Page 374 - Fundamentals of Magnetic Thermonuclear Reactor Design

352 Fundamentals of Magnetic Thermonuclear Reactor Design

12.1 INTRODUCTION
Apart from being machines with unique physics features, magnetic fusion re-
actors (MFRs) are structures operating under heavy mechanical loads [1–3].
Most of the mechanical issues to be considered in the design of an MFR are
traditional for electrical engineering. To address them, it is important to do the
following:
l Conduct a comprehensive stress analysis under mechanical, thermal and
electromagnetic loads;
l Carry out structural assessment based on linear theory of elasticity;
l Assess the load-bearing capacity in an elastic–plastic approximation;
l Estimate life-time according to low cycle fatigue and fracture criteria;
l Identify residual stresses and strains related to manufacture and installation
operations;
l Assess the effect of components’ geometry and size distortions on the load-
bearing structures; and
l Identify potential risks of facility damage in off-normal and accident sce-
narios.

MFR-specific issues are quite diverse and are addressed with the
following:
l Analysis of the magneto-mechanical stability of the superconducting coils.
l Thermal mechanical computations related to neutron flux effects and super-
conducting coil cooling.
l Computation of the dynamic effects of plasma disruption on the reactor
structure.
l Anisotropic material strength computations.
This list of mechanical aspects in the MFR design is illustrative but not
exhaustive.
The mechanical strength and thermal stress analysis should factor in
the entire scope of loads on the machine under design. They include grav-
ity, technology-related risks (e.g. aircraft falling from the sky), atmospheric
pressure, seismic activity and electromagnetic (ponderomotive) forces. The
latter represent the greatest mechanical load on systems contained inside
the cryostat. An important operational feature of the MFR is the wide range
of operating temperatures: from close to absolute zero (in superconduct-
3
ing coils) to ∼10 K on the surfaces of the first wall, divertor plates and
limiters.
This chapter deals with the mechanical aspects of the design of the MFR’s
most loaded components, namely, the superconducting magnet and the vacuum
vessel (VV). The appendices at the end provide the details of some computa-
tional methodologies and design regulation guidelines.