TF NEUP 2011

Project Summary

We propose to develop a gaseous detector sensitive to fast (100 keV - 100 MeV) neutrons which may be used to monitor the neutron flux in nuclear reactors. The monitoring of a reactor core's neutron flux has been a long standing problem due to the high neutron and gamma intensity.

Neutron fluxes in reactors

according to http://www.bnl.gov/bnlweb/history/HFBR_main.asp

a 40 MW reactor at Brookhaven's High Flux Beam Reactor (HBFR) produced a neutron flux of [math]1.5 \times 10^{15} \frac{n /cm^2}{s}[/math] for experiments. The neutron flux was a maximum outside the core because the neutrons were directed tangentially to the core instead of radially.

1e11 to 1e12 neutrons per cm^2 per second may be more typical

Let's assume this flux is an upper limit for a detector to measure neutron fluxes in a reactor core. The pulse width of a regular GEM detector is [math]50 \times 10^{-9}[/math] sec. Because of the high gain a signal may be observed over a surface area of 3 cm^2 (10 cm by 300 \times 10^{-3} cm ). A GEM detector with this active area would only be able to count neutron fluxes of [math]1 \times 10^{7} \frac{n /cm^2}{s}[/math] if the detector efficiency was 100 %. A detector efficiency of 10^{-5} would be able to see rates of 10^{11}.

The pulse width of a standard ionization chamber is on the order of 300 nsec, so a standard GEm detector would only be able to have a factor of 6 higher rate than a typical ionization/fission chamber.

Deliverables and outcomes

1.) Neutron sensitive ionization chamber (no position readout)

Budget

Each year

2 grad students ($50k)

2 faculty summer months ($20k)

Beam time: electron experiment which produces isotropic neutrons. Compare neutron rates seen by several know detectors to the rate from the THGEM based detector.

Bibliography

1. File:NEUP Pre-app RFP.pdf
2. "Fission chambers for CANDU SDS neutronic trip applications", V. Mohindrs, M. Vartolomei, and A. McDonald, 28th Annual Canadian Nuclear Society (CNS) conference, June 3-6, 2007New Brunswick, Canada Media:Virender_CANDU2007.pdf
3. GE builds fission chambers http://www.ge-mcs.com/en/nuclear-reactor-instrumentation/neutron-monitoring-instrumentation/ex-core-fission.html
4. GEs thermal neutron device for in core http://www.ge-mcs.com/en/nuclear-reactor-instrumentation/neutron-monitoring-instrumentation/moveable-detectors.html

Forest_Proposals