# **8.0 Research and Development**

#  **(R&D)**

# **[Introduction]{.underline}**: 

## FIRE has relatively modest R&D requirements since it is a cryo-cooled copper magnet tokamak and can draw upon a great deal of existing data from CIT/BPX, ALCATOR C-Mod, IGNITOR, and other high field, copper magnet tokamaks. The planned areas of R&D described below concentrate on items which fill in gaps in the existing data, permit higher performance, higher reliability, and help to keep costs as low as possible. ![](media/image1.wmf){width="2.7041666666666666in" height="3.4694444444444446in"}

# 

# **8.0-1 Copper Conductor and Design Criteria**

## [Background]{.underline}: 

## The available data base requires assessment and extension for plates of the size to be procured for the full scale TF and PF conductor. The properties assumed require validation.

## [For Inner TF Coil Legs]{.underline} 

## C17510 BeCu (68% IACS) in thick plate (36mm) form is used in the inner leg. The principal stresses are primarily axial tension and azimuthal compression. Required: Ultimate Tensile Strength 800 MPa; min. yield: 724 MPa. 

## [For Outer TF Coil Legs]{.underline}

C10200 (OFHC) 36 mm thick is required. This task will verify that the
plate properties can be obtained in the thicknesses required. Required:
0.2% min. yield strength 200 Mpa ; minimum elongation of 12%, and a room
temperature conductivity of \>100% IACS.

## [For Central Solenoid Coil]{.underline}

## Uses cold worked C10200 copper in thick plate (38mm) form. Required: Ultimate Tensile Strength 350 Mpa; Yield Strength 300 Mpa (43,350 psi). Min. 15% elongation at RT.

## 

## [R&D Tasks]{.underline}:

## Obtain samples from full size plate stock and carry out a mechanical testing program to assure that static and crack growth properties at room and LN2 temperatures are adequate. The design criteria will be peer reviewed. 

# **Conductor Joint Development**

## [Background:]{.underline} The TF and PF coil conductors require a high strength joining process which does not result in an annealed zone. The conductors of the TF and PF coils are much different in size and strength requirements and therefore they may or may not employ the same technique. Three areas of investigation are: 

## (1) The baseline design uses C17510 BeCu for the inboard leg of the TF coils and C10200 copper for the balance of the coils. A cost effective, reliable high strength method for joining C15520 to C10200 copper is required.

## (2) The C-shaped outer portions of the TF coil, consisting of the horizontal legs and the outer leg vertical section, will be manufactured from three plates to reduce costs. A practical, high strength reliable joining process is required. 

\(3\) A joining process is required for the outer PF coil conductors.
The same joining processes developed for the TF coil may possibly be
applicable, but the smaller size of the PF conductor may make it
possible to consider methods which would not be applicable to the larger
TF conductors.

## 

## [R&D Tasks]{.underline}: 

## Develop manufacturing processes and carry out a mechanical testing program to assure adequate mechanical properties and to validate design criteria for the joints. Potential candidate processes include friction stir welding and e-beam welding. In addition, electroform welding, which was successfully developed and used for Alcator C-Mod, will be considered for use in the PF coils. 

# **Radiation Resistant Insulating Materials**

## [Background]{.underline}: Data from the BPX insulation test program indicates that there are several glass/epoxy formulations (CTD-101; Shikazima) which can meet FIRE's requirement for radiation exposure capability of 1.5 x 10^10^ rads. This is a high leverage R&D item, since it has the potential to permit a greater number of full power D-T shots and may permit the experimental program to be expanded with possibly only a minor impact on costs. 

## 

## [R&D Task:]{.underline} 

## The plan is to collaborate with an SBIR which is underway at Composite Technology Development (CTD) to develop high radiation resistant insulating materials with good processing characteristics.

### 

# **Insulation Frictional Requirements**

Criteria used in the design of the TF and CS coil systems require that
selected interface areas retain a desired level of either low or high
friction during operation.

# 

# Low Friction Insulation Characterization

## [Background]{.underline}: FIRE employs a segmented CS with a variation of currents among the 5 coils in the stack during a pulse. Adjacent coils in the CS operate with different temperature and electromagnetic load profiles during a pulse. Adjacent coils will strain differently and relative radial motion between coils in the CS will occur. Interface must lock the coils azimuthally, maintain the coils co-axial, and allow relative radial motion with low friction.

### 

## [R&D Tasks:]{.underline}

## Prototypes of the interface areas will be fabricated and tested under simulated operating conditions to verify operation and adequate life. 

## Apply low friction materials to substrates on a scale consistent with fabrication methods for FIRE. 

## Perform mechanical tests to assure that expected surface friction performance is consistent with design criteria and reliable for the lifetime of the machine.

## Plans are to survey the significant work done in this area by CIT, IGNITOR, and ITER. We may only have to downselect from materials already identified.

![](media/image2.png){width="1.2395833333333333in"
height="2.0104166666666665in"}

## Torsional Shear Stress Distribution in the Inner Leg shown in Fig. 8.0-4 Indicates Amount of slippage / fretting.

### Continuous Axisymmetric Contours Indicates No Slippage; \"Spots\" Mid Build Indicate Bending Shear and some Slippage at the Wedge Surface. 

## [Background]{.underline}: Overturning moments on the TF coils are reacted by wedging action at the inboard legs and by shear between interfaces of the outer intercoil structures on the TF cases. 

### A friction coefficient of \~0.3 is needed between TF inboard legs, and also to limit torsional motions between cases on the outboard side to reduce shear pin and bolting requirements

### 

## [R&D Task:]{.underline} Testing is required to verify friction coefficients and adequate life.

# 

#  **8.0-5 Ring Preload Jacking System**

## 

## [Background]{.underline}: A pair of large steel rings encircle the TF coils. The rings are pre-loaded at assembly using radial jacks to augment the wedge compression at the inboard faces of the TF coils and provide compression between the faces of the outboard intercoil structures during operation. The space available is very limited. Three jack concepts have been identified:

### A mechanical system (proposed by IGNITOR) consisting of opposing wedges 

### Stainless steel bladders with hydraulic fluid

### Commercial "Enerpac" jacks

## [R&D Task]{.underline}: Select one primary concept plus one back-up. Mock-up and test under expected operating conditions simulating assembly, cooldown, operational pressures, and temperatures.

**8.0-6 Fueling**

[Background]{.underline}: A new, twin screw, extruder concept has the
potential to run steady state with reduced hydrogen ice inventories
compared to existing linear piston extruders. In parallel, a cooling
concept based on a Gifford-McMahon cryocooler could be developed to
simplify operation of the pellet injector by removing the need for
liquid helium.

[R&D]{.underline}: Design, build and test a prototype twin screw
extruder with the goal of minimizing tritium inventory for safety and
siting flexibility. Demonstrate extruder cooling without LHe by using a
G-M cryocooler.

7.  **Pumping**

[Background]{.underline}: The design of cryopumps for the divertor
relies on the level of helium compression in the pump entrance region to
allow a compact, in-vessel system.

[R&D]{.underline}: Design, build and test a single cryopump module to
validate the expected inlet He compression which permits a compact
in-vessel pumping system.

**8.0-8 ICRF System**

[Background]{.underline}: R&D is needed to develop and validate the
design choices for the ICRF system.

[R&D Tasks:]{.underline}

1\. Develop and test RF sources.

2\. Fabricate and test antenna prototypes.

3\. Fabricate mock ups for remote handling development.

**8.0-9 Remote Handling**

[Background]{.underline}: Verification of designs and component
maintenance tasks should start in the design phase and be completed,
where possible, prior to final design completion, or at least prior to
fabrication of components. Six areas have been identified for remote
handling R&D:

1\. In-vessel transporter (articulated boom) and component handling end
effectors

2\. In-vessel inspection systems (laser metrology and video systems and
deployment mechanisms)

3\. Midplane and auxiliary port handling vehicles and dexterous
manipulator

4\. YAG laser based divertor pipe and port lip seal cutting, welding,
and inspection tools, and power fastener wrench

5\. Midplane port cask and air cushion transport vehicle

6\. Hot cell remote repair stations and fixtures for midplane port
assembly, divertor modules, and cryopump

[R&D Task:]{.underline} Develop remote handling system prototypes and
use in mock-up facilities to verify designs and to demonstrate
maintenance and task times. The goal should be to reduce cost and times
for replacement, repair and maintenance tasks.

# 

## **8.0-10 First Wall and Divertor**

[Background:]{.underline} The first wall and divertor components are
subjected to radiation, high heat flux, and high electromagnetic loads
during disruption events. Substantial development has occurred and
progress has been made in past programs, for example, ITER. However,
testing to validate design criteria and fabrication processes are
required for the specific performance requirements for FIRE. Fabrication
processes also need optimization to reduce cost because of the large
number of components involved. Areas identified for R&D are:

1\. Heat transfer enhancement techniques (swirl tubes,
hypervapotrons,...)

2\. Development of an effective, passive, heat transfer layer for the
first wall (e.g. copper foam metals).

3\. Optimization of joining methods (e.g. tungsten rods to copper) to
improve reliability and reduce cost

4\. Optimization of a Be plasma spray technique to coat the first wall

[R&D Tasks:]{.underline}

Review status of heat transfer enhancement techniques and passive heat
transfer layers. Down select to one concept suitable for the FIRE
requirement plus one back-up then carry out a testing program to
validate the design features.

Develop an improved, cost effective joining method for tungsten rods to
Cu backing plates. Investigate methods for Be plasma spray coatings for
the first wall.

**8.0-11 Vacuum Vessel**

[Background]{.underline}: The double wall vacuum vessel (VV) includes a
passive stabilization structure and internal, active control coils.
Fabrication processes are complex and the vessel is assembled from
octants. Field welds must be capable of remote maintenance.

[R&D Tasks]{.underline}: Fabricate prototypes and mockups to develop
fabrication and assembly processes (Wherever possible, mockups should be
suitable for RM studies). Areas to be investigated are:

• Passive stabilizer bonding to the vv wall;

• Octant fabrication;

• Octant field joint remote welding and cutting demonstration;

• Port extension fabrication;

• Docking flange prototype and remote operation demonstrations;

• Gravity support link prototypes and testing.

**8.0-12 Power Supplies**

[Background:]{.underline} There are no feasibility issues with the power
supplies for the TF or PF coils since existing technology can be used.
There may, however, be opportunities for cost savings, particularly for
the TF power supplies. The latter are very high power, low voltage, and
have minimal control requirements compared to the PF coils.

Two areas may offer significant benefits:

1\. Semiconductor device optimization for high current switching,
including consideration of cryo cooled switches.

2.  Methodology optimization for control on the AC side rather than on
    the DC side.

    [R&D Task:]{.underline}

Perform computer simulations to investigate candidate switching and
control configurations. Select and/or develop candidates and perform
tests on subsections of the circuitry.