ML20116E602
| ML20116E602 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/11/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20116D885 | List:
|
| References | |
| FOIA-96-237 NUDOCS 9608060054 | |
| Download: ML20116E602 (5) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION n
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WASHINGTON, D. C. 20555
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ENCLOSURE 1 SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION TECHNICAL SPECIFICATIONS CHANGE REQUEST CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2 REACTOR VESSEL LEVEL MONITORING SYSTEM DOCKET NOS. 50-317, 50-318
1.0 INTRODUCTION
In a letter dated July 10, 1987, Baltimore Gas and Electric Company (BG&E) requested amendments to the Technical Specifications (TS) for the Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (CC-1/2) (Ref 1).
The proposed amendments address operability requirements for the Reactor Vessel Level Monitoring System (RVLMS).
The RVLMS is one of three systems used to indicate the potential for inadequate core cooling. The other two systems are the Subcooling Margin Monitor (SMM) and the Core Exit Thermocouples (CETs). As stated by the licensee, the purpose of the RVLMS is to help the operator 1) track an event, 2) assess the function-ing of automatic equipment, and 3) detect the consequences of mitigating actions.
The RVLMS uses a Combustion Engineering Heated Junction Thermocouple (HJTC) system to detect the presence of highly voided coolant above the top of the reactor core. The presence of highly voided coolant is inferred from the differential temperatures between vertically adjacent HJTC probes.
If two HJTCs indicate approximately the same temperature, the operator can infer that the same thermodynamic conditions exist at both HJTC locations.
If adjacent HJTCs indicate significantly different temperatures, the operator can infer that the hotter HJTC is in a highly voided region of the vessel, and the cooler HJTC is still in a region of the vessel that has low-void-fraction coolant.
The NRC staff originally proposed a TS action statement that required a plcnt shutdown within seven days if less than two channels of RVLMS were OPERABLE, and within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> if less than one channel was OPERABLE. The NRC staff and the Combustion Engineering Owners Group (CE0G) discussed the safety signiff-cance of not having the RVLMS available, and concluded that the proposed TS was too restrictive. The CE0G submitted a less restrictive TS, which was then proposed for Palo Verde Unit 1, which the NRC staff reviewed and approved (Ref 2).
The CE0G and Palo Verde Unit 1 TS requires that, with one RVLMS channel inoperable, either the system is restored to OPERABLE status within seven days or a Special Report must be submitted to the NRC within 30 days detailing the cause of the inoperability and the schedule for restoring the system to OPERABLE status. With the number of OPERABLE channels two less than required (no OPERABLE channels), operation may continue until the next scheduled refueling provided an alternative method of monitoring for core and reactor coolant system voiding is available, and the licensee submits a Special Report to the NRC within 30 days detailing the cause of the inoperability and the schedule for restoring the system to OPERABLE status.
The BG&E justifi-cation for the requested TS amendments is based on the staff's approval of the Palo Verde Unit 1 TS requirements.
9608060054 960731 PDR FOIA DINICOL96-237 PDR
L, 2.0 EVALUATION The staff accepts the licensee's proposed footnote at the bottom of TS Table 3.3-10.
This footnote defines an OPERABLE RVLMS channel as eight sensors in a probe, consisting of one or more operable sensors in the upper three, and three or more operable sensors in the lower five. This footnote is consistent with the previously approved TS definition of an operable RVLMS channel (Ref 2).
The licensee proposes changing the phrase " reactor coolant system inventory" to l
" reactor coolant system voiding" in Action Statement 35.1 of the standard RVLMS l
Technical Specifications (Ref 1), resulting in, " Initiate an alternative method of monitoring for reactor coolant system voiding." The licensee states that this statement is more consistent with the Emergency Operating Procedures (E0Ps) that give guidance in determining whether voids exist in the reactor l
vessel and reactor coolant system. The staff finds this change acceptable.
The licensee requests permission to substitute the words "at least one channel" for "the system" in Action Statement 35.3 of the TS, resulting in, " Restore at least one channel to OPERABLE status at the next refueling." The licensee claims that the use of " system" in Action Statement 35.3 is ambiguous because i
it does not define whether the " system" is comprised of one or both RVLMS channels. This statement is not consistent with the licensee's description of the RVLMS on Page 2 of their July 10, 1987, submittal (Ref 1), which states, "The RVLMS [ Reactor Vessel Level Monitoring System] consists of two independent i
safety channels. Each channel consists of a probe assembly, support tube, j
pressure boundary modifications, signal processing equipment, and an operator interface." There is no ambiguity in the use of " System" in the above descrip-4 tion; ergo, there is no ambiguity in Action Statement 35.3.
This requested amendment lessens the requirement for restoring both channels to OPERABLE l
during a refueling outage, and is therefore not acceptable.
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In a staff request for additional information (Ref 3), the licensee was asked to address return to 100% plant power with both RVLMS channels inoperable, based on the location of the failure (inside the reactor vessel, inside the containment, and outside the containment) for operating Modes 1-5 prior to refueling, Mode 6 (refueling), and Modes 1-5 post-refueling.
In response (Ref 4), the licensee states that if a Unit is in Modes 1-5 prior to refueling or in Mode 6, the plant cannot return to 100% power. This action is acceptable.
The licensee states that if the plant is in Modes 1-5 after refueling, the plant can return to 100% power if the failure is inside the reactor vessel, because replacement of a channel is not feasible during post-refuelitg Modes 1-5, and there is suf ficient redundant instrumentation to monitor reactor coolant system void indications. Given the diversity of instrumentation available to detect reactor coolant system void indications, and the necessity to cool down the plant prior to replacing a failed channel, the licensee's response is acceptable.
The licensee states that the plant can return to 100% power if a RVLMS failure occurs inside containment when the plant is in Modes 1-5 after refueling.
The licensee's justification is based on minimizing man-rem doses and (implied)
f short term parts availability considerations. The licensee qualifies their position by stating, "All attemtts will be made to repair at least one channel.
If repairs are not feasible, the Units can be operated until the next refueling shutdown as long as alternate methods of void detection are initiated." The staff notes that TS action statements concerning loss of an alternate method of monitoring voiding in the reactor coolant system (either SMM or CET) that cannot be restored to OPERABLE will force a plant shutdown.
Therefore, the staff accepts the licensee's proposed criterium.
The licensee states that if a RVLMS channel becomes inoperable due to failures outside the containment during post-refueling Mode 1-5 operations, the Units coula return to 100% power. The licensee comits to makirig all attempts to repair at least one channel as soon as possible. This response is only qualitative, but does indicate a commitment on the part of the licensee to address channel inoperability when it occurs. Given the number of diverse systems for indicating the potential for inadequate core cooling, and the licensee's commitment to repair failed RVLMS channels as soon as possible, the staff finds this portion of the licensee's requested amendment acceptable.
The licensee states (Ref 4) that the calibration frequency for the HJTC probes should be changed from R (Refueling interval) to N/A (Table 4.3-10. " Post-Accident Monitoring Instrumentation Surveillance Requirements") because, once installed, the RVLMS sensors cannot be recalibrated. Consequently, a channel check is the l
only surveillance performed on the HJTCs. This response is acceptable.
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3.0 CONCLUSION
S The licensee's request for exemption from restoration of a RVLMS channel during post-refueling operations (Modes 1-5) due to dose concerns, and physical access and short term parts availability constraints is acceptable. The licensee l
contends there is enough diversity in the inadequate Core Cooling Indications (ICCl) instrumentation that a failure of both RVLMS channels while in post-
-refueling Modes 1-5 does not justify a requirement for plant cooldown, removal of the upper head missile shield, and opening of the reactor vessel manway.
Based on the licensee's commitment to repair a failed RVLMS channel if it is feasible to do so, and the diversity of the ICCI instrumentation, the staff finds the licensee's commitment acceptable.
The licensee's request for a reduction in the number of RVLMS channels that must be returned to OPERABLE status prior to entering Mode 5 conditions following refueling operations (Mode 6) is not supported by the justifications for exemption discussed above. Consequently, the licensee's substitution of the phrase "at least one channel" for the phrase, "the system" in the proposed Action Statement 35.3 is not acceptable.
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REFERENCES i
1.
Letter from J. A. Tiernan (BG&E) to NRC Document Control Desk, dated July 10, 1987, "Calvert Cliffs Nuclear Power Plant Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318, Request for Amendment."
i 2.
Letter from D. M. Crutchfield (NRC) to R. W. Wells (CEOG), dated October 28,1986, " Safety Evaluation of Generic Technical Specification Proposed by Combustion Engineering Owners Group for the Reactor Vessel Level l
Monitoring System."
l 3.
Letter from S. A. McNeil (NRC) to G. C. Creel (BG&E), dated August 3, 1989, " Request for Additional Information - Technical Specifications for i
Reactor Vessel Level Monitoring System (Unit 1 TAC 67954; Unit 2 TAC l
67955)."
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4 Letter from G. C. Creel (BG&E) to NRC Document Control Desk, dated August 31,1989, "Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318, Response to Request for Additional Information Regarding Reactor Vessel Level Monitoring System."
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s ENCLOSURE 2 SALP INPUT FACILITY NAME: Calvert Cliffs Nuclear Power Plant, Units No.1 & 2 i
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SUMMARY
OF REVIEW:
L The instrumentation aspects of the Technical Specification changes proposed by the licensee for the Calvert Cliff s Nuclear Power Plant Units No.1 & 2 were reviewed by SICB/ DST /NRR staff. The proposed changes to the surveillance j
intervals, the maintenance requirements, and operating Modes without the i
minimum required RVLMS channels that were found acceptable to the NRC staff do not present an impact upon the safe operation of the Units.
l NARRATIVE DISCUSSION OF LICENSEE PERFORMANCE FUNCTIONAL AREA - ENGINEERING / TECHNICAL SUPPORT.
The licensee submittals indicate an assurance of quality including management involvement and commitment to NRC initiatives. The submittals indicate an understanding of technical issues and how these issues relate to safety.
The timely and comprehensive submittals indicate adequate and effective staffing.
AUTHOR: Michael E. Waterman DATE:
02/16/90
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