Immobilisation of Higher Activity Wastes from Nuclear Reactor Production of ⁹⁹Mo

Table 4

Leach rates for the HIPed sample shown in Figure 4. MCC-1 replacement test 0-1 and 1–7 day periods, 90°C, deionised water. Data from earlier work (0–7 days) [4] are also given; note that after the 7 d leach period the leach rates drop to less than or close to the detection limit for all elements.

Route	Normalised release rate (g⋅m^−2⋅d^−1)
	Latest data			Preliminary pyrochlore-rich work^# [4] small-scale
	Kneader dried			Alkoxide-route			Microsphere
Waste loading	40 wt%	40 wt%	25 wt%	35 wt%	40 wt%	44 wt%	40
Leach period	0-1 d	1–7 d	0–7	0–7	0–7	0–7	0–7
Al	<DL	<DL	<0.01	0.05	<0.02	nm	0.05–0.3
Ba	0.65	0.11	0.04–0.1	0.005	<0.004	0.02	0.003–0.08
Ca	0.12	0.03	<0.01	0.01	0.02	nm	0.006–0.4
Cs	np	np	0.03–1	0.08	nm	0.10–0.13	0.2–7.3
Sr	np	np	0.04–1.4	0.08	0.03	0.08–0.12	0.04–0.3
Ti	0.005	0.00017	<0.01	<0.0001	<0.0001	<0.0001	<0.0001
U	0.008	0.0006	<0.01	<0.0001	<0.0001	<0.0001	<0.0001
Zr	0.010	0.0002	<0.01	<0.0001	<0.0001	<0.0001	<0.0001

Nm: not measured; np: not present.
#Note: data are varied because several different routes that produced differing degrees of homogeneity and some different processing conditions were tested. In addition variations in the waste composition were also tested. Only in a few samples where the redox was not controlled or the sample was inhomogeneous did the Cs and Ba leach rates increase. In all cases the U-leach rates remained low.