ML20037D582
| ML20037D582 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 08/04/1981 |
| From: | Clark R Office of Nuclear Reactor Regulation |
| To: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8108270619 | |
| Download: ML20037D582 (3) | |
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AUG 041981 Get Fild B. Sheron NRC PDR J. Laaksonen Docket Nos. 50-317 L PDR and 50-318 NSIC TERA DRB#3 Rdg D. Eisenhut Mr. A. E. Lundvall, Jr.
OELD Vice President - Supply I&E-3 R. A. Clark Baltimore Gas & Electric Company.
M. Cenner P. O. Box 1475 Baltimore, Maryland 21203 P.M. Kreutzer-3 ACRS-10
Dear Mr. Lundvall:
J. Holtemes Gray Files We have been reviewing your March 23, 1981 submittal regarding boron dilution event positive alarm. We find that additional information, as delineated in the enclosure, is necessary to complete our review.
t We request that yourprovide the additional information requested within 60 days after receipt of tnis letter.
Sincerely.
Original signed by Robert A. Clark Robert A. Clark, Chief Operating Reactors Branch #3 Division of Licensing
Enclosure:
As stated l
CC: See Next page i
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Request for Additional Information Baltimore Gas and Electric Company Calvert Cliffs, Units _ No. I and 2 Dockets No. 50-317 and 50-318 1.
In the proposed Technical Specifications (TS) change you have :;plit section 3.1.1.2-in two parts. The second of them, subsection 3.1.1.2.2, to be ap-plied when partially draining the reactor coolant system in the cold shut-down mode, requires that the shutdown margin is increased to 4.3% and two charging pumps are taken out of service. An analysis of this parti. ally drained cold shutdown mode has given a minimum time of 51.7 minutes from
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,the initiation of the dilution event to criticality.
However, we do not think it is the most limiting case because:
a.
'he active volume of coolant circulatina in the reactor pressure vessel and the RHR loop during the cold shutdown mode with the primary loop filled up is not significantly larger than the active volume in the drained mode; and b.' The proposed TS 3.1.1.2.1 permits a shutdown margin of only 3.0% and does not limit the number of operable charging pumps.
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_ Provide either an analysis of an event caused by inadvertent operation of all three charging pumps during a normal cold shutdown mode, or consider upgraded limitations to the shutdown margin and to the number of. available charging pumps in the normal cold shutdown mode.
2.
The c.-iteria in SRP 15.4.6 do not refer to the time of initiation of a dilution event, but to the time of alarm.
In o'rder to determine that the l
time interval available for corrective measures meets the intervals stated in SRP 15.4.6, information on the method of determining alarm setting and alarm time is needed.
To support proposed Elarm settings, calculational results which describe the correlation between the neutron flux and boron dilution need to be provided. Also, identify the procedure (s) that will-j be modified to specify how the operating staff determines the correct alarm setpoints.
3.
It is the staff's position that the single failure criteria should be met when evaluating the capability to protect against boron dilution events.
To meet this criteria, two independent means should be available for de-tecting and alerting the operator to a boron dilution event during all modes of operation. Alerting means an audible signal.
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a We find your submittal unclear on this point.
Proposed TS Table 3.3-1 would require a minimum of 2 Criticality Alarms in the Shutdown Modes 3, 4, and 5.
The " Background" section indicates its two WRLC alarming through the single ccmputer with a backup plant boronometer.
The Calvert Cliffs FSAR Table _9-12 gives the range of the boronometer as 0-2000 ppm.
If this is correct, we do not understand how the boronometer can be used during cold shutdown or refueling.
We suggest you select two independent methods of alarming a boron dilution event and make applications for appropriate T.S.
Backup for either channel being out of service could be operator recording a reliable indication of reactivity status at stated time intervals, which, when added to the " alarm to event time (15 or 30 min)" is less than the calculated time from initiation of the boron dilution event to criticality. The backup monitoring should also be covered in the TS.
4 In your analyses, you do not take into account the possibility of having continous f',w of unborated water through the standing charging pumps.
Such flow might be established by the operation of a make-up pump controlling level in the CVCS tank. The capacity of that pump is not given in FSAR.
~ Please discuss the possibility of flow higher than 44 gpm with two charging pumps out of service.
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