ML20087L514
| ML20087L514 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 08/21/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20087L503 | List: |
| References | |
| NUDOCS 9508250314 | |
| Download: ML20087L514 (3) | |
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,# cao g UNITED STATES p*
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,j NUCLEAR REGULATORY COMMISSION
't WASHINGTON, D.C. 20566-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.102 TO FACILITY OPERATING LICENSE NO. NPF-30 MLQN ELECTRIC COMPANY _
CALLAWAY PLANT. UNIT 1 DOCKET NO. 50-483
1.0 INTRODUCTION
By letter dated April 17, 1995, Union Electric Company (UE), requested an i
amendment to Operating License NPF-30, which would change the Technical Specifications (TS) for the Callaway Plant, Unit 1.
The proposed amendment would revise TS 2.2.1, Table 2.2-1, " Reactor Trip System Instrumentation Trip Setpoints," and modify the Overpower Delta-T (0 PAT) setpoint.
The proposed changes are requested to reduce repeated alarms and partial reactor trips associated with the C-4 control system interlock and OPAT rod stop that have occurred in past cycles.
The C-4 interlock blocks control rod withdrawal and l
initiates turbine runback when its 2/4 logic coincidence is satisfied.
Typically, one channel will exceed the C-4 setpoint for its loop partially satisfying the C-4 logic requirement and resulting in an alarm on that channel. An upper plenum flow anomaly causes a temperature gradation which l
results in T greater than nominal for one loop and the C-4 setpoint being exceededfor,Thatloop. The licensee has proposed changes to the setpoint based on reanalysis.
The June 30, 1995, submittal provided suppiemental information which did not affect the initial proposed no significant hazards determination.
i 2.0 EVALUATION I
Callaway has had a flow anomaly in the upper plenum of the reactor vessel since Cycle 2.
The anomaly is characterized by a periodic, opposing step changes in loops 2 and 3 hot leg temperatures. During the anomaly transient, hotter water from the center of the core is redirected towards loop 2 while cooler water form the periphery of the core is redirected towards loop 3.
Callaway has experienced 1.5"F temperature swings occurring 3-4 times an hour.
The frequency and magnitude of the temperature swings vary from cycle to cycle and are not necessarily constant during a particular cycle. At the beginning of Cycle 7 (November 28, 1993 to March 26,1994) the average alarm rate was 1 alarm / day, however, on occasion as many as 7 alarms were received in one day.
Proposed changes are to the Total Allowance (TA), K, K, and the Allowable 4
6 Value in Table 2.2-1.
Westinghouse, the licensee's vendor, has confirmed that the revised OPAT function, in conjunction with the Overtemperature Delta-T (OTAT) and other reactor protection system functions, will continue to ensure that the core thermal limit lines are adequately protected.
In addition, the
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licensee has stated that their analysis indicates that the ;naximum core 9508250314 950821 PDR ADOCK 05000483
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3 thermal power for all American Nuclear Society Conditions II events will remain below 118.52% of rated thermal power as was previously evaluated for Callaway. While performing the evaluation to justify the changes in the OR6T setpoint function, Westinghouse determined that it was necessary to reanalyze j
the full power steam line break coincident with rod withdrawal transient.
i This transient was reanalyzed using the LOFTRAN computer code which simulates the neutron kinetics, reactor coolant system (RCS), pressurizer relief and safety valves, pressurizer spray, steam generator and steam generator safety i
valves. The code computes pertinent plant variables, including temperatures, i
pressures and power level. Upon initiation of the steamline break, control i
rods begin to withdraw. The rod withdrawal causes an increase in reactor power and core heat flux to the point at which the ORAT trip setpoint is reached. Then a reactor trip occurs and control rods insert.
The most limiting part of this transient occurs immediately prior to the reactor trip.
' A departure from nucleate boiling analysis determined that departure from nucleate boiling ratio was greater than the safety analysis limit values at all times during the transient. Additionally, the peak linear heat rate and l
j RCS pressure remained below their respective limits.
The staff has determined that the analyzed results were acceptable; therefore, the proposed changes are acceptable.
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3.0 STATE CONSULTATION
l In accordance with the Commission's regulations, the Missouri State official was notified of the proposed issuance of the amendment. The State official l
had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements.
The staff has determined that the amendment involves no significant increase in the amounts, and no l
significant change in the types, of any effluents that may be released offsite i
and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a j
proposed finding that this amendment involves no significant hazards.
consideration and there has been no public comment on such finding 1
i (60 FR 24922). Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
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5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(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 Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
M. Chatterton Date: August 21, 1995 i
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