T.F. Grimes

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.

Characterization and Optimization of a Tensioned Metastable Fluid Nuclear Particle Sensor Using Laser-Based Profilometry

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

State-of-the-art neutron detectors lack capabilities required by the fields of homeland security, health physics, and even for direct in-core nuclear power monitoring. A new system being developed at Purdue’s Metastable Fluid and Advanced Research Laboratory in conjunction with S/A Labs, LLC provides capabilities that the state-of-the-art lacks, and simultaneously with beta (β) and gamma (γ) blindness, high (>90% intrinsic) efficiency for neutron/alpha spectroscopy and directionality, simple detection mechanism, and lowered electronic component dependence. This system, the tensioned metastable fluid detector (TMFD), provides these capabilities despite its vastly reduced cost and complexity compared with equivalent present day systems. Fluids may be placed at pressures lower than perfect vacuum (i.e., negative), resulting in tensioned metastable states. These states may be induced by tensioning fluids just as one would tension solids. The TMFD works by cavitation nucleation of bubbles resulting from energy deposited by charged ions or laser photon pile-up heating of fluid molecules, which are placed under sufficiently tensioned (negative) pressure states of metastability. The charged ions may be created from neutron scattering or from energetic charged particles such as alphas, alpha recoils, and fission fragments. A methodology has been created to profile the pressures in these chambers by laser-induced cavitation (LIC) for verification of a multiphysics simulation of the chambers. The methodology and simulation together have led to large efficiency gains in the current acoustically tensioned metastable fluid detector (ATMFD) system. This paper describes in detail the LIC methodology and provides background on the simulation it validates.

Characterization and Optimization of a Tensioned Metastable Fluid Nuclear Particle Sensor Using Laser Based Profilimetry

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 ∼

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

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.

Development of a novel direction-position sensing fast neutron detector using tensioned metastable fluids

State of the art neutron detectors lack capabilities required by the fields of homeland security, health physics, and even for direct in-core nuclear power monitoring. A new system being developed at Purdue’s Metastable Fluid and Advanced Research Laboratory in conjunction with S/A Labs, LLC provides capabilities the state of the art lacks, and simultaneously with beta (β) and gamma (γ) blindness, high (> 90% intrinsic) efficiency for neutron/alpha spectroscopy and directionality, simple detection mechanism, and lowered electronic component dependence. This system, the Tensioned Metastable Fluid Detector (TMFD) [3], provides these capabilities despite its vastly reduced cost and complexity compared with equivalent present day systems. Fluids may be placed at pressures lower than perfect vacuum (i.e. negative) [4, 5], resulting in tensioned metastable states. These states may be induced by tensioning fluids just as one would tension solids. The TMFD works by cavitation nucleation of bubbles resulting from energy deposited by charged ions or laser photon pileup heating of fluid molecules which are placed under sufficiently tensioned (negative) pressure states of metastability. The charged ions may be created from neutron scattering, or from energetic charged particles such as alphas, alpha recoils, fission fragments, etc. A methodology has been created to profile the pressures in these chambers by lasing, called Laser Induced Cavitation (LIC), for verification of a multiphysics simulation of the chambers. The methodology and simulation together have lead to large efficiency gains in the current Acoustically Tensioned Metastable Fluid Detector (ATMFD) system. This paper describes in detail the LIC methodology and provides background on the simulation it validates.Copyright

Real-time monitoring of actinides in chemical nuclear fuel reprocessing plants

Centrifugally Tensioned Metastable Fluid Detector systems (CTMFDs) have a number of valuable advantages over other conventional, state of the art systems (e.g., 3He tubes). CTMFDs can be configured to attain intrinsic efficiencies over 90% for neutron energies from the thermal to the fast region (ev to MeV). TMFDs can detect alpha and fission recoil interactions exceeding 10 times lower activity than that of conventional spectrometers (i.e., <; ~0.05 Bq/g). The tension pressures used for detection (-10 bars) are over 1000 times greater than the fluctuations resulting from even extreme external events such as during earthquakes. TMFDs are also inherently gamma blind making them ideal for use in high gamma fields where traditional detectors fail such as in active interrogation applications. Unlike current state of the art active and passive interrogation systems, the CTMFD relies on simple to use, straightforward, and inexpensive electronics with lab-prototypes costing around ~

Fast neutron spectroscopy with tensioned metastable fluid detectors

100-1000. Finally, the CTMFD system can switch between detection of neutrons, alpha recoils, and fission products with simplicity within the same system. As a novel transformational advancement, the CTMFD has been re-configured to now allow for multiple detectors enclosed within the envelope of a single system, resulting in the Multi-Arm Centrifugally Tensioned Metastable Fluid Detectors (MAC-TMFDs). This system embodiment now allows for the creation of several independently operating sensing regions within a single TMFD. In this way, a single detector can effectively be converted into multiple situation-specific sensors within a simple package. This advancement allows for rapid neutron/alpha spectroscopy with a single system. As part of capability validation, alpha spectroscopy has been performed with a two sensitive volume region apparatus. This systems sensitivity shows significant improvement over state-of-the-art liquid scintillation counters ~ 1 to 10 times more sensitive than a Beckman LS6500TM spectrometer. Also, gamma blind neutron detection using (n, alpha) Pu-Be and fission 252Cf neutron sources have been possible to attain along with discrimination of each source. The resulting detection data has been shown to remain compatible with the underlying science of a traditional CTMFD system. Further analysis shows that the leap-ahead MAC-TMFD is amenable for on-demand scalability.