REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE

REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION Slovenian Industrial Radiography Event in 2013 Iztok Anželj Radiation Safety in Industrial Radiography, Vienna, 23 to 27 June 2014

Introduction • Company for Industrial Radiography has performed industrial radiography at the construction site of the new Slovenian Thermal Power Plant facility with HASS radiation source (Se-75, 1. 4 TBq, t 1/2 = 119 days). • The event happened in the night shift (between 30 to 31 October in 2013). • Exposed workers: – 2 have exceeded the annual dose limit of 20 m. Sv (20 and 27 m. Sv since the last reading); reconstruction (Authorized technical supporting organisation -TSO: Institute of Occupational Safety - IOS) showed 11 and 37 m. Sv, – 4 workers exceeded the monthly dose constrain of 1. 6 m. Sv. • Containers: from the Belgian Company (containers made in Russia). • Sealed radioactive sources produced in Russia and Germany. • Distributors of sealed radioactive sources : Belgian and Hungarian companies. REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 2

Container - for HASS radiation source (Se-75) REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 3

Container - for HASS radiation source (Se-75) source REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 4

Implementation of industrial radiography (configuration) Source cable Driving cable From the TSO`s Report of received doses (IOS) REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 5

Detailed description of the event • Control of welds approximately 8 m above the ground. • The NDT operators were at the distance of around 10 m from the container. • The first NDT operator installed the photographic film, second NDT operator triggered the exposition. • After completing the exposition, they were convinced that the source was safely in the container. • The container was put on the floor by a crane; when they wanted to disconnect the cables, they realized that something was wrong. • The first operator was not able to disconnect the source cable, which might imply that the source was not enclosed safely in the container. • According to the operators’ statements, none of the electronic dosimeters triggered an alarm. REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 6

Detailed description of the event (cont. ) • By shaking and dragging for about 1. 5 to 2 minutes (their subjective assessment) they managed to disconnect the source cable from the container and locked it. • Upon returning to the office, they noticed that their electronic dosimeters showed the measured dose of 26. 8 m. Sv and 20 m. Sv. • TSO (IOS) assumes that the safety lock of the container was not closed. When handling the source cable it had to be a slight drag of the cable to shift the source in to safety position in the container. It is assumed that the source was at least 10 cm away from the container. • There were different settings of alarm levels in electronic dosimeters: - most of them were set to 100 µSv/h - one was set to 10 Sv/h REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 7

The reconstruction of the event (Container with blind radiation source) First NDT operator – team leader Second NDT operator - assistant Team leader received a higher dose (4 Sv / hands) From the TSO`s Report of received doses (IOS) REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 8

The root causes of the event • Large amount of work, time pressure, several teams in the same area. • Not working according to the Operation Manual and company`s instructions for acting in case of an emergency. • Not using doze rate meters. • Use of a container, where the source was jamming in the tube. • Use of electronic dosimeters, with un-properly set alarm levels. • Composition of NDT team was not suitable (two less experienced workers worked together). • Electronic dosimeter did not trigger an alarm. • Use of a damaged container (found out on official service after the event). • Radiation protection officer has not been informed about the problems with the container. REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 9

Action after the event • Immediately after dosimeter readings; SRPA prohibited work with radiation sources of two overexposed NTD operators for 12 months. Two NDT operators were sent to medical examinations. • 11. Nov. 2013: joined inspection by the SNSA & SRPA. • 13. Nov. 2013: SNSA inspection; prohibited further use of a pertinent. container until it was closely inspected by the TSO (IOS). • 14. Nov. 2013: TSO (IOS) finds improperation of two more containers. • Containers were sent to the service. • 19. Nov. 2013: Reporting to the INES base (level 2). • 02. Dec. 2013: TSO (IOS) conducted a reconstruction of the event. • Notice for customers about the event: Radiation News No. 34 and 35. • 22. Jan. 2014: The SNSA informed Belgian regulatory body about the event in Slovenia. • 20. Mar. 2014: reply of the Belgian regulatory body (no problems identified in Belgium on that type of containers). • 21. Mar. 2014: Report of the service (cause: dirt and visible damage, possibly due to strong hit to the container housing). • 08. Apr. 2014: SNSA report on the analysis of the event. • 20. May 2014: Company for Industrial Radiography carried out all the actions / recommendations from the SNSA analysis. REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 10

Actions taken by the contractor of industrial radiography • Consistent use of dose rate meters and dosimeters. • Settings and checking of dose constraints on electronic dosimeters for levels of radiation as well as for received daily doses and record keeping. • Appropriate composition of the teams which will ensure one experienced worker in the team. • Strict compliance with work instructions and action in case of an emergency. • Overview of containers before use and maintenance. • Work instructions (proper translation of original instructions of the manufacturer). REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 11

Further activities in the SNSA • Proposals of minor changes of legislation in direction of detailed prescription. • Guideline for Control and Measurement of Radiation Sources (is being made): a) Authorized technical support organisation – TSO verifies responsiveness of protective equipment during the review of the radiation source (dose rate meters and electronic dosimeters) and defines an appropriate daily dose constraints. • SNSA inspection: a) Inspection of the implementation of industrial radiography in the field during expositions (usually in the afternoon or during the night), b) Immediate response of the SNSA inspection when dose constrain exceeds: - Prohibition on use of the device until an authorized technical support organisation – TSO review it or until it is sent to the authorized service for the radiation protection / Service. • Some minor changes in licensing procedure. REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 12

Suggestions for activities of other organizations • Trainers should modify the training programme with practical training. • Training with so-called blind radiation source (practical demonstration). • Creating brochures / posters with instructions how to implement industrial radiography on the field. REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 13

Thank you for your attention REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 14

REPUBLIC OF SLOVENIA MINISTRY OF AGRICULTURE AND THE ENVIRONMENT SLOVENIAN NUCLEAR SAFETY ADMINISTRATION 15