ML20084U794

Ro:On 800528,one Control Rod Drive Exceeded 5.3 for 90% Insertion & Others Showed Increased Scram Times.Drive & Drive Screen Condition Investigation Initiated

ML20084U794
Person / Time
Site:	Dresden
Issue date:	02/26/1970
From:	Hoyt H COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U733	List: ML20084U785 ML20084U794 ML20084U795
References
2077, NUDOCS 8306290263
Download: ML20084U794 (2)

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Commonweahh Edison Company OHE f" $ F4 G T NAF$0HAL a. A Z A

• CHICAGO. f t. L l P4 0 4 C Ad.*ress tepfr ser P0lf Ortatt tQX 767

• CHICAGO. lit f Ho f S 6 *J o 9 0 Drn. den Nucicar Fewar Station / IIi s.

R.R. J1 a (/ .

!iorris, Illinois 60450 py e, t Corrected June 29, 1970 f.y/ fr., c [ c .>.

Origin 11 Date:

June 26, 1970'-/.a [6 {, '

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Dr. Pcfer A. Morris, Director . .- 7 Divie,1cn of acactor Licena.ing j U. S. Atouf c F.nergy Cormdosion  !{Q Wa shint tact, D. C. 20545 N,3/ h. p e .'

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\(0 / ~l T.1.1 License DPR-19, Dresden Naclear Power Station Unit 2, Sec t icn 6.55'~ ,\.

Sim JE ce:

of the Technical Specifications.

Dear Dr. Morris; This is to report a condition reinting to the operation of the stotion in which control rod drives exceeded the 7.00 Second maximum insertion tiv a8 required for 907, insertion as required by section 3.3.C.2 of the Technical Spec-ifications.

Revicu of ncien timing traces taken on the 2') monitored drives during a scre un May 28, 1970 revcaled that one drive (in addition to D-3 reported in our letter to you of May 14, 1970) c::cceded 5.30 seconds for 90% insertion, and several othern showed an increaac in scram times to values icss than 5.30 seconda. As a result of thin information cdditional scram tests were perforned in the power operating condition on all of the remaining drives between May 28 and 31, 1970. These subsequent tests shoucd that additional drives execeded 5.30 seconds. In heaping with out letter to you dated December 15, 1969 sfened by Peter S. Van Nort we have tchulated all drives exceeding 3.6 seconds for 907.

insertion. The averano scram time to 907 insertion for all operable drives con-tinues to be between 2.4 and 3.1 seconds.

Scram Individual Drive Tests Scram Scram Individual Date 5/28/70 5/28-31/_70_

6/2/70 ,6]3/70 Drive tests C*ntrol Rod Drive 6/4/70

1. 1 #2 #3 ,

1. 4 #5 D-3* 14-11 9.98 11.35 8.06 **

H-8 11.23 30-31 35.57

[gJ-7 34 ' / 16.75 22.25 14.9 3.59 J A G-13 26-51 ,

11.77 g F-1 22-03 7.97 5.96 5.56 D-2 5.56 f 14-07 6.91 4.90 4.92 B-4 06-15 6.72 6.85 5.87 St 5.89 J-8* 34-31 5.28 5.56 3.51 3.14 3.59 eg J-9 H-10 34-35 5.01 )

30-39 4.21 W M-1 30-03 4.18 l E 'C-6 10-23 3.88 )

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A 10-31 6.71 C-6* 4,13 ,, ,

26-23 4.73 '

. 3.26 3.25 9052.9

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NOT!:: It.dividual Driu 'fe s t! - 61 All driveo sich were not continuent,c ren-it ored v. re ?ndiv! dually ecre- cd.

scrrn tins. P4 una perfor.wd altu; .1 12 and C - n lected clrive: were retested for

eriod of drive innertion t e posit to

. 00, in order t o "sonk" t he inner ccrean at ope ra t ing t orperni ure. #5 was perfotrnd af t er a period of f t'll cont rol ud rithdraual r.m. with test equipment connected to ch?ck  !

for r.ny ebstructicas in the scram discharge lines. Tcste shou'd that no cuch ob-t.truct ions existed.

• Drives which cre euron", the 29 .onitored drives cxhibiting great er than 3.6 en.c-

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or.da 904 inne rt ton t ir.en.

• • Scrma trace not available ca these drivea.

Operatin of the reactor subsequent to finding control rod drivec in excess of 7.0 . seconds was conducted in conformance t o the Technical Specifications. ,

l Further investinatien of drive and driv 3 screen conditions brwe been init ia t ed f olle 'in;; the shutdown of June 5, 1970, selected drises are bein" re-m.oved and disassecMed for inepection. A review of the problem will be conductad 3 and fut ure operr.riou will be evaluated nit cr complete review of the data and inferica tion obta in:cd. The situation to date has been reviewed by the Statloa Revieu board.

Very truly yours,

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H. K. Hoyt i Superintendent IIKH: glw 9

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