| Term | Definition |
|---|---|
| 304 L | An alloy of austenitic stainless steel, with low carbon content in order to resist intergranular stress corrosion cracking. |
| 316 N | An alloy of austenitic stainless steel. |
| 316 SS | A generic abbreviation for 316 stainless steel, an alloy of austenitic stainless steel. |
| a | minor plasma radius |
| abnormal event | An unintended change of operating state of plant or component not causing unscheduled down-time. |
| abnormal operating conditions | Conditions imposed on the plant or a component deviating from normal operation. |
| abnormal operation | Operating procedures or operating state of a plant or a component deviating from normal operation. Deviations include operating procedures for start-up, current drive, and shut-down, which deviate from the operating procedures of normal operation, or operation at fusion power deviating from its nominal value. |
| AC | alternating current |
| activation | The process of inducing radioactivity by bombardment with neutrons or with other types of radiation. |
| “active” environment | That part of the earth’s environment subject to attack from weathering which may lead to the more rapid spread of deposited contamination than if the contamination is buried where it can not suffer from such attacks (the “passive” environment). |
| additional heating | The application of beams of neutral particles and/or microwave radiation to the plasma from external apparatus so as to bridge the gap in heating between resistive heating due to plasma toroidal current (which gets weaker with increased temperature) and alpha-particle heating due to the slowing down of the helium reaction product in the plasma (which gets stronger with higher temperature). |
| ADS | atmospheric detritiation system |
| AFS | Andrew File System |
| AISI | American Iron and Steel Institute |
| ALARA | as low as reasonably achievable |
| AlBeMet | A proprietary alloy of aluminium used to join beryllium to copper because it avoids the formation of brittle intermetallic phases with the surrounding materials . |
| Alfvén wave | A type of oscillation of plasma particles, consisting of transverse waves propagating along the magnetic field lines in a plasma. Also called magnetohydrodynamic wave. |
| alpha particle | a-particle, the nucleus of the helium-4 atom |
| alpha-power | a-power, the component of fusion reactor power which comes from the alpha particle reaction product. |
| anomalous transport | Energy and particle transport which is higher than predicted by neoclassical predictions. |
| ANSYS code | A commercial software package that provides a finite element analysis for performing, evaluating and presenting analysis operations in a wide variety of fields. |
| armour lifetime | The time an armour material (i.e a material facing the plasma) component can fulfil its functional purpose in the ITER machine without exceeding its performance limitations. Lifetime can for instance be reduced by excessive erosion without redeposition in a suitable structural form. |
| armour-heat sink joint lifetime | The time the joint between the armour material (facing the plasma) and the underlying substrate (the “heat sink”) can be reliably predicted to fulfil its functional purpose. Such joints are typically affected by the number of operational cycles (leading to fatigue of the joint). |
| As low as reasonably achievable | ALARA, a policy that maintains occupational exposure to radiation at the lowest practical levels. |
| ASDEX-U | Axisymmetric Divertor Experiment Upgrade, located at Max Planck Institut für Plasmaphysik, Garching, Germany |
| aspect ratio | The ratio between the major and (minimum) minor radii of the plasma torus |
| atomic mass | The atomic mass number, A, is the total of the number of protons and the number of neutrons in the atomic nucleus concerned. The atomic mass unit is defined as 1/12 the mass of a 12C atom, i.e 1.660438 x 10-27kg, or 931.478 MeV in equivalent energy units. |
| austenitic stainless steel | One of the three main phases of stainless steel - the others being martensitic and ferritic. Austenitic steels have face-centred cubic crystals i.e atoms at the corners and centre of each face of the cubic crystal, whereas the other phases are body-centred cubic (i.e atoms at the corners and at the cube centre). The phase depends on the composition - austenitic steels hava a high nickel and/or manganese content - whereas martensitic steels have low, and ferritic steels high chromium and/or molybdenum content. |
| auxiliary heating | Systems to heat the plasma and to drive current in it. |
| auxiliary heating power | auxiliary heating = additional heating. The power usually refers to that absorbed by the plasma, and the electrical power connected to the auxiliary heating system will usually be considerably higher, to account for reflection, absorbtion in transmission, and internal inefficiencies of generation. |
| availability | The percentage of time that a system or plant is available to execute/or executing its operating cycle. |
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