Answer to Question #13006 Submitted to "Ask the Experts"

How should I check radiation in mineral baryte?

I will state up front that among the most common and suitable instruments that would be appropriate for measuring the radiations that might be expected from this material is one that incorporates a thin-window Geiger Mueller (GM) detector.

As you likely know, the mineral baryte, also known as barite, represents the compound barium sulfate, BaSO₄, sometimes containing other contaminating elements such as strontium, calcium, cerium, lead, and others. Among the others is radium, a naturally occurring radionuclide resulting from the decay of uranium in the earth. Most significant is ²²⁶Ra, which has a half-life of about 1,600 years. Radium, like barium, is an alkaline earth compound and forms similar compounds, including the radium analog of baryte, RaSO₄, which can be found in co-formation with the BaSO₄, often within the same crystalline lattice. The ²²⁶Ra is radioactive and decays primarily by alpha emission; its decay leads to a series of radioactive progeny with ²¹⁴Pb and ²¹⁴Bi being the most notable short-lived radionuclides that emit radiations subject to easy detection. Through further decay, longer-lived ²¹⁰Pb and its shorter-lived daughter ²¹⁰Bi are produced. Other radionuclides are also present in the decay chain of ²²⁶Ra, eventually to stable ²⁰⁶Pb; the ²¹⁴Pb, ²¹⁴Bi, and ²¹⁰Bi are perhaps most significant because they emit beta radiation, which may be detectable with an appropriate detector. The ²¹⁴Pb and ²¹⁴Bi are also the most significant gamma emitters in the decay series, and some of this gamma radiation may also be detectable. In theory, one could also use a thin window GM detector to detect alpha radiation but, even though several radionuclides in the radium decay chain emit alpha particles, these have very low penetrating power, and few would escape from the surface of the baryte material.

There are quite a few vendors of GM instruments. You can find some by searching the internet for Geiger-Mueller instruments. Prices vary, from less than $150 to more than $1,000, but you will likely have to spend at least several hundred dollars to obtain an acceptable instrument capable of measuring the different radiations emitted from the baryte. There are many cheaper ones, but I cannot vouch for their suitability; many of these lower cost instruments have little or no sensitivity to beta and alpha radiation.  Among those I would recommend are thin window (usually 2 to 3 mg cm^-2 density thickness) pancake-type detectors, usually cylindrical in shape with about 3.5 to 5 cm in diameter and 1 to 2 cm deep. Other thin end-window types would also be suitable. The thin window is advantageous to provide maximum sensitivity for low penetrating radiation such as beta radiation and even alpha radiation. Here are a couple of examples of instruments that have been fairly popular. The Gamma-Scout, is an instrument that has found appreciable use among people not necessarily concerned with radiation in their occupations but interested for other reasons; it has the thin window detector contained within the case but accessible to low penetrating radiation through openings in the back side of the instrument. You can probably find this and similar instruments selling for roughly $350 to $600 in the marketplace. Ludlum Instruments, is a company that provides a large variety of radiation detection and measuring instruments, especially to professionals concerned with radiation measurement and radiation protection. The link shows a picture of a commonly used thin window GM detector probe that is used in conjunction with a suitable ratemeter, such as the Model 3. The detector and ratemeter are listed at $288 and $645, respectively. The specific instruments referred to here are intended only to provide examples of some of the many available instruments and are not intended to represent specific recommendations by either this responder or by the Health Physics Society.

I wish you well in your mineral investigations.

George Chabot, PhD, CHP