gamma irradiator Brookhaven National Laboratory Gamma Radiation Source Facility BNL GRSF Jack Miller The Gamma Radiation Facility known as GRSF houses a cesium-137 gamma ray source which can provide gamma rays at a variety of dose rates. The gamma source is an industry standar dJ.L. Shepherd Mark I Model 68A 137Cs ? Irradiator. The photon energy from the source is 662 keV, with a Lineal Energy Transfer (LET) in water of approximately 0.8 keV/um. (https://www.bnl.gov/nsrl/grsf/) BNL GRSF