Radioactive waste treatment is planned in LWTF (Low-level radioactive Waste Treatment Facility, JAEA) for LLW generated from the Tokai-reprocessing facility. The target LLW consists of highly concentrated sodium nitrate (5 M NaNO_3) containing low-level ~(90)Sr. In this study, selective adsorption properties of Sr~(2+) for highly functional A type zeolites (A51-JHP, A51-J (Union Showa) and A-4, X type zeolite (F-9) and Titanic acid-PAN (polyacrylamide) were clarified by batch and column adsorption methods. The irradiation stabilities of these adsorbents were also evaluated. The distribution properties of Sr~(2+) on different adsorbents were compared in simulated waste solution (5 M NaNO_3, 0.1 ppm Sr~(2+), ~(85)Sr as tracer). The order of distribution coefficients (K_(d,Sr)) was Titanic acid-PAN ＞ A51-JHP ＞ A51-J ＞ A-4 ＞ F-9. The largest value of K_(d,Sr) for titanic acid-PAN was estimated to be 218 cm~3/g, while the saturated capacity (Q_(max)) was very small. Titanic acid-PAN had also the largest uptake rate of Sr~(2+) ions and the uptake attained equilibrium within 8 h. On the other hand, A51-JHP had a relatively large K_(d,Sr) value above 100 cm~3/g and a Q_(max) value of 0.65 mmol/g. The breakthrough properties of Sr~(2+) were examined by varying cations present (single and mixed solutions) and flow rate (0.08 and 0.17 cm~3/min). The components for the single solution were 400 g/L NaNO_3, 100 ppm Sr~(2+), ~(85)Sr as tracer, and the mixed solution contains 200 ppm Cs~+, 100 ppm Ca~(2+), 50 ppm Mg~(2+), 50 ppm RuNO~(3+) in addition to the single solution components. The breakthrough curve for Titanic acid-PAN column using single solution had an S-shaped profile, while the "concentration phenomenon" exceeding C/C_0 (breakthrough ratio)= 1 was observed in the case of mixed solution. As for the A51-JHP column, the breakthrough curve for single solution was similar to that for mixed solution and the 5% breakpoint was enhanced by decreasing the flow rate. The A51-JHP was stable under ~(60)Co-irradiation up to 2.54 MGy; K_(d,Sr) and Q_(max) values were almost constant. In contrast, Titanic acid-PAN was affected above 0.28 MGy, due to the radiolysis of PAN matrix, and this surface alteration led to the release of active component of titanic acid. The novel A type zeolite (A51-JHP) is thus expected for the selective removal of Sr~(2+) in LWTF. The optimization of particle size and flow rate should be examined before practical use.
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