Answer to Question #4963 Submitted to "Ask the Experts"

A 128 kV x-ray machine was recently purchased by our company for use in nondestructive analysis of mechanical parts. In particular, the users hope to take the machine to various work sites throughout the state of California and to Colorado and Florida and x ray very large items out in the field.

I am unable to find regulations or formulas that would help me determine the 2 mrem safe perimeter area around the x-ray machine (which is controlled remotely by a laptop and is no more than 12" x 18" x 12").

It has three focal spots (measured 3mm from the Beryllium output window):

8 watts, 11 roentgens/Min
16 watts, 28 R/min
39 watts, 55 R/min

How would I calculate the 2 mrem perimeter, or where might I find resources to answer this question? I am very reluctant to allow anyone to use the x-ray machine until we establish the perimeter.

The machine that you have purchased is a powerful x-ray machine and should only be operated by a trained and experienced "radiographer" who is licensed or approved by the state where the machine will be used. For example, someone holding his/her unshielded hand in the primary beam for several minutes could lose that hand due to radiation damage.

You must also register the x-ray machine as a "radiographic device" in each state that the x-ray machine will be used.

To determine the 2 mrem-per hour perimeter, which is only one of several safety perimeters required by law, you would need a calibrated air-ion chamber that has sufficient sensitivity at the lowest and the highest energies (kV or kVp) that the unit will generate.

Since each state will have different regulations for industrial x-ray machines you should review each state's regulations carefully before you try to operate the x-ray machine in that state. For example, the regulations for Texas (where I am from) are discussed on the Texas State Department of Health Services Web site.

In California contact the following radiographer trainers for more details on California's regulations:

Davis Laboratories, Inc.
Contact: James S. Davis
Brea, California
714-529-7291

Hellier Associates Pacific
Contact: G.V. Crowe
Fullerton, California
714-956-2274

Stephen M. Senne
Contact: Stephen M. Senne
Tujunga, California
818-353-5117

Test NDT
Contact: Richard A. Harrison
Brea, California
714-255-1500

Golden Gate Non-Destructive Testing
Contact: Walt L. Boteler
Livermore, California
925-606-8885

R.S. Consultants
Contact: Tom Cuthbertson
Cupertino, California
408-253-1349

Don Bosco Technical Institute
Contact: Fred J. Padilla
Rosemead, California
626-940-2000

Orange Coast Testing, Inc.
Contact: Paul R. May Jr.
Santa Ana, California
714-557-5844

These names are from California's Radiological Health Branch's Web site.

John P. Hageman, MS, CHP