ML20126J153
| ML20126J153 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 12/18/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20126J155 | List: |
| References | |
| NUDOCS 9301060055 | |
| Download: ML20126J153 (1) | |
Text
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REACTIVITY CONTROL SYSTEMS BASES 3/4.1.4_ CONTROL ROD PROGRAM CONTROLS (Continued)
The RBM is designed to automatically prevent fuel damage in the event of erroneous rod withdrawal from locations of high power density during high power operation.
Two channels are provided.
Tripping one of the channels will block erroneous rod withdrawal soon enough to prevent fuel damage.
This system backs up the written sequence used by the operator for withdrawal of control rods.
3/4.1.5 STANOBY LIQUID CONTROL SYSTEM The standby liquid control system provides a backup capability for bringing the reactor from full power to a cold, Xenon-free shutdown, assuming that the withdrawn control rods remain fixed in the rated power pattern.
To meet this objective it is necessary to inject a quantity of boron which produces a concentration of 660 ppm in the reactor core in approximately 50 to 125 minutes.
A normal quantity of 4587 gallons net of solution having a 13.4% sodium pentaborate concentration is required to meet a shutdown requirement of 3%.
There is an additional allowance of 25% in the reactor core to account for imperfect mixing.
The time requirement was selected to override the reactivity intertion rate due to cooldown following the Xenon poison peak and the required pumpinq rate is 41.2 gpm.
The minimum storage volume of the solution is estaollshedtoallowfortheportionbelowthepumpsuctionthatcannotbe inserted and the filling of other piping systems connected to the reactor vessel.
The temperature requirement on the sodium pentaborate solution is necessary to maintain the solubility of the solution as it was initially mixed to the appropriate concentration.
Checking the volume of fluid and the temperature once each 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> assures that the solution is available for injection.
With redundant pumps and explosive injection valves and with a highly reliable control rod scram system, operation of the reactor is permitted to continue for short periods of time with the system inoperable or for longer periods of time with one of the redundant components inoperable.
Surveillance requirements are estahlished on a frequency that assures a high reliability of the system.
Once the sofution is established, boron concentration will not vary unless more boron or water is added, thus a check on the temperature and volume once each 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> assures that the solution is available for use.
Replacement of the explosive charges in the valves at regular intervals will assure that these valves will not fail because of deterioration of the charges.
1.
C. J. Paone, R. C. Stirn and J. A. Woolley, " Rod Drop Accident Analysis for Large BWR's," G. E. Topical Report NEDO-10527, March 1972 2.
C. J. Paone, R. C. Stirn and R. H. Young, Supplement I to NEDO-10527 July 1972 3.
J. H. Haun, C. J. Paone end R. C. Stirn, Addendum 2. " Exposed Cores,"
Supplement 2 to NEDO-10527, January 1973 LA SALLE - UNIT 2 B 3/4 1-4
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