Jefferson Lab > EH&S > RadCon
Privacy and Security Notice

Site Postings

North and South Linacs

In order to convey status and entry requirement changes on the accelerator site, as part of the 12 GeV commissioning, the status and entry requirements of many service buildings on the accelerator site have changed. The Linac and most other service buildings will now be posted as Radiologically Controlled Areas (RCA) at all times.  Only Radiation Workers are allowed unescorted access to these buildings.  In addition, during beam operations, the buildings will be upgraded to Radiation Areas.  Access to the buildings under these conditions requires briefing, signing, and supplemental dosimetry associated with a new standing Radiation Work Permit (RWP).  Convertible "flip signs" at access points to these buildings will be flipped to display the Radiation Area posting when the machine is in beam permit.  All work in these areas during beam operations will be governed by Standing RWP 2014-S017.  When posted as Radiation Areas, contact the Crew Chief for access to these areas. SOTRs are responsible for communicating these new requirements to contractors.

      Experimental Halls

Portions of Hall B are typically posted as Radiological Areas. To enter any beam enclosure you must also review and sign in on the General Access RWP for the beam enclosure. This RWP can be found online at  

Experimental halls A and C contain equipment which continuously monitors for airborne radioactivity. As this monitoring is implemented, you will notice postings, lights, or lighted signs accompanying these Continuous Air Monitors (CAMs). The sign will state that when the beacon on the CAM is activated, the hall is considered an Airborne Radioactivity Area.

Just as we are required to post Radiological Areas at predetermined levels, these postings are required by Federal Law when the airborne radioactivity reaches a specified level. The level requiring the posting equates to an external radiation dose rate of about 2.5 milirem/hour. This radioactivity is in a gaseous state, and is not retained in the lungs or body as in the case of particulates or dust. Therefore, entry to the hall when the CAM indicates a level above the setpoint does not require any special controls such as respiratory protection equipment. In addition, your dosimeter is effective in monitoring your dose from this source. The CAMs may trigger this "alert" state during normal beam operations in the hall. Due to the very short half-life of the gases formed, the monitor alert should clear within a few minutes of termination of beam to the hall. However, during a controlled access there is no requirement to wait for the CAM to 'clear'. These indicators and signs are there to inform personnel of conditions, not as an emergency or evacuation alarm. Any "Alert" conditions noted during Restricted Access should be promptly reported to the Crew Chief or RCD. If you have any questions regarding these or any radiological posting, contact an RCD representative.


All radworkers who frequent the beam enclosure are encouraged to review the General Access RWP periodically. Copies of the permit are posted at enclosure entrances. A revised permit is issued at least once each year. You will need to review the permit and sign it electronically after each annual revision. We will post reminders when the new permit is issued.

Don't forget to store your dosimeter in the proper rack when not wearing it. If you would like to change your dosimeter storage location, please send an email to Becky Mosbrucker  at or call at 269-7236.  We ask that all radworkers leave their dosimeters in the racks on scheduled dosimeter changeout dates unless specifically needed to enter Radiological Areas. If you work "on shift", make sure you place the dosimeter in the rack following your shift. Dosimeters are collected at each rack several times over the course of the changeout period.

Your cooperation and attention to proper dosimetry handling procedures is important to the overall quality and accuracy of the dosimeter results. If your dosimeter is not available for collection during the changeout, it increases the probability for errors or potential loss of the exposure data. Please help us provide the best quality dosimetry service possible by following proper dosimeter use and storage procedures. Any questions, please contact Becky Mosbrucker at or call at 269-7236.