ML20148F226

Responds to Util & 720824 Supplemental Info Re Facility Control Rods.Authorizes Util to Proceed W/Control Rod Replacement During 721031 Scheduled Shutdown

ML20148F226
Person / Time
Site:	Yankee Rowe
Issue date:	08/25/1972
From:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
To:	Vandenburgh D YANKEE ATOMIC ELECTRIC CO.
References
NUDOCS 8011040724
Download: ML20148F226 (2)

Text

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, DISTRIBITTION h C W. Dooly, DR L

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H. Shapar, OGC N. Dube, L (5)

. Aug 2 51972 J. Buchanan, ORNL T. Laughlin, DTIE PDR-A RP cket File Reading.

l Docket No. 50-29 Branch Reading ECRS (16) ^

R. Boyd R. DeYoung Yankee Atomic Electric Company D. Skovholt ATTN: Mr. Donald E. Vandenburgh T. Carter

• Vice President R. Schemel 20 Turnpike Road (

A. Burger ,

Westboro, Massachusetts 01581 S. Teets I l

Centlemsn:

This refers to your letter dated August 7, 1972, and supplemental infor-mation contained in your teletype dated August 24, 1972, concerning the .

Yankee control rods. Your letter confirms the details of the recent failure of control rod No. 19 to complete one drop into the core and it also outlines Yankee's proposed actions including a scheduled reactor shutdown not later than October 31, 1972, for the installation of  ;

replacement cratrol rods. ., l The performance of the 24 Yankee control rods has been checked out ini-tially during Core I startup testing. Because control rod No.18 had then exhibited erratic performance and since few data vers available .,&

from the hot rod drop measurements made during Core I startup testing, [,

this control rod had to be considered inoperable. For this reason, Yankee ,g; is still required by Change No.100 to operate the reactor with more W restrictive control Rod Insertion Limits to meet the specified shutdown  : ih i l margin without taking credit for the contribution to the available . shut- T!

down reactivity from control rod No. 18. Change No.100 also requires J Yankee to carry out a more extensive control rod surveillance program,  ; yl including hot rod drop testing every fourth weekend. This surveillance ,

gr l proEram revealed previously during testing on June 9, 1972, an increase '

• l in the drop time of control rod No.19 of more than 0.3 second without ,

however exceeding the 2.4 seconds drop time required in the Technical '1 Specifications. You have reported this occurrence as required in Change '

No. 100. During the later surveillance testing on July 29,1972, only gi control rod No. 19 did not perform the intended function in a normal $t manner, as described in your letter dated August 7, 1972. All other t%

23 control rods, including control rod No. 18, met the specified hf performance requirements. .

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- M THIS DOCUMENT CONTAINS g17 l POOR QUAUTY PAGES r  ;

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t 1 4 j Yankee Atomic Electric Company - 2-q AllQ 2 51972  ?-.

l j 5 l We have examined the compreheuive set of control rod drop times included h

-t in your letter of August 7, 1972. These drop times were measured by 7 '

{ Yankee during the initial Core X startup testing and subsequent control  ?

-j rod surveillance testing. We find that these data do. net indicate a d sign! ficant pattern of degradation of control rod performance. Therefore,-

we conclude that the occurrences of off= normal performance that only  %@

'; involved control rods Nos.18 and 19, both located in the Shutdown Group D, 4 were random single events.

Q To reestabitsh confidence in the long-term ability of the control rode to perform the intended function when needed, Yankee will shut down the ~

i reactor not later than October 31, 1972, for the installation of replace-1 ment control rods you will install a set of 22 new rods, not including ,

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control rods Nos.17 and 21 which have already been replaced during the g.i Core X refueling outage. Until then, the reactor will be operated with g L the present restrictions on Control Rod Insertion Limits and power level, yl In addition, Yankee will further increase the frequency of the control  ?  !

rod surveillance program from every fourth weekend to every third weekend $

and will report to the Commission all measured control rod drop times.

The present reactor operating restrictions provide an acceptable increased

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S allowance for stuck rods of 3% delta k/k in shutdown reactivity to be @

available for meeting the specified shutdown margin, compared with the h. i total reactivity worth of about 4% delta k/k of the eight control rods $l

' in the entire Shutdown Group D; the performance of control rod No.18 han j d consistently improved and has met the specified drop time during the last f reported control rod surveillance testing; the insertability of control E rod No.19 has also been demonstrated during the last reported control rod T!

surveillance testing; aad the further increase in the test frequency of 4 the control rod survsillance program will permit even closer monitoring a of the operability of the control rods during the remaining period until yg rer.ctor shutdown for the scheduled replacement of the control rods.

p' on the basis of our review of the information you have submitted, we have concluded that operation of the reactor in the manner proposed does not %p involve significant hazards considerations not described or implicit in $

the Final Safety Analysis Report, and that there is reasonable assurance (i that the health and ' safety of the public will not be endangered. Accord- L\,

ingly, you are hereby authorised to proceed as outlined in your letter e?i dated August 7, 1972. .  !?;

hi sincerely, f

W /LL% co%

Donald J. Skovholt 4T a . . < . e . .,

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8/24/72

, form AEC.S ta (Rev,9-53) AECM 0240

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