Answer to Question #11555 Submitted to "Ask the Experts"

Category: Instrumentation and Measurements — Instrument Calibration (IC)

The following question was answered by an expert in the appropriate field:


Is Pylon 1025 (Pylon Electronics Inc.) considered a sealed source or unsealed source?


While the Pylon source that you cite is designed to allow radon-222 (222Rn) gas to escape for use in controlled studies, the radium-226 (226Ra) precursor is in the form of a dry preparation that is contained in an encapsulation intended to prevent the leakage of the radium from the encapsulation. In this sense, the source meets the condition described by the U.S. Nuclear Regulatory Commission (NRC) in 10 CFR 30.4 (see, which states "Sealed source means any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material." There are instances in which NRC-issued licenses list these specific Pylon sources as sealed sources; here is a link to one such.

As a result of changes to regulations brought about by the Energy Policy Act, sources of 226Ra described as discrete sources (whose activity has been enhanced by concentration techniques to make the material useful in various applications) may be considered byproduct material and thus fall under the regulatory oversight of the U.S. NRC (except in NRC agreement states).

One consideration that should be noted is that if the source contains less than 3.7 × 105 becquerels (Bq) of 226Ra, it is not likely to be subject to leak testing that would otherwise be required (see 10 CFR 35.67f at Similar exclusions would be expected to apply in U.S. NRC agreement states.

George Chabot, PhD

Answer posted on 4 April 2016. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.