Your IRS Electronic Filing Identification Number (EFIN) does not expire. Your IRS Preparer Tax Identification Number (PTIN) does expire every tax season. PTIN renewal occurs after October 15, and the identification number is valid through December 31 of the following year.
atomic bomb or A-bomb, weapon deriving its explosive force from the release of nuclear energy through the fission (splitting) of heavy atomic nuclei.The first atomic bomb was produced at the Los Alamos, N.Mex., laboratory and successfully tested on July 16, 1945.tomic bombs were subsequently developed by the USSR (1949; now Russia), Great Britain (1952), France (1960), and China (1964). A number of other nations, particularly India, Pakistan, Israel, and North Korea now have atomic bombs or the capability to produce them; South Africa formerly possessed a small arsenal.
Hiroshima. On August 6, 1945, a uranium fission bomb was detonated over the Japanese city of Hiroshima. The bomb, called Little Boy was a  gun-type  device which used an explosive charge to force two sub-critical masses of U-235 together.lutonium Bomb. Plutonium-239 is a fissionable isotope and can be used to make a nuclear fission bomb similar to that produced with uranium-235. The bomb which was dropped at Nagasaki was a plutonium bomb. Not enough Pu-239 exists in nature to make a major weapons supply, but it is easily produced in breeder reactors.