No abstract available

[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] The role of the Real Time Power Control system (RTPC) in the Joint European Torus (JET) is described in depth. The modes of operation are discussed in detail and a number of successful experiments are described. These experiments prove that RTPC can be used for a wide range of experiments, including: (1) Feedback control of plasma parameters in real time using Ion Cyclotron Resonance Heating (ICRH) or Neutral Beam Heating (NBH) as the actuator in various JET operating regimes. It is demonstrated that in a multi-parameter space it is not sufficient to control one global plasma parameter in order to avoid performance limiting events. (2) Restricting neutron production and subsequent machine activation resulting from high performance pulses. (3) The simulation of α-particle heating effects in a DT-plasma in a D-only plasma. The heating properties of α-particles are simulated using ICRH-power, which is adjusted in real time. The simulation of α-particle heating in JET allows the effects of a change in isotopic mass to be separated from α-particle heating. However, the change in isotopic mass of the plasma ions appears to affect not only the global energy confinement time (τ_E) but also other parameters such as the electron temperature at the plasma edge. This also affects τ_E, making it difficult to make a conclusive statement about any isotopic effect. (4) For future JET experiments a scheme has been designed which simulates the behaviour of a fusion reactor experimentally. The design parameters of the International Thermonuclear Experimental Reactor (ITER) are used. In the proposed scheme the most relevant dimensionless plasma parameters are similar in JET and ITER. It is also shown how the amount of heating may be simulated in real time by RTPC using the electron temperature and density as input parameters. The results of two demonstration experiments are presented. (author)

No abstract available

[en] A report is given on progress in the construction of the Joint European Torus (JET) at Culham in England. This large tokamak is expected to begin operation in 1983. The civil engineering work is essentially complete. Many components have already been delivered to the site and Torus assembly has begun. (U.K.)

[en] The Joint European Torus, JET, the largest and most successful Tokamak in the world, was conceived from the start as a research project with very ambitious aims and a bold approach to extrapolations of the physics and technology base as well as the international nature of its organisation. Throughout its operating life JET has maintained this approach and, with its innovative and flexible design, has extended its performance far beyond the initially intended boundaries thereby retaining a lead in virtually all areas of fusion research. JET has shown a willingness to venture far beyond the technology base of the time into new areas and dimensions. The paper will highlight a few examples which illustrate the approach taken in JET to work closely with industry and the European Associations to extend the technology beyond the current state of the art whilst maintaining a tight grip on the fundamental requirements of cost and time schedule. These range from large scale integrated systems as well as small scale technological breakthroughs. Large scale systems include the Active Gas Handling System for the on-line reprocessing of the tritium-deuterium fuel, the Remote Handling System which was integrated into the JET machine from the very beginning, the JET Power Supply system as well as, most importantly, the design of the JET structure itself which permitted the fast maintenance and repair of all major sub-units. Other notable advances include the Neutral Beam Injection and Radio Frequency Heating systems, the large open structure cryo-pumps and the novel cryo-transmission lines. Some of the associated technologies required major advances in the area of diagnostics, high power handling components, carbon fibre reinforced carbon materials as well as in the whole field of beryllium technology and beryllium handling. The success of JET has shown that it serves as a model for future machines both from an engineering point of view as well as in its approach to management, organisation and funding. (author)

[en] JET, the large nuclear fusion experiment conducted within the European fusion program, is at present being commissioned in Culham near Oxford, England. Its design parameters constitute a major step towards thermonuclear plasma burning. The scientific program has been designed to achieve parameters in a deuterium-tritium plasma which are close to those of a future fusion reactor. Construction of the JET apparatus, development of the diagnostic tools, and the execution of the planned experimental program are carried out in close cooperation by twelve European nations. (orig./HP)

[en] This volume is an appendix of vol. 1 and contains selected articles prepared by JET authors providing some details of the activities and achievements made on JET during 1991

[en] If the torus or other tritium containment is breached for maintenance or accidentally, the Exhaust Detritiation System (EDS) prevents the escape of tritium to the Torus Hall, and elsewhere, by maintaining the breached system al slightly sub-atmospheric pressure. The exhaust gas from the breached system is detritiated and discharged through the stack. The system includes catalytic recombiners for the oxidation of tritiated compounds, and molicular sieve driers for the recovery of water vapour. Provision for internal recirculation of the gas allows a fast start-up of torus detritiation operations (within to minutes) and processing of feed gas at a variable rate. An isotopic swamping technique is used, as required, to displace HTO from molecular sieve during the drier regeneration cycle. All major operations are controlled by a programmable control system. (author). 4 refs.; 5 figs.; 2 tabs

[en] After a presentation of the Jet and nuclear fusion, the results of Jet operations in 1985 are given: energy confinement, MHD activity and disruptive instabilities, impurities and radiation losses, plasma evolution, plasma boundary phenomena, control of plasma current, position and shape, RF heating. Technical achievements in 1985 are summarized: vacuum systems, first wall, multi-pellet injection for fuelling and re-fuelling, containment of forces during vertical instabilities, magnet systems, safety systems, power supplies, neutral beam heating, radio-frequency heating, remote handling, tritium handling, control and data acquisition, diagnostic systems are implied