# Presentation: 140677

## Neutronics Plans and Status

- Mohamed Sawan
- Fusion Technology Institute
- The University of Wisconsin

- FIRE Project Meeting
- November 7,8, 2002
- PPPL

## Impact of New Design on Neutronics Parameters

- Several design parameters changed as FIRE moved from the 2-m machine to the 2.14-m machine
- As a starting point for iteration with other design tasks neutronics parameters are scaled for the new machine design parameters
- To obtain initial preliminary neutronics parameters radial build was  assumed not to change. Change in IB FW/tiles thickness from 25 to 38 mm is the only observed change in the current design. This increase is mainly to accommodate diagnostics and might not impact TF shielding

## Changes in Machine Parameters

## Scaling of Neutronics Parameters

- FW radii increased by 7 cm IB and 21 cm OB
- Height increased by 14 cm for same plasma elongation
- FW area increases by 21%
- Average neutron wall loading for DT pulses with largest power of 150 MW is reduced by a factor of 0.62
- Average NWL was 3 MW/m2 for 200 MW DT pulse
- Average NWL in current machine is 1.85 MW/m2
- All parameters that scale with neutron wall loading such as flux, nuclear heating, damage rates, dose rates, decay heat, etc will reduce by 38%

## Impact on Cumulative Neutronics Parameters

- Goal is a combined total fusion energy of 5 TJ DT and 0.5 TJ DD
- Fluence dependent parameters (e.g., cumulative radiation damage, insulator dose, and radwaste classification) depend on cumulative FW fluence (MW-yr/m2) not fusion energy and will reduce due to larger FW area
- Cumulative neutronics parameters reduce by a factor of 0.83

## Impact of Tritium Burnup in DD Pulses

- 2% tritium burnup in DD pulses results in production of 14 MeV neutrons while reducing number of 2.45 MeV neutrons by 4.8%
- 14 MeV neutrons produced are only 2% of the 2.45 MeV neutrons produced in DD pulses with negligible impact on nuclear heating, etc during 1MW DD pulses. This is only 0.03% of neutrons produced in 150 MW DT pulse
- For 5 TJ DT 1.77x1024 14 MeV neutrons produced
- For 0.5 TJ DD 4.07x1023 2.45 MeV and 8.15x1021 14 MeV neutrons produced
- Impact on fluence dependent parameters is negligible

## Peak Nuclear Heating (W/cm3) for 150MW DT Shots

- For DD pulses with largest fusion power (1 MW), neutron wall loading is a factor of 0.003 of that for the DT pulses
- Nuclear heating values are at least two orders of magnitude lower

## in OB FW/Tiles 

- in OB FW/Tiles* *

- Nuclear Heating in OB VV at Midplane* *

## Nuclear Heating in Outer Divertor Plate

## Radial Variation of Nuclear Heating in IB TF at Midplane 

## Cumulative Damage in FIRE Components reduced by 17%

- Peak end-of-life cumulative radiation damage values in FIRE components are very low < 0.03 dpa
- He Production in VV < 1 appm Allowing for Rewelding

## Cumulative Peak Magnet Insulator Dose( 5 TJ DT Shots and 0.5 TJ DD Shots)

## Radiation Induced Resistivity in Cu

- Cumulative dpa and fluence in Cu TF coils reduced by 17%
- Component of resistivity increase from transmutation products reduces by 17%
- Reduction in dominating resistivity increase from displacement damage is smaller because of non-linear relation with cumulative dpa. Reduction is 12% at front and 17% at back

## Impact on Activation Results

- Activity and decay heat values at shutdown are almost fully dominated by activation during the last pulse
- Short term activity, decay heat, and dose rate following DT pulses are reduced by 38%
- Activity and decay heat generated following D-D shots are more than three orders of magnitude lower than the D-T shots
- Following DT shots hands-on ex-vessel maintenance is possible with
- The 110 cm long steel shield plug in midplane ports
- The 20 cm shield at top of TF coil
- Following DD shots immediate access for maintenance is possible behind OB VV
- WDR reduced by 17% and all components still qualify as Class C LLW (largest WDR is 0.15 for OB FW)

## Plans for FY03

- Update nuclear parameters for the machine components (e.g., FW/tiles, VV, divertor, magnets)
- This task involves significant iteration with other design tasks to converge on a self-consistent design
- This task is already underway and preliminary results are presented

## Plans for FY03(Continued)

- (2) Assess the impact of operation schedule and possible operation extension on key nuclear parameters such as insulator dose
- Dose was calculated for 5 TJ DT and 0.5 TJ DD
- Plans for higher fusion energy are being considered
- We need to make sure that the insulator dose does not limit that possible extension
- Include 14 MeV neutrons generated during DD pulses
- Define required spectra (neutron and gamma) for irradiation experiments to properly simulate FIRE conditions

## Plans for FY03(Continued)

- (3)	Investigate the effect of 3-D geometry on peak insulator dose and other Parameters at IB midplane
- Insulator dose is based on 1D model with plasma extended uniformly to infinity in the vertical direction
- This affects the angular distribution on neutrons incident on FW
- Comparison between 1D and 3D results in ARIES showed that 1D could overestimate radiation damage close to FW by 20-50%
- Will perform simple 3D calculations with emphasize on conditions at midplane where the worst parameters occur. Model does not have to include details for other components away from midplane
- This tasks starts in April after we get a new drawing with revised radial build

## 1-D Neutronics Yield Conservative Peak FW Damage Parameters

- 3-D results were compared to 1-D results for ARIES-ST and ARIES-AT
- 1-D calculations overestimated peak damage parameters at FW by up to a factor of 1.6 depending on the aspect ratio

## Plans for FY03(Continued)

- (4)	Estimate nuclear environment at sensitive diagnostics components
- Due to limited resources estimates will be based on 1D calculations and appropriate extrapolation
- Calculate the neutron and gamma fluxes and absorbed doses for the sensitive components (e.g. silica and alumina) at selected locations
- As starting point results given in memo of 2/25/2002 are to be scaled for new parameters
- Identify  a few cases where streaming is critical and perform simple 2D calculations

## Assumed Radial Build

## Radial Build of FW/Tiles

- Radial build and composition of FW/tiles
- 		5 mm Be PFC (90% Be)
- 		18 mm Cu tiles (80% Cu)
- 		2 mm gasket (50% Cu)
- 		25 mm water cooled Cu vessel cladding 			(80% Cu, 15% water)

## Radial Build of Outer Divertor Plate

## Radial Build of VV

- 1.5 cm thick inner and outer 316SS facesheets
- Space between facesheets includes 60% 304SS and 40% water except in IB region where 11% 304SS and 89% water is used
- VV thickness:
- 		IB midplane	5 cm
- 		OB midplane	54 cm
- 		Divertor		12 cm
- 1.5 cm layer of thermal insulation (10% Microtherm insulation) attached to back of coil-side VV facesheet

## TF Coil Model

- Baseline design with 16 wedged TF coils analyzed
- BeCu used in inner legs and OFHC in outer legs
- 90% packing fraction used in coils
- 304SS coil case used in OB region with 4 cm front and 6 cm back thicknesses