ISOTOPIC gamma spectroscopy waste determination

ISOTOPIC provides practical integrated solutions for various gamma ray measurement problems encountered in the analysis and characterization of radioactive waste applications. It can analyze high-resolution, high-purity germanium (HPGe) spectra and determine the measurement results of large volume samples.

ISOTOPIC can be used "out of the box" as part of easy-to-use mobile systems such as ORTEC ISO-CART-85, or integrated into automation systems, for example, for high-throughput measurements of large containers in retired projects.

applicability
Suitable for the following geometric shapes:

• Box, bucket, tube or surface (collimator detector)
• Closed geometric small containers (such as bottles with end caps)
• Large scale determination of soil and surface (non collimated detector: M-1 method)

ISOTOPIC provides many standard geometric "templates" from which specific measurement configurations can be developed. These templates include cylinders (from top and side; including lined cylinders (pipes)), boxes, point sources (far-field), closed geometric containers with end caps, and infinite planes. The bottle counting option on ISO-CART-85 is an example of a closed geometry with end caps. The infinite plane (soil) mode provides non collimated measurements of pollution, detachment, or large-scale leakage washed into or on an infinite plane, as seen in the measurement of soil on the ground.

method
In container mode, the detector is calibrated through a single point source measurement for counting packages, pipes, and surfaces, even when using a collimator. This primary calibration meets the certification standards of any detector and can be extrapolated or modeled to match the physical condition, container geometry, material, and matrix composition of the sample. The model is based on the "point kernel" method, which decomposes the entire measurement problem into multiple source/matrix pixels, calculates their contributions to the composite spectrum, and sums them up. This method is similar to the Monte Carlo method, utilizing user provided detector parameters (crystal diameter, crystal length, dead layer, and end cap thickness) as part of the measurement configuration. Apart from a single point source calibration, there is no need for special individual measurements to calibrate the detector.

ISOTOPIC includes an improved "closed geometry" algorithm, where the distance between the detector and the container is less than 15 centimeters.

For non collimated large-scale soil counting, the "1-meter" method developed by the US DOE EML2 and later Extension 3 can be used. It is suitable for many situations:

• Conduct purification assessment on previously used venues
• Assess the deposited nuclides in emergency situations
• Conventional environmental monitoring near nuclear facilities

The EML method simplifies complex measurement problems into the product of three easily determinable factors. The peak area of gamma rays is related to a specific nuclide activity through the product of three factors. A series of detector types and soil condition factors have been identified and listed in the program. Efficiency calibration is determined using the efficiency specified in ANSI/IEEE 325-1996 at 1.33 MeV, as well as crystal length and diameter.

To improve accuracy at low energy, users can use the same calibration as container mode instead of the EML method.

No special (and expensive) Monte Carlo calibration of the detector is required. Determine attenuation correction by selecting soil type and nuclide distribution type: recent (surface) sediments, older (washed in) sediments, or natural (uniform) sediments. Energy and peak shape calibration can be automated using multiple line sources. If you use ISOTOPIC, there will be no unexpected detector calibration costs.

Multiple measurements of a single container
When measuring any large waste container, multiple measurements are usually taken from different directions to ensure the results are obtained. If only one hardware system is available, measurements can be completed in sequence, and if multiple sets of hardware are available, measurements can be completed simultaneously. ISOTOPIC can automatically combine the results based on user-defined weighted averages. When multiple detectors are used simultaneously, the real-time spectrum of each detector can be displayed on the screen to ensure data accuracy.

Standard and custom reports
ISOTOPIC can provide flexible reporting in standard products. All modifiable parameters can be included in the standard output report. The analysis results are stored in a MS Access compatible database for easy printing or export, for further processing into a summary report. Custom reports can be generated using Crystal Reports.

Hardware compatibility
Like all ORTEC CONNECTONS application software products, ISOTOPIC is compatible with all ORTEC MCA hardware. Especially, it is very suitable for use with IDM-200-V, which is a complete and durable portable HPGe spectrometer system that does not require the use of liquid nitrogen.

Support system integrators
System integrators typically need to develop automation systems, where the details of hardware control and analysis are largely hidden by human operators beneath a software layer designed to provide a simplified user interface and/or allow for unmanned operations. The standard user documentation set contains a large number of documents, including example materials that illustrate how to control the analysis engine from the command line. The analysis parameters and results will be saved to an ACCESS compatible database. It provides all necessary file structure information, including the ISOTOPIC database file structure. The spectrum or SPC file structure is provided in a separate accompanying manual.

ORTEC hardware control is implemented through the so-called UMCBI, which provides a universal API for all supported spectrum hardware. The programmer's toolkit, as an option, can provide system integrators with instructions on how to easily control MCA hardware from their own developed programs. Usually, the basic ISOTOPIC program is used to set up system hardware and calibrate, and then the integrator's application will control the system during the regular operating cycle. By utilizing these tools and the provided document level, system integrators can easily develop complex measurement systems.

Using ISOTOPIC
ISOTOPIC has two modes: administrator and operator. The operator only needs to make a selection from the minimum subset of system options defined by the administrator. The administrator mode is used to define the operations that operators are allowed to perform. The wizard will guide the administrator to set up the operator program. The wizard displays parameters on the logically grouped screen and emphasizes the feasibility of the method.

The administrator/operator partition enables even semi skilled operators to collect good data on site, while reducing wasted repetition time (lower cost per measurement item). Of course, skilled users can choose to run two modes.

Administrators can calibrate the system, create libraries, define sample geometries, matrices, collimators, and other functions for future use by operators. Administrators can also define functions that allow operators to access.

The operator's main screen is determined by the permissions granted by the administrator and is much simpler than the administrator screen. In daily use, for container analysis, operators only need to initiate collection, select the standard container configuration, and then enter "record data" such as container ID, type, weight, and key measurement data (such as the distance from the detector to the container).

The standard container configuration and collimator configuration are defined and specified by the administrator. Container configuration includes default dimensions, materials, and substrate details. When needed, the operator can specify and call any number of these configurations.

analytical tool
Interactive result graph
After the analysis is completed, the operator can adjust the physical parameters of the container/substrate (such as substrate density or container wall thickness) by using the nuclide map to optimize the results.

This graph shows the percentage difference between the calibrated measured activity and the calculated reference peak activity for each nuclide. Administrators can choose to reference peak values. The operator can optimize the analysis by adjusting the weight fractions of the container, substrate, and uranium to optimize the results. If the points from multiple isotopes are normally distributed near the "zero line", it means that there are good results. When analyzing uranium, if U-235 enrichment is known, this value can be inputted to more accurately calculate the U-238 and U-234 values in samples containing weak uranium activity. This method can analyze uniform and non-uniform samples with higher accuracy. For packages with uneven material distribution, users will receive parameter combinations that can make some nuclide activity maps flatter. This chart, together with the spectrogram, can form part of the output report.

Field of view calculator
The field of view of the detector is an important parameter in measurement. The software algorithm performs "correction" or adjustment based on the content "seen" in the collimator field of view to analyze the content of the entire container. In general, selecting the field of view so that it is filled by the container will reduce the signal-to-noise ratio in the spectrum beyond this position, while approaching this position will make the measurement more susceptible to local non-uniformity (by measuring multiple times in different directions, the impact can be further reduced). A convenient field of view calculator enables operators to assess which part of the container is actually within the field of view of the collimated detector.

report
After completing the fine-tuning, the operator can select a report for each nuclide displaying activity and weight. Then print these results and archive them. The report file can be written in the form of a database summary or a complete report, which will display all input and correction information. The report generator option can be used to generate custom reports. The component table for error estimation can be used to help reduce overall uncertainty, for example, by extending counting time or repositioning detectors. If any correction appears too large, the user will also receive a warning. Calculate the minimum detectable activity (MDA) for each nuclide. Multiple measurements of activity, grams of U or Pu, or MDA can be reported as weighted averages. Weighting can be defined by the user.

Accuracy of results
The basic assumption of a single measurement is that the entire object contains the same volume of matrix and specific activity as the measured part. By taking multiple measurements from different points on the surface of an object and comparing similarities, the inaccuracy caused by incorrect assumptions can be reduced. These comparisons can be used to develop measurement strategies for individual objects, thereby reducing such systematic errors. If necessary, ISOTOPIC can provide a weighted average report, including the relevant minimum detectable activity.

Overall, the main factors affecting the accuracy of the results are: statistical and counting time, calibration uncertainty, number of repeated measurements taken on a single object (random uncertainty), non-uniformity of matrix density and nuclide distribution, and number of measurements taken on a single object from different directions (systematic error).

The accuracy range of 10 to 50% should be considered representative, with smaller ranges being clearly defined geometric shapes in uniform and lightweight matrices.

Analysis Library Manager
ISOTOPIC includes a comprehensive library editor for building custom analysis libraries. The editor allows operators to cut and paste nuclides and peaks from the main library, add identification tags (single escape peak, X-ray or other) and analysis (key lines or exclusion from activity calculations) to each peak, and save the library with any name. It also integrates the complete Nuclide Navigator library tool. ISOTOPIC will use the "Nuclide Navigator" to read the "Nuclide Navigator" library in Microsoft Access database format (no conversion required), and save the library in database format for use by the "Nuclide Navigator".

quality assurance
The quality assurance of ISOTOPIC meets the requirements of ANSI N13.30. For each detector, the following will be monitored:

• Detector overall background
• The total (decay corrected) activity of all calibrated nuclides
• Average FWHM ratio (spectrum and calibration standard)
• Average FW1/10M ratio (spectrum and calibration standard)
• Average peak offset from the library value
• Actual peak center energy

Calculation details

Overview of Isotope Modeling Methods for Containers
The activity of isotopes in a container is given by the following equation:

among which

A_isotope=Reported isotopic activity（Bq/MCi）.

PA_meas=The peak area count rate (c/s) of isotopic reference gamma rays measured. This quantity can be directly determined from the spectrum and collection time. If there are short half-life isotopes or rapid changes in sample activity in flowing samples, ORTEC's ZDT dead time correction algorithm will be very useful.

CF_item=Container, matrix, and sample self decay correction factors. ISOTOPIC calculates these data based on the physical data provided in the configuration.

CF_col=Collimator correction factor. Some gamma rays will penetrate the collimators around the germanium detector. The calibration factor of the collimator largely depends on the diameter of the collimator, the depth of collimation, the wall thickness of the collimator, as well as the angle and energy of the radiation.

The collimator correction factor can be determined by first calculating the activity portion that is not obscured by the collimator, and then calculating the length of the remaining activity penetrating the collimator. This is determined for each voxel of the tested item.

If there is no collimator, set it to 1.

BRray=Gamma ray branching ratio. This information is included in the nuclide library.

Det=detector efficiency measured using NIST traceable point sources (cps/Bq, μ Ci). A typical calibration distance is 30 centimeters, at which the detector and source can be considered as point objects. At close range, the length and diameter dimensions of the detector cannot be ignored. By providing these dimensions during the calibration process, simple "point detector" assumptions can be automatically corrected. The calibration of closed geometries is described in ISOTOPIC Administrator's Manual 1.

When it is necessary to report the gram quantity of isotopesMass_isotopeWhen, these are given by the following equation:


among which
N=number of atoms reporting isotopes.
λ_isotope=Report the decay constant of isotopes (s-1).
At=atomic number of the measured isotope (g/Av).
Av=Avogadro constant.

The average result of multiple measurements
After combining multiple measurement results together, the weighted average can be calculated according to the following formula:

A_average=∑A_iw_i/∑w_i

among which
A_i=Results of each activity (in grams or MDA).
w_i=User defined weighting factors.

Soil formula
The specific activity A (Bq/m2 or Bq/g) is related to the net peak count rate Nf:

among which
N_f/N₀=For a given source distribution in soil, the angle correction factor of the detector at that energy.
N₀ /Φ=The peak count rate per unit of collisional flux for parallel gamma ray beams with peak energy incident perpendicular to the detector surface(cpm/γs^–1).
Φ/A=The total non collision flux per unit of inventory reaching the detector at peak energy or the concentration of nuclides in the soil(γcm^–2s^–1)or(γg^–1s^–1).

The method of estimating calibration factors utilizes information about the detector and the distribution of the measured radioactive isotopes

• Detector efficiency (expressed as%)
• Detector direction (upward or downward)
• Detector aspect ratio (calculated as crystal length/crystal diameter)
• Sedimentary profile parameters α/ρ values

For all natural emitters, assume that α/ρ is 0 (uniformly distributed). For settlement on undisturbed soil, it is assumed that α/ρ is infinite (only for surface distribution).

Apply the Beck method in ISOTOPIC by calculating the values of each calibration parameter. Calculation will be performed for each gamma ray of all identified nuclides.
________________________________________

1Hagenauer，R.C.， Quantitative analysis of poorly characterized radioactive isotopes through non-destructive testing ", Proceedings of the Fourth Conference on Non Destructive Testing and Non Destructive Waste Characterization, Salt Lake City, 1995.

2H. L. Beck et al., "In situ Ge (Li) and NaI (Tl) gamma ray spectroscopy measurements," Environmental Measurement Laboratory, Department of Energy, United States, HASL-258， September (1972).

3I.K.Helfer and K.M. Miller, "Calibration Factors for Ge Detectors Used in Field Spectral Determination," Health Physics, Volume 55, No. 1, Pages 15-29 (1988).

Practice of NPL Nuclear Industry Capability Test in 2012. NPL Report IR 30 2013 (National Physical Laboratory, UK). The ORTEC system is numbered 9 in it.

For soil characterization in M-1 mode, it is recommended to use HPGe with crystal length/diameter ranging from 0.5 to 1.3. 80% of HPGe detectors meet this standard. The ORTEC PROFILE M series detectors are highly suitable for measuring this type of container with ISOTOPIC. Specifications-

General Specifications
The collection control and quantitative analysis functions are integrated into a concise program package, suitable for PC based in-situ gamma spectroscopy measurement systems, which can determine the radioactive content of containers, objects, surfaces, and soils.

operating system
Windows 7 64 bit hardware compatibility applies to all ORTEC instruments that use USB and TCP/IP connection protocols. Windows 7 and XP 32-bit operating systems also support these instruments as well as other traditional hardware.

Spectrum measurement hardware support
It is recommended to integrate ISOTOPIC with ORTEC IDM-V-200 HPGe spectrometer for use. But it is compatible with all ORTEC MCBs (past and present) and all other devices supported by ORTEC CONNECTION. Support advanced operations (hardware support required): amplifier gain/shaping control, automatic PZ, "optimization", and InSight ™ Mode, digiDART on-site mode, graphical settings of MCB spectrum stabilizer, and statistical uncertainty peak. It is generally recommended to use IDM-200-V for on-site measurements.

Supported file formats
ORTEC. SPC and CHN and ASCII ". SPE" are standard formats for file saving, calling, and comparison functions. You can use A49-B32 Data Master to import other file formats.

Quantitative spectral analysis method

Peak Search
The peak search of specified nuclides in the direction of the library and the Mariscotti peak search of non specified nuclides are used, both in the main library and supplementary ("suspicious") libraries.

Interactive batch sample parameter adjustment
Interactive substrate and container adjustment, as well as automatic attenuation correction for new substrates. Easy to use graphical display of relevant analysis results, capable of displaying the matrix.

Deconvolution method
Both peak finder and library can be used to guide the deconvolution process. If possible, automatically recalibrate the energy/channel based on the identified peak values.

Select detection limit form

• ORTEC Traditional
• ORTEC critical level
• No MDA (reported as zero if below MDA)
• KTA Rules
• Detection limit 2 Sigma - Japan
• Detection limit 3 Sigma - Japan
• Curie detection limit
• RISO MDA
• ORTEC LLD
• peak area
• Air Monitoring - Gimrad Method
• Regulatory Guide 4.16 Methods
• Counting Laboratory - USA
• DIN 25 482.5 detection limit
• DIN 25 482.5 detection limit
• GTN5/CEA/EDF (France)
• Nureg 0472

Decay correction

• Decay correction for any date/time, either backward or forward

Spectral correction

• Peak background correction
• Random Sum (High Rate Counting Loss)
• Peak interference correction based on library

report
Select the ORTEC standard report option:

• direct printing
• Automatically write to database
• Output in Crystal Report format
• Report in HTML format. You can save it as a disk file from there.

calibration

Energy calibration

• Multiple points, energy and FWHM squared
• Automatic Energy Calibration (No. 6006162)

Semi empirical efficiency calibration fitting options:

Isotope patterns
Establish point source calibration using one of the following methods:

• Single function polynomial (x points)
• Interpolation above and below the 'turning point'
• The user sets the square above or below the "turning point"
• User sets a linear curve above or below the 'turning point'

By calculating the point source kernel within the program, the point source calibration is extrapolated to the physical geometry of the substrate.

Infinite plane mode (applicable to soil and surface: non collimated detector)
The Beck21 meter method can be extended to a large detector size of 3 and is used by the Environmental Measurement Laboratory (EML) of the US Department of Energy. The EML method generates efficiency curves based on detector size and IEEE efficiency values. The soil density and attenuation are specified in the user editable alpha/ρ file.

Soil attenuation factor
In soil, attenuation depends on soil thickness and density, modeled by the parameters α/ρ (where α is the reciprocal of the relaxation length, defined as the soil thickness required to reduce flux by e times at a specific energy, and ρ is soil density, measured in gm/cc). For surface distribution, α/ρ is infinite, while for uniform (natural emitter) distribution, α/ρ is 0. The α/ρ values within the range of 0.05 to 0.5 were found to accurately describe the true settlement distribution, with longer settling times represented by smaller α/ρ values.

The α/ρ values are related to specific nuclides and stored in a table that can be edited by users to reflect measurement conditions.