[en] JET has completed its first stage of active operations, processing more than 100 g of tritium during the deuterium-tritium experiment (DTE1), the neutral beam intervention and remote tile exchange shutdown. The radiological safety of tritium handling operations has been of particular interest. A wide range of tritium operations has been carried out in the period 1995-98. This paper describes some of the radiological protection measures for work with tritium, and discusses Health Physics operational experience of handling tritium in this period. Descriptions are given of active operations in the gas handling plant; in the torus hall during DTE1; in related interventions, and of the remote exchange of in-vessel divertor modules. Workplace contamination levels over 100DAC (HTO) have been encountered, tritiated water with activity of 2TBq/litre and tritiated carbon with activities of ∼4TBq/g has been handled. Control measures involving the use of purge and extract ventilation, and of personal protection using air-fed pressurised suits are described. The project imposes tight limits on radiation exposures. Tritium doses to staff in this period have been very low (individual doses <170μSv/year, collective doses ≤2.1mSv/year). Aerial discharges have been <3% of annual authorised limits, and average environmental (HTO) levels have been a few Bq/m³. Lessons have been learnt concerning exposure control, large-scale permeation effects, and the appearance of residual tritium on exposed surfaces. Tritium operations at JET have been conducted without incident and with very low personnel exposures. The methodology of using containment and ventilation systems and tight radiological control has been successful in limiting doses. JET experience shows that large-scale tritium handling and exposure control can be achieved within stringent dose limits. (author)

[en] Some of the safety procedures and controls in place for work with tritium are described, and initial operational experience of handling tritium is discussed. A description is given of work to rectify a water leak in a JET neutral beam heating component, which involved man-access to a confined volume to perform repairs, at tritium levels about 100 DAC (80 MBq/m³. HTO). Control measures involving use of purge and extract ventilation, and of personal protection using air-fed pressurized suits are described. Results are given of the internal doses to project staff and of atmospheric discharges of tritium during the repair outage. (P.A.)

[en] The JET deuterium-tritium experiments in 1997 (DTE1) utilised 20 grams of tritium, produced more than 2.3 x 10²⁰ D-T neutrons, and generated peak fusion powers of 16 MW. Significant health physics input was required to measure and quantify the radiological consequences of high yield neutron and gamma production, and of processing large tritium quantities. This paper summarises the results of radiological protection monitoring carried out during the campaign. Figures are presented of neutron and gamma doses and tritium levels in occupied areas during the D-T operations. Results are given of aerial discharges of tritium and the levels found in the local environment. There has also been potential for measurable tritium exposure in torus operational areas during maintenance and repair activities. Operational health physics knowledge has been gained during work on tritium contaminated systems, and descriptions are given of the initial radiological protection experience of work in areas with high levels of surface and airborne tritium. Initial experience at JET shows that tritium exposure controls have been very effective, giving very low operator doses. JET results also show that the environmental impact of processing 0.1 kg of tritium is not significant. (authors)

[en] JET has developed many different techniques in the field of contamination control since 1989. Isolator techniques are well established for beryllium and tritium operations where containment factors of the order of 10⁶ and 10⁵ have been achieved. The issue of tritium permeation has been addressed by the incorporation of environmental and local exhaust ventilation. Double lidded technology has been applied in practice to transfer technology and respiratory protection has continued to be adapted to new applications. (authors)

[en] JET has completed its first stage of active operations, processing more than 100 g of tritium during the deuterium-tritium experiment (DTE1), the neutral beam intervention and remote tile exchange shutdown. The radiological safety of tritium handling operations has been of particular interest. A wide range of tritium operations has been carried out in the period 1995-1998. This paper describes some of the radiological protection measures for work with tritium, and discusses Health Physics operational experience of handling tritium in this period. Descriptions are given of active operations in the gas handling plant; in the torus hall during DTE1; in related interventions, and of the remote exchange of in-vessel divertor modules. Workplace contamination levels over 100 DAC (HTO) have been encountered, tritiated water with activity of 2 TBq/l and tritiated carbon with activities of ∝4 TBq/g has been handled. Control measures involving the use of purge and extract ventilation, and of personal protection using air-fed pressurised suits are described. The project imposes tight limits on radiation exposures. Tritium doses to staff in this period have been very low (individual doses <170 μSv/year, collective doses ≤2.1 mSv/year). Aerial discharges have been <3% of annual authorised limits, and average environmental (HTO) levels have been a few Bq/m³. Lessons have been learnt concerning exposure control, large-scale permeation effects, and the appearance of residual tritium on exposed surfaces. Tritium operations at JET have been conducted without incident and with very low personnel exposures. The methodology of using containment and ventilation systems and tight radiological control has been successful in limiting doses. JET experience shows that large-scale tritium handling and exposure control can be achieved within stringent dose limits. (orig.)

[en] Accumulation of dust on the equipment for remotely handled (RH) operations was studied in JET with the ITER-like wall (JET-ILW) during the shutdown period following the third ILW campaign. The topic is connected to licensing procedures for ITER: the need to assess risks related to the external transfer of beryllium and radioactive matter with tritium and activation products. Ten adhesive carbon pads were placed in different locations on the robotic arm operated in-vessel for 672 h. Also air samplers were used during the RH operation and smear tests of the RH boom were performed to quantify specific contamination levels by beryllium and tritium. Dust morphology was determined by microscopy techniques. The areal density of dust varies at different sticker position on the boom. On some parts (e.g. ‘wrists’ of the robot) the density of particles exceeds 1000 per mm². Their morphology is very diverse but most collected objects originate from the construction material (aluminium) of the RH equipment itself. The accumulation of Be- and W-based particles is negligible. The study confirms earlier experimental evidence that Be-rich co-deposits (and also W coatings on CFC) adhere well to plasma-facing components and they are not easily mobilised. (topical issue article)

[en] The power output of fusion experiments and fusion reactor-like devices is measured in terms of the neutron yields which relate directly to the fusion yield. In this paper we describe the devices and methods used to make the new in situ calibration of JET in April 2013 and its early results. The target accuracy of this calibration was 10%, just as in the earlier JET calibration and as required for ITER, where a precise neutron yield measurement is important, e.g., for tritium accountancy. We discuss the constraints and early decisions which defined the main calibration approach, e.g., the choice of source type and the deployment method. We describe the physics, source issues, safety and engineering aspects required to calibrate directly the Fission Chambers and the Activation System which carry the JET neutron calibration. In particular a direct calibration of the Activation system was planned for the first time in JET. We used the existing JET remote-handling system to deploy the ²⁵²Cf source and developed the compatible tooling and systems necessary to ensure safe and efficient deployment in these cases. The scientific programme has sought to better understand the limitations of the calibration, to optimise the measurements and other provisions, to provide corrections for perturbing factors (e.g., presence of the remote-handling boom and other non-standard torus conditions) and to ensure personnel safety and safe working conditions. Much of this work has been based on an extensive programme of Monte-Carlo calculations which, e.g., revealed a potential contribution to the neutron yield via a direct line of sight through the ports which presents individually depending on the details of the port geometry