| Term | Definition |
|---|---|
| saddleblock | see “monoblock” |
| safety actuation system | The collection of equipment required to accomplish the necessary safety actions when initiated by the protection system. |
| safety factor | 1) (Elec.) The amount of load, above the normal operating rating, that a device can handle without failure. 2) An overload factor in design to ensure safe operation. |
| safety function | A specific action, needed to ensure the safety of the facility and the protection of the public, workers, and the environment in operational states and during and following accident conditions. |
| safety system settings | Those points of actuation of appropriate automatic protective devices which are intended to initiate action to prevent a safety limit from being exceeded in the event of anticipated operational occurrences and accident conditions. |
| safety system support features | The collection of equipment that provides services such as cooling, lubrication, and energy supply required by the protection system and the safety actuation systems. |
| safety systems | Systems important to safety, provided to assure the safe shutdown of the plant or to limit the consequences of anticipated operational occurrences or accident conditions. |
| sawtooth, sawteeth | Magnetohydrodynamic instabilities that create oscillations in a plasma, which result in plasma disruptions. |
| sawtooth stabilization | Various methods of stabilizing sawteeth oscillations (which induce disruptions in the plasma) in tokamaks. |
| scaling laws | Laws stating that if two quantities are proportional and are known to be valid at certain orders of magnitude, then they can be used to calculate the value of one of the quantities at another order of magnitude. |
| scheduled down time | The down time of the plant according to plan. |
| scheduled non-operating state | When the plant or component is down according to plan for the length of the scheduled down time. |
| scrape-off layer | SOL, the region of plasma between the last closed flux surface and the surrounding walls. |
| second stability regime | A theoretically predicted regime of a plasma which can sustain very high plasma pressures. |
| second stable core regime | The second stability regime in the central region of a plasma. |
| separatrix | The last closed flux surface. |
| septum | (Electromag.) A metal plate placed across a waveguide and attached to the walls by highly conducting joints; the plate usually has one or more windows, designed to give inductive, capacitive or resistive characteristics. |
| severe accident | An accident which is beyond accident conditions and is a concept used exclusively for nuclear power reactors. |
| shear | See magnetic shear. Also mechanical shear, due for example to twisting of a body, a stress in the plane parallel to the twisting force. |
| shield | The tokamak component that absorbs neutrons and transfers heat, protecting the vacuum vessel and magnets. |
| shield-blanket | See “blanket-shield”. |
| shut-down time | The time span between the end of burn and the end of the plasma state; part of the operating time. |
| SI | (Système International), International Standards |
| simplified safety system | A system designed with a minimum number of components to achieve the related safety function and relying as little as possible on support systems. |
| single failure |
A random failure which results in the loss of capability of a component to perform its intended safety functions. Consequential failures resulting from a single random occurrence are considered to be part of the single failure. |
| single-null equilibrium | See double-null equilibrium |
| sintered | Agglomeration in metal (or ceramic particles) by heating and compression. |
| SN | single null (divertor) |
| SOB | start of burn |
| SOF | start-of-current flattop |
| SOFE | IEEE Symposium on Fusion Engineering |
| SOFT | Symposium on Fusion Technology |
| SOL | scrape off layer |
| spectroscopy system | A plasma diagnostic system based on observing the light emission from the plasma. |
| splice plates | Metal plates inserted between vacuum vessel sectors or between the vessel and port stubs to facilitate their welding. |
| SS | stainless steel |
| stagnation point | (Fl. Mech.) A point in a field of flow about a body where the fluid particles have zero velocity with respect to the body. |
| standards | 1) In the context of ITER, standard components, materials, and processes commercially available or used in multiple ITER systems. 2) Technical criteria, rules, and specifications to be used throughout the ITER project. 3) In general, technical criteria, rules and specifications authorized by a recognized authority or consensus group. |
| steady state operation | In particular application to ITER, the operation of the plasma in a way in which termination of the pulse is not determined by plasma behaviour, but is rather a choice of the operator. Operation which in principle can continue indefinitely. |
| steady-state | (Phys.) The condition of a body or system in which the conditions at each point do not change with time, that is, after initial transients or fluctuations have disappeared. In dynamic equilibrium, with entropy at its maximum. |
| Steady-State [Tokamak] Reactor | A reactor in which conditions such as temperature, reaction rate, and neutron flux do not change appreciably with time. |
| stellarator | A device invented by Lyman Spitzer for the containment of a plasma inside a racetrack-shaped tube. The toroidal device produces a poloidal field in a plasma with the use of external magnetic field coils. |
| storage (interim) | The placement of waste in a facility where isolation, environmental protection and human control (e.g. monitoring) are provided with the intent that the waste will be retrieved at a later time. |
| stroking valves | Construction and operation jargon which refers to closing and opening a valve to verify proper operation including full opening and seating. This verification is extremely important for remote controlled, inaccessible valves. |
| superconducting coil | Magnetic coils which use superconductors that have zero resistivity when cooled below the critical temperature. |
| superconducting magnets |
Superconducting magnet coils which circumscribe the torus to confine the plasma within and away from its inner surface. |
| superconductivity | The flow of electric current without resistance in certain metals and alloys at temperatures near absolute zero. |
| superconductor | A type of electrical conductor that permits a current to flow with zero resistance. |
| supercritical | Helium will remain liquid in a bath at 1 atmosphere pressure provided the temperature does not rise above 4.2K. If the ITER coils are placed in such a coolant bath and a high pulse of heat ensues in their operation, most of the helium must be vented to avoid large overpressures. To avoid this, the coils of ITER operate with pumped supercritical helium, just above the critical temperature, which retains a large measure of the heat transfer properties of liquid helium, without the risk of overpressure. |
| superinsulation | (Chem. Eng.) A multilayer insulation for cryogenic systems, composed of many floating radiation shields in an evacuated double-wall annulus, closely spaced but thermally separated by a poor-conducting fibre. |
| support systems | Systems which provide services to a main plant system or systems. The term is relative. Thus tokamak support systems include heating and cooling, whereas support systems for the heating system include their electrical and cooling systems. In general use, the conventional and subsidiary service supply systems of the ITER plant. |
| surface contamination | Contamination that is the result of the deposition and attachment of foreign materials to a surface. |
| SWG | (ITER) Special Working Group |
| synchrotron radiation | Radiation emitted by very fast, charged particles in a magnetic field as a result of their natural gyration in that field. Particle gyrations are at the cyclotron frequency. |
| system availability |
A figure-of-merit useful in quantifying system effectiveness, normally facility up-time divided by planned up-time. |
| system effectiveness | Probability that a system can effectively meet an operational demand within a given time period and when operated under specified conditions. System measures should be carefully tailored to, and agreed upon for, a particular application and cannot be applied indiscriminately. |
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