Developed by Los Alamos National Laboratory, PBX-9502 is an insensitive high explosive (IHE) in new and retrofitted nuclear weapons, including B61 Mods 3, 4, 6-10 bomb; W-61; W80 cruise missile warhead, W85 warhead for the Pershing II, W90 warhead for the AGM-131A SRAM II and W91 warhead for the AGM-131B SRAM-T.
It is a plastic bonded explosive composed of 95% TATB explosive and 5% Kel-F binder; the alternative IHE in U.S. weapons is LX-17, developed by Lawrence Livermore National Laboratory. It replaced PBX-9504 when that was found to have stability problems.
Use of this explosive is not unique to nuclear weapons. It is a booster in the U.S. Air Force demonstration of modified Mark 82 general-purpose bomb that meets the criteria for an Insensitive Munition. 
- John D. Corley, Gary H. Parsons, Alan C. Stewart, Fuzed Insensitive General Purpose Bomb Containing AFX-645