ML20041G368
| ML20041G368 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 03/17/1982 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| TASK-15-03, TASK-15-3, TASK-RR LSO5-82-03-079, LSO5-82-3-79, NUDOCS 8203220144 | |
| Download: ML20041G368 (6) | |
Text
.o March 17, 1982 o
4 Docket No. 50-213
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GECEIND LS05-82-03-079
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Mr. W. G. Counsil, Vice President 7,
Nuclear Engineering and Operations
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Connecticut Yankee Power Company 4
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Post Office Box 270 llartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
HADDAM NECK - SEP TOPIC XV-3, LOSS OF EXTERNAL L AD, TURBINE TRIP, LOSS OF CONDENSER VACUUM, STEAM PRESSURE REGULATOR FAILURE By letter dated September 30, 1981, you submitted a safety assessment report for the above topic. The staff has reviewed this assessment and our conclusions are presented in the enclosed safety evaluation report, h
which completes the review of this topic for the lladdam Neck plant.
This evaluation will be a basic input to the integrated assessment for your facility. The evaluation may be revised in the future if your facility design is changed or if HRC criteria relating to this topic are modified before the integrated assessment is completed.
Sincerely, i
Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 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 Russell Library 119 Broad Street Middletown, Connecticut 06457
.. u Board of Selectmen Town Hall Haddam, Connecticut 06103 State of Connecticut Office of Policy and Management ATTN: Under Secretary Energy Division 80 Washington Street Hartford, Connecticut 06115 U. S. Environmental Protection Agency Region 1 Office ATTN: Regional Radiation' Representative i
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-JFK Federal Building Boston, Massachusetts 02203 l
Resident Inspector Haddam Neck Huclear 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 Office of Inspection and Enforcement 631 Park Avenue King of Prussia, Pennsylvania 19406 o
SYSTEMATIC EVALUATION PROGRA'1 TOPIC XV-3 HADDAM NECK TOPIC:
XV-3, LOSS OF EXTERNAL LOAD, ' TURBINE TRIP, LOSS OF CONDENSER VACUUM, AND STEAM PRESSURE REGULATOR FAILURE I.
INTRODUCTION These events can result in a sudden, unplanned decrease in heat removal by the secondary system, and they could lead to excessive increases in reactor coolant and steam temperatures and pressures if suitable protec-tion is not provided.
If during these events no credit is taken for mitigation by non-safety grade systems, the consequences are determined by the actions of the Reactor Protection System and the independent primary and secondary. system safety valves.
The Connecticut Yankee Atomic Power Company (CYAPC) provided an analysis of these four events (Reference 1) which shows that the most severe consequences occur at Haddam Neck when there is a complete loss of external load without a turbine trip and therefore no immediate reactor trip.
CYAPC had previously analyzed this event and discussed the consequences in References 2 and 3.
~
II, REVIEW CRITERIA Section 50.54 of 10 CFR Part 50 requires that each applicant for a construction permit or operating license provide an analysis and evalua-tion of the design and performance of structures, systems and components of the facility with the objective of assessing the risk to public health and safety resulting from the operation of the facility, including determination of the margins of safety during normal operations and transient conditions anticipated during the life of the facility.
Section 50,36 of 10 CFR Part 50 requires the Technical Specifications to include safety' limits which protect the integrity of the physical barriers which guard against the uncontrolled release of radioactivity.
The General Design Criteria (Appendix A to 10 CFR Part 50) establish minimum requirements for the principal design criteria for water-cooled reactors.
GDC 10 " Reactor Design" requires that the core and associated coolant, control and protection systems be designed with appropriate margin to assure that specified acceptable fuel design limits are not exceeded during normal operation, including the effects of anticipated operational occurrences,
,. GDC 15 " Reactor Coolant System Design" requires that the reactor coolant and associated protection systems be designed with sufficient margin to assure that the design conditions of the reactor coolant pressure boundary are not exceeded during normal operation, including the effects of anticipated operational occurrence.
GDC 26 " Reactivity Control System Redundancy and Capability" requires that the reactivity control systems be capable of reliably controlling reactivity changes to assure that under conditions of normal operation, including-anticipated operational occurrences, and with appropriate margin for malfunctions such as stuck rods, specified acceptable fuel design limits are not exceeded.
III.
RELATED SAFETY TOPICS Various other SEP to. pics evaluate such items as the reactor protection system.
The effects of single failures on safe shutdown capability are considered under Topic VII-3.
IV.
REVIEW GUIDELINES The review is conducted in accordance with SRP 15.2.1, 15.2.2, 15.2.3, and 15.2.5.
The evaluation includes review of the analysis for the event and identification of the features in the plant that mitigate the consequences of the event as well as the ability of these systems to function as required.
The extent to which operator action is required is also evaluated.
Deviations from the criteria specified in the Standard Review Plan are identified.
V.
EVALUATION Of these four events a loss of external load without an immediate turbine trip results in the most severe transient at the Haddam Neck plant.
A turbine trip is less severe because the Reactor Protection System (RPS) is designed to guarantee that a turbine trip will also trip the reactor, and when the reactor is tripped concurrently with the turbine the time interval of primary-secondary power nyismatch is greatly reduced.
A loss of condenser vacuum is less severe because it will also trip the turbine and hence the reactor.
A steam pressure regulator can cause a rapid decrease in the heat removal in the secondary system by failing in the closed positica.
Since this causes the turbine control valves to close, the consequences will be similar to and bounded by those of the loss of load event.
In a loss of load event at Haddam Neck it is possible to rapidly reduce the speed of the turbine to the station service level by closing the turbine control valves.
In this event the reactor may not be concurrently tripped, and reactor power will not decrease as rapidly as steam generator power; so there will be an excess amount of steam generated.
This will normally go through the turbine bypass valves to the condenser.
If the bypass valves or condenser fail to operate, the steam generator safety valves would control the pressure in the secondary system.
. As described in Reference 4 there are 16 code safety valves in the 4 main steam 1:nes at Haddam Neck. These are designed to relieve 1.22 times the' full load steam flow; so they can prevent excessive pressure in the secondary system following the bounding event of a complete load rejection without a reactor trip.
Thus these safety valves would adequately control the pressure in the secondary system following the worst case loss of external load event.
In this worst case event the reactor would be tripped by a high pressure signal from the pressurizer.
If it is assumed that the reactor is initially at 103 percent power and the pressurizer spray and power operated relief valves (PORV's) are operated in a normal manner, this trip would occur about 7 seconds after the loss of load.
These actions would keep the primary system pressure below the safety valve setpoint.
The minimum departure from nucleate boiling (DNB) ratio, which is calculated with the most positive moderator temperature reactivity coefficient, is 1.44.
This is well above the minimum limiting value of 1.30.
If the pressurizer spray and PORV's were not operable, as assumed above, the primary system pressure might have to be limited by three safety valves on the pressurizer.
As stated in Reference 5 the combined capacity of these three safety valves is equal to or greater than the maximum surge rate resulting from a complete loss of load without a reactor trip.
Since in the worst case loss of external load event the reactor would be tripped at about 7 seconds, this case would be less severe, and these safety valves would adequately control the primary system pressure.
VI.
CONCLUSIONS As part of the SEP review for Haddam Neck, all of the events in Topic XV-3, which could result in an unplanned decrease in heat removal by the secondary system, have been evaluated. We have concluded that the con-sequences of all of these events in the Haddam Neck plant are bounded by those of a loss of external load without an immediate reactor trip.
We have also concluded that the consequences of this limiting event are in conformance with the criteria of SRP section 15.2.1 - 15.2.5 and are therefore acceptable.
REFERENCES 1.
Connecticut Yankee Atomic Power Company; Systematic Evaluation Program Safety Assessment ReportsSection XV Topics, Haddam Neck Plant; Berline Connecticut; Sections 2.1-2.4; Septembe r 30, 1981.
2.
Connecticut Yankee Atomic Power Company; Facility Description
& Safety Analysis, Volume II; Berlin, Connecticut; page s 10.3.5-1 to 10.3.5-4; Julyr 1966.
3.
Connecticut Yankee Atomic Power Company; Plant Design Change
- 21; Berlin, Connecticut; O c t ob e r, 1967.
4.
Connecticut Yankee Atomic Power Company; Facility Description
& Safety Analysisi Volume II; Berlin, Connecticut; page 8.1-2; Julyr 1966.
5.
ibid; Volume I, page 5.222-3.
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