Hidematsu Ikeda

Experimental verification of photostability for free- and bound-amino acids exposed to γ-rays and UV irradiation

The photo-stability of simulated free and bound amino acids exposed to photon sources of 1.2–1.3 MeV γ-rays from a 60C° source and ultra-violet (UV) irradiation from a 10 eV deuterium lamp was examined. The free amino acids in aqueous solution were drastically decreased while the bound amino acids in aqueous solution were slightly decreased with the duration of γ-rays and UV irradiation. The apparent half-lives (t1/2) of bound serine and threonine under γ-rays irradiation were more than 10.6 and 27.9 times as stable as the free amino acids, respectively. The photo-stability of bound amino acids was greater than that of free amino acids under irradiation by high-energy photons. These results strongly suggest that bound, but not free, amino acids could be found in extraterrestrial environments. Radio- or photo-alteration processes are mainly decomposition pathways, with the production of secondary amino acids via decomposition of the α-carboxylic group; β-alanine and γ-aminobutyric acids, α-decarboxylation products of aspartic acid and glutamic acid, respectively, were detected.

Radiolysis of n-dodecane and its physical property change based on the dose in one pass through a reference HA column

The radiolysis of n-dodecane which is used both as diluent and as scrub solution and its physical property change were studied by irradiation from a 60Co γ-source under the relative condition of the HA column in Purex process. First, the radiation exposure of organic phase in one pass through the HA columns were calculated by using the reference HA columns. Then, the radiolysis of the commercial n-dodecane without purification was investigated under the several dose conditions based on the absorption in one pass through the reference HA columns. A large variety of additional n-alkane degradation products was observed and they were increased with dose. The G-value in lower exposure was a high yield, and the absolute G-value decreased with increasing radiation exposure to 1.01 W·h/l. Several expected inferable species from previous literature and three schemes for both principal radiolysis products and reaction of n-dodecane were suggested. These chemical products were probably formed in open system with ga...

Empirical Correlations for Radiolytic Degradation of n-Dodecane Density, Viscosity and Phase Separation Time

The n-dodecane is usually used not only as a diluent of tri-n-butyl phosphate (TBP) but also as a cleaner of degraded TBP. Fresh dodecane is used to recover the organic fragments from the product streams in the TBP scrubbers of Purex system. The raffinate from the high active (HA) column in Purex system is also scrubbed with fresh dodecane. The degradation products affect the decontamination of fission products, the retention of plutonium in the organic phase, the interfacial crud formation, and the phase separation time. The effects of radiation exposure on decompositions of liquid system in Purex syatem have been investigated since early 1950s, 1) and basic data for application of TBP involved radiolysis were reviewed by Schulzet al.2) Several reports on Purex liquid degradation by the wet method are devoted mainly to studies of TBP degradation products. 1–8) A process simulation code to calculate of the amount of din butyl phosphate (DBP) in Purex system was reported by Tsukada and Takahashi. 9)

Safety Design of Purex Liquids System The Flash and Fire Points

The n-dodecane is usually used not only as a diluent of trin-butyl phosphate (TBP) but also as a cleaner of degraded TBP. Fresh dodecane is used to recover the organic fragments from the product streams in the TBP scrubbers of Purex system. The raffinate from a high active (HA) column in Purex system is also scrubbed with fresh dodecane. The 30 vol%TBP/dodecane is used as the major actinides extractant by all scenes in the Purex system, while 80 vol%TBP/ dodecane is used as the washing solution to recycle the solvent for re-use in the degraded solvent scrubber. Both n-dodecane and TBP are classified into the third oils of the fourth category (4-III oils) in the Japanese Fire Service Law. Such solvents classified into this group are inflammable liquids, and their flash points ranged from 70 to less than 200 C. The handling notes and the stock volume have been defined in this regulation law. The allowed stock volume of the solvents in this class is 2,000 l as water non-soluble liquids. If they are soluble in water, their allowed stock become twice. However, n-dodecane and TBP are not soluble in water. Kerosene is also used as a diluent of TBP besides n-dodecane. Its classification is the second oils (4-II oils) though it is of the same category as n-dodecane. Solvents classified into this group are inflammable liquids, and their flash points ranged from 21 to less than 70 C. Kerosene with low flash point is included here, and it is also not soluble in water. The allowed stock volume of the solvents in this class is 1,000 l as non-soluble liquids. If they are soluble in water, their allowed stock become twice. For the above reasons, we do not worry to the stock volume of the solvent used in the laboratory and facilities, if kerosene is not used as a diluent of TBP. This is because a combination of dodecane and TBP of any mixture ratio is restricted as the 4-III oils in the Japanese Fire Service Law. There were not studies in the past by the relation to the Japanese Fire Service Law for the stock volume of both the mixture solvent and its radiolytic degraded solvent used in Purex process. The degradation products affect the decontamination of fission products, the retention of plutonium in the organic phase, the interfacial crud formation, and the phase separation time. The effects of radiation exposure on decompositions of liquid system in Purex process have been investigated since early 1950s, and basic data for application of TBP involved radiolysis were reviewed by Schulz et al. Several reports on Purex liquid degradation by the wet method are mainly devoted to studies of TBP degradation products. Although these previous studies proposed many useful data for analysis of degradation process in Purex liquid system, basic data of the flash point and the fire point for the Purex solvent used in facilities are still insufficient. In the present work, we report basic data of the flash point and the fire point for Purex solvent. Both the fresh solvent and the degraded solvent were used for this purpose. The latter was obtained by irradiation from a Co -source under the relative condition of HA column in Purex system. Data of the flash point and of the fire point obtained through this work are useful for the safety design of the stock volume of Purex solvent in storage. The stock volume of dangerous chemicals is regulated by the Japanese Fire Service Law.

Two‐color resonance ionization spectroscopy of autoionization states of Pb

Two‐color resonance ionization spectroscopy was performed to observe even parity autoionization states. Following Rydberg series converging to the second ionization limit, we determined the second ionization limit 6s26p 2P3/20 as 73899.5 cm−1.

Finite time settling control of pulsed columns

An application of a modern control to a pulsed column is considered. Experimentally, a finite time settling control (FTSC) with finite time settling observer (FTSO) algorithms as a modern control scheme for a single-loop controller of pulsed columns was selected. The FTSC with FTSO algorithms in this study was based on the step response pattern such as the dynamic behavior for the transfer function. The control objective was to keep the solute concentration in the product stream. First, the control system was designed from the measurement data of a step response using 30% tri-n-butyl phosphate in a kerosene-acetic acid-water system. Then, the control algorithms were applied to the Purex liquid system using the published experimental data of uranium concentration during a transient operation. The controllabilities of pulsed columns are discussed in the direct digital control simulation studies.