ML19269E913
| ML19269E913 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 05/18/1979 |
| From: | Switzer D CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| CYH-79-152, NUDOCS 7906290812 | |
| Download: ML19269E913 (6) | |
Text
N.
lO r CONNECTICUT YANKEE ATOMIC POWER COMPANY BERLIN. CO N N ECTIC U T P
O. BOX 270 H ARTFORD. CONNECTICUT 06104 203-666 6911 May 18, 1979 CYH 79-152 Docket No. 50-213 U. S. Nuclear Regulatory Commission Region 1 Office of Inspection and Enforcement 631 Park Avenue King of Prussia, Pennsylvania 19406 Attn: Mr. Boyce Grier, Director
Reference:
(1)
Facility Operating License No. DPR-61 (2)
Docket No. 50-213 (3) USNRC IE Bulletin 79-06A (4) USNRC IE Bulletin 79-06A, Rev.1 (5) Letter, W. G. Counsil to B. Grier, CYH 79-137, dated April 24, 1979.
Dear Mr. Grier:
The following information is submitted to supplement the responses by Connecticut Yankee Atomic Power Company to IE Bulletin 79-06A, Rev. 1 on April 24, 1979 (Reference #5).
Item #2 a)
The operator has no direct indication of void formation in the reactor cooolant system, however, various parameters can be monitored that provide a means for determining the presence of voids.
Since the likelihood of void formation increases as the pressure in the reactor coolant system decreases towards the saturation pressure, monitoring of this relationship provides an effective means for recognizing the possibility.
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. Instrumentation available to aid the operator in monitoring pressure /
temperature relationships are:
Pressure 1)
Pressurizer pressure - 3 independent channels that read out on the Main Control Panel.
- 2) Reactor Coolant Loop #4 - 2 independent channels that read out on the Main Control Panel.
- 3) Drain Header Pressure - 1 channel that reads out on the Main Control Panel.
Drain Header Motor operated shutoff valve must be in open position.
- 4) Heisne Gage - 1 channel that reads out in the Primary Auxiliary Building.
Temperature; 1)
Loop T cold - 4 channels that read out on Main Control Panel.
2)
Loop T..ve - 4 channels that read out on Main Control Panel.
3, Loop Delta T - 4 channels that read out on Main Control Panel.
4)
Reactor Vessel Head Thermocouple - 1 channel that reads out on Main Control Panel.
5)
Pressurizer Surge Line Thermocouple - 1 channel that reads out on Main Control Panel.
6)
Pressurizer Liquid Space Thermocouple - 1 channel that reads out on Main Control Panel.
7)
Pressurizer Steam Space Thermocouple - 1 channel that reads ou*.
on the Main Control Panel.
- 8) Reactor Core Outlet Thermocouple - 40 channels that read out through an IBM 1800 process computer.
Range up to 750FO.
Additional indications of void formation available to the operator are reactor coolant pump vibration alarms and erratic or unstable ammeter readings.
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Procedures have been revised to alert the operators to the problems and recognition of void formation in the reactor coolant system.
Item #4)
The review of containment isolation design is ongoing and is being conducted on a high priority basis.
It requires a substantial interaction with the NSSS vendor and the corporate engineering service group.
This review is also interrelated with Item #7.
At the completion of the review it is expected the necessary hardware design changes will be implemented.
Item #6)
The low pressure Reactor Coolant System Overpressure Protection System at Connecticut Yankee is separate from all other pressure relief systems on the pressurizer.
It consists of two spring loaded relief valves, each capable of being isolated by two in-series motor operated block valves. Whenever the Overpressure Protection System is in service the two block valves are open and the motor operator breakers deenergized.
Conversely, whenever the system is out of service the block valves are closed and deenergized.
Item #7 a)
Although operators are trained to ensure the continued operation of engineered safeguards (specifically the ECCS) following initiation, there are particular situations in which they have been instructed to terminate the operation of specific components prior to the expiration of the time span advocated in IE Bulletin 79-06A.
Terminating theoperation of a specific component may be required if:
1) its function can be performed by some other component or system more capable of performing that function, 2) continued operation may needlessly endanger the component or components of other systems used for long term cooling, 3) continued operation of the component presents an increased hazard to the public health and safety.
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These instructions are specific as to what conditions must exist before shutting down ECCS components.
Examples of each set of conditions are:
1)
For a large LOCA, full ECCS delivery will empty the Refueling Water Storage Tank to a critical level in less than 20 minutes.
Switchover to high or low pressure recirculation from the containment sump is then required.
Low pressure recirculation utilizes two Residual Heat Removal pumps each rated at 2200 gpm @ 130 psig.
The high pressure recirculation mode utilizes these same two pumps and two Charging Pumps, each rated at 360 gpm
@ 2300 psig.
The shutoff head of the charging pumps is 2375 psig.
- 2) For the steam line rupture or small LOCA, the Low Pressure Safety Injection Pumps (LPSI) would operate in a shutoff head situation for the duration of the incident. Once stable system conditions are schieved (as defined in the emergency procedures) the operators are instructed to shut down the LPSI pumps to avoid possible overheating and damage.
Valves and system arrangement are left in the incident configuration.
- 3) For a Steam Generator Tube Rupture incident reactor coolant may result in total flooding of the steam generator. With the High Pressure Safety Injection Pumps (HPSI) operating the steam generator could be pressurized above the secondary side safety valves setpoint resulting in a radioactive liquid release to the environment.
To minimize this possibility one of the HPSI pumps may be shut down.
In each of the above examples, terminating the operation of ECCS components may occur prior to the minimum 20 minute operating guide-line depending on the incident, plant conditions and/or break size.
However, in all cases, the operator is required to verify that the reactor coolant system is in a stable, subcooled condition prior to shutting down a ECCS component.
Efforts are in progress to further evaluate the possible consequences related to implementing the 79-06A guidelines in light of the above examples.
During the interim period pending completion of this evaluation the guidelines supplied by the NSSS vendor have been incorporated into the plant Emergency Operating Procedures.
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^ Item #7 c)
Evaluation of continuing to run Reactor Coolant Pumps (RCP) following ECCS initiation is in progress and in conjunction with the NSSS vendor.
Presently the vendor is opposed to continued operation of the RCP's during this situation.
If the evaluation determines the feasibility of continued operation to provide forced loop flow then design changes will have to be engineered and implemented.
The evaluation is being conducted in conjunction with Item #4 of 79-06A on an expeditious basis.
Item #7 d)
Emergency Operating Procedures have been revised and are in the review and approval cycle.
The revisions include specific instructions to not shut down ECCS components on the sole basis of pressurizer level indication.
They are instructed to use other indications and parameters such as:
1)
Reactor Coolant System temperature and pressure; 2)
Steam Generator availability (pressure and level);
3)
Refueling Water Storage Tank level; 4)
Pressurizer pressure, as well as pressurizer level.
The procedures are written to be as specific as possible for operator guidance without causing _aedless restriction or confusion.
Item #8 and #10 Review f all procedures is scheduled to be completed prior to June 30, 1979.
During the interim period any unreviewed procedure will be reviewed and revised where necessary prior to its use.
Item #9 Review of lines which normally carry radioactive liquids and/or gases from the containment and could be involved in inadvertent transfer upon reset of containment isolation safety features has been completed.
Four lines have been identified that could be in use during an incident.
They are:
1)
Loop Drain Leg Sample line; 2)
Pressurizer Steam Space Sample line,
- 3) Pressurizer Liquid Space Sample line; and 4)
Loop #1 Hot Leg Sample line.
The isolation trip valves on these four lines will automatically reopen upon reset of the HCP switches.
These lines are normally open only during sampling operations.
Instructions will be included in the emergency procedures to close or verify closed shutoff valves on these lines prior to resetting of containment isolation switches.
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t.. -
Item #10 b)
A Quality Assurance Procedure QA 1.2-11.3, entitled Test Requirements is in effect which requires functional testing of Category I systems, structures and components fe'% wing maintenance, modification and refueling.
Its purpose is to ensure that equipment that has been removed from service will perform satisfactorily when returned to operation.
Specifically this procedure requires that testing be accompl.shed in accordance with requirements delineated on the Connecticut Yankee Work Permit.
The Job Supervisor, Operations Supervisor or Shift Supervisor is responsible for establishing test requirements or designating the applicable test procedure to be used.
Item #10 c)
The Shift Supervisor, who holds a Senior Operators License, is the person on each shift that grants authorization to remove equipment from service or return equipment to service.
This is controlled through Quality Assurance Procedure QA 1.2-14, entitled Equipment Control (Locking and Tagging).
Administrative Procedure ADM 1.1-44, entitled Shift Relief and Turnover, requires all shift personnel to review and initial the " shift turnover sheet" which includes a list of all inoperative equipment.
Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY (S
D. C. Switzer President 2142 174
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