ML19320D417
| ML19320D417 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 07/17/1980 |
| From: | Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| 633, NUDOCS 8007210337 | |
| Download: ML19320D417 (3) | |
Text
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VIMUINIA ELucriuC AND POWER CO)IPANY nrenuoux),vruorm cocot July 17, 1980
.Mr. Harold R. Denton, Director Serial No. 633 Office of Nuclear Reactor Regulation N0/FHT:ms Attn:
Mr. B. Joe Youngblood, Chief Docket No. 50-339 Licensing Branch 1 License No. NPF-7 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Dear Mr. Denton:
NORTH ANNA POWER STATION UNIT 2 SPECIAL TESTS EXPERIENCE SUMFIARY From July 3, 1980, through July 9, 1980, and on July 16, 1980, North Anna Power Station Unit 2 conducted a series of Special Tests intended to characte-rize plant parameters during natural circulation conditions. The performance y
of the tests also served to expose the licensed operators and other personnel to actual natural circulation operation.
The test results will be forwarded for your review in a report entitled " North Anna Power Station Unit 2 Natural Circulation Test Report" within a few weeks.
The following preliminary information is for your immediate use.
Although the probability of a loss of forced reactor coolant flow (loss of reactor coolant pumps (RCPs)) is stall, it is not negligible.
This was realized recently at another facility when RCP cooling was lost and the plant was successfully cooled down by natural circulation.
This points to the importance of training operators in the control indications and plant behavior during natural circulation operation in order to insttre rapid plant stabiliza-tion.
To this end, we have performed various natural circulation tests at power levels of from 1% to 3% of full power at North Anna Unit 2.
The tests performed are described in our letter Serial No. 528 dated June 13, 1980.
Special Tests 2-ST-6 and 2-ST-11 were each performed once.
Test 2-ST-S was performed five times and 2-ST-9 was performed four times.
The requirements for operator participation and observation as described in our letter of March 19, 1980, Serial No. 251, have been met.
5 8007210337
Y viumm Encune no Pown Coxrwy tu Mr.
Harold R.
Denton 2
The test results are summarized below:
2-ST-6, Cooldown Capability of the CVCS With maximum charging (106 CPM) and letdown flows, Tavg decreased by 1.4*F per hour. This was held for 30 minutes.
Charging and letdown were then decreased to the minimum (about 53 GPM) and Tavg increased by 2.2*F per hour.
2-ST-8, Natural Circulation Verification Af ter tripping the reactor coolant pumps and maintaining 3% power, the plant stabilized in 15-20 minutes with a core AT of 36*-40*F.
Pressurizer heaters were then deenergized and the plant cooled down t a rate of 5.24'F per hour.
System pressure decreased at about 38.4 psig per hour, though this varied each time the test was performed. Charging and steam dump flows -were varied to observe the corresponding changes in the saturation margin.
2-ST-9, Natural Circulation with Simulated Loss of Power Conditions With the reactor at 1% power, a loss of of fsite power was simulated by selec-tive deenergization of plant equipment.
Auxiliary feedwater flow was estab-lished to all three steam generators.
A loss of onsite AC power was then simulated.
Stable flow conditions to all steam generators were estab'ished via the steam driven AFW pump.
2-ST-11, Effect of Stean Generator Secondary Fida Isolation on Natural Circu-lation Af ter establishing natural circulation and a stable plant at 1% power, the 3 loop ATs were about 20*F.
The "B" steam generator was then isolated on the secondary side.
"B" Loop AT decreased to about l'F while "A" and "C" loop ATs increased to about 30*F.
This showed that a minimum of heat transfer occurred in "B" steam generator and that the other two loops compensated as predicted.
Numerous plant parameters were recorded during the performance of the tests.
This information will be utilized to improve our operator training progrca and to upgrade the capabilities of our Simulator Facility at Surry Power Station.
This will insure a more comprehensive understanding of plant behavior and control on the part of the operators, and will significantly add to operator confidence and prompt action in the event of a loss of forced reactor coolant flow.
Viuotsir EttcTHIC AND POWi:N COMPANY TO Mr.
Harold R.
Denton 3
The performance of the tests can be considered a success and the plant behaved as expected.
Different methods for decay heat removal, including cooldown capability of the Chemical and Volume Control System, were utilized.
Complete results and a summary of each test will be included in the Natural Circulation Test Report which will be forwarded as soon as it is available.
Very truly yours, h,
. we G.,R.
Sylvia Manager - Nuclear Operations and Maintenance cc:
Mr. James P. O'Reilly
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