ML20207P462

Forwards Comments on Answers to Questions H.01 & H.11 of Section H, Reactor Theory, Re Test Administered to R Berlin

ML20207P462
Person / Time
Site:	05000199
Issue date:	12/10/1986
From:	Kane G MANHATTAN COLLEGE, RIVERDALE, NY
To:	Coe D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20207P449	List: IR 05000199/1986003 ML20207P448 ML20207P462
References
NUDOCS 8701160157
Download: ML20207P462 (7)

Text

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ATTACHMENT 2 L ,. H.

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. MANHATTAN COLLEGE PARKWAY PHYSICS DEPARTMENT

't-Mamastan RIVERDALE, NEW YORK 10471

, (212) 920-0368, 920-0369 1

December 10, 1986 i

Mr. Douglas Coe.

U.S. Nuclear Regulatory. Commission Region -. I i 631 Park Avenue l King of Prussia, Pa. 19406 f-

Dear Mr. Coe:

I have enclosed coments on the answers to questions 11.01 and 11.11 of Section Il-Reactor Theory on the test recently administered to Dr. Robert Berlin.

I trust that these coments will be of some assistance to you.

Sincerely, pWkiP' ] $0%d-Brother Gabriel Kane, F.S.C . , Ph.D.

Senior Reactor Operator BGK:mk 8701160157 870109 i PDR ADOCK 05000199 V PDR

.g ROBERP BERLIN'S REEXAMINATION Eglution to H.01 The reference given for the answer to H.01 is correct; but everything connected with the answer given is coupletely wrong.

The reference given is the MCZPR experiment on " Approach to Criticality,"

in this experiment two curves are shown. One is an " Overconservative Approach" and the other on a "Non-conservative Approach".

From the data given for H.01, this is definitely a Non-conservative Approach.-

The four points given were plotted on a graph paper. Exrapolating back to zero fuel elements in the core, it was estimated that the source strength (No) was about 24 cps.

Using a French curve and extrapolating carefully beyond the loading of the thirteenth fuel element, it was calculated that the reactor would become critical shortly before the loading of the fifteenth fuel element.

Since the candidate probably did not have access to a French curve on a set of curves, it is possible that his freehand extrapolation could have varied slightly from the one using a more precise method.

Coments on Answer Given for Answer to H.01 In the answer given to H.01,1/M is plotted against the runber of fuel elements loaded into the core. Now, 1/M represents No/N where No is the reading in counts per second with only the source present in the core and N is the reading at some particular fuel' loading.

It makes no sense therefore, to choose the starting point for 1/M arbitrarily at some other point than zero loading as was done on the graph given with the answer to H.01.

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H.ll Question One of the equations given on the equation sheet is a sinplified form of the unknown equation and relates reactor period to reactivity for small reactivity changes made to a critical mass. If the effective delayed neutron fracticn is 0.007 and the effective precursor decay constant for all precursor graphs is 0.08 per second, what reactor period would result if 5.0 cents of positive reactivity were inserted into this critical reactor?

Answer Given

" (beta - rho)

(rho x lambda)

= *007 J .05 x .007)

(.05 x .007 x .08)

Solution Beta = .007 A = .08/sec P"**'

Coment The first term on the right hand side of Coe's answer .007 is obviously incorrect; .007 equals beta a dimensionless quantity, which cannot be equated with time (T).

Substitutingg) andf for Coe's nturerical values T"8 g(x Coment The original equation was factored incorrectly. It should have been:

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"yxA ~1 Continuina with the correct Substitution A 1 "fx}.007

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.05 x .007 x .08/sec ~58/sec 1 1

" .05 x .08/sec ~ .08/sec

" ~I 57sec 1 see 1 .05 '

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• 35 3p) sw = 40 x 10- y sec j

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" ~40 x 10" sec = 40 x 10 .

9500 950 . s. M

" lu-sec = 4 sec g

= 237.5 second Correct answer agrees with answer given. ~ , .

s Conment (

Answer is correct but approach to solution is incorrect. The separation i of terns on the first step is incorrect. The approach given would have given an incorrect answer.

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W* m Q' s ATTACHMENT 3 f NRC response to Facility conwents on Written Examination of December 3,1986.

Question. Response H.01 - Not accepted. The plot provided by the Facility in support of this comment does not appear to conform to the 1/M plot construction method given in the referen'ce "MCZPR experiment Approach to Criticality". .Specifically, the plot is a graph of actual counts versus fuel e elements loaded, whereas the give_n-reference directs that reciprocal multiplication-(1/M) be plotted against fuel loading, In addition, it can easily be shown,that, for an ideal approach to criticality (source detector geoinetry not influencing the plot),' re-initializing the plot at some point other than zero fuel will render the same final result.

H.11 Comment accepted. Brackets enclosing the numerator of the equation were inadvertently t left off. No change to the numerical answer.

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