ML20054C348
| ML20054C348 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 04/14/1982 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsel W CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| TASK-06-07.B, TASK-6-7.B, TASK-RR LSO5-82-04-040, LSO5-82-4-40, NUDOCS 8204200410 | |
| Download: ML20054C348 (5) | |
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April 14,1982 Docket flo. 50-213 LS05-82-04-040
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!!r. W. G. Counsil, Vice President
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fluclear Engineering and Operations
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Hartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
FORWARDING DRAFT EVALUATION REPORT OF SEP TOPIC VI-7.B (SYSTEliS), ESF SWITCl!OVER FR0fi INJECTI0fl TO RECIRCULATION
!!0DE (AUTOMATIC ECCS REALIGNf1ENT) FOR THE HADDNi NECK PLAf{T Enclosed is a copy of our draft evaluation of SEP Topic VI-7.0, ESF Switchover From Injection to Recirculation Mode. This assessment compares your facility, as described in Docket No. 50-213.with the criteria currently used by the regulatory staff for licensing new facilities.
Please inform us if your as-built facility differs from the ifcensing basis assumed in our assessment.
We have previously issued an evaluation of the adequacy of the instru-mentation provided to the operator for switchover on May 21, 1 981'.
Both that letter and the enclosed evaluation recommend changes to the plant design.
The need to actually implement these changes will be determined in the integrated plant safety assessment.
This evaluation will be a basic input to the integrated safety assess go /
Coments are requested within 30 days of receipt of this letter.
t ment for your facility unless you identify changes needed to reflect
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the as-built conditions at your facility. This assessment may be
//I revised in the future if your facility design is changed or if NRC 4 gfh criteria relating to this subject are modified before the integrated assessment is completed.
Aos:
Sincerely, Dennis M. Crutchfield, Chief e204200410 e20414 Operating Reactors Branch No. 5 PDR ADOCK 05000213 P
PDR Division of Licensing
Enclosure:
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Mr. W. G. Counsil cc Day, Berry & Howard Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Superintendent Haddam Neck Plant RFD #1' Post Office Box 127E East Hampton, Connecticut 06424
. Mr. Richard R. Laudenat Manager, Generation Facilities Licensing Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 Board of Selectmen Town Hall Haddam, Connecticut 06103 State of Connecticut 0Ffice of Policy and Management ATTN:
Under Secretary Energy Division 80 Washingten Street Hartford, Connecticut 06115 U. S. Environmental Protection Agency Region I Office ATTN:
Regional Radiation Representative JFK Federal Building Boston, Massachusetts 02203 Resident Inspector Haddam Neck Nuclear Power Station c/o'U. S..NRC East Haddam Post Office East Haddam, Connecticut 06423 Ronald C. Haynes, Regional Administrator Nuclear Regulatory Commission, Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 e
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SYSTEMATIC EVALUATION PROGRAM TOPIC VI-7.B HADDAM NECK TOPIC:
VI-7.B. ESF SWITCHOVER FROM INJECTION TO RECIRCULATION MODE (AUTOMATIC ECCS REALIGNMENT)
I.
INTRODUCTION Following a loss of coolant accident (LOCA), safety injection is auto-matica11y initiated by a safety injection signal (SIS). The signal starts the two low pressure safety injection pumps, the two high pressure safety injection pumps and automatically transfers the suction of the two centrifugal charging pumps from the volume control tank to the refueling water storage tank (RWST).
To avoid damage to these ECCS pumps and assure abundant cooling water supply to the core, ECCS pump suction must be switched to the contain-ment building sump before the RWST is emptied. The operator should start the switchover when the capacity of the RWST is down to 100,000 gallons.
However, there is no alarm available that will alert the operator to start the switchover when the level in the RWST is down to the 100,000 gallon level.
The only low level alarm on the RWST is initiated when the borated water volume in the RWST is 230,000 gallons.
II.
REVIEW CRITERIA The plant design was reviewed with regard to Appendix A,10 CFR 50, General Design Criteria - 35, " Emergency Core Cooling," which requires that a system to supply abundant emergency core cooling be provided.
III.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited to avoid duplication of effort since some aspects of the review were performed under related j
topics. The related topics are identified below:
III-6 Seismic Design Considerations III-10. A Thermal-overload Protection for Motor Operated Valves III-11 Component Integrity l
III-12 Environment Qualification IV-1.A Operation With less Than all Reactor Coolant Loops in j
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V-10.B RHR Reliability l
V-11 High Pressure / Low Pressure Interface VI-10. A Testing of ESF System i
. IV.
REVIEW GUIDELINES Item 19 of the review procedures in SRP Section 6.3 states that the complete sequence of ECCS operation from injection to long term core cooling (recirculation) is examined to confirm that a minimum of manual actions is required and that where manual action is needed, sufficient time (about 20 minutes) is available for the operator to respond.
Further guidance on timing of operator actions is provided by draft ANSI Standard N660.
V.
EVALUATION The switchover from injection to the recirculation mode is a fully manual procedure that requires an extremely precise execution of manual actions by the operator in order to assure no interruption of core cooling flow following a design basis LOCA.
The operator should have a redundant low level alarm that alerts him to start the switchover procedure.
The low level alarm comes on when the RWST volume is 230,000 gallons.
At this level, the operator cannot start the switchover because the water level in the sump is still very low.
He has to wait for at least 7 minutes before he can start the switchover.
Within these 7 minutes he is required to complete several other manual actions.
There is no alarm to alert him that the 100,000 gallon level has been reached and that he should start the switchover, Thus, if we assume a single failure in the low level alarm at 230,000 gallons (the RWST capacity is 250,000) the operator will be left with no alarms to alert him that switchover procedures should begin.
The RWST capacity is 250,000 gallons and the ECCS pumps flow rates are as follows:
Two Charging Pumps 600 gpm Two High Pressure Safety Injection Pumps 5600 gpm Two i n Pressure Safety Ir.section Pumps 6700 gpm Total flow out of the RWST Tank 12,900 gpm Thus, if the operator starts the switchover when the RWST level is at 100,000 gallons he has about 4.64 minutes before he reaches the 40,000 gallons limit (5.5 feet of borated water) for vortex suppression.
However, according to the operator LOCA procedures, once the RWST is nearing the 100,000 gallons limit he is required to perform about five other manual actions before he starts the switchover.
Assuming each action consumes one minute then five minutes would have elapsed and, therefore, the switchover would not be completed.
- VI.
CONCLUSION The Haddam Neck Plant switchover system is deficient in several areas as stated in the following:
1.
The RWST capacity is 250,000 gallons and there is only one low level alarm at 230,000 gallons.
2.
There are no alarms at the critical 100,000 gallons level to alert the operator to start the switchover.
3.
The manual procedures for switchover do not appear tolerant to small time delays.
Based on the above, we cannot conclude that the present design provides adequate assurance that manual switchover will be accomplished on a timely basis.
The following are our recommendations of possible improve-ments:
1.
Installation of an automatic switchover feature for the HPSI, LPSI and charging pumps.
2.
Installation of redundant alarms on low level of the RWST, preferably at 5.5 feet (100,000 gallons).
3.
Installation of sump level alarms indicating when switchover can take place, instead of relying on the operator.
Other proposed solutions will be considered for acceptability.
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