ML19343D259

Responds to NRC 810320 Ltr Re Investigation of Voids, Separations or Honeycombs in Concrete.Qualification Record Must Be Performed to Evaluate If 95% Reliability w/95% Confidence Exists

ML19343D259
Person / Time
Site:	Marble Hill
Issue date:	03/26/1981
From:	Cassaro M LOUISVILLE, UNIV. OF, LOUISVILLE, KY
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19343D254	List: ML19343D253 ML19343D259
References
NUDOCS 8105040053
Download: ML19343D259 (2)

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, /N i ) Michael A. Cassaro, Ph.D.,PE Professor of. Civil Engineering Speed Scientific School Dept. of Civil Engineering University of Louisville Louisville, Kentucky 40208 March 26, 1981 United States Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137 ATTN: Mr. James G. Keppler, Director Re: STN 50-546 STN 50-547

Dear Mr. Keppler:

The NRC letter of March 20, 1981 is quite detailed and reasonably comprehensive.

Most of the points in my letter of September 26, 1980 have been discussed and handled. It is the March 4, 1981 letter of mine that has not been completely answered and is the subject of this correspondence.

The NRC must rely on microseismic investigation to determine if voids, separations or honeycombs exist in the concrete since all observable voids are considered " surface concrete defectives". Since the NRC has established the criteria, 95% reliability with 95% confidence, using Equation 2, it mttst be recognized that this is a probabdistic equation implying no instrument or human error associated with the statistical approach.

The March 4 letter gives an acceptible procedure for determining and including the human error and the instrument error in the test program. Several examples of this type of error are cited in the March 4 letter. For example, if the interpretor declared a "noneycomb" the same day.he based the qualification test and the honeycomb turned out to have significant bubbles in the concrete, then there appears to be reasonable room for error.

l EXHIBIT "A" 810504 Di>53

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. Mr. James G. Keppler Nuclear Regulatory Comm.

March.26,J1981 Page 2.

We do not question Mr. Muenow's qualifications. However,

. everyone - is capable af. making an error. It appears that no written-qualification exists in the record at Marble Hill. A qualification. record must be~ performed to evaluate if we have 95% reliability with 95% confidence.

As it now stands, thereiscertainlyless_than95%rebiability as outlined in the March 4 letter, and we believe that no_ verbiage will erase that reality, only clear statistics.

This writer awaits the further response of the NRC.

Sincerely, QA d QQ - kafw Michael A. Cassaro, Ph.D., PE MAC/mjb u

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