ML20003D517
| ML20003D517 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/23/1981 |
| From: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| To: | Clark R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20003D518 | List: |
| References | |
| NUDOCS 8103270570 | |
| Download: ML20003D517 (4) | |
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BALTIMORE GAS AND ELECTRIC CHARLES CENTER. P.O. BOX 1475 BALTIMORE, MARYLAND 21203 ARTHum E. LUNOVALL. JR.
March 23, 1981 va
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Office of Nuclear Reactor Regulation g
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G U. S. Nuclear Regulatory Commission Washington, D. C. 20555 J
S-li l.lo, 2 g IS8 l am. -Il ATTENTION: Mr. R. A. Clark, Chief u.s, k f h R 5
Operating Reactors Branch #3 Division of Licensing f
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SUBJECT:
Calvert Cliffs Nuclear Power Plant m gs-Units 1 and 2, Docket Nos. 50-317 and 50-318 Detection of Boron Dilution Incident REFERENCES (A):
R. A. Clark to A. E. Lundvall letter, dated 12/12/80, Unit i License Amendment No. 48 (B):
R. A. Clark to A. E. Lundvall letter, dated 2/10/81, Unit 2 License Amendment No. 31 Gentlemen:
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References (A) and (B) issued Amendment Numbers 48 and 31 to the Facility l
Operating Licenses for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 respectively. These amendments noted that no positive alarm presently exists to l
alert the operator to a dilution event that may be in progress and required that such an alarm be provided. BG&E agreed to develop a means of such notification I
during the current cycle for each unit.
Background
We find that operator notification can be provided with minimal hardware modifications and minor sof tware modifications by monitoring the Wide Range Log Channels (WRLC) of the Nuclear Instrumentation with the plant computer when in Modes 3 through 6.
Operability of at least.wo WRLC of Nuclear Instrumentation is presently required by Technical Specifications and computer availability to date is better than 98% for both units. The computer alarm causes a flashing indication on the computer monitor adjacent to the reactor control panel and the alarming parameter is also logged by the Alarm Typewriter. As a backup to this system, the plant boronometer is also available when the Charging and Letdown system is in operation and may also be used to monitor the Shutdown Cooling system when in cold shutdown and during refueling. In the unlikely event that both the WRLC alarm and the boronometer are inoperable when shutdown, i
shutdown margin will be increased and/or the WRLC signals will be logged such that the operator will be alerted with sufficient time to respond.
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810327o57o
Office of Nuclear Reactor Regulation Page two Technical Specification Change To provide the required time for operator action while avoiding spurious alarms,
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additional margin will be provided when in cold shutdown with the Reactor Coolant System filled to the center of the hot leg pipes.
This will be accomplished by requiring 4.3% shutdown margin when the pressurizer level is below 90 inches in mode 5 and by limiting dilution sources to the capacity of one charging pump (44 GPM). These steps increase the time from initiation of the dilution event until shutdown margin is lost from 19.6 to 51.7 minutes.
Proposed modifications to Technical Specification Pages 3/41-3,3/43-3,3/43-4, 3/4 3-5,3/4 3-8,3/4 3-9 and 3/4 9-2 are attached.
Safety Analysis It should be noted that plant equipment, practice, and administrative controls provide significant margin above that assumed for the boron dilution incident.
1.
Operation of the makeup system to borate or dilute actuates an annunciator on the control panel which sounds until acknowledged by the operator.
2.
Although the most limiting case for cold shutdown and refueling assumes that the RCS is filled only to the center of the reactor coolant hot leg pipes and that all Control Element Assemblies (CEA's) are fully withdrawn, the plant has never been in this configuration to date.
3.
During refueling, the analysis assumes 3 charging pumps (44GPM each) to be operable, although plant gractice is to tag out at least two pumps when RCS j
i temperature is below 275 F.
4.
In cold shutdown the analysis assumes 2 charging pumps to be operable, although plant practice is to tag out at least two pumps when RCS temperature is below 275 F.
5.
During refueling operations, inverse multiplication is calculated as each fuel assembly is loaded or CEA removed from the core.
CEA swaps are performed one at a time over the core or in the CEA Change Machine in the refueling pool. CENs are removed to the spent fuel pool only for inspection so that fen CENs are withdrawn at any one time. All CENs are fully inserted at all other times. The analysis assumes all CEAs are removed and the RCS is filled to the center of the hot leg pipes.
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Office of Nuclear Reactor Regulation Page three
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6.
The plant is not routinely in cold shutdown with the RCS filled only to the center of the RCS hot leg pipes. CEA withdrawal in this mode would involve at most one CEA at a time to check drive and position indication equipment. The analysis assumes all CEA's are fully withdrawn.
7.
The analysis assumes a RCS volume of 2778 cubic feet when the system is filled to the center of the hot leg pipes. This includes only the volu'ne in the Reactor Vessel to the bottom of the hot leg pipes and does not include the volume of the Shutdown Cooling System, which is required to be operable, or the volume of the RCS piping that is partially filled.
8.
When shutdown, the signal from one operable WRLC is trended continuously on a dedicated pen recorder on the reactor control panel, providing the operator with a visual indication of trend in neutron population.
9.
The analysis assumes 4.0% shutdown margin in hot standby (Mode 3) and hot shutdown (Mode 4) although 4.3% shutdown margin is actually provided.
Incorporation of the WRLC alarm feature and increasicg the time to criticality when the RCS is partially drained provides additionaf margin in the event of inadvertent boron dilution. The Plant Operations and Safety Revie
- Committee (POSRC) and the Offsite Safety Review Committee (OSSRC) have a aciuded that the proposed modification does not constitute an mreviewed safety question and that the proposed action does not present an undue risk to the health and safety of the public.
Very truly yours, BALTIMORE GAS AND ELE IC COMPANY A. E. Lunfvall, Jr.
y Vice Pre (ident - Supplyl STATE & MaRYI.#0, CITY CF BALTIMRE,10 WIT:
Arthur E. Lundvall, 3r., being duly sworn states that he is Vice l
Office of Nuciear Reactor Regularion Page four President of the Baltinnre Gas and Electric Carpany, a corporation of the State of Maryland; that he executed the foregoing Anendnent for the purposes therein set forth; that the statements nude in said Anendnent are true and correct to the best of his knowledge, inf omation, and belief;and that he was authorized to execute the Anendnent on behalf of said Corporation.
WI"IMESS, My Hand and Notarial Seal this 4 7 tctday of
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1981.
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Notary Public
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My Ccmnission Expires:
1 i-AtIachment AEI./fEB/db cc: 3. A. Biddison, Esquire G. F. Trowbridge, Esquire Messrs.
E. L. Conner, Jr.,P@C P. W. Kruse, l
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