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 measure-ment of MDCT fan speed is therefore an important maintenance and safety requirement. To that end, we have developed an algorithm for automatically predicting the rotational speeds of multiple, simulta-neously operating fan rotors using contactless, infrasound measurements. The algorithm is based on identifying the blade passing frequencies (BPFs), their harmonics, as well as the motor frequencies (MFs) for each fan in operation. Using the algorithm, these frequencies can be automatically identified in the acoustic waveform's short-time Fourier transform spectrogram. Attribution is aided by a set of fil-ters that rely on the unique spectral and temporal characteristics of fan operation, as well as the intrinsic frequency ratios of the BPF harmonics and the BPF/MF signals. The algorithm was tested against infra -sound data acquired from infrasound sensors deployed at two research reactors: the Advanced Test Reactor (ATR) located at Idaho National Laboratory (INL) and the High Flux Isotope Reactor (HFIR) located at Oak Ridge National Laboratory (ORNL). After manually identifying the MDCT gearbox ratio, the algo-rithm was able to quickly yield fan speeds at both reactors in good agreement with ground truth. Ultimately, this work demonstrates the ease by which MDCT fans may be monitored in order to optimize operational conditions and avoid infrastructure damage.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

This paper describes the fabrication, testing, and characterization of long-length, up to 50 m, scintillating fibers for the purpose of radiation monitoring in inaccessible radiological and nuclear waste repositories. The fabrication aspect was focused on ruggedizing the 1-mm diameter fiber and limiting external light interference for fibers. Testing and characterization were performed in a laboratory setting with radiation sources, a photosensor module and a multi-channel analyzer. Light attenuation was studied as a function of distance by analyzing both the spectrum and count rate. Additionally, the scintillating fibers were coupled to optical communication fibers (100 m) to extend the reach of the system. This paper also includes the optical spectrometry results from the sensitivity and response of the signal attenuation. Lastly, the paper covers the field testing of the scintillating fibers in a relevant environment.

rings (including physical sampling and gamma scanning) fission product concentration profiles within the rings can be determined. These data can be used to elucidate fission product transport parameters (e.g. diffusion coefficients within the test materials) which will be used to inform and refine models of fission product transport. After irradiation in the Advanced Test Reactor (ATR) had been completed in April 2014, the AGR-3/4 experiment was shipped to the Hot Fuel Examination Facility (HFEF) at the Materials and Fuels Complex (MFC) for inspection, disassembly, and metrology. The AGR-3/4 test train was received at MFC in two separate shipments between February and April 2015. Visual examinations of the test train exterior did not indicate dimensional distortion, and only two small discolored areas were observed at the bottom of Capsules 8 and 9. No corresponding discoloration was found on the inside of these capsules, however. Prior to disassembly, the two test train sections were subject to analysis via the Precision Gamma Scanner (PGS), which did not indicate that any gross fuel relocation had occurred. A series of specialized tools (including clamps, cutters, and drills) had been designed and fabricated in order to carry out test train disassembly and recovery of capsule components (graphite rings and fuel compacts). This equipment performed well for separating each capsule in the test train and extracting the capsule components. Only a few problems were encountered. In one case, the outermost ring (the sink ring) was cracked during removal of the capsule through tubes. Although the sink ring will be analyzed in order to obtain a mass balance of fission products in the experiment, these cracks do not pose a major concern because the sink ring will not be analyzed in detail to obtain the spatial distribution of fission products. In Capsules 4 and 5, the compacts could not be removed from the inner rings. Strategies for removing the compacts are being evaluated. Sampling the inner rings with the compacts in-place is also an option. Dimensional measurements were made on the compacts, inner rings, outer rings, and sink rings. The diameters of all compacts decreased by 0.5 to 2.0 %. Generally, the extent of diametric shrinkage increased linearly with increasing neutron fluence. Most compact lengths also decreased. Compact lengths decreased with increasing fluence, reaching maximum shrinkage of about 0.9 % at a fast fluence of 4.0x1025 n/m2 E > 0.18 MeV. Above this fluence, the extent of length shrinkage appeared to decrease with fluence, and two compacts from Capsule 7 were found to have slightly increased in length (< 0.1 %) after a fluence of 5.2x1025 n/m2.

The restart of the Transient Reactor Test Facility (TREAT) at Idaho National Laboratory and consequent refurbishment of the Fuel Motion Monitoring System (FMMS), or Hodoscope, offers the opportunity to upgrade the detector system used for neutron imaging. Silicon photomultipliers (SiPMs) are a viable option for updating the Hodoscope to yield improved fuel monitoring capability. The Hodoscope uses ZnS(Ag) proton recoil scintillators (PRS) that provide good gamma-ray suppression and discrimination. Previous work showed that the Hamamatsu S13360-6075CS SiPM offers the best neutron detection and gamma-ray discrimination capability with the ZnS PRS. This work optimizes a SiPM-based detector and develops a PRS prototype for testing. Specifically, possible overvoltages for use are determined by confirming steady operation over extended measurement times. In addition, various SiPM-circuit implementations are tested to optimize the detector according to desired properties, and ultimately a PRS prototype is developed with modifiable components for versatile testing. Measurements of the neutron detection efficiency and gamma-ray rejection efficiency of SiPM-based PRS detectors and a reference PMT-based detector are also carried out. Neutron detection efficiency ranges between 1–2%, and detected gamma-ray rejection efficiency is on the order of 10−7. Use of a low-pass filter only or a low-pass filter and 50-ω shunt resistor is recommended for the SiPM-based detector, and both configurations demonstrate improved performance over the PMT-based detector.

Additively manufactured respirators (AMRs) made using rigid plastic can be fitted with repurposed filter media to yield a wearable mask capable of passing a quantitative fit test with criteria set for commercial, N95 health care particulate respirators. This has been verified through an evaluation study assessing AMR masks fabricated using open-source design files and a commercial fused-filament fabrication machine, using N95 filter cloth and a P100 respirator cartridge. A few examples of filter media not designed for human respiratory protection were also evaluated in an AMR mask but did not demonstrate filtering sufficient to pass the N95 test criteria. All attributes of an AMR mask system must be considered during design and when testing performance, including the mask frame, gasket, and the cord used to secure the mask to the face. AMR masks are not the same as commercially available respiratory masks. If AMR masks are used as personal protective equipment (PPE) during a crisis when there is a shortage of regular PPE it is important that wearers are fully informed of the differences, tradeoffs, and risks associated with their use. Quantitative fit testing and proper training on how to don and doff the AMR mask are important to help achieve the best possible outcome when they are used.

The Transient Reactor Test (TREAT) facility, located at Idaho National Laboratory, restarted transient operations in 2018 following an extended shutdown. It is of interest to establish a methodology and capability to obtain an accurate estimate of the total number of fissions produced in a fissionable test item during a transient at TREAT. Uranium wires were irradiated in TREAT as part of a transient prescription test program, and gamma-ray spectrometry was performed on the wires following irradiation using a high-purity germanium detector. Many fission products are useful for estimating the number of fissions produced in a sample using gamma-ray spectrometry; at TREAT with the time periods used for analysis, the isotopes of interest include Zr-95, Nb-95, Ru-103, Ba-140, and La-140. The number of fissions per gram of U-235 determined from these measurements establishes an estimate for future experiments to be performed in the core when a similar configuration is used with a similar transient prescription.

In support of the Accident Tolerant Fuels program, experiment devices are being developed to enable transient testing of pressurized water reactor (PWR) type fuel specimens. In fiscal year 2019 several fueled tests were conducted in the Transient Reactor Test Facility (TREAT) using the Separate Effects Test Holder (SETH). Five different SETH capsules (SETH A-E) were assembled, each holding a 10-pellet rodlet with 4.9% enriched, commercially-produced fresh UO2 pellets in zirconium alloy cladding with pellet dimensions having typical PWR radial dimensions and a total pellet stack length measuring 10.16 cm. The rodlet’s length allows the specimen to be axially positioned in the center of the core with minimal flux variation over the height of the rodlet. The fuel motion monitoring system (FMMS) is located on the north side of the TREAT reactor. Having direct line-of-sight of the core enables the FMMS to collect spatially-resolved data for fast neutrons generated due to fission occurring in experiment specimens. The FMMS contains 360 channels that make up a 10 (horizontal) by 36 (vertical) array of viewing slots; for the SETH A-E test series 96 proton-recoil scintillator (PRS) detectors were installed in the system. The fast neutrons are detected in the PRS detectors from light produced by the recoil of protons interacting with ZnS(Ag) grains in each detector's scintillator button. This report focuses on the FMMS data captured in the SETH A-E experiments, with multiple transients varying in reactivity addition and length. The first three experiments had a total reactor energy of 101 MJ each and were critical in understanding the FMMS field of view, lead shielding, and other TREAT data acquisition systems. SETH-B2 and C had a reactivity addition of almost double the previous transients and served as a demonstration of the detector array behavior under increased reactor energy. The final two SETH experiments (D and E) were aimed at reaching cladding melting temperatures with a reactor energy over 500 MJ for each test. In preparation for the higher energy transients, the FMMS lead shielding was reduced to 0.5 inches from the 6 inches used in SETH A-C. This was expected to saturate the detectors at the peak of the transient in exchange for higher sensitivity at lower energies after the peak, when the motion was expected. SETH-D was clipped at approximately 3 seconds, which was too early for the FMMS to capture any rodlet motion. SETH-E had the same reactivity addition as SETH-D but the transient time was extended to 18 seconds. The FMMS captured the downward motion of the rodlet in SETH-E as the count rate significantly changed for the detectors viewing the specimen. Snapshots taken throughout the transient helped identify the approximate time at which the motion initiated. Further analysis of the individual detector data captured on a per-millisecond time basis resulted in a determination that the approximate time for the onset of the downward motion was 2.84 ± 0.02 seconds. Neutron radiographs confirmed that downward motion occurred for SETH-D and SETH-E. Motion in SETH-D could also have been captured by the FMMS if the transient time had been longer for SETH-D. Ultimately, these final two tests served to demonstrate the FMMS's ability to track fuel motion during transient experiments at TREAT.

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 Reactor of Idaho National Laboratory (INL). Two sets of certified reference material (CRM) samples were characterized. The U-235 enrichment of the first set is constant at 93.2 wt%, and the UO2 mass ranges between 0.5 and 4 kg. The second set includes samples of increasing enrichment (from 20 wt% to 97 wt%) and constant UO2 mass of 230 g. We used two AmLi sources to induce fission reactions in the samples. Despite the intense gamma-ray background of the UO2 and interrogating sources, the system could measure induced fission neutrons emerging from the interrogated samples without additional shielding surrounding the sample and only relying on pulse shape discrimination to classify neutron and gamma-ray pulses. The overall neutron count rate and time-correlated counts are well correlated with the sample fissile mass. We also proved that CRM samples can be used to build a calibration curve to assay the U-235 mass of unknown samples of different mass, geometry and enrichment, with an average bias error of 8%, for U-235 mass higher than 390 g.

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 were made using 3He proportional counter arrays embedded in polyethylene, either bare or wrapped with Cd or B filters. All data was analyzed in 900-s intervals starting one day before the eclipse and extending to one day after the eclipse. More detailed analyses were made in 90-s intervals for the photon data and 110-s intervals for the neutron data. Meteorological data was simultaneously recorded in 60-s intervals, recording solar radiance, temperature, air pressure, relative humidity, and dew point. For the observations described here, no statistically-significant (> 3σ) variations in signal count rates were observed in either the photon or neutron data. This level corresponds to the lack of observed photon variations exceeding 2.1%, 12.2%, 21.6%, or 43.2% of mean values in the four photon energy groups, respectively; it corresponds to a lack of observed neutron variations exceeding 25.3%, 25.6%, or 16.1% of mean values in the three neutron detector arrays, respectively.

................................................................................................................................................ iii ACRONYMS ............................................................................................................................................... xi 1. Introduction ........................................................................................................................................ 1 1.1 Why Infrasound and Low-Frequency Signals? ........................................................................ 1 1.2 Processing Signals .................................................................................................................... 2 1.2.1 Raw Signal Analysis ................................................................................................... 2 1.2.2 Resampling ................................................................................................................. 2 1.2.3 Spectrogram ................................................................................................................ 3 1.2.4 Power spectrum ........................................................................................................... 3 1.3 Experiment Set-Up ................................................................................................................... 5 2. Acoustic Signatures ............................................................................................................................ 7 2.1 Backup Diesel Generator Startup/Shutdown............................................................................ 7 2.1.1 Generator Startup ........................................................................................................ 7 2.1.2 Generator Steady State .............................................................................................. 10 2.1.3 Generator Shut Down ................................................................................................ 11 2.2 Manipulator Operations in Hot Cells ..................................................................................... 14 2.3 Conveyor Transfer Operations ............................................................................................... 16 2.4 Cell Off-Gas & Vessel Off-Gas Ventilation Trains ............................................................... 21 2.5 HFIR Reactor Bay Crane Movements ................................................................................... 23 2.5.1 Unloaded Hand-Crane Bridge Movements ............................................................... 23 2.5.2 3and 50-Ton Unloaded Crane Operations .............................................................. 31 2.5.3 3-Ton Loaded Operations ......................................................................................... 41 2.6 HFIR Truck Bay ..................................................................................................................... 45 2.6.1 West Truck Bay Door No Entry/Exit ........................................................................ 45 2.6.2 East Truck Bay Door No Entry/Exit ......................................................................... 47 2.6.3 Loading the Sugarman Capsule ................................................................................ 47 2.7 HFIR Coolant and Clean-up Pumps ....................................................................................... 54 2.8 HFIR Air Conditioning and Cooling Operations ................................................................... 55 3. Appendix 1 Maps ........................................................................................................................... 57 4. Appendix 2 Quick Signature Reference ......................................................................................... 64 5. References ........................................................................................................................................ 68

The Transient Reactor Test Facility (TREAT) at Idaho National Laboratory is an aircooled, graphite-moderated reactor designed to evaluate reactor fuels and structural materials under conditions that simulate various types of transient overpower and under-cooling situations in a nuclear reactor. Fuel meltdowns, metal-water reactions, thermal interaction between overheated fuel and coolant, and the transient behavior of ceramic fuel for high-temperature systems can be studied. A key instrument that monitors fuel motion as these events take place is t he fast neutron hodoscope. The hodoscope is designed to allow for pre-, during-, and post-transient imaging of fuel in a test loop in the center of the reactor's core. The preferred technique for imaging is detection of fast neutrons produced by fission in the test fuel, travelling unmoderated through a core slot and then a multi-slot collimator to a 360detector array collinear to the collimator channels. Due to the age of the instrument, a refurbishment of the hodoscope's fast neutron detection capability is necessary. Described here is a Multi-Purpose Test Station (MPTS) that was designed to simultaneously qualify and characterize up to eight photo-multiplier tubes using a distributed light source. The MPTS also provides a means to characterize up to eight fast neutron detector assemblies consisting of ZnS(Ag) scintillators coupled to photomultiplier tubes, using a radiologic source.

This paper details with work being performed to evaluate, refurbish, and characterize proton-recoil scintillator (PRS) assemblies being used in a 360-channel detector array for the measurement of fast neutrons in the Fuel Motion Monitoring System (FMMS) at the Transient Reactor Test Facility (TREAT). The TREAT FMMS measures the real-time movement and displacement of experimental fuel during transient experiments, correlating fast-neutron signals to the mass of fuel in each of 360 pixels at the center of the reactor's core. The detectors in the FMMS have stood dormant for over 20 years and significant degradation must be addressed before the system can be brought back to operational status. The PRS refurbishment process began by decoupling the scintillators from their matched photomultiplier tubes (PMTs) and treating the PRSs with ethanol. This process cleans the surfaces, removing paint and legacy labels/markings. During this procedure many physical variations were observed. After cleaning, the PRSs were measured using a digital caliper and the dimensions documented. Following this, a well-controlled fiber-coupled 280-nm light-emitting diode light source was used to stimulate the PRSs to produce an emission spectrum inside a light integration sphere. This emission spectrum was measured using an ultra-violet light enhanced optical spectrometer. Spectral measurements were recorded from 185-nm to 580-nm in 0.4-nm steps. The PRSs were then lightly sanded on the nonPMT mating surfaces and painted with commercially available reflective paint. A final emission spectrum was recorded for each PRS after painting.

This document is a report summarizing FY2017 efforts related to the Transient Reactor Test Facility (TREAT) Fuel Motion Monitoring System, "hodoscope," refurbishment campaign. TREAT is an air-cooled, graphite-moderated, heterogeneous test facility designed to evaluate reactor fuels and structural materials under conditions that simulate various types of transient overpower and under-cooling situations in a nuclear reactor. Fuel meltdowns, metal-water reactions, thermal interaction between overheated fuel and coolant, and the transient behavior of ceramic fuel for high-temperature systems can be studied. A key instrument that monitors fuel motion as these events take place is the fast neutron hodoscope. The hodoscope is designed to allow for pre-, during-, and post- transient imaging of fuel within a test loop in the center of the reactor core. The preferred technique for imaging is detection of fast neutrons produced by fission in the test fuel, travelling unmoderated through an empty row of core fuel assemblies and then through a multi-slot collimator to a 360-detector array. Due to the age of the instrument, a refurbishment of the hodoscope’s fast neutron detection capability is necessary to support real-time, fuel-position experimental data collection. One particular challenge in this regard is related to the refurbishment of the fast-neutron-sensing detector elements in the detector array. This report summarizes major activities and accomplishments related to the FMMS refurbishment in FY2017. Of particular note was work related to identifying options for new proton recoil scintillator wafer and initial examination of the TREAT proton recoil proportional counter detectors.

Research is underway to develop instruments and methods to determine the activity of radionuclides present in the fallout debris from the detonation of a radiological dispersal device (RDD). Handheld instruments, including commonly used health physics survey instruments, have been incorporated into a portable telemetry kit containing a global positioning system receiver, WiFi and radio communications, and a small microcomputer to facilitate data processing, logging, and transmission. An operator carries the system and walks through the RDD post-blast environment, real-time radiological data is logged, stored locally, and transmitted to a base station outside of the RDD hot zone. A map of the distributed radiological dispersal is generated, subdividing the world into 1-m(2) squares. Separate measurements of ground activity taken at a finite number of discrete locations is used to cross-correlate the survey data, transforming the health physics data (e.g., mrem hr(-1)) to surface activity (Bq m(-2)). The map data, smoothed using standard Kriging approaches, is then analyzed by summing each discrete square area, producing an estimate for the total dispersed ground activity. The instrumentation and method have been field tested multiple times at Idaho National Laboratory during field exercises using short-lived radionuclides detonated in small-scale experiments.

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 into the design of the x ray optics system as a function of the source emission, multilayer coating characteristics, and general experimental configurations. The experimental results are compared to the predictions from our simulation toolkit to illustrate the ray-tracing capability and explore the effect of modified optics in future measurement campaigns.

Thermal neutrons (with mean energy of 25 meV) have a scattering mean free path of about 20 m in air. Therefore it is feasible to find localized thermal neutron sources up to ~30 m standoff distance using thermal neutron imaging. Coded aperture thermal neutron imaging was developed in our laboratory in the nineties, using He-3 filled wire chambers. Recently a new generation of coded-aperture neutron imagers has been developed. In the new design the ionization chamber has anode and cathode planes, where the anode is composed of an array of individual pads. The charge is collected on each of the individual 5x5 mm2 anode pads, (48x48 in total, corresponding to 24x24 cm2 sensitive area) and read out by application specific integrated circuits (ASICs). The high sensitivity of the ASICs allows unity gain operation mode. The new design has several advantages for field deployable imaging applications, compared to the previous generation of wire-grid based neutron detectors. Among these are the rugged design, lighter weight and use of non-flammable stopping gas. For standoff localization of thermalized neutron sources a low resolution (11x11 pixel) coded aperture mask has been fabricated. Using the new larger area detector and the coarse resolution mask we performedmore » several standoff experiments using moderated californium and plutonium sources at Idaho National Laboratory. In this paper we will report on the development and performance of the new pad-based neutron camera, and present long range coded-aperture images of various thermalized neutron sources.« less