The End of Helium-3 As We Know It: The Helium-3 Problem
Within the last decade, the amount of available He-3 has become limited, while the demand has significantly increased, especially for science and national security applications. The largest demand for He-3 is in gas proportional counters for neutron detection. No other currently available detection technology offers the stability, sensitivity, and gamma/neutron discrimination of He-3 neutron tubes. Such neutron detectors are used in many applications including neutron scattering research, international and homeland security, defense applications, and well logging. The limited supply has curtailed use of He-3; therefore, alternative neutron detection technologies must be implemented. There are additional uses of He-3 for medical imaging (MRI lung imaging), targets, missile guidance, He-3-He-4 dilution refrigerators, and condensed matter research.
The production of He-3 from tritium decay has declined as the nuclear weapons stockpile has been reduced, resulting in a lowered need for tritium to maintain the stockpile. The worldwide, steady state production of He-3 is about 10-20 kliter/y, while the demand is much higher. This has driven the search for alternate neutron detection technologies to replace the use of He-3.
One of the two large uses for He-3 has been in radiation portal monitors deployed for homeland security both domestically and internationally. This use is no longer permitted by U.S. government policy. Thus, an alternative had to be found and deployed over a short period of time. The nuclear physics community successfully met this challenge. Nuclear safeguards and neutron scattering science are no the challenges being addressed. This talk will provide an overview of the He-3 supply problem and the application of neutron detectors.
Radiation Detection at International Borders
Countries around the world are deploying radiation detection instrumentation to interdict the illegal shipment of radioactive material crossing international borders at land, rail, air, and sea ports of entry. These efforts include deployments in the US and a number of European and Asian countries by governments and international agencies. Items of concern include radiation dispersal devices, nuclear warheads, and special nuclear material. Radiation portal monitors (RPMs) are used as the main screening tool for vehicles and cargo at borders, supplemented by handheld detectors, personal radiation detectors, and x-ray imaging systems. Individuals with nuclear medical treatments and cargo containing naturally occurring radioactive material trigger “nuisance” alarms in RPMs at these border crossings. The operational impact of nuisance alarms can be significant at border crossings. Methods have been developed for reducing this impact without negatively affecting the requirements for interdiction of radioactive materials of interest. This talk discusses the experience to date on interdiction of radioactive materials at international borders.
Radiation Detection and Its Applications
The detection of ionizing radiation is a little over 100 years old, when natural radioactivity was first observed. Today, radiation detection plays a key role in diverse fields from medicine to defense to basic science. In basic science, radiation detection is used at large accelerators looking for rare interactions and in deep underground cavities seeking to understand the basic forces of nature. For energy production, radiation detection is important to nuclear power, providing ~20% of US power needs. For national security, countries around the world are deploying radiation detection instrumentation to interdict the illegal shipment of radioactive material crossing international borders at land, rail, air, and sea ports of entry. For safeguards, radiation detection is used to assure accountancy for nuclear materials in order to protect us from the illicit production and use of nuclear weapons. In medicine, ionizing radiation is used for diagnostics and for treatment of diseases. A wide range of scientists and engineers develop and use radiation detection instrumentation. This talk will discuss some of these aspects of radiation detection.
Neutrinos: A Personal Journey
Neutrinos are weakly interacting neutral particles that are emitted in processes such as beta decay. Since their first observation in 1956, neutrinos have provided a number of surprises. Observations of solar neutrinos verified that the sun generates energy by nuclear fusion, but ”The Solar Neutrino Problem” grew out of the fact that only 1/3 as many were observed as predicted by models of the sun. From several experiments involving solar, atmospheric and accelerator produced neutrinos, it became clear that flavor oscillations were responsible for the ”The Solar Neutrino Problem.” A variety of experiments have now constrained the parameters associated with neutrinos, but much remains to be done. One series of experiments is looking for the possibility of neutrinoless double beta decay. The Majorana Collaboration is searching for neutrinoless double beta decay using 76Ge, which has been shown to have a number of advantages in terms of sensitivity and backgrounds. The observation of neutrinoless double-beta decay would show that lepton number is violated, that neutrinos are Majorana particles, and would simultaneously provide information on the electron neutrino mass. Attaining sensitivity to neutrino masses in the inverted hierarchy region, 15-50 meV, will require large, tonne-scale detectors with extremely low backgrounds, at the level of ~1 count /(tonne-year) or lower in the region of the signal. There are surprises ahead in the discoveries to be made about neutrino physics.
Borehole Muon Detector for 4D Density Tomography of Subsurface Reservoirs
Muons can be used to image the density of materials through which they pass, including geological structures. Numerous subsurface applications are injecting or producing fluids underground, with more and more concerns about the fate of the injected fluids and the risks they could represent for the environment, like induced seismicity or leakage. Geological carbon storage, natural gas storage, enhanced oil recovery, compressed air storage, aquifer storage and recovery, waste water storage and oil and gas production are the most important ones. It is thus crucial to monitor in quasi real time the behavior of these fluids, and several monitoring techniques can be used. Among them, those that track density changes in the subsurface are the most relevant. Current density monitoring options are gravimetric data collection and active or passive seismic surveys. One alternative, or complement, to these methods is the development of a muon detector that is compact and robust enough for deployment in a borehole. Such a muon detector would provide tomographic data to detect small changes in density at depths up to 1.5 km. A detector with these capabilities has been developed and successfully tested. Monte Carlo modeling methods have being used for detector simulations and to optimize the detector design. The robustness of the design comes primarily from the use of scintillating rods, as opposed to drift tubes that are used in many large muon detectors, where the polystyrene scintillating rods are arrayed in alternating layers to provide a coordinate scheme. Testing and measurements were performed using a prototype detector to test the performance of the scintillators, in both the laboratory and shallow underground facilities. A satisfactory comparison with a large drift tube-based muon detector performed in a tunnel is presented.
Richard Kouzes is a Laboratory Fellow at the U.S Department of Energy’s Pacific Northwest National Laboratory working in the areas of neutrino science, neutron detection, homeland security, and non-proliferation. His work on homeland security has been for the development and deployment of radioactive material interdiction equipment at U.S. borders, and he was the Principle Investigator and Technical Lead for the U.S. Customs and Border Protection’s Radiation Portal Monitor Project. He is a Fellow of the Institute of Electrical and Electronics Engineers and a Fellow of the American Association for the Advancement of Science. He is an adjunct Professor of Physics at Washington State University. He has been awarded the NPSS Richard F. Shea Distinguished Member Award and the PNNL Director’s Award for Lifetime Achievement. Dr. Kouzes earned his Ph.D. in physics from Princeton University in 1974. He is an author of over 400 papers.