Effect of chlorinating reagents on Zr recovery from Zircaloy-4 hull wastes: reaction behavior simulation by using the HSC code

Abstract

Chlorination reaction behavior of Zircaloy-4 (Zry-4) was simulated by using the HSC code for three different chlorinating reagents of Cl2, HCl, and CCl4. Four major components (Zr, Sn, Fe, and Cr) of Zry-4 and their oxides which were produced during an oxidative declad- ding process were considered for the theoretical calcula- tion. The simulation results revealed that Cl2 might convert metallic Zr, Sn, Fe, and Cr into their chloride forms, while oxides might not react with Cl2 at 380 C. When HCl was employed as the chlorinating reagent, it was suggested that metallic Zr, Sn, and Cr might react with HCl while Fe and oxides might not. In the case of CCl4, it was shown that CCl4 could react with all of the metallic and oxide com- ponents to produce most amount of ZrCl4 when compared with Cl2 and HCl cases. Reaction behavior of the chlori- nating reagents with residual spent nuclear fuel constitu- ents (U3O8, MoO3, Pd, BaO, Y2O3, SrO, Rh2O3, RhO2, La2O3, CeO2, and Nd2O3) was also performed, and it was revealed that Cl2 and HCl might produce (PdCl2, BaCl2, SrCl2, RhCl3, LaCl3, and NdCl3) and (BaCl2, YCl3, SrCl2, RhCl3, LaCl3, and NdCl3), respectively. Although these by-products are produced, it was suggested that highly pure ZrCl4(g) which contains FeCl3(g) and SnCl4(g) as impu- rities might be recovered when Cl2 or HCl is employed as a chlorinating reagent because other by-products have higher boiling point than the reaction temperature of this study (380 C). On the other hand, the theoretical calculation results showed that CCl4 might react with all the residual spent fuel constituents to produce additional gaseous impurities of UCl6 and MoCl5 to reduce the purity of ZrCl4 product.