TF NEUP 2011

Technical Work Scope Identifier: FC-3

An evaluation of a fission chamber's temporal response using gas electron multiplication

Project Summary

This project seeks to improve the response of a fission chamber by transferring a technology, known as Gas Electron Multiplication, developed in the late 1990s for high energy physics detectors. A Gas Electron Multiplier functions as a preamplifier when immersed in the detector's gas. The response time of a fission chamber can be improved by reducing the detector's components in size because of the increased free charge produced by the preamplifier. This technology has demonstrated an improvement in an ionization chamber's response time by at least a factor of 3. The faster detector signal will extend the detectable neutron flux beyond the current signal pile up region. The increased signal amplification may also be used to improve the detector's ability to measure the location of the incident particle on the entrance to the detector. We propose to measure the improved performance of a fission chamber equipped with Gas Electron Multipliers and evaluate its use as a neutron tomography imaging device.

Importance and relevance of proposed work

The NEUP's 2012 request for pre-applications calls for Program Supporting and Mission Supporting R&D in Fuel Cycle Research and Development, Reactor Concepts Research, Development and Demonstration, and Nuclear Energy Advanced Modeling and Simulation. Previous calls for similar pre-applications have identified a need for the detection of fission multiplicity and measurements of the incident neutron energy spectrum to support the mission goals defined in the Nuclear Energy Research and Development Roadmap. The April 2010 Roadmap report to congress identified the "Obsolete analog instrumentation and control technologies" as one of the major challenges facing the current nuclear power plant fleet. We propose to investigate an upgrade to this instrumentation by transferring an innovation developed for gaseous detectors in the late 1990s. Fission chambers equipped with this technology could have their neutron detection rise time decreased by a factor of 3 ind increase their ability to sustain higher neutron fluxes compared with what is currently deployed in the fleet.

From the RFP

his research topic will also pursue advanced measurement techniques that could complement the ongoing measurement program. In particular, fission multiplicity and fission neutron spectrum measurements as a function of incident neutron energy have been identified as important data in recent sensitivity analyses. Key university research needs for this activity include: " New and improved detector systems and sensor materials that can be used to increase the accuracy, reliability, and efficiency of nuclear materials quantification and tracking from the perspective of the operator or state-level regulator. Such systems could include new neutron coincidence/anti-coincidence counting, spectroscopic analysis, chemical, calorimetric, or other non-nuclear methods, as well as any other novel methods with potential MC&A benefits;

Mission Supporting R&D is considered creative, innovative, and transformative (blue-sky), but must also support the NE mission. Mission-supporting activities that could produce breakthroughs in nuclear technology are also invited to this solicitation. This includes research in the fields or disciplines of nuclear science and engineering that are relevant to NE’s mission though may not fully align with the specific initiatives and programs identified in this solicitation. This includes, but is not limited to, Nuclear Engineering, Nuclear Physics, Health Physics, Radiochemistry, Nuclear Materials Science, or Nuclear Chemistry. Examples of topics of interest are new reactor designs and technologies, advanced nuclear fuels and resource utilization, instrumentation and control/human factors, radiochemistry, fundamental nuclear science, and quantification of proliferation risk and creative solutions for the management of used nuclear fuel. Program supporting research requested by this solicitation is detailed as discreet workscopes in Appendix A. The information is organized by program area with each specified workscope providing the basis for a stand-alone R&D pre-application submittal.

Fuel Cycle Research and Development New and improved detector systems and sensor materials that can be used to increase the accuracy, reliability, and efficiency of nuclear materials quantification and tracking from the perspective of the operator or state-level regulator. Such systems could include new neutron coincidence/anti-coincidence counting, spectroscopic analysis, chemical, calorimetric, or other non-nuclear methods, as well as any other novel methods with potential MC&A benefits;

Logical pathway to work accomplishments

The first year of effort will focus on the production of pre-amplifiers for ionization chamber. A fissionable material will be added to the ionization chamber in year two followed measurements of the chamber's neutron detection efficiency.

Deliverables and outcomes

The project will construct a fission chamber equipped with gas electron multiplier pre-amplifiers. The temporal response of the fission chamber to fast neutrons will be quantified.

Timeline

This project spans a three year period. year one will be devoted to machining the components of a fission chamber equipped with gas electron multipliers. Assembly of the detector with a fission target will be completed in year 2. In the final year, the device will be tested using neutrons generated by the bremstrahlung photons from electrons accelerated by a 16 MeV Linac that impinge on a target of Deuterated water.

Budget

We request total of $290,000 for a period of three years to defray the costs of this Program Supporting development of an improved fission chamber. The main expense will be for a graduate student ($50k) and some faculty mentor time ($20k) per year. equipment construction and beam time expenses are also requested in the amount of $30k per year.

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)

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 nuclear reactor instruementation http://www.ge-mcs.com/en/nuclear-reactor-instrumentation/

Forest_Proposals