ML20031F211

Comments on Field Insp Procedure, of Westinghouse Rept on, Steam Generator Retubing & Refurbishment. Discussion on Cracked Ligaments Is Too Cryptic

ML20031F211
Person / Time
Issue date:	05/18/1979
From:	Abramson L NRC OFFICE OF MANAGEMENT AND PROGRAM ANALYSIS (MPA)
To:	Liaw B Office of Nuclear Reactor Regulation
Shared Package
ML13319A640	List: ML13319A639 ML13319A705 ML16138A447 ML17250A292 ML17250A294 ML17258A950 ML17338A640 ML17340A761 ML19273C366 ML19273D734 ML19275D923 ML20030A306 ML20031F023 ML20031F050 ML20031F059 ML20031F064 ML20031F069 ML20031F073 ML20031F076 ML20031F077 ML20031F080 ML20031F085 ML20031F102 ML20031F104 ML20031F111 ML20031F128 ML20031F130 ML20031F133 ML20031F138 ML20031F142 ML20031F147 ML20031F149 ML20031F153 ML20031F156 ML20031F157 ML20031F160 ML20031F162 ML20031F169 ML20031F174 ML20031F176 ML20031F180 ML20031F185 ML20031F189 ML20031F193 ML20031F195 ML20031F196 ML20031F199 ML20031F203 ML20031F211 ML20031F215 ... further results
References
FOIA-81-313 NUDOCS 8110190360
Download: ML20031F211 (2)

Text

_.

d'

1. g ** "' 44'q, l

UNITED STATES

['

'(

NUCLEAR REGULATORY COMMISSION g

E WASHINGTON, D. C. 20555

. N

,e /

.oss

, - - ~

May 18, 1979 MEMlRANDUM FOR:

B. D. Liaw, Engineering Branch, Division of Operating Reactors NRR THRU:

Roger H. Moore, Chief, Applied Statistics Branch, MPA FROM:

Lee R. Abramson, Applied Statistics Branch, MA

SUBJECT:

WESTINGHOUSE REPORT ON " STEAM GENERATOR RETUBING AND REFURBISHMENT", W-9398, JANUARY 1979 Per J. Strosnider's request, I have reviewed Section 7.2.7, "Fie:d Inspection Procedure",of the subject report and have the following coments.

Page 7-8 1.

There is no discussion of the assumptions on which Figure 7-4 is based.

Presumably, it was assumed that hole size.in the regt'n to be sampled has a Gaussian distribution with the same 4nean and v:ri=nce for all holes. How valid are these assumptions and what woulu be the effect of reasonable departures from them?

2.

There is no discussion of the tradeoffs among sample size, tolerance coverage, confidence level, and the cost of making the wrong decision.

How are the sample size, tolerance coverage and confidence levels to be chosen?

Page 7-9 The discussion on cracked ligaments is too cryptic.

I don't understand what is being assumed or what statistical procedure is being proposed.

Much more ditail is needed.

Page 7-15

^

According to the text (page 7-8), Figure 7-4 presents one-sided tolerance limits. However, the contours do not correspond to one-sided 90% coverage tolerance limits. They are much closer to one-sided 95% coverage or two-sided 90% coverage tolerance limits.

For example, at 90% confidence, the one-sided k-factor for 90% coverage for n = 6 is 2.49, the one-sided k-factor far 95% coverage is 2.09 and the two-sided k-factor for 90%' coverage is 3.13.

The corresponding tolerance limits for an average enlarged hole size of 890 c.ils are g og y a10e27 ifwp a:,-313 PDR

. J 7.e

8. D. Liaw May 18, 1979

.s23rf. c 2.-.

-- ~ 1 L(.90)=890+(2.49)(4)=900.0',

j L (.95) = 890 + (3.09)(4) = 902.4,

j L(.90)a 890+(3.13)(4)=902.5.

2 ThevaluesofL(.95)andL(.90)correspondmuchmorecloselytoFigure7-15 3

2 than does L (.90).

j l

1 will be glad to further discuss the report with you.

-fe L %

Lee R. Abramson Applied Statistics Branch Division of Technical Support Office of Management and Program Analysis cc:

J. Strosnider EB V. Noonan, EB Norman M. Haller, MPA b

e

,___,m-.--

-