ML19330B047
| ML19330B047 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 07/16/1980 |
| From: | Anderson N Office of Nuclear Reactor Regulation |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8007300099 | |
| Download: ML19330B047 (7) | |
Text
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E WASHINGTON, D C. 20555 k..... j July 16,1980 Docket No. 50-339 MEMORANDUM FOR: Dennis L. Ziemann, Chief Procedures and Test Review Branch l
Division of Human Factors Safety FROM:
Newton R. Anderson 1
Procedures and Test Review Branch Division of Human Factors Safety j
SUBJECT:
REPORT OF TRIP TO NORTH ANNA POWER STATION TO CBSERVE SPECIAL LOW POWER TEST PROGRAM ON UNIT 2 The North Anna Special Low Power Test Program as described in Staff SER dated June 30, 1980, was conducted at North Anna Unit 2 starting on July 3,1980.
The first run-through of each of the special tests was j
observed by either myself or Brent Clayton.
One of the Resident Inspectors at North Anna was also present during the initial test series.
Zach of the tests is summarized below.
Most of the test data have not been reduced or evaluated yet.
A more complete assessment of each test will be supplied by VEPCo when all test data have been analyzed.
1.
Test ST-6 (Sequoyah Test 6) Cooldown Cacability of the CVCS This test was the first in the series and was conducted at zero power with one reactor coolant pump running and all three steam generators isolated.
Heat was removed from the primary system using the charging and letdown systems, The maximum charging and letdown flow rate of 123 gpm resulted in a PCS temperature decrease of 2.1*F per hour.
The minimum flow rate of 40 gpm resulted in a temperatare increase of approximately 2.6 F per hour.
Data were taken and the temperature changes averaged over a 30 minute time period.
2 Test ST-8 (Sequoyah Tests 1, 3 and 5) Natural C.irculation Verification With the reactor at 3% power and heat being remcved with all three steam generators, all reactor coolant pumps were tripped and natural circulation was established.
Primary system pressure increased to i
~
2310 psig where one PORY lifted.
The PORY reseated and the pressure was controlled using auxiliary sprays. The primary coolant system stabilized at approximately 36*F aT.
i 80073000TS
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Dennis L. Ziemann July 16,1980 Following this portion of the test, a core flux map was run in natural circulation for comparison with the zero power flux map taken before the test. Results.are not yet available, In stable natural circulation the core exit thermocouple reading was 581 *F.
The average of the three hot leg RTDs was 580,5'F, A map of core exit thermocouple readings indicated that the core flow distribution did not change.
Location of the high and low thermocouple readings stayed the same. There was a 6*F difference in high and low readings in natural circulation and a 3 F difference with forced flow.
The second part of this test was to demonstrate that PCS saturation margin can be maintained without pressurizer heaters.
With natural circulation established, all pressurizer heaters were turned off, Both auxiliary and main spray valves were closed to ensure that spraying would not influence pressure drop, The depressurization rate over a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> period was approximately 38 psi per hour, PCS temperature decreased at about 5 F per hour and PCS subcooling margin decreased by about 6*F per hour.
The last part of the test was to determine the effect of decreased subcooling margin on natural circulation and the effects of charging and steam flows on saturation margin.
System pressure was decreased using pressurizer sprays to a subcooling margin of approximately 30*F, Saturation margin could not be increased by changing steam dump rate'alone.
Charging flow or pressurizer heaters were needed to substantially increase saturation margins.
3.
Test ST-9 (Sequoyah Tests 2 and 7) Natural Circulation with Loss of Offsite Power and Simulated Loss of All Offsite and Onsite AC Power This test was ' conducted at 1% reactor power.
To simulate loss of offsite power the following actions were taken:
A.
Motor driven auxiliary feedwater control valves were closed, B,
Steam dump controllers were placed in manual control.
C.
Pressurizer backup heater groups 2 and 5 and control heaters group 3 were tripped and locked out.
O, All three reactor coolant pumps and the operating main feedwater pump were simultaneously tripped.
Approximately eight minutes after initiation of the test, a PORY lifted at 2305 psig, Pressure was controlled using atmospheric steam dumps, The PORV reseated and the pressure remained below j
the-PORV setpoint. Auxiliary feedwater was initiated normally and 1
stable natural circulation was achieved with cold leg temperatura l
of 547 F and aT of 22 F.
j
i July 16,1980 Dennis L. Ziemann To~ simulate loss of all AC, both motor driven auxiiiary feed pumps were turned off.
The feed pump house exhaust fans were also turned off.
This test deviated from a real loss of all AC in that the steam turbine driven auxiliary. feed pump was aligned to feed all three steam generators. The normal alignment at North Anna is to have each of the three auxiliary feed pumps feeding one steam generator.
If all AC were lost, only one steam generator would receive feedwater.
This realignment did not preclude. meeting test objectives.
Operators were sent to the auxiliary feed pump house with sound powered phones to realign the feedwater system to feed all three steam generators and to control feed flow by manually adjusting control valve position at the direction of the control room operator.
Steam generator levels were initially 40 to 45%.
Levels dropped to about 35% and stabilized.
By manually controlling flow, levels were maintained within between 35% and 43% on narrow range scale throughout the test. Auxiliary feedwater flow varied from 50-75 gpm.
Stabl e natural circulation was established and maintained at approximately 22' aT.
4.
Test ST-il (Seouoyah Test 4) Effect of Steam Generator Secondary Side Isolation on Natural Circulation This test was initiated by tripping all three reactor coolant pumps with the reactor power maintained at 1% power. After stable natural circulation was achieved with a aT of approximately 21*F, the 3 steam generator was isolated. The P-250 computer went off during the initial stages of this test losing some of the early tMi data.
It was decided to continue the test after recovering the computer and collecting the lost data during scheduled re-runs of the test.
'Following isolation of the 8 steam generator, AT in the isolated loop slowly decreased to about 9*F in one hour, ai in the other loops was at 27' and 25*.
At this time it was suspected that some leakage was occurring around the feedwater isolation valve and steam isolation valve.
Operators were dispatched to manually close feedwater bypass valve and tighten the other isolatian valves.
The test then continued another 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> at which time the isolated loop had a AT of 3 F and was holding stable.
The test was terminated at. this time.
VEPCo plans to repeat the test series throughout the week to provide training to all licensed operators. All operators will have participated in at least one test and observed 2 others. A few operators are on vacation or othenvise unavailable will participate in.a rerun of selected tests at a later date.
Dennis L. Ziemann July 16,1980 To avoid lifting the PORV, ubsequent tests will be corducted with an initial pressure of 2100 psig, then as pressure increases, the controller will be adjusted to 2230 psig.
It is my opinion that the Special Low Power Test Progrc.a was successful both from the standpoint of collecting basic plant information and for operator training.
The tests were conducted effectively an ' smoothly.
The test engineers and shift supervisor maintained excellent discipline in the control room and all control manipulations were handled confidently and ef fectively. One SRO commented that he got more ' benefit from watching a test than participating because it allowed him to follow the course of the transient rather than concentrating on a particular control task such as manually controlling steam generator levels.
I am also of the opinion (based on observing the test series) that conducting the Special Low Power Tests on the plant is more effective as a training tool than running the tests on a simulator.
,N
'm fiewton R. Anderson Procedures and Test Review Branch Division of Hunan Factors Safety cc:
S. Hanauer V. Moore D. Eisenhut R. Tedesco J. Youngblood c '~A. DromerttHb B. Clayton S. Bryan (IE)
T. Webster (IE) l
Mr. J. H. Ferguson Executive Vice President - Power Virginia Electric & Power Company P. O. Box 26666 Richmond, VA 23261 cc: Mr. Anthony Gambaradella Clarence T. Kipps, Jr., Esq.
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