Instrument Testing for Radiation Detection Systems

As part of the building 245 modernization project, NIST has built a new facility designed to allow the testing of small radiation detection instruments, such as radionuclide identification devices or personal radiation detectors, very large systems like radiation portal monitors, and other types of detectors in between. This facility is equipped with a linear motion system (LMS) composed of 2 tracks (i.e., high-speed, and heavy-load tracks) that were design to allow for the testing described in IEEE and IEC performance standards (e.g., IEEE N42.34, IEEE N42.35, IEC 62401, IEC 62694) covering these types of instruments. The LMS can move bare or shielded radioactive sources along a 16 m long track and can hold a constant speed for a length of 8 m in the middle section of the track that is equipped with speed sensors at 1 m intervals along the track to ensure a constant speed. The system also allows for static measurements by stopping the source at any location on the track for an extended period (up to 30 min). The system is computer controlled and the parameters used in the measurements are logged in a database. The high-speed track can operate at speeds from 0.01 m/s to 18 m/s, depending on the weight of the load, at heights from ground level up to 5 m above the ground. It can move loads less than 7 kg at speeds from 0.01 m/s to 18 m/s and loads up to 15 kg at speeds from 0.01 m/s to 3 m/s. The heavy-load track can move a load of up to 225 kg at speeds from 0.01 m/s to 2.5 m/s and can be synchronized with the high-speed track in time or position along the track. The facility is equipped with radioactive sources, source holders, source shielding materials, phantoms, stands, and video cameras required for testing of radiation detection instruments.

Testing of radiation detection instruments is a critical component to ensure that users of radiation detection instruments are selecting the appropriate instruments to be deployed at the different required locations. Some of the uses for this type of facility includes, for example, testing instrument used for:

• homeland security and detection of illicit trafficking of radioactive materials,
• to secure cities and major event venues,
• to response and recover from a radiological event,
• measurements at laboratories, nuclear facilities, or other facilities where radiation is measured and/or monitored.

NIST recently carried out a test for the Federal Emergency Management Agency (FEMA) for relocatable radiation portal monitors and handheld instruments for detection of alpha, beta, and gamma radiation. The test was designed to characterize the instruments’ response to several radioactive sources with different activities and surface areas as a function of source speed, source to detector distance and source height (the change is height only applied for the radiation portal monitors). These measurements were performed to allow for the update and expansion of the FEMA-REP-22 and FEMA-REP-21 documents for FEMA-Radiological Emergency Preparedness