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Evaluation of Indications in Peach Bottom 3 Jet Pump Instrumentation Nozzle Safe End Reducer Weld
	ML20092D712
Person / Time
Site:	Peach Bottom
Issue date:	06/30/1984
From:	Ranganath S; GENERAL ELECTRIC CO.
To:	;
Shared Package
ML20092D702	List: ML20092D697; ML20092D707; ML20092D712; ML20092D718; ML20092D721;
References
	MAR-84-19, NUDOCS 8406220118
	Download: ML20092D712 (9)
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ATTACHMENT B PHILADELPHIA ELECTRIC COMPANY PEACH BOTTOM ATOMIC POWER STATION UNIT 3 DOCKET NO. 50-278 .

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EVALUATION OF THE INDICATIONS IN THE PEACH BOTTOM 3 JET PUMP INSTRUENTATION N0ZZLE SAFE END-REDUCER WELD June 1984

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1. EVALUATION BASIS

!Q Evaluation was performed for two sets of assumed flaw configurations as measured flaw sizes.

(I) A Loop welda Composite fIaw 1.87 inches Iong 0.075 inch deep B Loop weld: 0.75 inch long, 0.175 inch deep circumferential flaw These flaw sizes were based on best estimates of Level 11 Inspector.

(11) In the second evaluation, a through-wall flew equal to 1/6 of the circumference (16.7%) was postulated. This conservative assumption was made since the UT inspection was somewhat restricted over opproximately 1/3 of the circumference. The Level lll Inspector felt that in this position, the UT results were effective over half the length (or 1/6 of the circumference). The assumption of a 16.7% through-wall flaw therefore represents a !!miting condition.

O The following stress values were used for the purpose of predicting crack growth and allowable flaw sizes.

Pm = 3 ks! (pressure stress - pd/4t)

Pm+Pb = 5 ks!

The P,+ Pb was an estimate sinco the Information was not evallable in the str==s rape.rt: Navarthala==, I+ in ransonable since the reducer is not connected to any piping and therefore experlences no Piping loeds. Seismic loads are also insignificant.

For crack growth analysts a residual (banding) stress of 30 ksi is assumed.

Crack growth rates corresponding to f urnace sensitized material In 8 ppm oxygonated water (Figuro.1) was used. This is appropriate since the environmont In the reducer is stagnant.

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2. EVALUATION OF CRACKS PER UT SIZING O Figures 2 and 3 show the allowable flow sizes per IWB-3642 (safety factor of JJ on the same plot, the as-measured initial flew size, and predicrea crack is shown. Based on the assumed conservative f urnace sensitized crack growth rate, both cracks are predicted to grow to through-wall in approximately 3000 heur:. Alth :ch : threuch-w:!! cr::h != =r:d!cted. It != ct!!! with!n the

' allowable value since the safety f actor of 3 can be maintained with a through-woll crack of over 405 of the circumference. Even after the crack .

becomes through-wall, further circumferential crack growth can be tolereted before the Code allowable length is exceeded. Thus, the component is acceptable for continued operation for at least 3000 hours0.0347 days 0.833 hours 0.00496 weeks 0.00114 months .

3. EVALUATION ASSUMING THROUGH-WALL FLAW in this limiting calculation a through-wall crack of 16.7% circumference is assumed. Figure 4 shows that this is within the allowable crack length per IQ IWB-3642 of Section XI ASE Code. Assuming an average circumferential crack growth rate of 2 x 10~4 In/hr (corresponding to the plateau growth rates for furnace-sensitized material), it would take 9000 hours0.104 days 2.5 hours 0.0149 weeks 0.00342 months before the Code limits are reached. Thus, the flaw is acceptable even with the limiting essumptions.

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l 4 LEAK-BEFORE-BREAK CONSIDERATIONS Experience has shown that cracks In cmall diameter piping lead to leeks which are detected by leak detection systems. The circumferential variations In weld residual stress produce pref erential crack growth which leads eventually ,

iu iucai ivak. in inci, if une anumw= a liisuuwii weil u 6 J aquei to 1/0 of i the circumference, the expected leakage rate is of the order on 0.5 gpm. This could be detected by special leak monitors such as moisture sensitive tape, in any case, leak-before-break remains valid and provides inherent safety -

margins.

S. CD4CLUS 10N Continued oporetIon cen be justIfled for at ienst 3000 hours0.0347 days 0.833 hours 0.00496 weeks 0.00114 months of operation, even with conservativo assumptions on Initial crack size and crack growth rate. Even if the Indicotton becomes a through-well flew, Code safety umibrgins

.O .ouid be preserv.d for a much ionger ,oriod. teak-before-break ,rovides additional safety margin.

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ML20092D712

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