The yield of 49, the efficiency of production of 49, and poisoning in a power plant are discussed. Only the crudest of estimates of the poisoning are possible: these indicated that production will probably not be hampered by poisoning. In this case the yield of 49 could be as high as 3 kg/ton but only about 2 kg/ton is compatible with a fairly high efficiency. In the case that production is stopped by poisoning, smaller yields, proportional to the tolerable loss in k, are obtained. In this case the yield will be improved by a factor of 2 or 3 if only the most poisoned parts are extracted and replaced by new uranium.