Patent Number: 046577319
Section: description

EXAMPLE A column capable of containing ion exchange resins is connected to the primary circuit of a pressurized water reactor such that a portion of the reactor coolant exiting from the heat exchanger-boiler will flow downwardly through any ion exchange resin contained by said column. A mixed resin bed comprising 40 volume parts of a strong base resin and 60 volume parts of a highly cross-linked, macroporous, strong acid resin is added to the column. The strong acid resin is the sulfonated derivative, in H.sup.+ form, of a highly cross-linked, macroporous copolymer derived from 80 percent styrene and 20 percent divinylbenzene. The reactor coolant is flowed downwardly through this mixed resin bed at a rate of 50 BVs based on the volume of strong acid resin, per hour. The concentration of the radioactive isotopes in the reactor coolant as it enters the column and as it exits from the column, following ion exchange treatment, are measured using conventional gamma spectrometry techniques. Curve A in the Figure represents the exceptional performance obtained using the mixed resin bed comprising the highly cross-linked, macroporous strong acid resin to purify the reactor coolant. Specifically, the number of bed volumes, based on the volume of the strong acid resin, of reactor coolant passing through the mixed resin bed prior to any leakage of the cesium (i.e., prior to the coolant exiting from the column containing the mixed resin bed is found to contain a measurable amount of cesium isotopes) is measured to be 38,000. Of greater importance, 95,000 bed volumes, based on the volume of the strong acid resin, of the reactor coolant pass through the mixed resin bed prior to reaching a cesium decontamination factor of 2 wherein the cesium decontamination factor is defined as the ratio of cesium in the reactor coolant entering the ion exchange column to the amount of cesium in the reactor coolant exiting from the column. Alternatively, as indicated by Curve B in the Figure, using the same techniques except employing a mixed resin bed comprising an identical strong base resin but a macroporous, strong acid resin derived from 88 percent styrene and only 12 percent divinylbenzene, only 47,000 bed volumes of the reactor coolant, based on the volumes of strong acid resin, pass through the mixed resin bed prior to obtaining a decontamination factor of 2. Alternatively, only 30,000 bed volumes of the reactor coolant pass through an identical mixed resin bed except comprising, as the strong base resin, a gel, strong acid resin derived from 92 percent styrene and 8 percent divinylbenzene prior to reaching a decontamination factor of 2. (See, Curve C of the FIGURE). Moreover, initial leakage of cesium occurs much sooner using these mixed resin beds to purify the reactor coolant than when the mixed resin bed comprising the highly cross-linked, macroporous, cation exchange resin is employed for said purification. As evidenced by these results, the results of the purification of the reactor coolant using mixed resin bed of the present invention which comprises a highly cross-linked, macroporous, strong acid resin is surprisingly superior to the results obtained in the purification of the reactor coolant using a mixed resin bed comprising a more lightly cross-linked, strong base resin, of the gel or macroporous type.