Wayne State University

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Science Under the Dome


Join us Friday, January 22, 2016 at 7:00pm for

If you can't stand the hot (stones), get out of the kitchen!

presented by Professor W.J. Llope

Department of Physics & Astronomy, Wayne State 

University, Detroit, MI 

Ionizing radiation, the subatomic particles with energies large enough to cause genetic mutations and potentially cancer, surrounds us. It rains on us from above, is in our food, rises into the air from the ground under our homes, and is key to many beneficial medical diagnostic and therapeutic procedures. Physicists, like myself, that smash nuclei together at high speeds are aware of and comfortable with an additional exposure beyond this natural background resulting from our research. One day a few years ago, I was asked to appear in a local TV news piece investigating a homeowner's claim that his granite kitchen countertops had killed his dogs and was thus assumed to be greatly endangering his family. This propelled me into few year hobby to understand the physics of radiation from granite countertops. Along the way, I ran into (unnecessarily) angry granite retailers, a public already overly worried about radiation risks, local and national media coverage, and several forms of subtle industrial subterfuge. At the same time, I collected a wide variety of samples of granite countertops available for sale to homeowners from random granite dealers, and then measured the radiation rates and activity concentrations of the major radioactive sources, 40-K, U-nat, and 232-Th, using a "full spectrum analysis". An anthropomorphic phantom and the "geant4" physics simulation package was used to relate the measured activity concentrations to the potential yearly direct-radiation doses to kitchen occupants. The results were published [1]. In this talk, I will share with you some of the things I learned from this hobby.

[1] W.J. Llope, "Activity concentrations and dose rates from decorative granite countertops", Journal of Environmental Radioactivity, Volume 102, Issue 6, June 2011, Pages 620-629, ISSN 0265-931X,


The Wayne State Planetarium is dedicated to the promotion of science. We are proud to feature a series of free public lectures covering modern topics in science.