Jeffrey A. Webster

Towards Leap-Ahead Advances in Radiation Detection

Tension metastable fluid states offer unique potential for leap-ahead advancements in radiation detection. Such metastable fluid states can be attained using tailored resonant acoustics to result in acoustic tension metastable fluid detection (ATMFD) systems. ATMFD systems are under development at Purdue University. Radiation detection in ATMFD systems is based on the principle that incident nuclear particles interact with the dynamically tensioned fluid wherein the intermolecular bonds are sufficiently weakened such that even fundamental particles can be detected over eight orders of magnitude in energy with intrinsic efficiencies far above conventional detection systems. In the case of neutron-nuclei interactions the ionized recoil nucleus ejected from the target atom locally deposits its energy, effectively seeding the formation of vapor nuclei that grow from the sub-nano scale to visible scales such that it becomes possible to record the rate and timing of incoming radiation (neutrons, alphas, and photons). Nuclei form preferentially in the direction of incoming radiation. Imploding nuclei then result in shock waves that are readily possible to not only directly hear but also to monitor electronically at various points of the detector using time difference of arrival (TDOA) methods. In conjunction with hyperbolic positioning, the convolution of the resulting spatio-temporal information provides not just the evidence of rate of incident neutron radiation but also on directionality — a unique development in the field of radiation detection. The development of superior intrinsic-efficiency, low-cost, and rugged, ATMFD systems is being accomplished using a judicious combination of experimentation-cum-theoretical modeling. Modeling methodologies include Monte-Carlo based nuclear particle transport using MCNP5, and also complex multi-dimensional electromagneticcum-fluid-structural assessments with COMSOL’s Multi-physics simulation platform. Benchmarking and qualification studies have been conducted with Pu-based neutron-gamma sources with encouraging results. This paper summarizes the modeling-cum-experimental framework along with experimental evidence for the leap-ahead potential of the ATMFD system for transformation impact on the world of radiation detection.Copyright

Transformational nuclear sensors — Real-time monitoring of WMDs, risk assessment & response

Transformational nuclear particle sensor systems have been developed for detecting a variety of radiation types via interactions with ordinary fluids such as water and acetone placed under metastable states of tensioned (yes, sub-zero or below-vacuum) liquid pressures at room temperature. Advancements have resulted in the development of lab-scale prototypes which provide real-time directionality information to within 10 degrees of a neutron emitting weapons of mass destruction (WMD) source, with over 90% intrinsic efficiency, with ability to decipher multiplicity and to detect WMD-shielded neutrons in the 0.01 eV range, to unshielded neutrons in the 1–10 MeV range, and with the ability to detect alpha emitting special nuclear material (SNM) signatures to within 1–5 keV in energy resolution, and detection sensitivities to ultratrace levels (i.e., to femto-grams per cc of SNMs such as Pu, and Am). The tension metastable fluid detector (TMFD) systems are robust, and are built in the laboratory with costs in the ∼

Gamma-blind transformational nuclear particle sensors

100+ range — with inherent gamma blindness capability. A multi-physics design framework (including nuclear particle transport, acoustics, structural dynamics, fluid-heat transfer, and electro-magnetics), has also been developed, and validated.

Development of a 4π directional fast neutron detector using tensioned metastable fluids

Purdue University is developing novel, multi-purpose tension metastable fluid nuclear particle detectors (TMFDs) by which multiple types of nuclear particles can be detected with high (90%+) intrinsic efficiency, directional specificity, spectroscopic capability, rapid response, large standoff and significant cost-savings compared with state-of-the-art systems. This paper presents uses of these novel detector systems specifically for neutron detection in the presence of extreme gamma fields. Various experimental results are presented in order to illustrate the unique ability of the TMFDs to discriminate out photon flux in the presence of neutron or alpha sources. Finally, a theoretical analysis is performed building upon experimental data which estimates the ultimate limits for gamma rejection/discrimination ability to be ~ 1023 γ/cc/s.

High-Efficiency Gamma-Beta Blind Alpha Spectrometry for Nuclear Energy Applications

The development of directional-position sensing neutron detector technologies has the potential to embody transformational impact on to the field of nuclear security and safeguards. Directional neutron detectors offer vastly superior background suppression enabling the detection of smaller quantities of special nuclear materials (SNM) at larger standoffs. Additionally, the ability to image the SNM neutron source directly would be particularly advantageous in active interrogation scenarios where one needs to discriminate interrogating neutrons from neutrons resulting from SNMs. A directional fast neutron detector utilizing the acoustic tensioned metastable fluid detector (ATMFD) system has been developed that is not only comparable in technical performance with competing directional fast neutron technologies but also offers a significant reduction in both cost and size while remaining completely insensitive to gamma photons and non-neutron cosmic background radiation. Past assessments by our group have shown that an ATMFD system (with a 6cm × 10cm cross-sectional area) would be capable of detecting a 8 kg Pu source at 25m standoff with a resolution of 11.2°, with 68% confidence within 60 s. While previous ATMFD system configurations were limited to determining angular resolution in 2π, a new ATMFD sensor system capable of ascertaining directionality in 4π fields is now presented. Characterization and validation of the AMTFD system in cylindrical and spherical geometries as developed includes Monte-Carlo based nuclear particle transport assessments using MCNP-PoliMi and multi-physics based assessments accounting for acoustic, structural, and electromagnetic coupling of the ATMFD system via COMSOLs multi-physics platform. A methodology based on geo-positioning-scheme (GPS) and a higher harmonic based scheme were successfully developed. The spherical (higher-harmonic) technology offers the tantalizing capability for rapid-fire (within tens of seconds) the direct visualization based directionality of incoming neutron radiation via line-of-sight tracks - effectively comprising multiple single detectors within the envelope of a single spherical ATMFD.

Beyond He-3 nuclear sensors — TMFDs for real-time SNM monitoring with directionality

A novel, centrifugally tensioned metastable fluid detector (CTMFD) sensor technology has been developed over the last decade to demonstrate high selective sensitivity and detection efficiency to various forms of radiation for wide-ranging conditions (e.g., power, safeguards, security, and health physics) relevant to the nuclear energy industry. The CTMFD operates by tensioning a liquid with centrifugal force to weaken the bonds in the liquid to the point whereby even femtoscale nuclear particle interactions can break the fluid and cause a detectable vaporization cascade. The operating principle has only peripheral similarity to the superheated bubble chamber-based superheated droplet detectors (SDD). Instead, CTMFDs utilize mechanical “tension pressure” instead of thermal superheat, offering a lot of practical advantages. CTMFDs have been used to detect a variety of alpha- and neutron-emitting sources in near real time. The CTMFD is blind to gamma photons and betas allowing for detection of alphas and neutrons in extreme gamma/beta background environments such as spent fuel reprocessing plants. The selective sensitivity allows for differentiation between alpha emitters including the isotopes of plutonium. Mixtures of plutonium isotopes have been measured in ratios of 1∶1, 2∶1, and 3∶1 Pu-238:Pu-239 with successful differentiation. Due to the lack of gamma-beta background interference, the CTMFD is inherently more sensitive than scintillation-based alpha spectrometers or SDDs and has been proved capable to detect below femtogram quantities of plutonium-238. Plutonium is also easily distinguishable from neptunium, making it easy to measure the plutonium concentration in the NPEX stream of a UREX reprocessing facility. The CTMFD has been calibrated for alphas from americium (5.5 MeV) and curium (∼6 MeV) as well. Furthermore, the CTMFD has, recently, also been used to detect spontaneous and induced fission events, which can be differentiated from alpha decay, allowing for detection of fissionable material in a mixture of isotopes. This paper discusses these transformational developments, which are also being considered for real-world commercial use.

Benchmarking and Qualification of PAC-Femlab for Resonant Acoustic Chamber Design

Due to He-3 shortages as well as other fundamental limitations of 60-y nuclear power technology being adapted for present-day sensor needs, transformational nuclear particle sensor system developments have sponsored by DARPA, DoE, DHS and NSF. These systems dispense with need for conventional He-3, liquid scintillation or solid-state devices. The novel systems detect a variety of radiation types via interactions with ordinary fluids such as water and acetone placed under metastable states of tensioned (yes, sub-zero or below-vacuum) liquid pressures at room temperature. Advancements have resulted which: enable directionality information in 30s to within 10 degrees of a weapons of mass destruction (WMD) neutron source at 25m (80ft); offer over 90% intrinsic efficiency; offer the ability to decipher multiplicity of neutron emission characteristic of spontaneous and induced fission from fissile isotopes; and, enable one to detect WMD-shielded neutrons in the 0.01 eV range, to unshielded neutrons in the 1–10 MeV range, coupled with the ability to detect alpha emitting special nuclear material (SNM) signatures to within 1–5 keV in energy resolution, and detection sensitivities to ultra-trace levels (i.e., to femto-grams per cc of SNMs such as Pu, and Am). The novel tension metastable fluid detector (TMFD) systems are robust, and are presently built in the laboratory with material costs in the ∼

High Efficiency Gamma-Beta Blind Alpha Spectrometry for Nuclear Energy Applications

50+ range — with inherent gamma blindness capability. A multi-physics design framework (including nuclear particle transport, acoustics, structural dynamics, fluid-heat transfer, and electro-magnetics), has also been developed, and validated. Comparison against He-3 technology is presented along with adaptation to variety of scenarios ranging from border crossings, to spent nuclear reprocessing plants to portals and moving platforms.

The MAC-TMFD: Novel multi-armed Centrifugally Tensioned Metastable Fluid Detector (Gamma-Blind) — Neutron-alpha recoil spectrometer

The design of high-powered resonant acoustic systems capable of inducing large pressure oscillations in the 105 Hz to 106 Hz range requires a validated simulation platform, one that includes complexities of multi-dimensional fluid-structure interactions. Past efforts at designing such systems have relied mainly on time-consuming, trial-error based heuristic approaches (West et al., 1967; Taleyarkhan et al., 2002;2004). A robust design-cum-simulation platform is required to enable rapid strides and motivated this study for which the PAC-Femlab model was developed and successfully qualified against detailed experiment data as well as against data from a second independent experiment conducted elsewhere (Cancelos et al., 2004).Copyright

Tensioned Metastable Fluid Detectors for active interrogation of Special Nuclear Materials

A novel, Centrifugally Tensioned Metastable Fluid Detector (CTMFD) sensor technology has been developed over the last decade to demonstrate high selective sensitivity and detection efficiency to various forms of radiation for wide-ranging conditions (e.g., power level, safeguards, security, and health physics) relevant to the nuclear energy industry. The CTMFD operates by tensioning a liquid with centrifugal force to weaken the bonds in the liquid to the point whereby even a femto-scale nuclear particle interactions can break the fluid and cause a detectable vaporization cascade. The operating principle has only peripheral similarity to the superheated bubble chamber based superheated droplet detectors (SDDs); instead, CTMFDs utilize mechanical “tension pressure” instead of thermal superheat offering a lot of practical advantages. CTMFDs have been used to detect a variety of alpha and neutron emitting sources in near real-time. The CTMFD is selectively blind to gamma photons and betas allowing for detection of alphas and neutrons in extreme gamma/beta background environments such as spent fuel reprocessing plants or under full power conditions within an operating nuclear reactor itself. The selective sensitivity allows for differentiation between alpha emitters including the isotopes of Plutonium. Mixtures of Plutonium isotopes have been measured in ratios of 1:1, 2:1, and 3:1 Pu-238:Pu-239 with successful differentiation. Due to the lack of gamma-beta background interference, the CTMFD’s LLD can be effectively reduced to zero and hence, is inherently more sensitive than scintillation based alpha spectrometers or SDDs and has been proven capable to detect below femtogram quantities of Plutonium-238. Plutonium is also easily distinguishable from Neptunium making it easy to measure the Plutonium concentration in the NPEX stream of a UREX reprocessing facility. The CTMFD has been calibrated for alphas from Americium (5.5 MeV) and Curium (∼6 MeV) as well. The CTMFD has furthermore, recently also been used to detect spontaneous and induced fission events which can be differentiated from alpha decay allowing for detection of fissionable material in a mixture of isotopes. This paper discusses these transformational developments which are also being entered for real-world commercial use.Copyright