How Accelerators can save the planet
Roger Barlow
Manchester Christmas MeetingJanuary 5th 2010
Wednesday, April 19, 2023 Roger Barlow
We have to stop burning fossil fuels
04/19/23 Roger Barlow
Climate change
Political dependence
They’re running out anyway
Renewables can’t fill the gap
04/19/23 Roger Barlow
Even major (country-scale) developments will not be enough
Improved efficiency and insulation can only be part of the answer
Nuclear Power
04/19/23 Roger Barlow
Could supply the gap – but public resistance
Safety (Chernobyl )Waste (Yucca Mountain)Proliferation
Safety : the ADSR
Build a sub-critical reactor (k<1)Supply extra neutrons from a spallation target Inherently safe: ‘big red switch’
04/19/23 Roger Barlow
OFFYou need to run the accelerator – lower efficiency but only 5-10%
Thorium232Th is fertile232Th (n,γ) 233Th 233 Pa 233U
233U is fissileUse Thorium as a fuel in an ADSR• Long-lived waste essentially eliminated• Very difficult to make bombsHence Thorium fuelled ADSRs – Energy Amplifier
(Rubbia) – Sam’s talk 04/19/23 Roger Barlow
Alternative Plan
Separate Accelerator and Reactor
1.Take conventional fuel rod filled with Thorium (or Thorea: ThO2)
2.Expose to neutrons from spallation source to form 233U.
3.Use rod in conventional PWR
04/19/23 Roger Barlow
How enriched?
Simulation using MCNP program (standard).
Typical PWR geometry. 1cm diameter rods in 2cm rectangular grid, water moderator, lead reflector.
Plot criticality versus concentration
04/19/23 Roger Barlow
Green is 235U in 238U. Need ~1.2% Blue is 233U in 232Th. Need ~1.8%
What next for the fuel rod?
In the reactor 233Pa hangs around for ~27 days and absorbs neutrons
Detailed studies of scenarios needed
04/19/23 Roger Barlow
For 1.7% 233U in 232Th, dependence of k on percentage of 233Pa.
How to make them?
Simulate Thorium rod in D2O moderator surrounded by Lead
Spallation-spectrum neutrons generated along z axis
04/19/23 Roger Barlow
Simulation results
04/19/23 Roger Barlow
Units are nuclear conversion probability per neutronX 1026
Optimum radius ~ 20 cm
Conclusion
• Conversion Probability ~ 10-26 per neutron• For 3 mA proton beam, 25 neutrons per
spallation: 4 x 106 seconds=1000 hours• Too expensive: need further optimisation and
neutron multiplication
04/19/23 Roger Barlow