Kenneth G. Wilson (1923). The Columbia Guide to Standard American English. 1993.
unrepairable, irreparable (adjs.)
Both are Standard meaning not repairable, but irreparable (pronounced ir-REP-uhr-uh-bul) is much the more frequently used. Note its spelling: irrepairable is a misspelling. Unrepairable is pronounced uhn-ree-PER-uh-bul. See also INCOMPARABLE.