ML20148H220

Safety Evaluation Supporting Amend 31 to License DPR-3

ML20148H220
Person / Time
Site:	Yankee Rowe
Issue date:	11/23/1976
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20148H200	List: ML20148H195 ML20148H207 ML20148H220 ML20148H225
References
NUDOCS 8011170405
Download: ML20148H220 (3)

Text

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-%g NUCLEAR REGULATORY COMMISSION wAsmNG TON, D. C. 20665 o e o i SAFETY EVALUATION BY THE OFFICC 0F NUCLEAR REACTOR REGULATION i SUPPORTING AMENDMENT N0. 31 TO FACILITY OPERATING LICENSE NO. DPR _3_

YANKEE ATOMIC ELECTRIC COMPANY I; .

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YANKEE NUCLEAR POWER STATION (YANKEE-ROWE)

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DOCKET N0. 50-29

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Introduction By application dated August 17, 1976, Yankee Atomic Electric Company #

(the licensee) proposed specific changes in the Technical Specifications j relating to the maximum potential ejected rod worth permitted during q the life of Core XII. This proposal irvolves replacement of certain 1

pages in the perfonnance analysis for the current reload core (Core XII) $

which is inccrporated b~y^ reference ~i~n~Bie prisint Technical Specifications. f The proposal also involves a concurrent change in Section 3.1.3.1 "Povable Control Rods - Control Rod Operability" in the new format Technical r Specifications (issued on July 14, 1976, with Amendment No. 27) which will become effective as of January 1, 1977. -k i

9 Discussion _ l .

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The licensee reported recently (initially by telephone on July 30, 1976) hy that they had discovered an error in the methodology that was previously vt used for calculating the ejected rod worth of the highest worth rod at ,3 zero power and Beginning of Life (BOL) conditions. This error was found in the Core XI rod ejection analysis using the CHICKIN code which was $(

[.$p the reference analysis for the Core XII rod ejection analysis. The b licensee reported that the limiting rod worth chould be 0.75 percent iky <

if instead of the presently specified value of 1.0 percent Ay. The licensee also reported that the measured potential ejected rod worth never exceeded 0.7 5 percent af. Based on our review of the shutdown margin at BOL and the @K l

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reduction in the excess reactivity due to depletion in the fuel as Core XII = b burns,we found that Core XII has been operated safely and could continue '

i to be operated safely. However, we requested that the licensee provide us a revised rod ejection analysis to support the necessary change in the E(

Technical Specifications before the end of the present Core XII life. f;b M

Responding to our request the licensee submitted the revised analysis and 5 the associated proposed change in the fechnical Specifications with its August 17, 1976 application for license amendment.

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Evaluation $

The licensee's ejected rod worth analysis for Core XI (which was said to contain an error in methodology) considered only the hot channel to M@

detennine the reactivity transient. Because of this, reactivity feedback $

effects from the rest of the core were not accounted for. This resulted in a less conservative calculation. The revised calculations were done f;..

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in two steps. First the rod ejection for the average core was calculated, g9) then the reactivity effects on the hot channel were superimposed and l .'

the limiting ejected rod worth was computed. The results of the revised rod ejection accident analysis are shown in the following table.

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Parameter Calculated at Full power Calculated at Zero power Damage Threshold 3 lw '

Maximum Average Enthalpy at hot 134 cal /gm 183 cal /gm 200 cal /gm l[ t a spot (clad ,

damage threshold) d

g Maximum Fuel 209 cal /gm 213 cal /gm 250 cal /gm j Center Line r Enthalpy at hot 5 Spot fMR s

We agree with the calculational method used by the licensee in the revised analysis and find that the procedure is more correct and results in an i

. acceptable conservative calculation. We also find that the revised analysis supports the change in the specified limiting potential ejected rod worth .

{h 4 (from 1.0 percent of o 0.7 5 percent af) for the worst Core XII initial t

y condition for this accident, viz. zero power at BOL. We therefore conclude '/

that the changed potential ejected rod worth limit provides an acceptable ,4 ,,5 -

safety margin for operation of Yankee-Rowe during the life of the present if Core XII. gy w

We have deternined that the amendment does not authorize a change in  %

effluent types or total amounts nor an increase in power level and will %Y not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an W

action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 151.5(d)(4), that an environmental impact statement ,

%g or negative declaration and environmental impact appraisal need not be g prepared in connection with the issuance of this amendment. ,y b'

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We have concluded, based on the considerations discussed above, that: $

(1) because the amendment does not involve a significant increase in the 4 probability or consequences of accidents previously considered and does t

! not involve a significant decrease in a safety margin, the amendment [Er l"

does not involve a significant hazards consideration, '(2) there is reasonable assurance that the health and safety of the public will not

, be endangered by operation in the proposed manner, and (3) such hetivities  ;

l will be conducted in compliance with the Commission's regulations and the w. _

j issuance of this amendment will not be inimical to the common defense and g;

! security or to the health and safety of the public. i b

w Date: November 23, 1976 n:

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