ML20205M526

Safety Evaluation Denying Util 860819 Proposal to Reproduce Radiographs on Microfilm

ML20205M526
Person / Time
Site:	Prairie Island
Issue date:	03/27/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20205M507	List: ML20205M503 ML20205M526
References
NUDOCS 8704020422
Download: ML20205M526 (5)

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I SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION

.' NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT

?- UNIT NOS. 1 AND 2 PROPOSED MICROFILM REPRODUCTION OF RADIOGRAPHS l f

Principal Contributor:

William J. Collins, Sr. Metallurgist Office of Inspection and Enforcement ho04020422870327 p ADOCK 05000282 PDR

INTRODUCTION By lett-r dated August 19, 1986, Northern States Power Company (NSP) requested NRC to review and concur with their proposal to microfilm radiographs of the piping system welds of the subject plants in accordance with paragraph IWA-6320ofASMECodeSectionXI(1980 Edition, Winter 1981 addenda) requirements.

In response to this request, a meeting was held on December 17-18, 1986 4

between representatives of NSP and NRC at Micro Media Inc., Minneapolis, Minnesota, to review the proposed microfilming activities and quality assurance program. Enclosure 1 identifies the attendees of this meeting.

EVALUATION ,

Micro Media Inc., is a small local microfilming company who has been

, assisting NSP efforts to develop a suitable method of radiograph reproduction

g by microfilming. Their facilities essentially consist of comercial photographic equipment and automated film processing systems that are designed and primarily being used for microfilming medical x-ray records. No formal quality control system is employed by Micro Media. Rather, the final product is directly dependent on the skill and experience of trained technicians and line supervision.

Following a tour of the MMI facility, the procedure NSP proposed to use in microfilming the subject weld radiographs was discussed. Briefly, the procedure would employ a multiple exposure technique to provide five microfilm images, in 35 nun format, of each radiograph to accommodate the expected film density range of 1.5 to 4.0. Using this approach, NSP anticipated that at least one microimage would feature the actual density and equivalent sensitivity level of the original radiographs. The resulting microfilms would then be reviewed against the respective radiographs tc assure that all ASME Code requirements are met.

To demonstrate the methodology proposed, Micro Media was asked to microfilm a representative sample of 12 industrial radiographs furnished by the NRC staff. These radiographs were of carbon steel and austenitic stainless steel piping welds ranging from 0.5 to 1.3 inches in wall thickness, respectively.

Measured film density ranged from 1.8 to 3.5 across the areas of interest.

Plaque type penetrameters shimmed to simulate weld thickness were present on each film. A 4T penetrameter sensitivity as required by code specifications

, was visible on the majority of films. For the radiographs of the thin-wall pipe samples of carbon steel, a 2T sensitivity index was also visible, i Collectively, the sample radiographs featured various code rejectable indications in the weldments. These included porosity, root burn through,

inclusions, weld undercut, lack of fusion, cracking and various film artifacts. The indications varied from being very obvious and easily seen to very subtle, requiring expert interpretation. In order words, the visibilit

' of the indications and penetrameter sensitivity (i.e., image quality index) y ranged from marginal to excellent depending on the contrast and resolution achieved.

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Five microfilm images were made of each radiograph in 35 mm format as described above. A standard film density strip was required by the NRC staff to be microfilmed with each radiograph to aid in interpretation. In microfilming, no automated circuitry was used to vary the light intensity or relative exposure to acconnodate the density gradient inherent in the 1 radiographs. Hence, the microfilm images merely showed different levels of density of which only one appeared interpretable.

Two viewers were made available by Micro Media for microfilm review by the task group (Messrs. Nelsen, Martinson, Dahlman and Collins). Unfortunately, the equipment was designed for viewing medical x-ray film and as a result proved inadequate for evaluating details of the microfilm images of the industrial radicaraphs.

The reproductions were then placed on an industrial radiograph viewer and i [~ *,

compared directly with the original radiographs utilizing a hand-held optical

. loupe (8x mag.) as a visual aid. As expected four of the five microfilm images were uninterpretable due to excessive film density. The remaining image was quite comparable to the original radiograph on the bases of film density strip estimates. However, the image showed no penetrameter sensitivity index (complete loss of 2T and 4T hole visibility) and relatively low resolution of certain flaw details. This was particularly evident in the microfilms of the heavy pipe thickness and was attributed to light scatter bridging the density gradients of the radiographs during microfilming. In certain film, image aberrations occurred due to improper camera focusing which also degraded image quality and clarity of details. The lack of a capability to properly enlarge the microfilm and absence of a calibrated scale precluded further evaluation of the reproductions in accordance with code specifications.

CONCLUSION Based on the above, the group concluded that the microfilming techniques as presently proposed were not an acceptable alternative for the original radiographs. The group also concluded that several critical constraints in the existing methods and procedures need to be resolved by NSP. Specifically, these include:

1. The microfilm viewer must be designed with sufficient operational capability in terms of variable focusing, lighting, calibrated scale and image enlargement to permit definitive interpretation of microfilm against code specifications.

2. Special film types need to be evaluated to ensure equivalent sensitivity, contrast, and resolution characteristic of the original radiograph.

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3. Camera equipment designed with finite focusing, spatial alignment and variable lighting controls are necessary to optimize filming conditions. This must be accomplished in con,iunction with item 4.

4. During the filming of a target film, the standard film density strip and the calibrated scale need to be filmed with the radiographs to aid interpretation and more importantly, verification that the microfilms are accurately reproduced from the original radiographs.

5. A photographic film stability test, such as provided for in ANSI PH 4.8, 1978, needs to be considered as a means.to control film processing parameters and ensure archival quality of microfilms.

., 6. The quality control program for microfilming radiographs is the .

(; responsibility of NSP and is currently in draft form. The program procedures need to be finalized before microfilming can commence. The y procedure (s) must provide for control of all microfilming activities and final review processes to ensure the final product meets code specifications.

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. is Enclosure 1 LIST OF MEETING ATTENDEES t a R. I. Nelson NSP, Quality Control Supervisor a

L. C. Dahlman NSP, Materials and Special Processes Division K. B. Martinson NSP, Quality Control Supervisor G. Eckholt NSP, Nuclear Support Services J. McMerty Micro Media Inc.

N. Giannaccini Micro Media Inc.

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fik; W. J. Collins U.S. NRC, IE, DEPER .

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