ML20084C987

Forwards Response to Re Inverted Control Tubes. Surveillance Requirements to Maintain Adequate Shutdown Reactivity Margins & Monitor Poison Distribution Changes & Control Rod Changeout Schedules Discussed

ML20084C987
Person / Time
Site:	Dresden, Quad Cities, 05000000
Issue date:	10/11/1973
From:	Abel J COMMONWEALTH EDISON CO.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084C976	List: ML20084C977 ML20084C987
References
NUDOCS 8304080430
Download: ML20084C987 (2)

Text

r . m

-p C: maw =lth Edis:n One Fi j:ional Plaza Chicago. Ilhnois O .

Addrsss Reply to: Post Office Box 767

.** Chicago, Illinois 606SO l October 11, 1973 A

Mr. D. J. Skovholt z. RECEIVED  %

Assistant Director for Z OCT 151973 I--

Operating Reactors "

9 U.S. Atomic Energy ,}

Directorate of Licensing Comminion Regulatory Office of Regulation # "

U.S. Atomic Energy Commission 4 #^*

E Washington, D.C. 20545 A v'

Subject:

Dresden Units 2 and 3, Quad-Cities Units 1 and 2 - Inver_ted Control Rod Tubes -

AECDkts"50-237}50-249, 50-234 nnd 50-265

Dear Mr. Skovholt:

In response to your letter dated September 5, 1973, the following information concerning our program for possible inverted control rod tubes is supplied. Your letter indicated six specific items of concern. Our response to Items 4 and 5 is attached. Completed answers to Questions 1, 2, 3 and 6 are current.ly in preparation and are expected to be submitted by October 31, 1973.

Questions 1 and 2 of your letter involved information concerning possible extent and effect of loss of negative reactivity due to inverted control rod tubes. These questions are addressed in a report submitted on the Millstone Unit 1 docket and the answers in that report are generally applicable to the Dresden and Quad-Cities units. The spccific answers for Dresden and Quad-Cities, expected to be submitted by October 31, -

1973, will include consideration of the higher shutdown margins which exist at our plants compared to Millstone.

One signed original and 39 copies of this letter are provided for your use.

b Very truly yours, M J. S. Abel V Nuclear Licensing Administrator -

> Boiling Water Reactors l

8304080430 740401 ff l PDR ADOCK 05000237 P PDR 1 COPY S/RI}EGIO j t

i -

,. 1 Control Blade - Response to the AEC (4) Surveillance requirements to maintain adequate shutdown

, reactivity margins and monitor changes in poison distribution.

A significant mnount of operation allowing for compaction of boron has accrued, and in addition, a recent demon-stration of 1%z1K/K margin for each control blade was performed on all 4-800 MW BWR's. A monthly equivalent reactivity anomaly check is performed and a planned check of all blades during the forthcoming refueling outages obviate the need for an extensive amount of surveillance.

However, in order to provide additional assurance during the remainder of the present operating cycles, a 1%21K/K margin check for two or more selected rods and a local critical check will be performed for any unit (D2, D3, QC1, QC2) in the cold Xenon free condition (72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or longer outage). Additionally, for each startup following a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> outage during the remainder of the present operating cycles, the control rod pattern at the time of achieving criticality will be recorded and evaluated.

Anomalies of 1%21K/K or more will be reported as an abnormal occurrence and significant deviations of less than 1% 6K/K will be reported as an unusual event (30 day letter).

(5) Plans and schedules for changeout of control rods.

Commonwealth Edison Company will check all of the control '

blades in Dresden 2 and 3 and quad Cities 1 and 2 by using a detector (probably an eddy current device used by General Electric) to check for the steel wood packing in the tubes which should be at the bottom of the tubes.

Any blades, sheaths or tubes found to be inverted will

be reported-to the AEC at the completion of the checking program for each unit. Any control blade with a

, significant number of inverted tubes will be replaced.

I Commonwealth Edison Company plans to -accomplish the checking and-any necessary replacement of blades during the forthcoming scheduled refueling outage for each unit and in any event within'two refueling outages.

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