ML20041D874
| ML20041D874 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 03/01/1982 |
| From: | Linder F DAIRYLAND POWER COOPERATIVE |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-04-02, TASK-15-08, TASK-15-8, TASK-4-2, TASK-RR LAC-8121, NUDOCS 8203090393 | |
| Download: ML20041D874 (3) | |
Text
-
D DA/RYLAND COOPERAT/VE
- PO BOX 817
- 2615 EAST AV SOUTH
- LA CROSSE. WISCONSIN 54601 (608) 788 4000 March 1, 1982 In reply, please refer to LAC-8121 DOCKET NO. 50-409 Director of Nuclear Reactor Regulation ATTN:
Mr. Dennis M. Crutchfield, Chief J3.a
~[i g Operating Reactors Branch No. 5 DP'
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Division of Operating Reactors Vg U. S.
Nuclear Regulatory Commission
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Washington, D. C.
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SUBJECT:
DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR (LACBWR)
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PROVISIONAL OPERATING LICENSE NO. DPR-45 SEP TOPIC IV REACTIVITY CONTROL SYSTEMS.
4 DESIGN AND PROTECTION AGAINST SINGLE FAILURES
Reference:
(1)
NRC Letter, Crutchfield to Linder, dated December 15, 1980.
(2)
DPC Letter, Linder to Crutchfield, LAC-7574, dated June 1, 1982.
(3)
NRC Letter, Crutchfield to Linder, dated January 25, 1982.
Gentlemen:
Reference (3) transmitted the draft Safety Evaluation of subject for the La Crosse Boiling Water Reactor.
The following information is presented as a response to Reference (3).
Under Section V, Evaluation, your conclusion was that the following may occur as a result of single failures:
1)
A control rod may not move when commanded to move (including scram).
2)
A control rod may continuously move even though no movement is commanded.
3)
Tuo centrol rodo may continuously move at the came time.
4)
A partial or full acram may occur when not commanded.
< j g 8203090393 820301 PDR ADOCK 05000409 P
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-Mr. Dennis M. Crutchfield, Chief LAC-8121 Operating Reactors Branch No. 5 March 1, 1982 In regard to conclusion 1):
a.
The relay circuitry controlling the scram solenoid valves is duplicated in its entirety to form two independent control circuits, either of which when deenergized will independently cause all rods to scram.
The output contact arrangements from each of the two relay circuits controlling the scram solenoids are identical.
Two contacts are provided in series to the pair of scram solenoid valves controlling each rod drive, and each of these contacts is controlled by one of the two relay circuits.
Each of the two full scram circuits is capabic of being tested in its entirety (including relay dropout) without scramming the reactor.
The rod control and safety system thus ensures a full scram despite the occurrence of single hot shorts.
b.
There is a totally redundant string of the scram signals, so the lack of a single scram signal would not preclude a scram.
c.
The scram of a single control rod is a high speed insertion by means of an independent hydraulic system for each rod.
d.
Any of the redundant scram signals also initiates the insertion of the control rod by the normal control rod drive electric motor.
c.
Any of a number of single failures can prevent the withdrawal of a control rod, but this should not be considered a safety problem.
In regard to conclusion 2) :
a.
This condition is highly improbable, for a single rod to be withdrawn, there are seven switch contacts, seven relays to pick up, and duree power sources that must be energized.
b.
For a single rod to be inserted, there are four contacts to make and four relays to pick up, and two power sources that must be energized.
c.
The electric drive motor, both in and'out, is a three-phase motor, even a double hot'short on two of the motor leads will not cause the rod to move.
.O 4
4 Mr. Dennis M. Crutchfield, Chief LAC-8121 Operating Reactors Branch No. 5 March 1, 1982 In regard to conclusion 3):
a.
A discussion of this phenomena, in the form of a two rod withdrawal, was presented in Amendment No. 18 (ACNP-66518, December 1965) to the LACBWR Safeguards Report for Operating Authorization (ACNP-65544, Revised 1967).
b.
The analysis for continuous withdrawal of a singic rod from a cold-clean core is presented in Section 14.3.1.1 of the Safeguards Report.
The calculated maxinium reactivity in-sortion rate of 1.2 x 10-8 ak/k/sec (16C/sec) is based on an abnormal rod pattern and is greater than the reactivity inser-tion rate due to simultaneous withdrawal of any two rods from a cold-clean core with a permissible rod pattern.
Thus, for permissible control rod patterns the effect of two-rod with-drawal would be no more severe than previously analyzed.
c.
Two control rods inserting continuously would be more of an operational problem than a safety problem.
In regard to conclusion 4):
a.
This is true, but, again, this would be an operational problem and not safety related.
We concur with your belief that a control rod drop accident would be caused by multiple failures.
See Docket No. 50-409, letter L505 12-010, Crutchfield to Linder, dated December 5, 1990 (sic. 198 0) for a complete evaluation of a control rod drop for the La Crosse Boiling Water Reactor.
We are submitting this supplemental.information to show why these types of failures cannot occur at,LACBWR or show that the health and safety of the public is not' endangered by these failures as part of SEP Topic IV-2, Reactivity Control Systems; in lieu of including these items in SEP Topic XV-8,' Evaluation'of Control Rod Misoperation Events for the LACBWR Reactor.
If you have any further questions, please contact us.
Very truly yours, DAIRYLAND POWER COOPERATIVE MS C
Frank Linder, General Manager FL: HAT:af cc:
J.
G. Keppler, Reg. Dir., NRC-DRO III NRC Resident Inspector
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