Answer to Question #8626 Submitted to "Ask the Experts"

Category: Accelerators

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


What protocols or guidance are appropriate for operational checks of safety equipment (e.g., interlock testing, warning lights, etc.) for electronic devices that produce ionizing radiation? The question arises because of bench-top units that could be damaged by improper ramping up or shutting off the high voltage or from devices that generate soft x rays that are difficult to detect with standard radiation-detection equipment.


Depending on the institution where you are working, you may be under a Department of Energy or Nuclear Regulatory Commission regulation, and the state regulations if you are not in an agreement state. The following standards and reports provide information on the protocol that should be followed for testing radiation-generating safety devices.

Please note that if you are producing x rays with energies higher than 10 keV, there are radiation detectors on the market that can give you a dose-rate reading, which would be needed for the level of safety program that you may need to implement.

For the safety interlocks that cannot be tested every time before use, for example, at large accelerators or the device that you are concerned with, the general consensus is that your radiation safety interlocks have to be tested biannually. Of course you will need to come up with a test procedure that will test the interlock safety devices without damaging the devices they are trying to protect. The procedure has to be reviewed and approved by a system expert to demonstrate that you are adequately testing all the aspects of the radiation safety interlock system. The testing procedure should be acceptable by whatever regulatory agency your institution/laboratory/company is required to comply with.

The following standards can provide guidance for the tabletop nonmedical devices:

  • ANSI N43.3-2008, American National Standard for General Radiation Safety - Installations Using Non-Medical X-Ray and Sealed Gamma-Ray Sources, Energies Up to 10 MeV (available for free from the Health Physics Society.
  • Radiation Alarm and Access Control Systems, NCRP Report 88, National Council on Radiation Protection and Measurements, Washington, DC; 1986.
  • DOE guidance DOE G 441.1-5, with details of program/protocol to control such devices.

The following references are also useful for the radiation safety interlocks:

John E. Anderson, Fermilab AD Safety Department Head

Kamran Vaziri, PhD


Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 4 November 2009. 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.