Table 4. Contribution of Element Groups to Fission Product Activity Time after test: Percent Contribution 25d lyr. 10 yrs. 20 yrs. Rare earths* 50 63 42 30 Alkaline earths 17 5.7 39 46 Noble metals 10.6 5.7 0 0 Nb, Zr* 10.0 0 0 Element Group 23 Rare gases** 5.3 0.4 2.7 2.0 Halogens** 4.8 0 0 0 Oxygenated anions 1.6 0 0) 0 17 21 Alkali metals v0 1.5 *Refractory **Not condensable 564