We are pleased to report that Digital Radiography (DR), hailed by many as the defining symbol of the latest advance in non-destructive radiographic examination of welds, has arrived in our manufacturing operations. Film radiographic technology, which has been the mainstay of pressure vessel volumetric weld examination for well over 80 years, will soon pass into history.
As befits the transition to a new technology, Holtec’s manufacturing organization has spent the past four years testing qualifying, improving techniques, and preparing procedures required to produce Code quality images with maximum fidelity, process sensitivity, and sharpness with its DR system. The input and support of external technical experts and the Holtec User Group in this long-term effort are gratefully acknowledged.
Due to a drastic reduction in radiographic exposure times associated with Digital Radiography (DR), when compared to film, Holtec associates now have the added major safety benefit of As-Low-As-Reasonably-Achievable “ALARA” dose levels during site welding operations, such as the multi-purpose canister (MPC) lid welding. This DR process has been inducted into our manufacturing quality program for the nondestructive inspection of MPCs at the Advanced Manufacturing Division (AMD) under the leadership of our DR subject matter expert Mr. Brian Farnsworth, P.E., ASNT Level III.
The procedures developed for DR are in full compliance with the required ASME Codes: Section III NB Class 1 components; Section V “Nondestructive Examination,” Article 2 “Radiographic Examination and Mandatory Appendix IX “Radiography using a Digital Detector System.” Holtec views DR to be particularly valuable for the nuclear industry whose historical challenges with the issues of senescence, slow deterioration and inability to rapidly retrieve archival film are now completely resolved. The instant portability and file organization of the digital images in electronic space now enables remote viewing and interpretation of the DR images by our stakeholders, anytime, anywhere. High fidelity digital images can be maintained, archived indefinitely, and rapidly retrieved from the redundant, secure Holtec hard drives when needed.
The intellectual property developed during the past four years of painstaking work with extreme attention to detail has been chronicled in the “Sourcebook on Digital Radiography of Thru Thickness Pressure Vessel Welds” which is available to Holtec’s clients under proprietary safeguards.
We are working on developing the knowledge software to make the interpretation of the digital images fully automatic ensuring complete objectivity and code compliance as the last remaining development step of the DR process for our pressure vessels. Another item for future DR development is making the process transportable with wireless Wi-Fi connectability. In-service inspection of the safety-related welds can occur as a part of a preventative maintenance program, reducing or eliminating the need for such inspections during plant outages. Our SMR-160 reactor will be a certain beneficiary of this technology.