Simple point defect configurations may be produced in alkali halides such as KBr by irradiation with X-rays at temperatures attainable with liquid helium. An understanding of their thermal stability aids in the interpretation of the mechanisms of radiation damage. Experiments are discussed in which the stability of single negative ion vacancy-interstitial pairs are examined as a function of temperature and the presence of impurities in the KBr lattice. The order of the annealing processes indicates that the first three stages in pure KBr are correlated recombinations between the vacancies and interstitials and a fourth stage, the recombination of more distant defect pairs through a free migration of an interstitialcy. The presence of a Cl⁻ impurity in KBr stabilizes the X-ray produced defects and arguments are advanced to show that this is the result of the substitution of Cl⁻ interstitials for Br⁻interstitials as a result of the radiation damage process. These ideas are applied to the formation processes of di-negative ion vacancy centers, and an apparent discrepancy between simple geometrical probability arguments and experiment is resolved.