of fission recoil fragments. The thermal neutron dose during irradiation was monitored using high purity cobalt wire, and energy deposition (extending to t5 x lo?' e.v. per g. of solution) was calculated assuming 1 G O Nev. of recoil energy released per fission event,? and a thermal neutroii fission cross-section for U23j of 5SO barns.3 The main products were hydrogen, oxygen and nitrogen, with smaller amounts of carbon dioxide, and, in the case of concentrated nitrate solutions, nitrous oxide. 'Ol.'ith more dilute solutions, precipitation of some GO4 during irradiation was encountered. -1s this phenomenon would have introduced uncertainty into energy deposition data, it was prevented by adding about 100 p.p.in. of iron as ferric nitrate to the solutions ; this presumably catalyzed the deposition of H 2 0 2sufficiently to prevent peroxide precipitation. N o peroxide and only traces of nitrite were found in solution after irradiation. h plot of GII? us. (XO3-)'/a is linear, and obeys an equation of the type GR?= A - k ( S 0 3 - ) " 3 , (1)whereA = 2.0andk = 0.8: theGH,dataof Bovle solutions and Mahlman for Th(SOJI-U23J02(S03)2 also lie on this line. The results can therefore be explained qualitatively in terms of a theory1 involving reaction of diffusing H atonis with pI;O3-: NOJH + NO? OH- (a),where the parameter k is a measure of the probability of reaction (a). Values of Gx, are more than an order of magnitude greater than those obtained for fast neutron-y energy. Figure 1 shows a log-log plot of
+
+
respond to temperatures ranging from 37' to 300'; temperature has therefore no significant effect on GN?. Below a nitrate concentration of about 4 U , nitrogcn yields can be evpressed by the empirical relationship Gx, = 0.004(N03-)1.5 ( 3 ) , though nothing can be
