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 well suited to Grid use

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

Other stuff

2009• BaBar• LHCb• EMMA• ThorEA• Rolling Grant

2010• BaBar• LHCb• EMMA• Grid will work!• ThorEA• Drift chambers for homland

security• Merlin+Wakefields• Negative weights

04/19/23 Roger Barlow