The decommission project

Background

The Svedberg Laboratory (TSL) is a particle accelerator facility under decommissioning. The facility also included a radiochemistry laboratory. The decommissioning is done in accordance with SSMFS 2018:3, the Radiation Safety Authority's regulations on exemptions from the Radiation Protection Act and on declassification of materials, building structures and areas. This is because large parts of the facility have been exposed to ionizing radiation or radioactive contamination during operation

Time overview

1951 – 2016 The facility was in operation, with interruptions for renovations.

2015-06-10 Decision on implementation of liquidation was made by the consistory 2016 A new organization for the decommissioning work, where TSL decommissioning is a department under the Department of Physics and Astronomy was formed. Ongoing irradiation projects were completed and the last run was carried out.

2016-07-01 The facility was shut down forever.

2017 - 2020 Waste management with self-inspection for declassification of potentially contaminated material as well as cleanup and control prior to declassification of the radiochemistry laboratory's building structures was carried out.

2020-12-11 TSL liquidation applied to SSM for declassification of the radiochemistry laboratory

2021-01-27 Exemption decision for the radiochemistry laboratory was made by SSM

2021 - 2024 Handling of material and implementation of control programs for declassification of potentially activated material are ongoing.

2025 Control before the application for declassification of building structures in the experimental halls is planned to be carried out. Then follows the application for exemption. Handling of remaining material is planned to be carried out in parallel.

2026 Mapping of the accelerator hall is planned to be carried out and then the TSL decommissioning project will be completed.

The project group

When the decommissioning began, a project group of five people was appointed to carry out the decommissioning. During the course of the work, the group has been expanded and then reduced. At most, twelve people have been linked to the group. Today it consists of seven people.

For cleaning and dismantling work, the group takes the help of contracted contractors.

The work place

A relatively large and challenging part of the work involves maintaining a good working environment during the liquidation process. Both the physical work environment and the organizational and social work environment are extra difficult to manage, not only with regard to radiation protection, but also precisely because the business involves decommissioning.

Everyone in the workplace may undergo an internal radiation protection training adapted to the nature of the work.

Phases in the decommissioning work

The decommissioning work was divided into two phases. The first involved the radiochemistry laboratory containing a large amount of potentially contaminated equipment and contaminated material where the building structures were also potentially contaminated. The second includes accelerators and experimental halls that contain potentially activated equipment and materials and where the building structures are also potentially activated.

Strategy for handling equipment and materials

The watchword for handling is recycling. In the first place, options are chosen that aim at the reuse of equipment in its original function and, secondarily, the reuse of materials. Only when it is found to be impracticable does the waste go to incineration or landfill.

Strategy for free classification

History, i.e. knowledge of the facility during the operating period together with mapping of activation are the foundations of the clearance process. On site, we make gamma spectroscopic measurements and measurements with hand instruments. To solve the problem with nuclides that we cannot measure on site, we use nuclide lists and nuclide vectors that are developed through literature studies combined with our own measurements, simulations and also results from sampling where the samples have been analyzed at other laboratories.

In order to ensure that those who carry out sampling, measurement, analysis and make clearance decisions have sufficient competence to do this, we have developed an adapted clearance training.

Free classification of material

Contaminated material

By taking samples of extra exposed objects, such as waste boxes and ventilation parts, as well as knowledge of which radiation sources are present at the facility, we have produced a nuclide list of the contamination we can expect to find. Based on this, we have then chosen an operational limit value for direct measurements. All material that may have been contaminated has then iteratively been directly measured and cleaned so that when the measurement results fall below the limit value it is cleared.

Activated material

To assess the risk of activation in materials, we start from plant knowledge as well as mapping and controls. Above all, we use results from the control of a few selected types of material, those found in concrete and cable, which occurred throughout the plant and in several, very exposed positions.

'We then use, depending on how much knowledge we have of the material, what risk of activation there is and the activity distribution, one of the following three clearance methods; justification, measurement of the entire quantity and measurement of a representative subset of the material.

Free classification of building structures

The radiochemistry laboratory has been declassified mainly based on results from direct measurements. Walls and floors have been cleaned and divided into squares. Accurate measurements have been carried out on the number of boxes that were needed so that we can with great certainty, using statistical calculations, assess the risk of us missing any contamination as very small.

Declassification of experimental halls that are not contaminated but only activated and that with a known distribution is planned to be carried out based on results from sampling.

What happens next?

When the equipment is gone and building structures around the accelerator facility have been declassified, the contract of the premises will be terminated against the property owner Akademiska hus. The project group is dissolved.