Page 316 - Fundamentals of Magnetic Thermonuclear Reactor Design

296 Fundamentals of Magnetic Thermonuclear Reactor Design

10.3 BLANKET DESIGN ALGORITHM
Input data, used as reference in the blanket design, include the plasma major and
minor radii, plasma elongation, port dimensions, heat and neutron wall loads
2
2
(MW/m ); neutron fluence (MW year/m ); and the plasma physics limitations
on the blanket radial dimension.
One relies on the existing experience and heuristic reasoning to select the
tritium breeder and coolant(s) types, as well as parameters, such as the poloi-
dal, toroidal and radial dimensions of the blanket sections; the main dimen-
sions and materials of the radiation shield and the blanket frame; minimum
input and maximum output temperatures of the coolant(s); and tentative radial
distribution of the tritium breeding materials, coolants and structural materials
over the (breeding zone) BZ depth. Then, iterative methods for optimisation
are employed to calculate the neutron, thermal hydraulic, MHD (for molten
metals) and strength properties in a 1D approximation. Their purpose is to
identify the BZ’s optimum geometry. The criteria, to be used individually or
collectively, may include, first, maximum achievable TBR and coolant tem-
perature values; second, a minimum loss of coolant pressure, and hydraulic
power. A selected option has to be checked with more complicated 2D and
3D models.
Let us illustrate this with an example of the DEMO-S self-cooling blanket
[2]. In that project, lithium acts as a tritium breeder and a coolant. The design
input data are listed in Table 10.1. Lithium input/output temperature is selected
based on past experience with sodium-cooled fast neutron reactors. The number
and dimensions of the poloidal and toroidal sections of the inboard blanket (IB)
and the outboard blanket (OB) are selected based on the number and dimen-
sions of the blanket ports. The IB and OB have 32 and 48 sections, respectively.
The poloidal dimensions are 500, 750, 2900 and 7300 mm, depending on where
a section is located.
Neutron calculations have been performed for two reactor layouts. Number
one placed no limitation with respect to the blanket radial dimension. Number
two limited this dimension to 500 mm, including the 120-mm beryllium layer,

TABLE 10.1 Blanket Components’ Optimal Radial Lengths (mm)
Reactor layout

IB/OB components #1 #2
Breeder zone 500/750 500/510
Radiation shield 400/300 400/300
Vacuum vessel 400/400 400/400
Beryllium layer − −/120