ULNRC-03198, Application for Amend to License NPF-30,changing Table 2.2-1 of TS 2.2.1 to Reduce Repeated Alarms & Partial Reactor Trips Associated w/C-4 Control Sys Interlock & Overpower Delta-T,which Occurred in Past Cycles
| ML20082M936 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 04/17/1995 |
| From: | Schnell D UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20082M938 | List: |
| References | |
| ULNRC-03198, ULNRC-3198, NUDOCS 9504240449 | |
| Download: ML20082M936 (16) | |
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1901 Chouteau Avenue y~ ~ ^4 Post 0mce Box 149 l St. louis. Missoun 63166 !
314-554 7650 Donald F. Schnell 1 UNION senio, we e,esisea
~ILLECTIUC nuces, j' @) April 17, 1995 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-137 Washington, D.C. 20555 Gentlemen: ULNRC-0 319 8 DOCKET NUMBER 50-483 CALLAWAY PLANT QPTIMIZATION OF OVERPOWER DELTA-T REACTOR TRIP
References:
- 1) ULNRC-2196 dated April 12, 1990, RTD Bypass Elimination
- 2) ULNRC-1822 dated August 30, 1988, Steam Generator Low-Low Level EAM/TTD Modification Union Electric Company herewith transmits an application for amendment to Facility Operating License No. NPF-30 for the Callaway Plant.
This amendment application includes changes to Table 2.2-1 of Technical Specification 2.2.1 in order to reduce repeated alarms and partial reactor trips associated with the C-4 control system interlock and Overpower Delta-T (OPAT)that have occurred in past cycles. The C-4 interlock blocks control rod withdrawal and initiates turbine runback when its 2/4 logic coincidence is satisfied. The C-4 alarm setpoint is set slightly below the OPAT reactor trip setpoint.
Typically, one channel will exceed the C-4 setpoint for its loop on any given occurrence, partially satisfying the C-4 logic requirement and resulting in an alarm on that channel. In some of these events, a partial reactor trip on OPAT also occurs. This situation has led to power reductions during past surveillance testing in order to avoid reactor trips since the channel being tested is placed in the tripped condition.
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The changes to the Total Allowance (TA) , K, 4 K 6 , and Allowable Value in Table 2.2-1 have been justified through the use of available margin._ The '
editorial change to the Overtemperature Delta-T (OTAT) equation in Table 2.2-1 represents the manner in which -
these signals have always been electronically processed.
The Bases changes discuss the correlation between time constants for lag cards in the 7300 Process Protection System and the total lag time' assumed in safety analyses which credit OTAT or OPAT for protection.
The Callaway Plant Onsite Review Committee and ,
the Nuclear Safety Review Board have reviewed this amendment application. Attachments 1 through 4 provide the Safety Evaluation, Significant Hazards Evaluation, Environmental Consideration, and proposed Technical Specification revisions, respectively, in support of this request. It has been determined that this amendment application does not involve an unreviewed safety question as deterr. tined per 10CFR50.59 nor a significant hazard consideration as determined per 10CFR50.92.
Pursuant to 10CFR51.22 (b) , no environmental assessment need be prepared in connection with the issuance of this amendment.
If you have any questions on the attachments, please contact us. ,
very truly yours, >
&"w= l onald F. Schnell GGY/kea Attachments: 1 - Safety Evaluation 2 - Significant Hazards Evaluation i 3 - Environmental Consideration 4 - Proposed Technical Specification !
Revisions !
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STATE OF MISSOURI )
Alan C. Passwater, of lawful age, being first duly sworn upon oath says that he is Manager, Licensing and Fuels (Nuclear) for Union Electric Company; that he has read the foregoing document and knows the content thereof;.that he has executed the same for and on behalf of said company with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge,
- information and belief.
By Alan C. Passwater i
Manager, Licensing and Fuels Nuclear SUBSCRIBED and sworn to before me this /7 day of /f Ati( , 1995. '
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BARBAR4 J. FAf "h NOTARY PUBUC-STATE OF MISSOURI MY COMMISSION EXPlRES APRIL 22,199Z ST. LOUIS COUNTY i
'cc: T. A. Baxter, Esq.
Shaw, Pittman, Potts & Trowbridge 2300 N. Street, N.W.
Washington, D.C. 20037 M. H. Fletcher Professional Nuclear Consulting, Inc.
19041 Raines Dr Derwood, MD 20855-2432 M. J. Farber Chief, Reactor ProjectsSection III A U.S. Nuclear Regulatory Commission Region III 801 Warrenville Road Lisle, IL 60532-4351 Bruce Bartlett Callaway Resident Office U.S. Regulatory Commission RR#1 Steedman, MO 65077 L. R. Wharton (2)
Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 1 White Flint, North, Mail Stop 13E21 11555 Rockville Pike Rockville, MD 20852-2738 Manager, Electric Department Missouri Public Service Commission P.O. Box 360 Jefferson City, MO 65102 Ron Kucera Department of Natural Resources P.O. Box 176 Jefferson City, MO 65102
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0 ULNRC- 0 319 8 ATTACHMENT ONE SAFETY EVALUATION i
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Attachment One
. Page 1 of 5 SAFETY EVALUATION INTRODUCTION This amendment application includes changes to Table 2.2-1 of Technical Specification 2.2.1 in order to reduce repeated alarms and partial reactor trips associated with the C-4 control system interlock and Overpower Delta-T (OPAT) that have occurred in past cycles. The C-4 interlock blocks control rod withdrawal and initiates turbine runback when its 2/4 logic coincidence is satisfied. The C-4 alarm setpoint is set slightly below the OPAT reactor trip setpoint. Typically, one channel will exceed the C-4 setpoint for its loop on any given occurrence, partially satisfying the C-4 logic requirement and resulting in an alarm on that channel. In some of these events, a partial reactor trip on OPAT also occurs. This situation has led to power reductions during past surveillance testing in order to avoid reactor trips since the channel being tested is placed in the tripped condition.
The changes to the Total Allowance (TA), K, 4 K, 6 and Allowable Value in Table 2.2-1 have been justified through the use of available margin. The editorial change to the Overtemperature Delta-T (OTAT) equation in Table 2.2-1 represents the manner in which these signals have always been electronically processed.
The Bases changes discuss the correlation between time constants for lag cards in the 7300 Process Protection System and the total lag time assumed in safety analyses which credit OTAT or OPAT for protection.
IMPACT ON SAFETY ANALYSES As depicted in FSAR Figure 15.0-1 and discussed in Section B-2 of WCAP-8745-P and WCAP-8746, " Design Bases for the Thermal Overpower AT and Thermal Overtemperature AT Trip Functions,"
March 1977, the Overpower AT protection line has two segments.
With Tavg less than or equal to its nominal value, 588.4 F, the trip protection line has a constant value equal to the product of the loop-specific ATo and the safety analysis limit (SAL) for K 4, 1.165, which is not being revised by this amendment application.
Therefore, this line segment portion of the trip protection line ;
is unaffected. With Tavg greater than 588.4 F, the trip
- protection line has a slope calculated using the intersection points of the overpower limit curve (118.52% of rated thermal power (RTP) at minimum measured flow plotted as a function of with the core thermal limit lines (for a DNBR equal to the Ta[e)ty sa analysis limits) . This line segment has been redrawn by Westinghouse based on analysis margin. Since the value for K6 18
1 Attachment One Page 2 of 5 directly proportional to the slope of this line segment, a reduction in the value for K6 from 0.006S/*F to 0.0015/*F has been justified by Westinghouse. Westinghouse has confirmed that the revised OPAT function, in conjunction with the OTAT and other RPS functions, will continue to ensure that the core thermal limit lines are adequately protected with the reduced K6 value. The maximum core thermal power for all ANS Condition II events will remain below 118.52% of RTP, as has been previously evaluated for Callaway (see FSAR Table 15.0-4). The only non-LOCA transient affected by this change, the steamline break coincident with rod withdrawal at power event discussed below, was reanalyzed by Westinghouse and it was determined that all applicable acceptance criteria continue to be met.
No changes have been made to the K4 SAL and the reduction in the value for K6 has been discussed above. There will be no impact on any previously performed analyses which credited OPAT (e.g.,
steamline break in the turbine building with coincident rod withdrawal as discussed in FSAR Section 3.11(B).7 and steamline breaks smaller than 0.24 square feet at full power conditions as discussed in WCAP-9226-P and WCAP-9227, " Reactor Core Response to Excessive Secondary Steam Releases," Revision 1, January 1978).
OPAT is assume:f to provide protection for some categories of plants in WCAP-10961-P, "Steamline Break Mass / Energy Releases for Equipment Environmental Qualification Outside Containment";
however, it was not required for the Category 1 plants, including Callaway, as shown in Tables III.B-1 through III.B-4 of WCAP-10961-P.
OPAT SETPOINT TERMS The current setpoint analysis for this trip function was submitted to NAC in ULNRC-2196 dated 4-12-90 in support of the RTD Bypass Elimination. The changes to that analysis due to this amendment application are a result of the change in the K4 setpoint. The Total Allowance (TA) reflects the difference between the nominal trip setpoint, in this case K 4 , and the SAL specified in FSAR Table 15.0-4. The SAL of 1.165 is unchanged.
The available margin between the SAL and the K4 setpoint, the latter being changed from 1.080 to 1.090, is used to accomplish the objectives of this amendment application. It follows that an increase in the K4 setpoint will lead to a corresponding decrease in TA from 5.7% AT span to 5.0% AT span. Using the equations for T 1, T, 2 and T3 in WCAP-11884 submitted in ULNRC-1822 dated 8-30-88, the limiting value for T, in this case T2 , is dacreased since the value for TA is decreased. The limiting valae for T corresponds to the Allowable Value which is reduced from 3.0% AT span to 2.4% AT span. The available setpoint margin, used to justify the increase in the K4 setpoint, is decreased since the Channel Statistical Allowance remains unchanged but, again, the value of TA has decreased. The K6 value is not a factor in the i
- e Attachment One Page 3 of 5 setpoint calculations and can be changed without affecting the available setpoint margin.
CTAT EOUATION AND BASES CHANGES The OTAT equation in Table 2.2-1 shows the lead-lag compensation associated with the term (1 + t 4 s)/(1 + Tss ) to be applicable to the T' term. This is incorrect. This error c&n also be found in Revision 4a of NUREG-0452, the Standard Technical Specifications (STS) at the time Callaway was licensed, as well as Revision 0 of the new STS NUREG-1431. This error apparently was taken from Section A-3 and Figure A-1 of WCAP-8745-P and WCAP-8746 as well as from Figure 6.1-4 of WCAP-7907-P-A, "LOFTRAN Code Description," April 1984. The latter reference has been corrected in Figure 6.1-4 of WCAP-7878, "LOFTRAN Code Description and User's Manual," Revision 5, November 1989. The lead-lag compensation applies only to the measured Tavg. This is consistent with the manner in which the electronics have always <
processed the OTAT setpoint signal, as depicted on Westinghouse drawing 8756D37 sheets 7-10 (referenced in FSAR Section 1.7 and submitted to NRC in Attachment 3 of ULNRC-1822 dated 8-30-88).
The Bases changes provide more description regarding the safety analysis treatment of first order lags in analyses crediting OTAT and OPAT, based on FSAR Table 15.0-4 and Table 7-1 of Attachment 1 to ULNRC-2196. i Changes discussed in this section are minor in nature and are not discussed further.
DETERMINATION OF NO UNREVIEWED SAFETY OUESTION The proposed changes to the Technical Specifications do not involve an unreviewed safety question because the operation of Callaway Plant in accordance with these proposed changes would not:
(1) Involve an increase in the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety previously evaluated in the FSAR.
Overall protection system performance will remain within the bounds of the accident analyses documented in FSAR Chapter 15, WCAP-10961-P for Category 1 plants such as Callaway, and WCAP-11883 since no hardware changes are proposed.
The OPAT reactor trip function provides protection against excessive power (fuel rod integrity protection within the fuel temperature design basis). No credit is taken for the OPAT trip in the Chapter 15 licensing basis accident analyses. The OPAT trip function is credited in non-
Attachment One l Page 4 of 5 licensing basis analyses of various steamline breaks (e.g.,
steamline break in the turbine building with coincident rod withdrawal as discussed in FSAR Section 3.11{B).7 and steamline breaks smaller than 0.24 square feet at full power conditions as discussed in WCAP-9226-P Rev. 1). ,
i The OPAT trip will continue to function in a manner consistent with the plant design basis. There will be no change to the OPAT safety analysis limit listed in FSAR Table 15.0-4. Therefore, there will be no degradation in the performance of or an increase in the number of challenges to equipment assumed to function during an accident situation. 1 The reactor trip system response time, as defined in the Technical Specifications, will be unaffected.
These Technical Specification revisions do not involve any I hardware changes nor do they affect the probability of any event initiators. There will be no change to normal plant !
operating parameters or accident mitigation capabilities. ,
Therefore, these changes will not increase the probability or !
consequences of an accident or malfunction.
(2) Create the possibility for an accident or malfunction of a different type than any previously evaluated in the FSAR.
As discussed above, there are no hardware changes associated with these Technical Specification revisions nor are there any changes in the method by which any safety-related plant ;
system performs its safety function, Revisions to the OPAT l values for K 4 and K6 will require scaling changes for summing amplifier cards (NSA cards) in the 7300 Process Protection !
System. These scaling changes are straightforward and similar in nature to those performed to implement OL Amendments 72 and 84 associated with the implementation of relaxed axial offset control (RAOC) and a revised OTAT f t I (AI) penalty function. The summing amplifier card that establishes the OPAT setpoint and implements K4 will require j a new bias whereas the summing amplifier card that implements K6 will require a new gain. These scaling changes will not affect the normal manner of plant operation. There will be a reduction in the incidence of C-4 alarms and partial reactor trips. There will be less of a need to reduce power during on-line surveillance testing.
No new accident scenarios, transient precursors, failure mechanisms, or limiting single failures are introduced as a result of these changes. There will be no adverse effect or challenges imposed on any safety-related system as a result of these changes. Therefore, the possibility of a new or different kind of accident is not created.
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There are no changes which would cause the malfunction of safety-related equipment, assumed to be operable in the accident analyses, as a result of the proposed Technical Specification changes. No new mode of failure has been created and no new equipment performance burdens are imposed.
Therefore, the possibility of a new or different malfunction of safety-related equipment is not created.
(3) Involve a reduction in the margin of safety as defined in the basis for any Technical Specification.
There will be no change to the Overpower AT safety analysis limit listed in FSAR Table 15.0-4. Available setpoint calculation margin will be used to increase the K4 value, reflected as a new bias on a summing amplifier card in each of the four protection loops. This will also require corresponding decreases in the OPAT Total Allowance and Allowable Value in Technical Specification Table 2.2-1.
Available margin in the OPAT trip protection function will be used to decrease the K6 value, reflected as a new gain on a summing amplifier card in each of the four protection loops.
As discussed above, the response time of the G.\T reactor trip function will remain unchanged.
It has been confirmed that the Z and S terms currently listed in Table 2.2-1 for the OPAT trip function will remain conse rvative . The change in K4 will require a decrease in the Total Allowance and Allowable Value for OPAT; however, this does not affect any margin of safety since the safety analysis limit, which preserves the overpower safety margin, is unchanged.
There will be no effect on the manner in which safety limits or limiting safety system settings are determined nor will -
there be any effect on those plant systems necessary to assure the accomplishment of protection functions. There will be no impact on the overpower limit, DNBR limits, Fg, FAH, LOCA PCT, peak local power density, or any other margin of safety.
Based on the information presented above, the proposed amendment does not involve an unreviewed safety question and will not adversely affect or endanger the health or safety of the general public.
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s ULNRC-03198 ATTACHMENT TWO SIGNIFICANT HAZARDS EVALUATION .
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Attachment Two
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. Page 1 of 3 SIGNIFICANT HAZARDS EVALUATION This amendment application includes changes to Table 2.2-1 of Technical Specification 2.2.1 in order to reduce repeated alarms and partial reactor trips associated with the C-4 control system interlock and Overpower Delta-T (OPAT) that have occurred in past cycles. The C-4 interlock blocks control rod withdrawal and initiates turbine runback when its 2/4 logic coincidence is satisfied. The C-4 alarm setpoint is set slightly below the OPAT reactor trip setpoint. Typically, one channel will exceed the C-4 setpoint for its loop on any given occurrence, partially satisfying the C-4 logic requirement and resulting in an alarm on that channel. In some of these events, a partial reactor trip on OPAT also occurs. This situation has led to power reductions during past surveillance testing in order to avoid reactor trips since the channel being tested is placed in the tripped condition.
The changes to the Total allowance (TA), K,4 K, 6 and Allowable Value in Table 2.2-1 have been justified through the use of available margin. The editorial change to the Overtemperature Delta-T (OTAT) equation in Table 2.2-1 represents the manner in which these signals have always been electronically processed.
The Bases changes discuss the correlation between time constants for lag cards in the 7300 Process Protection System and the total lag time assumed in safety analyses which credit OTAT or OPAT for protection.
The proposed changes to the Technical Specifications do not involve a significant hazards consideration because operation of Callaway Plant in accordance with these changes would not:
(1) Involve a significant increase in the probability or consequences of an accident previously evaluated.
Overall protection system performance will remain within the bounds of the accident analyses documented in FSAR Chapter 15, WCAP-10961-P for Category 1 plants such as Callaway, and WCAP-11883 since no hardware changes are proposed.
The OPAT reactor trip function provides protection against excessive power (fuel rod integrity protection within the fuel temperature design basis). No credit is taken for the OPAT trip in the Chapter 15 licensing basis accident analyses. The OPAT trip function is credited in non-licensing basis analyses of various steamline breaks.
The OPAT trip will continue to function in a manner consistent with the plant design basis. There will be no change to the OPAT safety analysis limit listed in FSAR Table 15.0-4. Therefore, there will be no degradation in the
- . l Attachment Two l
. . Page 2 of 3 performance of or an increase in the number of challenges to equipment assumed to function during an accident situation.
The reactor trip system response time, as defined in the Technical Specifications, will be unaffected.
These Technical Specification revisions do not involve any hardware changes nor do they affect the probability of any event initiators. There will be no change to normal plant operating parameters or accident mitigation capabilities.
Therefore, these changes will not increase the probability or consequences of an accident or malfunction.
(2) Create the possibility of a new or different kind of accident from any accident previously evaluated.
As discussed above, there are no hardware changes associated ,
with these Technical Specification revisions nor are there any changes in the method by which any safety-related plant system performs its safety function. Revisions to the OPAT values for K 4 and K6 will require scaling changes for summing amplifier cards (NSA cards) in the 7300 Process Protection System. These scaling changes are straightforward and similar in nature to those performed to implement OL Amendments 72 and 84 associated with the implementation of relaxed axial offset control (RAOC) and a revised OTAT f1 (AI) penalty function. These scaling changes will not affect the normal manner of plant operation. There will be a reduction in the incidence of C-4 alarms and partial reactor trips.
There will be less of a need to reduce power during on-line surveillance testing.
tio new accident scenarios, transient precursors, failure mechanisms, or limiting single failures are introduced as a resu?.t of these changes. There will be no adverse effect or challenges imposed on any safety-related system as a result of these changes. Therefore, the possibility of a new or different kind of accident is not created.
(3) Involve a significant reduction in a margin of safety.
There will be no change to the Overpower AT safety analysis limit listed in FSAR Table 15.0-4. Available setpoint calculation margin will be used to increase the K4 value, reflected as a new bias on a summing amplifier card in each of the four protection loops. This will also require corresponding decreases in the OPAT Total Allowance and Allowable Value in Technical Specification Table 2.2-1.
Available margin in the OPAT trip protection function will be used to decrease the K6 value, reflected as a new gain on a -
summing amplifier card in each of the four protection loops.
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Attachment Two
... . Page 3 of 3 As discussed above, the response time of the OPAT reactor trip function will remain unchanged.
It has been confirmed that the Z and S terms currently listed in Table 2.2-1 for the OPAT trip function will remain conservative. The change in K4 will result in a decrease in the Total Allowance and Allowable Value for OPAT; however, this does not affect any margin of safety since the safety analysis limit, which preserves the overpower safety margin, is unchanged.
There will be no effect on the manner in which safety limits or limiting safety system settings are determined nor will there be any effect on those plant systems necessary to assure the accomplishment of protection functions. There will be no impact on the overpower limit, DNBR limits, Fg, FAH, LOCA PCT, peak local power density, or any other margin of safety.
Based upon the preceding information, it has been determined that the proposed changes to the Technical Specifications do not involve a significant increase in the probability or consequences of an accident previously evaluated, create the possibility of a new or different kind of accident from any accident previously evaluated, or involve a sigriificant reduction in a margin of safety. Therefore, it is concluded that the proposed changes meet the requirements of 10CFR50.92(c) and do not involve a significant hazards consideration.
ULNRC-0319 8 ATTACIDENT THREE ENVIRONMENTAL CONSIDERATION -
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Attachment Threc Page1ofI
- ENVIROBDENTAL CONSIDERATION !
This amendment application includes changes to Table 2.2-1 of !
Technical Specification 2.2.1 in order to reduce repeated alarms and partial reactor trips associated with the C-4 control system interlock and Overpower Delta-T (OPAT) that have occurred in l past cycles. The C-4 interlock blocks control rod withdrawal and initiates turbine runback when its 2/4 logic coincidence is satisfied. The C-4 alarm setpoint is set slightly below the '
OPAT reactor trip setpoint. Typically, one channel will exceed l the C-4 setpoint for its loop on any given occurrence, partially !
satisfying the C-4 logic requirement and resulting in an alarm on l that channel. In some of these events, a partial reactor trip on OPAT also occurs. This situation has led to power reductions !
during past surveillance testing in order to avoid reactor trips ;
since the channel being tested is placed in the tripped 4
condition.
The changes to the Total Allowance (TA), K, 4 K, 6 and Allowable l Value in Table 2.2-1 have been justified through the use of ,
available margin. The editorial change to the Overtemperature !
Delta-T (OTAT) equation in Table 2.2-1 represents the manner in ;
which these signals have always been electronically processed.
The Bases changes discuss the correlation between time constants i for lag cards in the 7300 Process Protection System and the total lag time assumed in safety analyses which credit OTAT or OPAT :
for protection :
The proposed amendment involves changes with respect to the use :
of facility . components located within the restricted area, as defined in 10CFR20. Union Electric has determined that the proposed mmendment does not involve: i i
(1) A significant hazards consideration, as discussed in Attachment 2 of this amendment application; (2) A significant change in the types or significant increase in ;
the amounts of any effluents that may be released offsite; j
, (3) A significant increase in individual or cumulative ;
occupational radiation exposure.
l Accordingly, the proposed amendment meets the eligibility criteria for categorical exclusion set forth in 10CFR51.22 (c) (9) .
- Pursuant to 10CFR51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the i issuance of this amendment. l l
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