David Chichester

• ScD
• Researcher at Idaho National Laboratory

Surrogate nuclear explosive debris (SNED) is critical to post-detonation nuclear forensic science. We report a systematic study optimizing the dissolution characteristics of sol–gel based SNED. Total carbon analyses of sol–gels indicate elimination of unreacted carbon from residual ethyl groups when samples are annealed above 500 °C. Sol–gel SNED a...

Explosion monitoring is performed by infrasound and seismoacoustic sensor networks that are distributed globally, regionally, and locally. However, these networks are unevenly and sparsely distributed, especially at the local scale, as maintaining and deploying networks is costly. With increasing interest in smaller-yield explosions, the need for m...

For prompt detection of large (>1 kt) above-ground explosions, infrasound microphone networks and arrays are deployed at surveyed locations across the world. Denser regional and local networks are deployed for smaller explosions, however, they are limited in number and are often deployed temporarily for experiments. With the expanded interest in sm...

Sample return capsules (SRCs) entering Earth's atmosphere at hypervelocity from interplanetary space are a valuable resource for studying meteor phenomena. The 2023 September 24 arrival of the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer SRC provided an unprecedented chance for geophysical observations o...

Explosion monitoring is performed by infrasound and seismoacoustic sensor networks that are distributed globally, regionally, and locally. However, these networks are unevenly and sparsely distributed, especially in the local scale as maintaining and deploying networks is costly. With increasing interest in smaller yield explosions, the need for mo...

Sample Return Capsules (SRCs) entering Earth's atmosphere at hypervelocity from interplanetary space are a valuable resource for studying meteor phenomena. The 24 September 2023 arrival of the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) SRC provided an unprecedented chance for geophysical o...

Advanced instruments and methods need to be developed now to create a technical basis to support the negotiation of future nuclear arms control treaties. One new capability that is anticipated is the ability to confirm either the declared presence or declared absence of high explosive (HE) material in the presence of special nuclear material (SNM)....

Post detonation nuclear forensic materials which resemble the size, color, elemental composition, and radionuclide content of real nuclear debris would be valuable for developing and validating new nuclear forensic techniques. As nuclear fallout types vary significantly, the ability to tailor each of these parameters accurately is desired to produc...

Persistent low-frequency (<180 Hz) acoustic detection took place within the boundaries of Oak Ridge National Laboratory to monitor full power operations of the High Flux Isotope Reactor. Three acoustic sensors were installed at distances of 69, 101, and 914 m from the northeast corner of the cooling towers to monitor and assess four reactor power g...

Mechanical draft cooling towers (MDCTs) serve a critical heat management role in a variety of industries. For nuclear reactors in particular, the consistent, predictable operation of MDCTs is required to avoid damage to infrastructure and reduce the potential for catastrophic failure. Accurate, reliable measurement of MDCT fan speed is therefore an...

A prototype gamma-ray scanning system was designed to perform post-irradiation examination measurements of nuclear fuel. The system is composed of a coaxial high-purity germanium (HPGe) detector, a collimator, and mechanical positioning stages that translate the fuel sample across the front of the collimator. This paper documents the design process...

Scintillator geometry affects light-collection efficiency (LCE) and, as a consequence, detector-performance metrics that depend on LCE, such as particle-type identification. This work compares the neutron–gammapulse-shape discrimination (PSD) performance of two trans-stilbene crystals of different geometries: a cylinder and cone. Both geometries ha...

Neutron detectors for measuring a neutron yield of a neutron generator may include at least one particle counter disposed in a housing and at least one removable cartridge for receiving at least one collection medium. The at least one removable cartridge configured to be at least partially inserted into the housing to position the collection medium...

Single-crystal (sc) chemical vapor deposition (CVD) prepared diamond semiconductor detectors have been used as alpha spectrometers to analyze untreated, thick-matrix materials with high beta radiation emission rates. Tests using a scCVD diamond detector to assay alpha emissions from high burn-up irradiated nuclear fuel show the ability to produce r...

Observations of photon and neutron background radiation were made in Rigby, Idaho, during the Great American Eclipse on August 21, 2017. Photon measurements were made using a mechanically-cooled, high-purity germanium gamma-ray spectrometer, segmenting the data into four energy bands of < 1 MeV, 1–2 MeV, 2–3 MeV, and 3–7 MeV. Neutron measurements w...

Fission neutron anisotropy, due to the kinematics of the fission process, has been studied for non-multiplying sources and highly multiplying subcritical plutonium metal assemblies (i.e. relatively long fission chains). The studies on highly multiplying assemblies show that the observed neutron-neutron angular distribution appear isotropic, while t...

We developed a fast-neutron multiplicity counter (FNMC) based on stilbene and EJ-309 organic scintillators. The system can detect and discriminate correlated photon and neutron multiplets emitted by fission reactions. We used the system to estimate the fissile mass of uranium oxide samples in active interrogation mode at the Zero Power Physics Reac...

An increase in light-collection efficiency (LCE) improves the energy resolution of scintillator-based detection systems. An improvement in energy resolution can benefit detector performance, for example by lowering the measurement threshold and achieving greater accuracy in light-output calibration. This work shows that LCE can be increased by modi...

Silicon photomultipliers have received a great deal of interest recently for use in applications spanning a wide variety of fields, including nuclear safeguards and nonproliferation. For nuclear-related applications, the ability of silicon photomultipliers to discriminate neutrons from gamma rays using pulse shape discrimination when coupled with c...

This paper summarizes efforts to characterize and qualify a computed radiography (CR) system for neutron radiography of irradiated nuclear fuel at Idaho National Laboratory (INL). INL has multiple programs that are actively developing, testing, and evaluating new nuclear fuels. Irradiated fuel experiments are subjected to a number of sequential pos...

Neutron multiplicity counting (NMC) techniques are widely used for nuclear materials accountability and international safeguards applications to quantitatively evaluate characteristic properties pertaining to fissile material. Mathematical models for NMC moments have been previously derived for systems that use capture-based detectors; however, the...

We demonstrated the application of a fast-neutron multiplicity counting (FNMC) system to detect small variations in an assembly of uranium-oxide pins. The current version of the FNMC includes eight liquid organic scintillators (EJ-309 7.62 cm diameter x 7.62 cm) and eight crystal organic scintillators (stilbene 5.08 cm diameter x 5.08 cm) in a chec...

Neutron multiplicity analysis is a non-destructive assay technique that involves detection of the multiplets of neutrons emitted by an unknown sample to estimate its fissile mass. Typically, multiplicity analysis is conducted by means of a neutron multiplicity counting (NMC) system that uses capture-based thermal detectors (e.g. 3 He-gas detectors)...

We developed a fast-neutron multiplicity counter based on organic scintillators (EJ-309 liquid and stilbene). The system detects correlated photon and neutron multiplets emitted by fission reactions, within a gate time of tens of nanoseconds. The system was used at Idaho National Laboratory to assay a variety of plutonium metal plates. A coincidenc...

Technological advances in the ability to verify, account, and control special nuclear materials (SNM) are needed to support the aims of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). Neutron multiplicity counting is a widely used technique to verify and safeguard SNM; however, these systems traditionally rely heavily on He-3. Recentl...

The use of a grazing incidence optic to selectively reflect K-shell fluorescence emission and isotope-specific lines from special nuclear materials is a highly desirable nondestructive analysis method for use in reprocessing fuel environments. Preliminary measurements have been performed, and a simulation suite has been developed to give insight in...

The core components of nuclear reactors (e.g., fuel assemblies, spacer grids, control rods) encounter harsh environments due to high temperature, physical stress, and a tremendous level of radiation. The integrity of these elements is crucial for safe operation of nuclear power plants; post-irradiation examination (PIE) can reveal information about...

Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Idaho National Laboratory (INL) has multiple nuclear fuels research and development programs that routinely evaluate irradiated fuels using neutron radiograp...

A fast neutron multiplicity counting system based on organic scintillators, i.e. EJ‐309 and stilbene, has been developed and experimentally tested at the University of Michigan. The system is able to detect correlated photon and neutron multiplets emitted by the fission reaction, within a gate time of tens of nanoseconds. This counting strategy is...

Methods and apparatus to capture images of fluorescence generated by ionizing radiation and determine a position of a beam of ionizing radiation generating the fluorescence from the captured images. In one embodiment, the fluorescence is the result of ionization and recombination of nitrogen in air.

The ability to quickly identify and characterize special nuclear material remains a national security challenge. In counter-proliferation applications, identifying the neutron multiplication of a sample can be a good indication of the level of threat. Currently neutron multiplicity measurements are performed with moderated 3He proportional counters...

Statistical analyses have been performed to develop bounding estimates of the expected performance of a conceptual fast-neutron multiplicity system (FNMS) for assaying plutonium. The conceptual FNMS design includes 32 cubic liquid scintillator detectors, measuring 7.62 cm per side, configured into 4 stacked rings of 8 detectors each. Expected respo...

The present disclosure relates, according to some embodiments, to apparatus, devices, systems, and/or methods for real-time detection of a concealed or camouflaged explosive device (e.g., EFPs and IEDs) from a safe stand-off distance. Apparatus, system and/or methods of the disclosure may also be operable to identify and/or spatially locate and/or...

A new deuterium ion source is being developed to improve the performance of existing compact neutron generators. The ion source is a microfabricated array of metal tips with an integrated gate (i.e., grid) and produces deuterium ions by field ionizing (or field desorbing) a supply of deuterium gas. Deuterium field ion currents from arrays at source...

One-dimensional fiber-bundle arrays may prove useful in a number of radiation sensing applications where radiation detection over large areas is needed. Tests have been performed to evaluate the light generation and transmission characteristics of 15-meter long, 10-fiber bundles of BCF-10, BCF-12, and BCF-20 scintillating fibers (Saint Gobain) expo...

A new multiplying test assembly is under development at Idaho National Laboratory to support research, validation, evaluation, and learning. The item is comprised of three stacked, highly-enriched uranium (HEU) cylinders, each 11.4cm in diameter and having a combined height of up to 11.7cm. The combined mass of all three cylinders is 20.3kg of HEU....

We present new results on passive measurements and simulations of mixed-oxide fuel-pin assemblies. Potential tools for mixed-oxide fuel pin characterization are discussed for future nuclear-nonproliferation applications. Four EJ-309 liquid scintillation detectors coupled with an accurate pulse timing and digital, offline and optimized pulse-shape d...

Access to SNM, in many different forms, is a key requirement for the advancement of the state-of-the-art for radiation detection and measurement in support of material protection control and accountancy, safeguards, nonproliferation, arms control, treaty verification, and nuclear forensics. 1NL, as the custodian of a singularly important inventory...

In the past few years, efforts to develop new measurement systems to support nuclear nonproliferation and homeland security have increased substantially. Monte Carlo radiation transport is one of the simulation methods of choice for the analysis of data from existing systems and for the design of new measurement systems; it allows for accurate desc...

The use of an electrostatic field desorption (EFD) ion source would constitute a significant advance in the design and operation of neutron generators. The results would directly benefit the use of neutron generators for active interrogation in the search for special nuclear material and the replacement of radioisotopic sources, particularly in man...

At nuclear facilities, domestically and internationally, most measurement systems used for nuclear materials' control and accountability rely on He-3 detectors. Due to resource shortages, alternatives to He-3 systems are needed. This paper presents preliminary simulation and experimental efforts to develop a fast-neutron-multiplicity counter based...

A new multiplying test assembly is under development at Idaho National Laboratory to support research, validation, evaluation, and learning. The item is comprised of three stacked, highly-enriched uranium (HEU) cylinders, each 11.4 cm in diameter and having a combined height of up to 11.7 cm. The combined mass of all three cylinders is 20.3 kg of H...

A comprehensive modeling study has been carried out to evaluate the utility of multiple active neutron interrogation signatures for detecting shielded highly enriched uranium (HEU). The modeling effort focused on varying HEU masses from 1 kg to 20 kg; varying types of shields including cement, wood, polyethylene, aluminum, and steel; varying depths...

We present new results on the measurement of correlated, outgoing neutrons from spontaneous fission events in a Cf-252 source. 16 EJ-309 liquid scintillation detectors are used to measure neutron-neutron correlations for various detector angles. Anisotropy in neutron emission is observed. The results are compared to MCNPX-PoliMi simulations and goo...

One-dimensional fiber-bundle arrays may prove useful in a number of radiation sensing applications where radiation detection over large areas is needed. Tests have been performed to evaluate the light generation and transmission characteristics of IS-meter long, 10-fiber bundles of BCF-10, BCF-12, and BCF-20 scintillating fibers (Saint Gobain) expo...

Neutron resonance transmission analysis (NRTA) is an activeinterrogation nondestructive assay (NDA) technique capable of assaying spent nuclear fuel to determine plutonium content. Prior experimental work has definitively shown the technique capable of assaying plutonium isotope composition in spent fuel pins to a precision of approximately 3 perce...

Ever since there has been spent fuel (SF), researchers have made nondestructive assay (NDA) measurements of that fuel to learn about its content. In general these measurements have focused on the simplest signatures (passive photon and total neutron emission) and the analysis has often focused on diversion detection and on determining properties su...

Active interrogation is a vigorous area of research and development due to its promise of offering detection and characterization capabilities of special nuclear material in environments where passive detection fails. The primary value added by active methods is the capability to penetrate shielding—special nuclear material itself, incidental mater...

An ion source based on the principles of electrostatic field desorption is being developed to improve the performance of existing compact neutron generators. The ion source is an array of gated metal tips derived from field electron emitter array microfabrication technology. A comprehensive summary of development and experimental activities is pres...

Digital pulse shape analysis (dPSA) has been used with a Cuttler-Shalev type (3)He ionization chamber to measure the fast-neutron spectra of a deuterium-deuterium electronic neutron generator, a bare (252)Cf spontaneous fission neutron source, and of the transmitted fast neutron spectra of a (252)Cf source attenuated by water, graphite, liquid nitr...

Many applications of neutrons for non-invasive measurements began with isotopic sources such as AmBe or Cf-252. Political factors have rendered AmBe undesirable in the United States and other countries, and the supply of Cf-252 is limited and significantly increasing in price every few years. Compact and low-power deuterium-tritium (DT) electronic...

Multiplicity counters for neutron assay have been extensively used in materials control and accountability for nonproliferation and nuclear safeguards. Typically, neutron coincidence counters are utilized in these fields. In this work, we present a measurement system that makes use not only of neutron (n) multiplicity counting but also of gamma-ray...

Parametric studies using numerical simulations are being performed to assess the performance capabilities and limits of active neutron interrogation for detecting shielded highly enriched uranium (HEU). Varying the shield material, HEU mass, HEU depth inside the shield, and interrogating neutron source energy, the simulations account for both neutr...

Ionizing radiation passing through air leads to the ionization of nitrogen in the air; as this nitrogen de-excites it is accompanied with the emission of near-ultraviolet (NUV) light. NUV-sensitive optical imaging may be used to analyze this light to infer the spatial location and distribution of ionizing radiation fields in air. Due to their high...

This is an end-of-year report (Fiscal Year (FY) 2011) for the second year of effort on a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-wat...

Many different nondestructive analysis techniques are currently being investigated as a part of the United States Department of Energy's Next Generation Safeguards Initiative (NGSI) seeking methods to quantify plutonium in spent fuel. Neutron Resonance Transmission Analysis (NRTA) is one of these techniques. Having first been explored in the mid-19...

Active neutron interrogation has been used as a technique for the detection and identification of special nuclear material (SNM) for both proposed and field‐tested systems. Idaho National Laboratory (INL) has been studying this technique for systems ranging from small systems employing portable electronic neutron generators to larger systems employ...

A Cuttler‐Shalev (C‐S) 3 He proportional counter has been used to measure the energy spectrum of neutrons from a portable deuterium‐deuterium electronic neutron generator. To improve the analysis of results from the C‐S detector digital pulse shape analysis techniques have been used to eliminate neutron recoil artifacts in the recorded data. Da...

Idaho National Laboratory is experimenting with electrical neutron generators, as potential replacements for californium‐252 radioisotopic neutron sources in its PINS prompt gamma‐ray neutron activation analysis (PGNAA) system for the identification of military chemical warfare agents and explosives. In addition to neutron output, we have recentl...

Neutron Resonance Transmission Analysis (NRTA) is an analytical technique that uses neutrons to assay the isotopic content of bulk materials. The technique uses a pulsed accelerator to produce an intense, short pulse of neutrons in a time-of-flight configuration. These neutrons, traveling at different speeds according to their energy, can be used t...

This is an end-of-year report for a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larg...

Ionizing radiation passing through air leads to the ionization of nitrogen in the air; as this nitrogen de-excites it is accompanied with the emission of near-ultraviolet (NUV) light. NUV-sensitive optical imaging may be used to analyze this light to infer the spatial location and distribution of ionizing radiation fields in air. Due to their high...

Experiments have been carried out to investigate the feasibility and utility of using neutron interrogation and small-scale, portable prompt gamma-ray neutron activation analysis (PGNAA) instruments for assaying uranium for safeguards applications. Prior work has shown the potential of the PGNAA technique for assaying uranium using reactor-based ne...

It is generally accepted that active neutron interrogation is a reliable means of detecting the presence of shielded special nuclear material, in particular highly enriched uranium. We are facilitating the deployment of portable active neutron interrogation systems for field detection applications by developing a new atomic deuterium ion source for...

Technologies that have been developed for microelectromechanical systems (MEMS) have been applied to the fabrication of field desorption arrays. These techniques include the use of thick films for enhanced dielectric stand-off, as well as an integrated gate electrode. The increased complexity of MEMS fabrication provides enhanced design flexibility...

Field emission arrays that are used for ion desorption must be capable of operating at high applied voltages. The large electric fields can lead to dielectric breakdown or electron emission from the gate, both of which may result in catastrophic failure. Methods were developed to fabricate tip arrays with integrated gate electrodes, separated from...

In a continuing effort to examine portable methods for implementing active neutron interrogation for detecting shielded fissionable material research is underway to investigate the utility of analyzing multiple time-correlated signatures. Time correlation refers here to the existence of unique characteristics of the fission interrogation signature...

New results are presented on the passive measurement of mixed-oxide fuel pin assemblies. A fast and robust methodology for the characterization of mixed-oxide fuel pins is discussed. Four EJ-309 liquid scintillation detectors coupled with an accurate pulse timing and digital, offline, optimized pulse-shape discrimination method were used. Measureme...

He proportional counters have long been used as neutron detectors for both passive and active detection of Special Nuclear Material (SNM). The optimal configuration of these detectors as far as gas pressure, amount of moderating material, and size are concerned is highly dependent on what neutron signatures are being used to detect and identify SNM...

A measurement plan and preliminary Monte Carlo simulations are presented for the investigation of well-defined mixed-oxide fuel pins. Measurement analysis including pulse-height distributions and time-dependent cross-correlation functions will be performed separately for neutrons and gamma rays. The utilization of Monte Carlo particle transport cod...

Multiple small-scale projects have been undertaken to investigate advanced instrumentation solutions for safeguard measurement challenges associated with advanced fuel cycle facilities and next-generation fuel reprocessing installations. These activities are in support of the U.S. Department of Energy's Fuel Cycle Research and Development program a...

Experiments have been performed at Idaho National Laboratory to study methodology and instrumentation for performing neutron active interrogation die-away analyses for the purpose of detecting shielded fissionable material. Here we report initial work using a portable DT electronic neutron generator with a ³He neutron detector to detect...

Pulsed neutron interrogation measurements have been performed on highly enriched uranium (HEU) oxide fuel pins and depleted uranium (DU) metal using a D-D neutron generator (2×106 neutrons-s-1) and moderated 3He tubes at the Idaho National Laboratory Power Burst Facility. These measurements demonstrate the ability to distinguish HEU from DU by coin...

Active interrogation, a measurement technique which uses a radiation source to probe materials and generate unique signatures useful for characterizing those materials, is a powerful tool for assaying special nuclear material. The most commonly used technique for performing active interrogation is to use an electronic neutron generator as the probe...

For over 40 years Idaho National Laboratory (INL) and its predecessor organizations have maintained and operated the Zero‐Power Physics Reactor (ZPPR) as a test bed for studying reactor physics and nuclear reactor design. Although ZPPR is no longer operated as an active research reactor, its infrastructure (radiation shielding, safety systems, phy...

Prompt Gamma Neutron Activation Analysis (PGNAA) systems employ neutrons as a probe to interrogate items, e.g. chemical warfare materiel-filled munitions. The choice of a neutron source in field-portable systems is determined by its ability to excite nuclei of interest, operational concerns such as radiological safety and ease-of-use, and cost. Ida...

A new laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for deuterium-tritium (DT) fusion (14.1 MeV) neutron generators (2 x 10(8) n/s), deuterium-deuterium (DD) fusion (2.5 MeV) neutron generators (1 x 10(7) n/s...

A new approach to deuterium ion sources for deuterium-tritium neutron generators is being developed. The source is based upon the field desorption of deuterium from the surfaces of metal tips. Field desorption studies of microfabricated field emitter tip arrays have been conducted for the first time. Maximum fields of 3 V/Å have been applied to the...

Portable electronic neutron generators (ENGs) may be used to interrogate suspicious items to detect, characterize, and quantify the presence of fissionable material based upon the measurement of prompt and/or delayed emissions of neutrons and/or photons resulting from fission. The small size (<0.2 m3), light weight (<12 kg), and low power consumpti...

A new approach to deuterium ion sources for deuterium-tritium neutron generators is being developed. The source is based upon the field desorption of deuterium from the surfaces of metal tips. Field desorption studies of microfabricated field emitter tip arrays have been conducted for the first time. Maximum fields of 30 V/nm have been applied to t...