The Uranium Mystery, by Mary Adrian (epub/Kindle/pdf)
The Frontier Motel was the pride and joy of the Price family, especially David, aged twelve, who helped to run it. In three years they would own it, free and clear of debt, so David was willing to work hard taking care of the place and serving in their little restaurant. He had spare time, though, which he spent with his friends, Laurie and Johnny Smith, looking for uranium. His father had taught him a good deal about radioactivity and minerals and there was always a chance that he might find a deposit with his Geiger counter and help the family fortunes.
Miss Adrian’s latest mystery has this intriguing background and as usual her plot has satisfying speed coupled with interesting scientific facts which youngsters of today can easily absorb as they read swiftly along.