ML20148H297

Forwards Request for Addl Info Re Proposed Change to Tech Specs to Reduce Number of Operable Incore Neutron Detector Thimbles.Response Required by 780410

ML20148H297
Person / Time
Site:	Yankee Rowe
Issue date:	03/16/1978
From:	Ziemann D Office of Nuclear Reactor Regulation
To:	Groce R YANKEE ATOMIC ELECTRIC CO.
References
NUDOCS 8011170936
Download: ML20148H297 (4)

Text

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.= "4 DISTRIBUTION Docket RBaer  !

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%s, . . Local PDR i D >cket 'No.7 50-29ydf# W y .,,, d, ..% .y.-ORB #2 Reading F ' .:'

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Fe7 d' MAR 101978 0 ELD Yankee Atomic Electric C$n'yG 1978. -

iean ATTN: Mr. Robert H. Groce .. . ABurger. .

i Licensing Engineer ~ _ . . . WRu s sel l . . . i

,, 20 Turnpike Road . . . RMDi gg s  !

I 7 , Westboro, Massachusetts 0158'.1. -... . ..DEisenhut..... .... , . . ,

'2 . 17 ' . *JTBAbernathy 7 v' v. Gentlemen: . ,J J

.. ....- J.JRBuchanan

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This is in response to your ap.p_lication r 1 ce)nse amendment dated  !

December 14, 1977, which supdrsides 'you'r iriitiaf'apiplicatifon dated ~

l September 8,1977. You propos!ed ac.hiange' td'the Techn'ical Speciff-cations for the Yankee-Rowe reactor to reduce t,he r,cquired numbe.r of operable incore scutron detectors'from 17 to 12. . -

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W ,, We have reviewed your request"and f,ind that the additional infamation C

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' ~ identified in the enclosure t'o.,',t.h.is ,1.etter ]s[r_iciuired ito 'c'ompl'ete .our[' -

review. We havo discussed ttig items in the enclosure durin ~ '

r tel ephone conversati ons with y.o'.u.'r.' i.t.'af.f..", . .,7. . . ". . .' ~. . ."..~. .". . ~g. recent. . . . . . " . ' '

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To maintain our review scheduTe your response is required by April 10,1978. Please provi.de youf'scriedul'e' ~fdrs'ubniit tal of' ' .

this information. ... ... -. .....

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[ Original Signed h7:' FW' we ..o . . . 'Donnio L. Zicmannj i F~ '~

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OWDennis' L. Ziemann, C'hief '

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Request for Additional ~ ""

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l RE0' JEST FOR ADDITI0'!AL I!lF09!'AT!0?!

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1. Provide the results of your study that demonstrates the Loility Ri' to detect fuel misloadings during startup tests with the reduced compliment of inco.'e detector thimbles, considering the following: l

a. The incore detector sysic.i must bc able to detect severe fuel misloadings. The most sevcre misloadings which would go undetected should he computed, and the presence of such 'r a uisloading should be assumeri in the preparation of the k"AM technical specifications. A 2D PDQ for the misloaded core should be adequate to generat e activations to be used in d~

this study. A suf ficient number of casec should be run to give a ueaningful statistical data base.

2. Provide 'the results of your r.tudy to determine the increased  ;

uncertainty in the Waking factor <. when they are computed f or  ;

use of the reduced compliment of incore detector thimble;, I m

considering the following:

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a. Increased incertainty during operations could be addressed in two ways. Whichever method is chosen, a sufficient number of cases should be run to give a r,!eaningful si-atistical data base.

(1) ~ Compare previous cycle maps.

(a) Take activation signals from previous raps. NN

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(b) In a rand:n fashion discard all but il of these d$O-a c'. iva t i on s .

(c ) Run ItiCORE with these ti activations. ,,

(d) Compare these It! COPE results with those obtained gM in the original map to determine the increase M*

in uncertainty, h2Y-

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(2)

• Compare with PDQ febM N J$,.

ns (a) Run PDQ which coupstes detector activations and 'IAw power distribution

, (b) Pick a random sample of fl of these activations. f.,#g7 (c) Run I?!CCRE with these !! activations. p yJT (d) Compare t.hese It CCRE results with the PDQ results i" V I to determine the uncertainty due to the synthesis procedure.

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3. Describe how you plan to monitor core tilt, and provide your analyris to support the proposed method. In addition, please gy respond to the following: plfy. A

a. Monitoring core tilt via loop flaws and temperature has been suggested by Yankee Rowe. Has this uethod been ,

duaonstrated viable?

b. It <,eems reasonable that the technical specifications .

be revised to require t hat at least one set of quadrant syuattric detector paths remain operable which would h,W' f.',-

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be used te monitor core tilt. If the core tilt is to be based on thir only, then the four trace <, (one per quadrant) should be taken in succension. Further, to check the data, these f reces should be taken ente at the beginning of the inap and once a t the end.

4 propose changes to the Technical 5pecifications, as appropriate, L..

based on the results of the altve studies for the reduced *N, compliraent of incore neutron detec tor thimbles. for your h-W$

response you may consider the following:

a. Call the ntoaher of rc.aolning opei able pa ths N. Ther will be uncertainty in the results 01 incore mea surements when N is reduced below some critical (yet to be determined) number. Below this critical number the uncertainly will increase at N decreases. This increased uncertainty should i be factored into the technical specifications. Maximum '++

operatirig flexibility at all times would be assured if the f

uncertainty factored into the technical specifications '

were a function of the current value of N. i n .=v

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