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Inspection of bottom and lid welds for disposal canisters

Technical Report:

Abstract

This report presents the inspection techniques of copper electron beam and friction stir welds. Both welding methods are described briefly and a more detailed description of the defects occurring in each welding methods is given. The defect types form a basis for the design of non-destructive testing. The inspection of copper material is challenging due to the anisotropic properties of the weld and local changes in the grain size of the base material. Four different methods are used for inspection. Ultrasonic and radiographic testing techniques are used for inspection of volume. Eddy current and visual testing techniques are used for inspection of the surface and near surface area. All these methods have some limitations which are related to the physics of the used method. All inspection methods need to be carried out remotely because of the radiation from the spent nuclear fuel. All methods have been described in detail and the use of the chosen inspection techniques has been justified. Phased array technology has been applied in ultrasonic testing. Ultrasonic phased array technology enables the electrical modification of the sound field during inspection so that the sound field can be adjusted dynamically for different situations and detection of different defect  More>>
Authors:
Publication Date:
Sep 15, 2010
Product Type:
Technical Report
Report Number:
POSIVA-10-04
Resource Relation:
Other Information: 99 refs.
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 42 ENGINEERING; RADIOACTIVE WASTE DISPOSAL; COPPER; CONTAINERS; ELECTRON BEAM WELDING; FRICTION WELDING; INSPECTION; TESTING; DEFECTS; DETECTION; SPENT FUELS
OSTI ID:
1010730
Research Organizations:
Posiva Oy, Helsinki (Finland)
Country of Origin:
Finland
Language:
English
Other Identifying Numbers:
Other: ISBN 978-951-652-175-9; TRN: FI1104004
Availability:
Available in fulltext at http://www.posiva.fi/files/1412/POSIVA_2010-04_web.pdf or as a soft back edition from Posiva Oy, Olkiluoto, 27160 Eurajoki, Finland, tel. +358-2-837231
Submitting Site:
FIN
Size:
98 p. pages
Announcement Date:
Apr 11, 2011

Technical Report:

Citation Formats

Pitkaenen, J. Inspection of bottom and lid welds for disposal canisters. Finland: N. p., 2010. Web.
Pitkaenen, J. Inspection of bottom and lid welds for disposal canisters. Finland.
Pitkaenen, J. 2010. "Inspection of bottom and lid welds for disposal canisters." Finland.
@misc{etde_1010730,
title = {Inspection of bottom and lid welds for disposal canisters}
author = {Pitkaenen, J}
abstractNote = {This report presents the inspection techniques of copper electron beam and friction stir welds. Both welding methods are described briefly and a more detailed description of the defects occurring in each welding methods is given. The defect types form a basis for the design of non-destructive testing. The inspection of copper material is challenging due to the anisotropic properties of the weld and local changes in the grain size of the base material. Four different methods are used for inspection. Ultrasonic and radiographic testing techniques are used for inspection of volume. Eddy current and visual testing techniques are used for inspection of the surface and near surface area. All these methods have some limitations which are related to the physics of the used method. All inspection methods need to be carried out remotely because of the radiation from the spent nuclear fuel. All methods have been described in detail and the use of the chosen inspection techniques has been justified. Phased array technology has been applied in ultrasonic testing. Ultrasonic phased array technology enables the electrical modification of the sound field during inspection so that the sound field can be adjusted dynamically for different situations and detection of different defect types. The frequency of the phased array probe has been chosen to be 3.5 MHz. It is a compromise between good sizing and defect detectability. It must be taken into account that ultrasonic testing is not suitable for detection of defect types which are in the direction of the beam. Ultrasonic and radiographic testing techniques complement each other in case of planar defects. Positioning of the indication in the radial direction is rather limited in radiographic testing. Surface inspection has been added to the inspection routine because indications from the outer surface of the canister cannot be distinguished from weld defects in the radiographic image. A 9 MeV linear accelerator has been used in the radiographic testing for this study. Other radiation sources cannot penetrate the wall thickness sufficiently. Defects detected in visual testing will be sized using eddy current testing. Special inspection techniques have been developed for sizing using low frequency (LF) eddy current testing. High frequency (HF) coils are used to evaluate the area of the surface defects. In the case of copper inspection, 30 kHz is considered a high frequency and 200 Hz a low frequency. The acceptance criteria define the defect detectability requirements of the inspection methods. The defect detectability of the methods is under further study to ascertain their viability. In the case of a single defect, the inaccuracy of the sizing method is less important. The significance of the inaccuracy in sizing is more pronounced when there are two or more defects in the corrosion path of the canister. The sizing capability will be studied and subsequently inspection techniques qualified on the basis of the recommendation of ENIQ (European Network for Inspection Qualification). This type of qualification is applied in Europe. In the USA, the qualification in nuclear applications is based on the performance demonstration part of ASME XI. All required information (input information, inspection procedures, technical justifications, etc.) will be gathered in order to prepare for the qualification. At the moment in the NDT reliability study the defect detectability is in focus as well the inaccuracy of sizing of indications. The precise sizing is the clearly more safety-based and industrial acceptance of canisters can be carried out. Sizing will be also verified by a limited metallographic study of detected indications. The work of technical justifications will be started. By qualifying the inspectors and inspection methods, the defined quality requirements for manufacturing disposal canisters for spent nuclear fuel will be met. (orig.)}
place = {Finland}
year = {2010}
month = {Sep}
}