A two and one-half year period of extreme caution where titanium and nitric acid are involved has passed since the occurrence of the last and most serious uncontrolled incident involving titanium and nitric acid. During this period controlled explosions involving titanium and nitric acid have been routinely reproduced, additional laboratory and pilot plant experience has been gained and successful industrial applications have been appraised. Based on laboratory data and the known industrial experiences, it is concluded that titanium can be safely employed in systems handling nitric acid that contains more than two (2) percent water. It is recommended that the titanium heat exchanger recently fabricated by the Technical Shops be installed in the Purex Plant plutonium concentrator when replacement of the stainless steel unit now in service becomes necessary.

The introduction of aluminum in hot process water has been studied extensively and numerous reports have been issued on the subject. The conclusions reached have been largely empirical and can only be used to state what is happening under the given conditions existing in the corrosion experiments. It is only with difficulty and a great deal of uncertainty that these empirical results can be used to predict what will occur under a different set of conditions. If the fundamental mechanism of aluminum corrosion in water were known, it is possible that more accurate predictions could be made and that steps might be taken to affect the controlling factors and thus reduce the severity of corrosion. To keep the system as simple as possible one would attempt to study the corrosion mechanism by corroding aluminum in pure water. However, this is undesirable because of the extremely low corrosion rate of aluminum in pure water and the large water supply and treatment facility required to supply sufficient high purity water for circulation about the corrosion samples.

The stability of fluorothene (polytrifluorochloroethylene, Kel-F) to gamma radiation has been investigated to estimate the probable life expectancy of fluorothene equipment exposed to Purex process solutions. Samples of fluorothene were exposed to total gamma radiation dosages up to 10 degree R. The results of these tests substantiate the findings reported by Sisman and Bopp in their compilation of data on the affects of radiation on plastics.

This paper discusses technical bases, operating standards, and instrumentation systems required to achieve the goal of nuclear safety in operation of high-level reactors. Because of the relatively long neutron lifetime in a thermal reactor and the comparatively modest time rates of reactivity change associated with fission poison and temperature effects, the rod system used for compensating reactivity transients and for maintaining flux distribution control may be operated manually. Manual operation of the reactor and the prediction of pile reactivity statue during outages of course involve factors of human error, normal reaction time, and judgment. It is the aim to specify procedures for the operation such that manual control of the reactor may be adequately maintained at all times within the range of reasonably expected calculational errors and human reaction times. The technical considerations used in developing these standards, including the available monitoring indications are discussed first; then the automatic trip devices which should back up the procedures are also mentioned.

At the request of F. W. Albaugh of the Engineering Department, the corrosive effect of 1% uranium nitrate hexahydrate solution on aluminum at 100 C has been measured. The corrosion of aluminum in uranium nitrate solution has been shown in laboratory tests to be too severe to permit the use of aluminum for containing hot uranium nitrate solutions. A minimum corrosion penetration rate of 2 mils per day was observed with M-329 aluminum in 1% uranium nitrate hexahydrate in pH 2 aqueous solution at 100 C.