ML20042A488
| ML20042A488 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 03/15/1982 |
| From: | Nichols T SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8203230484 | |
| Download: ML20042A488 (3) | |
Text
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Mr. liarold R. Denton, Director f)
Office of Nuclear Reactor Regulation
/b U. S. Nuclear Regulatory Commission Washington, DC 20555 Subj ec t: Virgil C. Summer Nuclear Station Docket No. 50/395 Accumulator Discharge Valves SER Item 1.8.2
Dear Mr. Denton:
In Section 6.3.2 of Supplement 3 of the Safety Evsluation Report (SER) the NRC discussed the current design of the Accumulator Discharge Valves and notes that it violates the Reactor Systems Branch Technical Position RSB 5-1.
The Staff requires an acceptable alternative design be installed prior to startup af ter the first refueling outage.
It is SCE6G's position that the present plant design and procedural method for plant cooldown is acceptable and can be the alternative to the requirement of RSB 5-1.
Our conclusions are based on the following:
During the course of a normal cooldown operation, operators are required to isolate the safety injection accumulators when Reai. tor-Coolant System (RCS) pressure is reduced to 1000 psi.
This action requires operator action to energize the accumulator isolation valves by closing the appropriate breakers in the auxiliary and intermediate buildings. Following completion of the isolation, the operating procedure is signed to verify that the task has been accomplished.
It is highly unlikely that the step will be forgotten when the cooldown is performed in accordance with operating procedures.
In addition, even though closing the breakers occurs outside the con-trol room, it is a very controlled evolution which would only take approximately five to ten minutes to perform.
The accumulator isolation valves have control bear, position indica-tion on the Engineering Safety Features Monitor Panel. This serves as a reminder to an operator during the cooldown operation.
3Ds IO 8203230484 820315 PDR ADOCK 05000395 E
Mr. Harold R. Denton March 15, 1982 Page Two The required actions to achieve RHR initiation during a plant cooldown include borating the RCS, dumping steam generator steam to cool the RCS to 350oF, and de:.t assuring the RCS to 400 psig.
These actions have been determ'om. to require 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> of operator time.
In order to achieve RHR initiation in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, the balance of available time, 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />, may be utilized to perfora various tasks which may arise.
If an inadvertent fail tre to isolate the accumulator at 1000 paia occurred, the 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> of available time could be used to correct the situation. When RCS pressure eventually decreases to 600 psi f rom the depressurization operation, the pressure differential bet-ween the accumulator (600 psi) and RCS will equalize. Any subse-quent RCS depressurization will result in a gradual accumulator injection into the RCS. The injection will terminate the RCS depressurization and stablize overall system pressure terminating the accumulator injection. Repeated RCS depressurization attempts will result in repeated gradual injections followed by pressure stabilization. As this occurs, numerous indications are available to the operator which would alert him of presence of abnormal condi-tions. The RCS depressurization rate would slow down and stop, the pressurizer level would begin increasing, and the alarming of low accumulator water level and nitrogen pressure would occur.
It would become obvious to the operator that the cooldown operation was not proceeding normally.
The operator would stop the cooldown at this point and take the required action to isolate the accumulator and terminate the injections.
The Operator could then utilize the 25 additional hours available to letdown the injected inventory.
RHR initiation could be achieved in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
Based on the above, SCE&G requests acceptance of this alternative position to the RSB 5-1 requirements.
If you have any questions, please let us know.
Very truly yours s
T. C. Nichols, Jr.
RBC:TCN:rh cc: Page Three
Mr. Harold R. Denton March 15, 1982 Page Three cc:
V. C. Summer G. H. Fischer H. N. Cyrus T. C. Nichols, Jr.
M. B. Whitaker, Jr.
J. P. O'Reilly H. T. Babb D. A. Nauman C. L. Ligon (NSRC)
W. A. Williams, Jr.
R. B. Clary O. S. Bradham A. R. Koon M. N. Browne G. J. Braddick J. C. Ruoff J. L. Skolds J. B. Knotts, Jr.
B. A. Bursey J. B. Cookinham NPCF File J