John Leonard Yarnell, a resident of Los Alamos, NM passed away peacefully on Friday March 10, 2017. He was born in 1922 in Topeka, Kansas to his parents Ray and Ruth Yarnell. He attended the University of Kansas and the University of Minnesota, attaining a PHD in Physics. In the middle of his college career, he served in the US Army Signal Core during World War 2. While at the University of Minnesota, he met and married his wife Hazel. He accepted a job at the Los Alamos National Labs, and he and Hazel moved there in 1952 where they remained as they raised their four children. He and his colleagues at the Labs designed, built and operated the Omega West Nuclear Reactor for 36 years doing research and making isotopes for medical use. In 1981, after 29 years at the Labs, John decided to retire and move on to new adventures. He enjoyed many things including reading, photography, camping, being a pistol marksman, and traveling. He traveled extensively and was able to visit all 7 continents along the way. He and Hazel bought a cabin near Chama, NM in 1975, where family and friends spent many relaxing weekends. He was a kind, caring and loving husband, father and friend. He was preceded in death by his wife Hazel. He is survived by his four children and their families: Barbara Yarnell in Los Alamos, NM with her son Eric Barsness, his wife Kelli and their children Kaiya and Keelan in Kauai Hawaii; Tom Yarnell in Boulder, CO with his wife Vivian and their children Lindsey and Katie; Ann Yarnell in Los Alamos, NM; and Martha Yarnell in Albuquerque, NM. Personal comments for the family can be entered online at www.devargasfuneral.com. A Memorial service and reception will be held on Saturday, March 25, 2017, at 11:00 a.m. at Bethlehem Lutheran Church in Los Alamos, 2390 North Road, Los Alamos, NM. The family of John Leonard Yarnell has entrusted their loved one to the DeVargas Funeral Home & Crematory of the Espanola Valley, 505-747-7477 www.devargasfuneral.com