the temperature dependent precipitatable borates of such waste solution soluble in the ambient temperature range a second primary aspect of the invention relates to the disposal of the bottoms i e evaporator bottoms or other bottoms generated in the cleanup of the reactor cooling waters prior to recirculation to the reactor the method as practiced with regard to this special application utilizes the combined and advantageous steps of adding to the waste solution one or more bases of the defined group in an amount effective to produce soluble borates in the ambient temperature range and cooling such wastes to a temperature within the ambient temperature range prior to or in conjunction with admixing of the waste in a liquid binder material which binder material is solidifiable for producing a solid binder waste matrix the order of such steps is not necessarily critical since as the examples below demonstrate that the additives specified herein can effectively return the precipitate to solution such as where precipitation has occurred prematurely high borate content radioactive wastes as are particularly the subject of the invention characteristically contain from between about 5 to about 12 weight percent borate solids content extremely high borate content waste solutions as contemplated within the broad definition of the invention however may contain as much as about 50 percent by weight borate solids the effective amount of additives to treat such waste solutions in any given case is determined experimentally based on a given additive and specific waste solution depending on the exact content of any such given waste solution the effective amount necessary to produce water soluble borate salts within the defined ambient temperature range can vary in addition.