Understanding and Mitigating Corrosion and Electromagnetic Interference (EMI) in Stack monitoring system

Introduction

Radiation detection systems are essential across various industries, and Rotem’s stack- monitoring system exemplifies this critical role. However, these systems are susceptible to environmental conditions, which can affect their reliability. The effects of temperature, humidity, vibration, weather conditions, and electromagnetic interference should be considered when deciding on the system design and appropriate compensation should be applied where necessary. Conditions such as corrosion and electromagnetic interference (EMI) can compromise the system performance. Corrosion poses a threat to the integrity and accuracy of the equipment, especially in humid environments. EMI disrupts signal processing, which can lead to false alarms and decreased sensitivity, both of which are critical for accurate radiation detection. To ensure operational efficiency, data accuracy, and compliance with safety standards, implementing protective measures, such as corrosion-resistant coatings and electromagnetic compatibility techniques, is essential to safeguard the reliability and integrity of radiation detection systems across various operational environments. The ISO 16640 standard presents various parameters to be considered in the design of a stack monitoring system for use in facilities producing radionuclides and radiopharmaceuticals.

Failure to address corrosion and EMI in radiation-detection systems can have severe consequences. Corrosion can compromise the structural integrity of equipment, leading to malfunctions and inaccurate readings. In critical industries, such as radiopharmaceutical production, inaccurate radiation measurement might result in undetected safety hazards, endangering the environment and population. In addition, unmitigated EMI can introduce signal noise and interference, leading to missed detections or false alarms. In high-stakes scenarios, such as security screening or environmental monitoring, false alarms can trigger unnecessary panic or overlook genuine threats, undermining the effectiveness of the entire detection system. Ultimately, failure to address these issues not only jeopardizes operational efficiency and data accuracy, but also poses significant risks to public safety.

The primary purpose of this white paper is to provide a comprehensive understanding of the challenges posed by corrosion and electromagnetic interference (EMI) in radiation detection systems and to propose effective solutions to mitigate these issues. By examining the detrimental effects of corrosion and EMI on equipment reliability, data accuracy, and safety standards, this document highlights the critical importance of addressing these challenges in various industries that rely on radiation detection technology. Furthermore, this white paper seeks to offer practical insights and recommendations for implementing protective measures to safeguard radiation detection systems from corrosion and EMI, thereby enhancing their operational efficiency, ensuring accurate data acquisition, and upholding stringent safety protocols. This white paper describes the resolution undertaken in the design of Rotem’s stack monitoring system and its validation through performance tests.

Problem Definition

General Context

The stack detector housing includes two types of radiation detectors: beta and gamma detectors. These detectors are specifically designed for installation in stacks that release effluent gases that may contain various radionuclides. The detectors’ exteriors were built to withstand exposure to harsh environmental conditions.

Specific Challenges from Users

Users identified two primary issues affecting the beta detector:

1. Electromagnetic Interference (EMI): EMI significantly impairs the functionality of beta
2. Corrosion: The flow of humid gas through the beta detector or condensation process causes

Detailed Description of Challenges

1. Electromagnetic Interference (EMI)
2. • Impact on Operations: EMI disrupts the beta detector's signal processing, leading to false alarms and decreased sensitivity. This diminishes the accuracy of the radiation detection, which is crucial for effective monitoring and safety.
   • Performance Issues: Continuous EMI can cause significant data inaccuracies, making it challenging to rely on detector readings for critical decisions.
3. 2. Corrosion:
4. • Operational Impact: Corrosion compromises the structural integrity of the beta detector, potentially leading to malfunctions. In environments with high humidity or corrosive substances, the longevity and reliability of the detector are severely affected.
   • Safety Concerns: Inaccurate readings due to corrosion can result in undetected radiation levels, posing significant risks in environments such as healthcare facilities or nuclear plants, where precise radiation monitoring is essential.

Example Scenarios Illustrating the Problem

1. Worker Safety: In facility producing medical radioisotopes, EMI from nearby equipment can cause the beta detector to miss radiation events, posing a risk to worker safety.
2. Environmental Monitoring: During environmental assessments, undetected radiation due to detector malfunction could lead to false assurances of safety, putting the public at

By clearly defining these challenges, we highlight the critical need for effective solutions to ensure the reliability, accuracy, and safety of beta-radiation detectors in various applications.

Solution Presentation

To address the challenges of EMI and corrosion in the beta detector, we implemented several technological solutions:

EMI:

• Changing the Detector's encapsulation: Initially, the detector's body was made of plastic using 3D printing technology. To reduce the EMI effect, we changed the material to aluminum by machining. This change in material resulted in structural improvements to the detector body.
• Adding an Aluminum Disk: We added an aluminum disk between the PCB (Printed Circuit Board) and the scintillator, which helped to reduce electromagnetic interference. (see figure 1)

Figure 1 - Exploded view of the system with reference to aluminum disk and body

Sealing:

• Adding an O-ring-type gasket: To prevent humidity from entering the detector, we added an O-ring-type gasket at the front of the case. To accommodate the gasket, we added a groove at the front of the beta detector (Figure 2).
• Increasing the Detector Cup Diameter: To ensure that the gasket aligns properly with the case edge and can seal effectively, we increased the diameter of the detector cup, creating a constraint for concentric alignment.
• Applying Pressure on the Gasket: We extended the back cork to create pressure on the gasket by pressing it against the gamma detector and other components. This pressure requires minimal length tolerance in the Additionally, we added a spacer between the gamma detector and beta detector, allowing the use of Scotch tape to couple the detectors for easier assembly (see figure 3).
• Adding Thread Inserts: We added thread inserts to the cork for screws that secured the cork position.

Figure 2 - The system is fully assembled including O-ring

Figure 3 - Stack system with cover and without cover

Principles behind the selected solutions

• Protective Materials: Using aluminum instead of plastic and adding an aluminum disk provides better protection against EMI.
• Sealing Techniques: Using an O-ring-type gasket and ensuring precise concentric alignment guarantees a seal against steam and humidity, preventing corrosion.

Addressing the Identified Challenges

The proposed solutions effectively address these challenges by improving electromagnetic shielding and sealing against humid gases, thus maintaining the reliability and accuracy of the beta detector under industry-specific environmental conditions.

Experimental Validation

• Overview of the Experimental Setup
  This section presents the testing process for the proposed solutions aimed at mitigating EMI and preventing corrosion in the beta detector of the radiation-monitoring system. A dedicated experimental setup was used to evaluate the effectiveness of structural modifications and sealing technologies applied to the detector, in accordance with the requirements specified in the IEC 60532 standard.
• Presentation of Experimental Data
  Detailed measurements, observations, and analyses were performed during testing. The collected data included a comparison of detector readings before and after implementing the proposed changes, focusing on the levels of EMI and humidity in the detector environment. The testing followed the IEC 60532 guidelines for maintaining the accuracy and stability under specific environmental conditions (see figure 4-5).
• Figure 4 - Experimental system 1
• Figure 5 - Experimental system 2
• Testing Description from the Relevant Standard
  The test procedure adhered to the IEC 60532 guidelines. Tests were conducted in a full- anechoic chamber with the system exposed to radiated fields across a frequency range of 20 MHz to 2500 MHz, in line with both IEC 60532 and ANSI 42.17A standards, which mandate that measurement deviations remain below 15%. The results confirmed that with the modifications, there were no deviations in accuracy, affirming compliance with the standard requirements.
• Figure 6 - Measurements from the test
• IP65 Sealing Compliance Testing
  Rigorous IP65 sealing tests verified the system’s resistance to dust and water ingress. The test exposed the detector to controlled dust and water jets from various angles to simulate real-world conditions where moisture and particulate matter could affect the sensitive components. No ingress was detected, confirming the robustness of the sealing mechanism and IP65 compliance, which ensured a reliable operation in challenging environments.
• Comparison of Results
  A comparative analysis demonstrated a significant reduction in EMI interference on the detector’s accuracy and successful moisture ingress prevention, enhancing the system reliability according to IEC 60532 standard requirements.

Conclusion

This white paper has explored the critical challenges of EMI and corrosion in radiation detection systems, specifically in stack monitoring applications. Through targeted modifications and experimental validation, the following insights and conclusions were obtained.

• Effectiveness of Structural Enhancements: The transition from plastic to aluminum for the detector body and the addition of an aluminum disk have been proven to be highly effective in reducing This structural adjustment significantly improves the ability of the detector to maintain accurate readings, even in high-interference environments.
• Sealing Solutions to Prevent Corrosion: Implementing an O-ring gasket and increasing the detector cup diameter effectively address moisture ingress, enhancing the detector's reliability in humid or corrosive These sealing solutions ensure an extended operational lifespan and reduce the risk of accuracy degradation owing to corrosion.
• Experimental Validation and Compliance: Experimental testing confirmed the system's compliance with IEC 60532 and ANSI 17A standards. No deviations in performance were observed during the tests under controlled high-humidity and high-EMI conditions, validating both the sealing mechanisms and EMI mitigation solutions.
• Recommendations for Future Development: Further research is encouraged to explore additional materials and technologies that could enhance corrosion resistance and EMI shielding. Improving the sealing techniques will further enhance the durability and reliability of radiation detection systems under various operational conditions.

To summarize, addressing EMI and corrosion is essential for accurate and reliable radiation monitoring. The solutions outlined provide a strong foundation for further advancements in detection systems, ensuring safety and operational efficiency in challenging environments.

References

• EC 60532 - "Radiation Protection Instrumentation - Installed Monitors for the Control of Radioactive Effluents," International Electrotechnical Commission, detailing standards for radiation detection systems and testing protocols.
• ANSI 42.17A - "Performance Criteria for Radiation Detection Systems Used for Homeland Security," American National Standards Institute, outlining guidelines for electromagnetic compatibility and performance standards.
• ISO 16640 - " Monitoring radioactive gases in effluents from facilities producing positron emitting radionuclides and radiopharmaceuticals," International Organization for Standardization, describing requirements for radiation monitoring in effluent gas