ML20031D820

Recommends That Surveillance Be Instituted in C-E-designed Reactors Using Lumped Burnable Poison to Eliminate Potential Development of Undetected Safety Problems

ML20031D820
Person / Time
Issue date:	09/01/1976
From:	Ross D Office of Nuclear Reactor Regulation
To:	Eisenhut D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
Shared Package
ML20031D800	List: ML20031D799 ML20031D803 ML20031D806 ML20031D809 ML20031D813 ML20031D814 ML20031D817 ML20031D819 ML20031D820 ML20031D822 ML20031D826 ML20031D829 ML20031D831 ML20031D833 ML20031D836 ML20031D837
References
FOIA-81-236 NUDOCS 8110140257
Download: ML20031D820 (1)

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Eisenhut, Assistant Director, for 'Op'erational -

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. y 7.F..E~. D.' F. Ross;,y.ssistant Director for Reactor. Safety t,'L,7 "'/

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SUBJECT:

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t NDNITORING FOR E C REACTIVITf ANOMALIES

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The recent bur;nable poiso....;n' anomaly experienced at 'the St. Lucie reactor '

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ranf fested itself ~as a' gain in predicted reactivity,~a quadrant. tilt,N. -

and 'an increase in arini pealring factor.. Our present technical specifi~a-c tions address' the first two of these factors', but not the third. It is at

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, least theoretically possible to violate the' power distribution analysis basis fron an' increasing axial peaking factor before an anonaly reaches.

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the limit of 1% Ak/k spacified' in the reactivity anomaly technical ~ specifi.

cation. ' Alsof surveillance for'the' reactivity 'anonaly technical specifica -

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tion. is, probably not conducted as frequently as this new problem varrants.

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We, therefore, s[ugg[est that the following surveillance be instituted in C r-

. designed reactors using lus: ped burnable poison, at least until such a time ~

as the burnable poison problen can be shown to be unique to the St. Lucie i

burnable poison rods.

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Sur've111ance for reactivity anomalies sh'uld be conducted veekly (more frequently, while possibly desirable, appears i

to be. unnecessary and it might be difficult.to achieve

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j equilibriun conditions on a daily basis).; -

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The axial peaking factor for at Icast a few instrunented -

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s assemblies at representative locations in a' core shon1d be

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determined daily and 's:enitored for increases., Comparisons,

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fI vith expected distributions should be conducted 'veeklyQ j

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We bel'icve this surveillance vill clininate chances that the reactors vould

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Denvood F. Ross, Assistant Director i

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Division of Systems Safety g

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f. Y-DISTRIBUTION:

K. Coller.

F. Coffman

- Central Files e-D. Silver NRR Reading File

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S. Weiss M eading F,ile-.- -

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R. Meyer i

DSS:CPB DSS:CPB DSS:CP3.

- DSS:RS R. Richings M. Dunenfeld D.'Fieno.

P.' Check -

'D.)Ross

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