Non-destructive testing

Some differences may exist between french and english regulations. Lessons learned are only a translation of those of french incident and are not adapt to english regulation.

pdf Exposure to persons during radiography of a barge (143 kB)

Description of the incident

Parties involved:

• Company A: Shipyard (and site owner).
• Company B: Sub-contractor for A, hydraulic equipment installation
• Company C: Sub-contractor for B, electrical equipment
• Company D: Sub-contractor for A, NDT company

The sequence of events was as follows:

• Company A manufactured a barge (6 m x 20 m) in its workshops, and subcontracted the installationof hydraulic equipment to B. No safety agreements were established between the two parties, although the duration of on-site work exceeds 400 hours.
• Company B sub-contracted electrical wiring of a control cabinet to company C (no safety agreements in place).
• Company A assigned Company D to carry out the verification of the welds on the barge by gamma radiography. A safety plan is formalized and signed between the two parties before the beginning of the work.

On the day of the incident:

• Two Company C electricians (a team leader and an apprentice) are working in the barge, as well as 15 employees of Company A. There is a lot of noise on site and the electricians are wearing ear defenders.
• At approximately 2:00 p.m., the electrician team leader (Company C) is called to another site for the same client. The apprentice works alone in the barge for the rest of the afternoon, still surrounded by employees of Company A.
• At approximately 4:30 p.m., two people from Company D arrive in the workshop to perform radiography on the welds; planned for 5:00 p.m. (Company A was advised of this several days before). They demarcate the workshop and have the personnel evacuated by a person from Company A. No one thinks to warn the apprentice from company C.
• A Company D employee goes down into the barge to set up the film and does not notice the presence of the electrician (the barge is partitioned into several compartments).
• Before proceeding with the exposure, one of the radiographers calls out to ensure that nobody is located in the exclusion zone. The apprentice electrician, who has not been informed of the radiography, does not hear this since he is wearing hearing protection. Therefore, he continued his work waiting for the return of his team leader.
• The area, including the apprentice, is then irradiated for 7 minutes and 30 seconds. At the end of the check, the film is recovered and the warning signs and barriers removed from the workshop. The operators of company D inform Company A that the work is complete and leave the premises without considering the incident that just occurred.

On a tour of the workshop, Company A’s workshop leader notes the movement of a portable electric cable on the pontoon. He then becomes aware that a person was present in the barge during the radiography.

Radiological consequences

The apprentice, who was not directly involved with the radiography, did not wear a dosemeter and knew nothing about the risks assocaited with gamma radiography. It was estimated that the apprentice received a dose of 0.4 mSv.

Lessons to be learned

The development of safety plans between a client and contractors is mandatory for potentially hazardous operations. These plans must define the safety measures and precautions which are to be taken by each party involved. In this incident, in addition to the lack of safety plans between companies A and B, and companies B and C, it appears that the various parties were not familiar with the planning of the various work activities being undertaken. This case illustrates an obvious lack of communication between the client and the various sub-contractors.

The existence of a safety plan does not remove the requirement for the radiographer to verify that nobody is located in the exclusion zone. This task may prove difficult, particularly if the exclusion area is of significant size or where a number of other parties are involved. However, a search must be made of the entire premises affected by the radiography area.

In this example, the construction was behind schedule, which may explain why a thorough search of all compartments of the barge had not been carried out. The radiography company was content to rely on the evacuation report prepared by Company A, who were not informed that the employees of company C were on site.

pdf Exposure to persons during radiography of a barge (143 kB)