to be met within one hour and at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter.

3) the hot channel factors are shown to be within the design limits of Specification 3.12.B.1 within 72 hours. Further, it shall be demonstrated that the value of Fxy(Z) used in the Constant Axial Offset Control analysis is still valid.

4) a reevaluation of each accident analysis of Table 3.12-1 is performed within 5 days. This reevaluation shall confirm that the previous analyzed results of these accidents remain valid for the duration of operation under these conditions.

ATTACHMENT 2 SAFETY EVALUATION SURRY POWER STATION UNITS 1 AND 2

Evaluation of Proposed Change Virginia Electric and Power Company submitted proposed changes to Technical Specification 3.12 for Surry Power Station for NRC approval in letter Serial 86-376, dated October 7, 1986. The proposal would remove the alternative insertion limits currently required in the event of an inoperable control rod and replace them with more detailed requirements for evaluation of the safety impact of the inoperable rod. The proposed Specification would allow continued operation, under certain restrictions, with a mechanically immobile rod, as does the current Specification.

In a telephone conversation on April 9, 1987, the NRC staff indicated that the proposed changes were considered acceptable provided an addition was made to proposed Technical Specification 3.12.C.5.b.3. Section 3.12.C.5.b outlines actions which must be taken to support continued operation with a control rod which has been declared inoperable. The subparagraph in question reads as follows:

3) the hot channel factors are shown to be within the design limits of Specification 3.12.B.1 within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

The addition requested by the NRC staff reads as follows:

Further, it shall be shown that the value of Fxy(Z) used in the Constant Axial Offset Control analysis is still valid.

Fxy(Z) is the axially dependent radial or planar peaking factor. During the reload design and analysis process Fxy(Z) is calculated for various allowable rod configurations as a function of cycle life. These values are then synthesized with values of the axial peaking factor Fz(Z) calculated with a one dimensional axial model for a range of load follow scenarios assuming operation within a Constant Axial Offset Control (CAOC) strategy, The synthesized local peaking factor (FQ) values are verified to be at or below the value assumed in the currently applicable LOCA/ECCS analysis in accordance with 10 CFR 50 Appendix K.

Under the initially proposed Specifications, an evaluation of the effects of operation with an inoperable control rod on various accidents analyzed in the UFSAR must be performed within 5 days. Among the accidents to be evaluated are the large and small break loss of coolant accidents. In order to perform the evaluation, verification of the validity of the CAOC FQ calculations must be performed. Thus, the requested addition does not actually add a new requirement, but only requires that the reevaluation be performed in a more timely manner (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> vs. 5 days) and makes the requirement to reevaluate Fxy explicit rather than implicit.

Implementation of the supplement change will be in two parts. First, measured INCORE Fxy values will be compared with the corresponding values used in the CAOC analysis for the subject fuel cycle. Consistent control bank positions and core burnups will be used in performing the comparisons. If it cannot be demonstrated that the measured Fxy values fall below those assumed in the analyses, then the inoperable control rod will be modeled, and a new Fxy(Z) distribution will be calculated. The new predictions will be compared to the measured data to confirm that the effects of the misaligned rod are being simulated correctly. Then the CAOC analysis will be reperformed including the effects of burnup and load follow maneuvers. The results of this analysis will be used to confirm that the power dependent FQ limit of Specification 3.12.B will continue to be met.

e This supplemental change augments the previously submitted change request and as such does not alter the 10 CFR 50.59 safety review or 10 CFR 50.92 significant hazards determination of the previous request.

10 CFR 50.59 Safety Review The supplemental change will not result in an unreviewed safety question as defined in 10 CFR 50.59. Specifically,

1. the added specification will not increase the probability of occurrence of any malfunction or accident addressed in the UFSAR.

The effect of the supplemental change is to impose a more stringent surveillance requirement for timely verification that radial power peaking is within appropriate limits. No equipment modifications or design changes are involved. Further, the consequences of UFSAR Chapter 14 accidents will continue to bounded by their associated analyses by virtue of the requirement to maintain the power peaking factors, shutdown margin and other significant safety parameters within appropriate design limits.

2. no new accident types or equipment malfunction scenarios will be introduced as a result of operating in accordance with the added specification.

3. since the existing safety analyses will remain bounding, there is no reduction in any safety margin.

\ .

e e 10 CFR 50.92 Significant Hazards Determination Pursuant to 10 CFR 50.92, the proposed change does not involve a significant hazards consideration because operation of Surry Units 1 and 2 would not:

1. involve a significant increase in the probability or consequences of an accident previously evaluated. The effect of the supplemental change is to impose a more stringent surveillance requirement for timely verification that radial power peaking Fxy(Z) is within appropriate limits. Accident probabilities will not change. The consequences of UFSAR Chapter_ 14 accidents will continue to be bounded by their associated analyses by virtue of the requirement to maintain the significant safety parameters within design limits.

2. create the possibility of a new or different kind of accident from any accident previously identified. No equipment modifications or design changes are involved.

3. involve a significant reduction in a margin of safety. The supplemental revision requires a more expeditious verification of Fxy(Z), than the current specification. Evaluation of Fxy(Z) provides added assurance that operation with a dropped or misaligned rod will not invalidate the UFSAR accident analysis basis and that corresponding safety margins are maintained.

The Commission has provided examples of changes considered unlikely to involve significant hazards considerations. Example ii, which was published in the Federal Register, Volume 48, No. 67, April 6, 1983, page 14864 partially states "a change that constitutes an additional limitation, restriction or control not presently included in the Technical Specifications: for example, a more stringent surveillance requirement". The proposed change is similar to this example. Therefore, pursuant to 10 CFR 50.92, based on the above evaluation it has been determined that this change does not involve a significant hazards consideration.

__J