Transcript A design for the DCLL inboard blanket

A design for the DCLL inboard
blanket
S. Smolentsev, M. Abdou, M. Dagher - UCLA
S. Malang – Consultant, Germany
2d EU-US DCLL Workshop
University of California, Los Angeles
November 14-15, 2014
Following the 1st EU-US workshop in 2013,
UCLA started a small project on DCLL DEMO
blanket design and analysis
• The design uses the layout of the European DEMO1 plant and is based on
the LT DCLL blanket concept as a low-risk solution.
• DEMO1 is a near-future technology pulsed machine (2-hr pulse). DEMO2
is the next steady-state design based on foreseeable advances in physics
and technology.
• DEMO1 is a large, high aspect ratio (major radius = 9 m, minor radius =
2.25 m, aspect ratio = 4.0), low power density machine. The average NWL
of DEMO1 is 1.269 MW/m2 .
• The LT concept can be viewed at present as an important intermediate step
on the pathway towards a more attractive HT blanket system.
• The present effort is limited to inboard (IB) blanket.
The blanket maintenance scheme is based on
the concept of Vertical Maintenance System
•
•
•
•
The blanket segments can be replaced
through the vertical port at the top of the
vacuum vessel. The port is also used for
routing of all necessary pipes.
To replace the segments, the port is opened
and the pipes coming from the segments are
cut. Then, the central OB segment located
under the opening is extracted vertically
using a crane.
Two other OB segments are moved
toroidally towards the port and then
extracted through the port in the same way as
the central OB segment extracted.
The two IB segments have to be moved first
radially and then toroidally to reach a
position under the vertical port opening to
allow for their vertical extraction.
US IB DCLL blanket design
• Long (~10 M) poloidal bananashape segments to match the
vertical maintenance scheme
• PbLi Tin/Tout=350°C/ 450°C to avoid
corrosion problems
• The poloidal flow velocity is 0.38 m/s
• The sandwich-type (steel-alumina
steel) FCI as electrical insulator.
• He Tin/Tout=350°C/ 450°C
• The magnetic field used in the
analysis is 10 T
PbLi flow path
• PbLi enters the inlet manifold of
the blanket segment through the
inlet pipe at the top and then
distributed into 5 rear poloidal
blanket ducts where it flows
downwards.
• At the bottom of the segment the
LM makes a U-turn and flows
upwards through the 5 front ducts
facing the plasma. It is collected
in the outlet manifold at the top of
the segment from which it is
extracted from the blanket
through the vertical outlet pipe.
Identification of key R&D and blanket analysis tasks
•
•
•
•
•
•
One of the main goals of the ongoing work is to use the proposed design to identify key R&D
tasks for IB DCLL blankets.
Four important tasks can be identified.
First, the MHD pressure drop needs to be evaluated for the whole blanket system, including the
blanket itself and access pipes, in which MHD flows experience high MHD pressure drop due to
3D MHD effects when the liquid crosses the magnetic field lines at the edge of the TF coils. Of
particular importance is the 3D MHD pressure drop in the manifolds and those caused by the
electric current leaking from the bulk flow at the FCI junctions.
Second, detailed velocity simulations have to be performed for the bulk poloidal flows (inside the
FCI box) and those in the thin gaps between the RAFM walls and the FCI. These velocity
distributions will be used in the corrosion and tritium permeation analysis to make sure that the
proposed design complies with the corrosion and tritium leak limits.
Third, it is important to investigate if the PbLi flow distribution in the inlet manifold leads to
sufficiently equal flow rates in the parallel poloidal ducts. Here, some design optimizations are
possible using the length of the entry expansion zone as an optimization parameter.
Fourth, there is a need to model the tritium transport in the PbLi primary loop to check if the
maximum tritium partial pressure in the blanket can be maintained at a sufficiently low level
(typically < 1 Pa), which would assure no need for tritium permeation coatings in the blanket. This
task will also require analysis of the performance of the tritium extraction system, which at present
is based on a vacuum permeator concept.
Concluding remarks
• The proposed blanket design does not show many
details as the main goal of the current work is to
introduce the most important design features needed for
the next MHD/Thermofluids R&D and blanket analysis.
• That is why the main focus of the current design work is
to specify the PbLi routes, while helium routing in the first
wall and other RAFM structures have not been shown.
• Also, any details of the high temperature shield and
attachment of the blanket segments to the rest of the
structure have not been worked out yet.