ML20196J677
| ML20196J677 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 12/08/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20196J676 | List: |
| References | |
| NUDOCS 9812100169 | |
| Download: ML20196J677 (4) | |
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g NUCLEAR REGULATORY COMMISSION
's WASHINGTON, D.C. 20656 4 001
.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 22 9 TO FACILITY OPERATING LICENSE NO. DPR 53 AND AMENDMENT NO. 204 TO FACILITY OPERATING LICENSE NO. DPR 69 BALTIMORE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS.1 AND 2 DOCKET NOS. 50-317 AND 50-318
1.0 INTRODUCTION
By application dated October 16,1998, Baltimore Gas and Electric Company (BGE or the licensee) requested changes to the Technical Specifications (TSs) (Appendix A to Facility Operating License Nos. DPR-53 and DPR-69) for Calvert Cliffs Nuclear Power Plant (CCNPP),
Unit Nos.1 and 2. The proposed amendment replaces the operating bypass input process variable, " THERMAL POWER," in Footnotes (a), (b), and (d) TS Table 3.3.1 1 and in the Note to Limiting Condition for -Operation (LCO) 3.3.2 with " NUCLEAR INSTRUMENT (NI) POWER." In addition, for clarification, the proposed change would add *NI POWER" to Footnote (e) of Table 3.3.1-1 as the input process variable. THERMAL POWER, as defined, is a term that includes decay heat, which is not a directly measurable parameter, thus is not a reasonable parameter for automatically establishing bistable conditions. The proposed change would clarify inconsistencies in terminology between the TS wording and the Design Bases as described in the TS Bases and the Updated Final Safety Analysis Report (UFSAR).
2.0 DISCUSSION TS Table 3.3.1-1, " Reactor Protective System (RPS) Instrumentation - Operating," Footnotes "a",
"b", *d", *e" and TS 3.3.2, " Reactor Protective System (RPS) Instrumentation - Shutdown," LCO 3.7 2 identify operating bypasses for RPS Trip Functions. The RPS Footnotes and Notes, as it pertains to the above, contains provisions for bypassing trip signals under certain conditions in order to perform tests, to perform maintenance, or to inhibit trip during special operational conditions. Some bypasses are actuated automatically while others must be actuated manually with a key-lock system. The automatic bypass removal features must function as a backup to manual actions for all trips credited in safety analyses to ensure the trip Functions are not operationally bypassed when the functions are not bypassed.
9812100169 981200 PDR ADOCK 05000317 P
PDR Enclosure l
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The following are the affected Footnotes to the TS Table 3.3.1-1 and the Note to LCO 3.3.2 with the corresponding Functions.
j Footnote (a) states, " Bistable trip unit may be bypassed when THERMAL POWER is < 10 %
d RATED THERMAL POWER (RTP) or > 12% RTP. Bypass shall be automatically removed when THERMAL POWER is 210 % RTP or > 12% RTP." Footnote (a) applies to RPS Function Rate
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d of Change of Power-High.
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- Footnote (b) states, " Bistable trip unit may be bypassed when THERMAL POWER is < 10 %.
d Bypass shall be automatically removed when THERMAL POWER is 210 % RTP. During testing d
pursuant to LCO 3.4.16, trips may be bypassed below 5% RTP." Footnote (b) applies to RPS Functions Reactor Coolant System Flow - Low, Thermal Margin / Low Pressure, and Asymmetric Steam Generator Transient.
Footnote (d) states, " Bistable trip unit may be bypassed when THERMAL POWER is < 15% RTP.
Bypass shall be automatically removed when THERMAL POWER is 215% RTP." Footnote (d) i applies to RPS Functions Axial Power Distribution - High and Loss of Load.
Footnote (e) states, " Trip is only applicable in MODE 1215% RTP." Footnote (e) applies to RPS Functions Axial Power Distribution - High and Loss of Load.
Note to LCO 3.3.2 states," Bistable trip units may be bypassed when THERMAL POWER is < 10'
'% RTP. Bypass shall be automatically removed when THERMAL POWER is 210 % RTP." The d
Note to LCO 3.3.2 applies to RPS Function Rate of Change of Power-High.
TS 1.1 defines THERMAL POWER as "the tota 1 reactor core heat transfer rate to the reactor coolant." In addition to the heat generated by the incore fission rate, this definition of THERMAL POWER includes energy deposited in the coolant from the radioactive decay of fission products generated by earlier fissions. This decay manifests itself through the emission, over a period of time, of gamma rays and beta particles. This gamma ray and beta particle heat source continues to exist after the fission process ceases and, for a previously operated commercial reactor, this decay heat source persists during any reactor shutdown. If a reactor that has experienced sustained power operation were to be subsequently maintained subcritical for an extended period, a long period of time would be required for this residual energy to decrease to a level where the core heat transfer rate to the coolant corresponds to 10 %, or less, of RATED d
THERMAL POWER. The level of decay heat has no relationship to the present reactivity of the core and, as such, it has no relevance in determining or anticipating the rate of change of reactor (fission) power due to potential reactivity changes, including those originating from subc.-itical conditions. Changes in core reactivity are most directly correlated to changes in the neutron population, and any consequential changes in the fission product inventory will follow after a time. The inherent nature of the fission product decay process, therefore, ensures that the energy released through fission product decay lags the initiating fission event. This delayed energy release effect provides a sound basis for concluding that power level determinations that require the inclusion of decay heat are not suitable for use as an operative parameter for those automatic protective system actions involving the detection of or response to excessive neutron multiplication. Typically, decay heat is not a parameter directly measurable by plant nuclear instrumentation.
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3 The zero power (provided by Footnote b) RPS operational bypass is designed to allow suberitical testing of the control element drive mechanism and to prevent false trips during normal heat-up and cool-down. As currently written, verbatim compliance with zero mode operational bypass provided by Footnote (b), would prevent plant start-up due to false trips.
3.0 EVALUATION l
The TS Table 3.3.1-1 notes "a", "b", and "d" as well as LCO 3.3.2 require automatic removal of the bypasses under specified conditions, which would require the use of a measurable parameter. Since the decay heat component of" THERMAL POWER"is not directly measurable, it is not suitable for use for an automatic action. The use of NI Power instead of " THERMAL POWER" as the process parameter would also make the TS consistent with the design bases for i
establishing and removing the bypasses. The CCNPP Unit 1 and Unit 2 TS 3.3.1 Bases, as well I
as the Bases for the Standard TS for Combustion Engineering designed plants (NUREG-1432) i use Ni Power to establish the 1E-4% RTP bypass. The UFSAR Section 7.5.2 describes the bypass setpoints in terms of NI power. This section also describes setpoints in terms of various measured parameters. In Subsections 7.5.2.4 and 7.5.2.5 it states in part that the " wide-range logarithmic channels" and the " power range linear channels" provide signal for the operating bypass permissive and trip enable bistables.
The TS Bases state in part, "Zero power mode bypass.. is manually enabled below the specified setpoint to permit low power testing. The wide range N/ Level 1 bistable in the wide range drawerprovides a signalto auxiliary logic, which then permits manual bypassing below the setpoint and removes the bypass above the setpoint. " The TS bases references NI multiple times and is clear 1y the obvious input for the process variable. Thus the intended, as well as the only physically possible means of generating a signal from a measured parameter to automatically remove the bypass, and the intended parameter used to determine when these trips can be bypassed, is neutron flux, which is measured by the nuclear instrumentation.
By replacing " THERMAL POWER" with "Ni POWER" in Footnote (a), (b), and (d) of TS Table 3.3.1-1, in the Note to LCO 3.3.2, and clarifying Footnote (e) of TS Table 3.3.1-1, will make the TS input process variable consistent with the Design Bases as described in the UFSAR and the TS Bases. In addition, neutron flux is, by design, the correct input process variable for the operating bypass permissive bistable values and therefor this proposed change is acceptable.
4.0 STATE CONSULTATION
in accordance with the Commission's regulations, the staff consulted with Maryland State official for comment on the proposed issuance of the amendment. The Maryland State official had no comment on the proposed amendment.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (63 FR 57320). Accordingly, the amendment
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meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmentalimpact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
6.0 CONCLUSION
The Commission 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 the amendment will not be inimical to the common defense and security or to the health and safety of the public.
PrincipalContributor. J. Foster Date:
December 8, 1998
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