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D5928-23 – Standard Test Method Technical Guide
📋 Practice Overview and Scope
This practice, designated D5928-23, provides a method for gross screening of waste materials for radioactivity. It covers α–, β–, and γ radiation above ambient background levels or user-defined criteria. The practice is applicable to liquid, sludge, or solid waste. It is intended for facilities that are prohibited from handling radioactive waste, serving as a rapid verification tool to check generator-supplied information and meet worker health and safety needs. It is not a substitute for more sophisticated quantitative analytical techniques.
🔬 Screening Procedure and Criteria
The procedure involves holding a waste sample at a user-specified distance from the detector window of a radiation survey meter. The distance is typically guided by the manufacturer’s instrument manual. The user defines application-specific negative and positive result criteria based on background radiation and intended use. A negative test result indicates radiation levels are below the established criteria, while a positive result indicates levels are above. This method allows for quick assessment of waste for radiation presence, ensuring compliance with facility restrictions.
| 🟦 Interference Source | 📏 Type | 🎯 Impact on Screening |
|---|---|---|
| Pacemakers | Medical Device | Can cause false positive results |
| X-ray generating equipment | Industrial/Medical | Produces ionizing radiation interference |
| Radium-based luminescent dials | Consumer Product | May indicate positive due to radium content |
| Polonium-based static eliminators | Industrial Device | Potential source of interference |
| Smoke detectors (radioactive) | Safety Device | Contains radioactive isotope; may cause positive |
| Large amount of potassium (K-40) | Natural Element | Naturally radioactive; can produce positive result |
⚠️ Interferences and Safety Considerations
Several sources can interfere with the screening results, including naturally occurring background radiation, medical devices, and industrial equipment. It is essential to periodically assess ambient background radiation levels to account for these interferences. Additionally, items like pacemakers, X-ray generators, radium dials, polonium eliminators, and smoke detectors with radioactive isotopes could cause positive results. Large amounts of potassium in waste may also contribute to positive readings due to the natural presence of potassium-40. Using the portable instrument specified in this practice can usually trace these interferences to their source.
⚠️ Warning: Naturally occurring background radiation can cause needle deflections or audible clicks on the survey meter. Always assess ambient background levels before screening to ensure accurate and reliable results.
💡 Tip: For best results, follow the manufacturer’s guidance on the appropriate sample-to-detector distance. Define clear negative and positive criteria based on your application requirements.
❓ Frequently Asked Questions
🔍 Question 1: What is the primary purpose of practice D5928-23?
This practice provides a gross screening method for detecting radioactivity in waste materials above ambient background or user-defined criteria. It is designed for facilities that cannot handle radioactive waste, helping them verify the absence of such materials quickly.
💡 Question 2: How is a positive result defined in this practice?
A positive test result indicates that the radiation levels from the sample are above the user-established criteria. This suggests the presence of radioactive materials above the specified threshold.
⚡ Question 3: What are common inter