An overview of the iter in-vessel coil systems

Abstract

-ELM mitigation is of particular importance in ITER in order to prevent rapid erosion or melting of the divertor surface, with the consequent risk of water leaks, increased plasma impurity content and disruptivity. Exploitable "natural" small or no ELM regimes might yet be found which extrapolate to ITER but this cannot be depended upon. Resonant Magnetic Perturbation has been added to pellet pacing as a tool for ITER to mitigate ELMs. Both are required, since neither method is fully developed and much work remains to be done. In addition, in-vessel coils enable vertical stabilization and RWM control. For these reasons, in-vessel coils (IVCs) are being designed for ITER to provide control of Edge Localized Modes (ELMs) in addition to providing control of moderately unstable resistive wall modes (RWMs) and the vertical stability (VS) of the plasma.

In-Vessel Coil Material Failure Rate Estimates for ITER Design Use

“…The IVCs need to withstand a 200qC bakeout temperature and a fast neutron fluence of up to 1E+23 n/cm 2 (Heitzenroeder et al 2009). …”

“…Copper irradiation studies will be will be needed to adjust the copper failure rate for high neutron fluence. Heitzenroeder et al (2009) gave an initial estimate of the neutron fluence as 1E+23 n/cm 2 for the IVCs. More recently, neutronics calculations for the VS and ELM coils give peak values of fast neutron flux (Sawan 2012).…”

“…The focus of this chapter is the stainless steel 316 jacket of the coil since there is a concern of release of foreign materials (the particulate MgO insulation if there is a major failure) or possibly coolant water into the vacuum vessel (Heitzenroeder et al 2009). The largest use of stainless steel tubing in a high radiation environment has been the fission fuel element cladding of fast neutron reactors.…”

“…Therefore, factors to account for hardening and embrittlement will be used to modify the failure rate from the Tore Supra TPLs to apply to the ITER IVCs. Heitzenroeder et al (2009) gave an initial estimate of the neutron fluence as 1E+23 n/cm 2 for the IVCs. More recently, the neutron exposure estimate was reduced to on the order of 3E+19 n/cm 2 of fast neutrons (Heitzenroeder 2012b).…”

“…Given that these coils are inside the vacuum vessel and the ITER neutron flux is a significant factor in material lifetime, an effort has been made to adjust an Inconel tubing failure rate for a nuclear environment. The IVCs need to withstand a 200qC bakeout temperature and a fast neutron fluence of 1E+23 n/cm 2 (Heitzenroeder et al 2009). The preliminary coil configuration is shown in Figure 2.…”