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Whitepaper "Rod source / point detector arrangement"

Whitepaper "Rod source / point detector arrangement"

Whitepaper "Rod source / point detector arrangement"

Product catalog summary
Introduction
This white paper examines radiometric level measurement arrangements, focusing on the benefits of using a rod source with a point detector, particularly with Cobalt-60 (Co-60), for enhanced measurement quality and accuracy.
Specifications and Design Considerations
Radiometric measurement design is influenced by process conditions, geometry, customer input, and site conditions. Two configurations are discussed: point source with rod detector and rod source with point detector. The latter, despite a higher initial cost, provides superior measurement quality.
Calibration and Accuracy
Calibration typically uses a two-point method, assuming a linear relationship between count rate and vessel level. The rod source/point detector setup achieves a linear relationship, enabling accurate calibration across the measurement range, unlike the nonlinear curve of the point source/rod detector arrangement.
Long-term Stability
Point detectors paired with rod sources offer better long-term and temperature stability than rod detectors, which suffer from material aging and decreased sensitivity.
Suppression of Process Influences
Point detectors with rod sources are less affected by external gamma radiation due to their small scintillator volume and effective shielding, reducing interference from non-destructive testing (NDT).
Background Radiation Influence
Co-60 sources are less sensitive to background radiation influences compared to Cs-137, providing more accurate readings.
Maintenance and Spare Parts
Rod sources with point detectors simplify spare parts management, requiring only one type of detector, thus reducing storage and replacement efforts.
Safety and Disposal
Co-60 rod sources are safely encapsulated and have a shorter half-life, making disposal more economical than Cs-137 sources.
Cost Considerations
Although rod sources are initially more expensive, the cost difference diminishes with longer measuring ranges, and the benefits in accuracy and process improvement can offset the higher initial costs.
Working Lifetime
The working lifetime of radiometric sources is influenced by radiation protection and technical factors. Co-60's higher gamma energy makes it more efficient, requiring less material for the same count rate. A 15-year working lifetime is recommended for both Co-60 and Cs-137 sources.
Background Radiation
Background radiation from natural and artificial sources can affect measurements, especially as source activity decreases. Rod detectors are more sensitive to these fluctuations than point detectors.
Installation Challenges
Rod source shields are heavier and more challenging to install, but the benefits, such as reduced downtime and better process stability, outweigh these challenges.
Conclusion
Rod source/point detector arrangements offer significant advantages, including reduced production downtimes, simpler spare parts inventory, and consistent process quality. Operators should consider both arrangements and their costs before deciding.
Company Information
Berthold Technologies specializes in radiometric process measurements, offering a wide range of products and solutions with a focus on customer support through a global network of skilled engineers and technicians.
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Catalog excerpts

Whitepaper "Rod source / point detector arrangement"-1

Long-lasting process quality due to advantageous measuring arrangement ROD SOURCE / POINT DETECTOR ARRANGEMENT

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Whitepaper "Rod source / point detector arrangement"-2

When planning a radiometric measurement, the technical design is fundamental. It is created and developed based on process conditions, process geometry, customer input as well as local background radiation, site conditions, and mounting space limitations. For the design of radiometric level or bulk flow measurements, a choice must be made between two arrangements: a point source with a rod detector (Fig. 1 top), or a rod source and a point detector (Fig. 1 bottom). Due to the slightly lower purchase price, the arrangement with a point source and rod detector is frequently selected. However, the...

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Whitepaper "Rod source / point detector arrangement"-3

Suppression of process influences In the operating process, there are often influences that can contribute to a falsification of the measured value, e.g., product build-ups and gas pressure fluctuations in level measurements and process deposits in bulk flow measurements. These variables influence the absorption of the gamma radiation emitted by the source. Especially Fig. 5 ogging (left) and yellowing (middle) of polymer scintillators compared to an unaltered polymer scintillator (right) F in the case of gamma radiation from cesium-137 (Cs-137), which has half the energy of gamma radiation from...

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Whitepaper "Rod source / point detector arrangement"-4

of these radioisotopes is radon-222, with a half-life of 3.82 days, which occurs as a daughter nuclide and as the only gaseous element in the uranium decay series. Radon is a very mobile gas that can diffuse freely through soils and is thus released into the atmosphere. Moreover, radon is additionally washed out of the atmosphere by precipitation, causing it to accumulate near the ground. Rn-222 is a pure alpha emitter. The daughter and grandchild nuclides of Rn-222 decay further by emitting gamma radiation. Consequently, during rainfall, the background radiation can almost double for a short...

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Whitepaper "Rod source / point detector arrangement"-5

Berthold Technologies stands for excellent know-how, high quality and superior reliability. The customer is always the focus of our solution. We know our business! Using our varied product portfolio, our enormous specialized knowledge and extensive experience, we develop suitable solutions together with our customers for new, individual measurement tasks in a wide variety of industries and applications. Berthold Technologies is specialized in radiometric process measurements for over 70 years. This is our core competence with state-of-the-art and innovative products and solutions covering a vast...

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*Prices are pre-tax. They exclude delivery charges and customs duties and do not include additional charges for installation or activation options. Prices are indicative only and may vary by country, with changes to the cost of raw materials and exchange rates.