The differential cross sections for elastic scattering of 14-Mev neutrons from nitrogen and oxygen were measured in the angular range from 17 to 140 deg , using liquid targets and annular ring geometry. Inelastic scattering to the 2.31 and 3.95-Mev levels in N/sup 14/ and to the levels near 6 and 7 Mev in O/sup 16/ was investigated over a more restricted angular range. The 2.31-Mev level in N/sup 14/ was not excited appreciably, in disagreement with previously reported results. For both elements, the elastic scattering cross sections (determined to an accuracy of 10%) were found to be appreciably higher than the optical model predictions by Rjorklund and Fernbach for scatterirg angles larger than 70 deg . The inelastic cross sections measured are, within experimental accuracy, the same as the corresponding (p,p') cross sections. (auth)

Effects due to elementary particle-like collisions within nuclear matter have been observed in several nuclear reactions caused by pions and protons. Simple nuclear reactions of the form ZA(a,an)Z/sup A-1/ and Z/sup A/(a,ap)(Z-1)/ sup A-1/ have excitation functions that are sensitive to changes in the elementary-particle cross sections. The excitation function for the reaction C/ sup 12/( pi /sup -/, pi /sup -/n)C/sup 11/ is measure d from 53 to 1610 Mev by bombarding targets of plastic scintillator with pions. The intensity of the pion beam is monitored with a two-counter telescope and 40 Mc scaling system. The scintillator target is mounted on a phototube and becomes the detector for the carbon-11 positron activity. Corrections are made for muon contamination in the beam, coincidence losses in the monitor system, carbon-11 activity produced by stray background at the accelerator, carbon-1l activity produced by secondaries in the target, and the efficiency of the carbon-11 detection system. The C/sup 12/( pi /sup -/, pi /sup -/n)C/sup 11/ cross sections rise to a peak of abo ut 70 mb at 190 Mev, that corresponds to the resonance in freeparticle pi /sup -/n scattering at 190 Mev. Calculations based on a knock-on'' collision mechanism and sharp-cutoff …

In May, 1961, it waa determined no renewed nuclear reaction in the SL-1 pressure vessel was possible as long as water was excluded. It was therefore possible to proceed with the final phase of the SL-1 recovery. This work consisted of moving the pressure vessel and core to the Hot Shop at the north end of the National Reactor Testing Station, dissecting and analyzing the reactor and its components, cutting up and burying the reactor building, and decontaminating the rest of the SL-1 area. These things were accomplished by the General Electric Company between May 1961 and July 1962. It was determined that the central control rod was bound in its shroud at a position corresponding to 20- inch withdrawal. Analysis of the pertinent data showed that the amount of reactivity associated with this rod position, inserted at a rate compatihie with manual withdrawal of the rod, can explain the significant evidence which was coliected. No other means of withdrawing the rod was found to be in accordance with the evidence. It was found that the relatively low yield (130 Mw-sec) nuclear excursion produced a water hammer with pressures up to 10,000 psi, which, in turn, caused the pressure vessel …