- Materials Holdup Measurements for uranium and plutonium.
- Everything you need — gathers data, analyzes, and documents nuclear materials.
- Lightweight mobile unit.
- Powerful base-station desktop computer stores calibrations, equipment setup, and results.
- Method taught in the Los Alamos National Laboratory (LANL) Holdup Training Course.
- Incorporates the LANL Generalized Geometry Holdup algorithms.
- Available as a complete ready-to-use system.
- Components available for individual system integration.
- Use of Windows CE based mobile bar-code readers.
"Holdup" refers to the accumulation of special nuclear material (SNM) inside the processing equipment of nuclear facilities. Holdup must be minimized and quantified: for radiation and criticality safety, safeguarding against theft or diversion, and economic reasons.
Accurate holdup measurements, while simple in principle, are demanding on the operator. The measurements by their nature are made in situ at specified points in the plant — often in awkward locations where SNM may be deposited, such as valves and ducts. The operator often must wear protective clothing, resulting in additional discomfort during the performance of the measurement under already unpleasant conditions of high temperature and humidity — perhaps up a ladder while holding a detector against a pipe with an outstretched arm. Beside those physical demands, the operator must keep track of the nuclear counting data and associated parameters (e.g., wall thickness, measurement distance).
The HMS4 holdup measurement system makes it all as easy as possible for the operator, who need carry only a small, lightweight mobile unit which guides the operation and automatically logs the data with unique coding. This nearly eliminates the expense of having to repeat a measurement due to a data entry error.
The mobile unit is set up ready to go at the base station. When the operator completes the measurements, the unit is returned to the base to download the data. The host computer maintains all history and current data in an easy-to-use database. All needed reports and QA are available there.
HMS4 was developed as a joint effort between LANL, ORNL and the Y-12 National Security Complex. Its predecessor, HMS3 was originally used and perfected for uranium holdup then extended for plutonium holdup.
The calculations in the HMS4 software are performed in accordance with the Generalized Geometry Holdup (GGH) method, which simplifies the measuring process by reducing the large number of possible geometries to three: point, line, and area. By examining the plant carefully and choosing appropriate measurement points, one of the three standard geometries can assay holdup with acceptable accuracy at each plant location. The GGH methodology gives rapid and accurate quantitative analysis of holdup in literally miles of duct work, hundreds of valves and pipes, and in dozens of pieces of process equipment — that is, every possible measurement location.
The HMS4 software includes two sets of programs; the main program that runs on a host personal computer (PC), and others running on a bar-code reader or portable PC.
The bar-code reader or portable PC is referred to as the Controller. The Host computer program performs setup and calibration of multichannel analyzer/detector pairs, loads the controller with operational parameters, receives measurement data from the controller, maintains measurements and derived results in databases, and prints reports.
The Field Controller programs control multichannel analyzer (MCA) setup functions, data acquisition, store measurement data as accumulated, and allow the user to review previous collected data and spectra.
The Field Measurements screen is the heart of the HMS4 Field MCA Control software. All of the data acquisition is done within this screen.
Four other host computer programs included in the distribution are: (1) the standalone Windows based Controller program, (2) a standalone MCA control selection program, (3) an upgrade program to be used to update existing older HMS3 databases to HMS4 format, (4) and a program for extracting the embedded Region of Interest (ROI) information from a Controller-saved spectrum.
The Windows-based HMS4 software provides the user with several enhancements over HMS3 versions. It offers the user a completely new menu based environment. It contains several new holdup correction algorithms such as the Finite Source correction and the Self-Attenuation correction. These algorithms have been integrated into the software for the capability of full error correction. HMS4 now supports twenty (20) spectral regions-of-interest (ROI) to aid the user measuring plutonium. The data from each Measurement Period (or campaign) is easily accessed from the main menu. All measurement data dumps are date and time stamped and allow for an 80-character comment field, which can be used for extra notes.
Many improvements have been made in the way that HMS4 performs background calculations, and now, the user has the flexibility to make 20 background measurements and reference the order needed.
A typical HMS4 System is a complete holdup system with the following components:
The NaI detector, compact and easy to use, includes shielding on the sides and back to minimize background interference from extraneous radiation sources. This improves the signal-to-noise ratio, resulting in short measurement times and accurate results. Several detector models are available to match specific measurement needs. The quality of the data (spectra) is assured by the use of a reference source (241Am) attached to the detector, which provides a signal for gain stabilization and resolution monitoring. Any resolution change is reported to the operator.
Portable Multichannel Analyzer
HMS4 supports the ORTEC digiDART and digiDART-R multichannel analyzers (MCAs).
The Intermec CN3 Series of Mobile PC with Windows Mobile 5 has been successfully tested with HMS4. It is the Field Controller of choice with full systems purchased from ORTEC. These portable devices with bar-code reader facilitate obtaining holdup measurements. As the operator travels around the facility, the Field Controller controls the MCA data acquisition and stores the count rate data along with a field location bar-code. (Bar-codes positioned around the plant specify the measurement locations.) This procedure, which dramatically simplifies the entire process of obtaining the right data at the right place, ensures reproducible measurements.
There is also a full Microsoft Windows version of the Controller software. This is for use by individuals who wish to use a laptop computer in the field.
The supervisor uses the host computer to set up and calibrate the multichannel analyzer/detector pairs and to program the bar-code readers before the operator takes the mobile unit to perform measurements. All of this is supported by an extensive, easy-to-use menu system. Upon the mobile unit’s return, the supervisor receives the measurement data from the bar-code reader/controllers. The measurement data and the derived results are stored in databases. The associated reports and data summaries can then be viewed and printed. A single host computer can support multiple field systems.
The results report may be sent to the screen or the printer. It is generated using Crystal Reports. Spectra can be re-analyzed as needed.