ML20002C735
| ML20002C735 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 07/01/1975 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8101100802 | |
| Download: ML20002C735 (4) | |
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DOCKET 50-155, LICENSE DPTt-6 BIG ROCK POINT PLANT On November 1,1974, Consumera Power Company submitted a request for change to the Technical Specifications for the Big Rock Point Plant. This proposed change was submitted to eliminate the minimum continuous control rod withdrawal rate limit.
The proposed changes reccgnized that additional data vould be re-quired and also requested Commission approval to perform a special test with the reactor suberitical to obtain this data. This test (as described in our February 5, 1975 letter) was conducted on June 7, 1975 This letter is written to provide the data obtained during this test.
On June 12, 1974, eight drives were individually tested with the reactor in the cold shutdown condition. These eight drives (25% sampling) were selected on the basis of the fastest withdrawal times in the test history of all 32 drives.
The fastest time recorded with the drives' rate-set valves fully open was 16 seconds, which corresponds to an average withdrawal rate of 0.35 ft/s.
Since the 23-second limit was based on the hot start-up accident analysis, the same 8 drives were retested on June 7,1975 with the reactor in the hot standby condition.
Prior to the test, standard shutdown margin checks had been success-fully performed. Furthermore, suberiticality had been verified with all 8 drives individually fully withdrawn during previously performed routine drives' test.
An optional two rods out shutdown margin check performed on June 6, 1975 had rendered the core supercritical by less than.000h7 do.
Suberiticality was therefore verified based on review of the above tests rather than as described on Page 2 of the November 1,197h Technical Specifications change request.
The only maintenance performed on the drives prior to the June 7 test was routine cleaning of the screens in the drives' block valves.
The fastest withdrawal time with the primary system at approximately 450'F vas 13 5 seconds, which corresponds to an average maximum velocity of 0.k2 ft/s (based on 68-inch active poison length). The test results for each of the eight selected drives at the cold and hot shutdown conditions are shown on the attached table.
All timing data was obtained by observation and timing of position indication lights. The unexpected decrease in velocity on two drives (C-1 and B-2)
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4 represent only one second or approximately 5% of the total withdrawal time and is therefore attributed to data gathering error.
The cold average velocity is approximately 0.302 ft/s, whereas the hot average velocity increased to 0.359 ft/s. This represents an average in increase in the velocity of 18.9%. The maximum increase (approximately 78%) was observed on drive D-1.
There is no apparent reason for this large change. No apparent correlation could be determined between core location and/or effect of recir-culation flow.
Based on these tests, we have concluded that there is reasonable assurance that control rod drive velocities will never approach 0.82 ft/s even with the withdrawal rate set valves fully opened (0.82 ft/s was the limiting value utilized in the analysis submitted with the November 1,1974 proposed Technical Specifications change). Therefore, we request that you proceed with review and approval of this change.
N iuRL Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USNRC i
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Tabla 1 MaxisnatVelocity(Withdrawal)**
Drive ID cela(ft/sec)
Bot (ft/see) change 33 039 o.k2*
J.S D-3 0 333 o.414
+e43%
A4 o.283 0 38
+34 3 y-4 0.298 o.366
+22.8%
D-1 0.202 0 359
+77.T%
B-6 0.283 0 306
+0.1%
c-1 039 o.33
-6.8%
B-2 o.315 0.298 54%
6/12/74 6/7/75 An: o.30ert/sec Avet o.359 ft/sec
+18 9%
e E d== Velocity
- hsed on Active length of 68" i
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