Radiation Treatment of Exhaust Gases, (X)

Effects of NH₃, NO, NO₂ and SO₂ on the N₂O formation were studied in the mixtures of H₂O, O₂ and N₂ irradiated with electron beams of 1.5 MeV energy. In the H₂O-O₂-N₂ mixture, the N₂O formation was enhanced markedly by addition of a small amount of NH₃. This enhancement may be brought about by the reaction of NH₃ with OH radical to form NH₂ radical leading to the formation of N₂O. In the NH₃-H₂O-O₂-N₂ mixture, the formation of N₂O was suppressed effectively by addition of NO, NO₂ and SO₂. The N₂O formation was not affected by the irradiation temperature range of 80–200°C.     

Radiation Treatment of Exhaust Gases, (XII) NO Removal in Moist NO-SO2-O2-N2 Mixtures Containing NH3

The NO removal by electron beam irradiation was studied in the moist NO-SO₂-O₂-N₂ mixtures containing NH₃. The NO removal was promoted markedly by addition of NH₃ and at the same time, SO₂ was removed. The formations of NO₂, N₂O, NH₄NO₃ and (NH₄)₂SO₄ were observed in the mixtures containing NH₃. The NO removal increased with H₂O and SO₂ concentrations and was hardly affected by the presence of 3–19.5% O₂. The degree of the NO_x(NO+NO₂) removal became larger with decreasing temperature in the range of 80–150°°C. The NO removal was independent of dose rate in the range of 3.1×10⁴–2.4×10⁶ rad/s. The promotion of the NO removal by addition of NH₃ is attributable to the effective decomposition of NO by NH₂ radical formed by the reaction of NH₃ with OH radical. The NO₂ yield decreased by addition of NH₃ and the N₂O yield increased.     

Radiation Treatment of Exhaust Gases, (IX)

The computer simulation method has been applied to the analysis of the NO and NO₂ decomposition in the NO-N₂ and NO₂-N₂ mixtures by electron beam irradiation. The calculated results regarding the NO and NO₂ decomposition were in good agreement with the experimental results in both mixtures. The NO and NO₂ decomposition is mainly induced by the radical reactions and is hardly induced by the ion reactions. That is, the NO decomposition in the NO-N₂ mixture is mainly induced by the attack of N formed by the radiolysis of N₂. The NO₂ decomposition in the NO-N₂ mixture is induced not only by the attack of N, but also by the attack of O formed through the reaction of NO₂ with N at low doses. At high doses, the decomposition of NO formed through the reactions of NO₂ with N and with O is mainly induced by the attack of N, in contrast to the NO₂ decomposition by the attacks of N and O at low doses. The G value of the formation of N(G(N)) by the computer simulation was 2.0.     

Radiation Treatment of Exhaust Gases, (XIV)

The computer simulation method has been applied to the analysis of the NO oxidation and decomposition in the dry and moist NO-O²-N²mixtures by electron beam irradiation. The calculated results were in good agreement with the experimental results for both mixtures. The NO in the dry NO-O²-N² mixture is decomposed by the reaction with N(⁴S) formed by the radiolysis of the O²N²mixture and is oxidized by the reactions with O and with O³ formed through the reaction of O² with O. The NO in the moist NO-O²-N²mixture is oxidized not only by the reaction with OH formed by the radiolysis, but also by the reaction with O³ formed through the reaction of O² with O at low dose. The G values of the formations of the active species obtained by the computer simulation were G(N(⁴S)) =1.1, G(N(²D))=0.9 and G(O)=1.7 for the dry NO-O²-N² mixture and G(O)=2.0 and G(HO²)= 0.17 for the moist NO-O²-N² mixture. Also, the analysis by the computer simulation confirmed the value of G (OH)=3.2 obtained in the moist O²-N² mixture by the competition method.     

Radiation Treatment of Exhaust Gases, (VII)

The NO decomposition by electron beam irradiation was studied in the NO-N₂ and NO-rare gas mixtures. The NO decomposition yields, G (?NO) at low doses in the case of the 500 ppm NO initial concentration were 4.04.4 and 1.2 for the NO-N₂, NO-He and NO-Ar mixtures respectively. A small amount of NO₂ was formed by irradiation of these mixtures. The NO decomposition is mainly attributable to the attacks of N and N₄ ⁺ (or N₂ ⁺), formed by the radiolysis of N₂on NO in the NO-N₂ mixtureand to the attacks of R⁺ and R^*, formed by the radiolysis of a rare gas (R)on NO in the NO-rare gas mixture. The NO decomposition in the NO-N₂ mixture was depressed markedly by the addition of a small amount of O₂. This may be mainly attributable to scavenging of N and N₄ ⁺ (or N₂ ⁺) by O₂.     

Radiation Treatment of Exhaust Gases, (VIII)

The NO₂ decomposition by electron beam irradiation was studied in the NO₂-N₂ and NO₂-rare gas mixtures. The NO₂ decomposition yields, G (-NO₂), at low doses in the case of the 500 ppm NO₂ initial concentration were 2.9, 10.4 and 5.9 for the NO₂-N₂, NO₂-He and NO₂-Ar mixtures respectively. A large amount of NO was formed by irradiation of these mixtures. The G (NO) was almost equal to the G (-NO₂). The N₂O was also formed in the NO₂-N₂ mixture. The NO₂ decomposition is mainly attributable to the attack of N, formed by the radiolysis of N₂, on NO₂ in the NO₂-N₂ mixture, and to the attacks of R⁺ and R*, formed by the radiolysis of a rare gas (R), on NO₂ in the NO₂-rare gas mixture. The NO₂ decomposition in the NO₂-N₂ mixture was depressed markedly by the addition of a small amount of O₂. This may be mainly attributable to the regeneration of NO₂ by the reaction of NO with O.     

Behavior of Nitrogen Compounds in Radiation Field and Nuclear Reactor Systems

Formation of nitrogen compounds in N₂-H₂O systems under radiation was studied. A reaction scheme with 24 species and 73 reactions was proposed. Two trigger reactions for nitrogen atom generation: N₂ → 2N (g-value of 1.6 μmol per 1 kJ absorbed energy in N₂ molecules), and N₂+H₂O^*→NH₂+NO (κ=3.0×10⁹ S^?1·M^?1 at 298 K with activation energy of 34.4kJ/mol) were included.

Calculated results with the reaction scheme agreed within an error factor of two with ammonium formation rates from an aqueous solution with dissolved nitrogen and hydrogen gasses under γ-irradiation at temperatures of 288~473 K. The reaction scheme was also verified with BWR plant observations on nitric acid formation from in-leaked air under hydrogen water chemistry and ammonium injection tests.     

Radiation Damage of Organic Extractant in Partitioning of High-Level Liquid Waste, (I)

Di(2-ethylhexyl)phosphoric acid (DEHPA), which is a useful extractant for the treatment of high-level liquid waste, was exposed to ⁶⁰Co γ-rays and the radiolysis products and their yields were determined.

The major radiolytic decomposition process of DEHPA was found to be a stepwise splitting of two alkyl groups resulting in MEHPA and H₃PO₄. 1-Methyl-1-ethylpentyl radical, C₄H₉-C(CH₃)-C₂H₅, was found to form with a large G value in the γ-irradiated DEHPA. Reactions involving 1-methyl-1-ethylpentyl radical were also discussed.     

Radiation Anneal Hardening of Neutron Irradiated Niobium

Experiments were carried out with a vertical rectangular channel simulating a sub-channel of the upgraded JRR-3 fuel element, in order to investigate the validity and the error of the correlations predicting the superheat at the onset of nucleate boiling. These correlations were used in the core thermal-hydraulic design of the upgraded JRR-3. As the results, the following were made clear: (1) The existing Bergles-Rohsenow correlation gives a good prediction for the relationship of heat flux vs. superheat at the onset of nucleate boiling, with the error of about 1 K against the lower limits of the measured superheat. (2) There are no significant differences in the characteristics of the relationship of heat flux vs. superheat at the onset of nucleate boiling between upflow and downflow. (3) There are no significant differences in the histories of relationship of heat flux vs. superheat from the forced convection single-phase flow to the subcooled boiling between increasing heat flux and decreasing heat flux, with little overshoot of superheat at the onset of nucleate boiling both in the upflow and in the downflow.     

Hydrazine and Hydrogen Co-injection to Mitigate Stress Corrosion Cracking of Structural Materials in Boiling Water Reactors, (III)

The effects of hydrazine on the corrosion of Zircaloy-2 were examined in supercritical water. Hydrazine could be used as a reducing agent to control the corrosive environment for the coolant of boiling water reactors (BWRs). Before the corrosion test, the applicability of supercritical water for corrosion testing of zirconium alloys was studied. Supercritical water was found to be a useful solvent for testing corrosion based on the following facts: (1) the weight gain of Zircaloy-2 in supercritical water followed the same cubic law with the activation energy of 133 kJ/mol as that in water and steam did, and (2) the weight gain in supercritical water at 723 K and 24.5 MPa was more than 8 times greater than that in water at 561 K and 7.8 MPa depending on immersion time. The corrosion tests in supercritical water at 723 K and 24.5 MPa under γ-irradiation for 1,000 h were conducted to study the effects of adding nitrogen and ammonia on the corrosion of Zircaloy-2. Nitrogen and ammonia are decomposed products of hydrazine. The measured weight gain, oxide film thickness, and amount of hydrogen pick-up had slight differences between cases with and without the additives. Based on these data, it was concluded adding hydrazine to the coolant has little influence on the corrosion of Zircaloy-2 used in BWR cores.     

Investigations on Sodium Boiling Accidents in a Large Fast Breeder Reactor, (I)

The radial propagation of sodium boiling by thermal process in a 1,500 MWe FBR is analyzed with the BOIP-T code. Since the model used embodies some uncertainty, several modes of molten fuel behavior are considered. The time required for boiling to propagate from one channel to its neighbor is calculated. Even on the most conservative basis, the boiling propagation requires at least 10 sec, which indicates that the radial propagation of sodium boiling could be prevented by a suitable core protection system.     

Improvement to the Calculation of Collision Probabilities in Annular System and Its Application to Cluster Geometry

A new method of calculating first-flight collision probabilities in cluster geometry is developed. The collision probabilities in an annular system as well as the transition probabilities for a neutron escaping from one subcell to reach other subcells are calculated and combined. The former is an improvement on Bonalumi's approximation and the latter is an extension of the Dancoff correction to subcells containing fuel rods and coolant. As applications of the present method, we calculate the collision probabilities in a hexagonal cluster with 7 fuel rods and in a square cluster with 28 fuel rods. Fairly good agreement is obtained by comparing the probabilities obtained from our method with the results obtained by the exact method. One-group calculations of the flux distribution are carried out in these systems.     

Effect of Gamma Radiation on Silica Gel, (II)

Radiolysis of N₂O adsorbed on silica gel degassed at 200, 450 and 600°C has been studied to investigate the behavior of electrons on the gel surface. The G-value of nitrogen as the major radiolytic product increases with an increase of N₂O concentration adsorbed approaching a plateau value which depends on degassing temperature of the gel prior to irradiation. By the competitive electron scavenging of N₂O with several electron scavengers, such as CCl₄, SF₆ and nitrobenzene, initial yield of electrons G (e ^?), and relative rate constant for reaction of electrons with scavenger to that with N₂O, k _s /k _N2O, have been obtained. The G (e ^?) is 3.8 and 2.0 for the gel degassed at 200 and 600°C respectively. In the former gel, the value of k _s /k _N2O is comparable with that in aqueous system, while in the latter, with that in non-polar hydrocarbon such as neopentane. The observed difference may be attributed to the presence of silanol groups and residual water which facilitate some form of hydration of electrons on the gel degassed at low temperature. Despite of the complexity of the heterogeneous system, Hammett's relationship is observed among the reactions of electrons with monosubstituted derivatives of benzene, providing the reaction constant ρ as 2.8.     

Economic Scale of Utilization of Radiation (I): Industry Comparison between Japan and the U.S.A

Utilization of radiation in the industrial field has been enlarged due to the variety of technologies. In the present paper, the economic scale between the U.S.A. and Japan is compared with selected industrial parameters such as sterilization, semiconductors, radiographic testing (RT) and radial tire production because the very large industrial markets make a whole comparison difficult. The economic scale revealed was about 56b$ (1$=121¥) for the U.S.A. and 39b$ for Japan. The former is large in magnitude by a factor of 1.4. With respect to the relative ratio versus the GDP, the former was 0.7% and 0.9% for the latter. This implied that utilization of radiation in industry is large in magnitude and is expected to be further developed. Regarding electron beam (EB) accelerators, for example, 648 units were installed in North America and 308 units for Japan during the past 29 years. The large number of the former is attributed to use in curing and heat shrinkable tubes (film).     

Snoek Peak of Neutron-Irradiated Fe-3.48% Ni Alloy

The Snoek peak of a neutron-irradiated Fe-3.48% Ni alloy was measured to determine the resolution of interstitial impurity atoms.

The internal friction was measured after isothermal annealing on specimens irradiated at 75° ± 10°C to a dose of ～3.6 × 10¹⁹ nvt.

The change of the Snoek peak height, which corresponds to the amount of nitrogen in solution, was analyzed upon assuming the applicability of the rate equation.

As a result of calculation, the order of the reaction was found to be about 2.6, and the activation energy for resolution of nitrogen atoms about 2.9 eV.     

Reduction of Plastic Anisotropy of Zircaloy Cladding by Neutron Irradiation, (II)

Initial plastic deformation behavior of zirconium alloy fuel cladding was described quantitatively by the deformation system of single crystal of α-zirconium, and a model was proposed to simulate the yield behavior of polycrystalline material. Based on the model, effects of crystallographic texture and stress state on the plastic deformation of the cladding were evaluated. Conclusions obtained from this investigation are:

(1) The proposed model shows good agreement with the von Mises' yield criteria for a material with isotropic properties.

(2) Plastic anisotropy of the cladding decreases when neutron irradiation affects prism slip more strongly than the other deformation systems.

(3) Dominant deformation systems for axial tension or internal pressurization of the cladding are predicted to be prism slip or tensile twin, respectively, when the stress state of the cladding reaches the yield condition.     

Hardening and Recovery of Neutron-Irradiated Pressure Vessel Steel (ASTM A533B)

Specimens of ASTM A533B steel were studied to gain information on the annealing process following irradiation, through measurements of internal friction and of hardness.

The specimens were quenched from 900°C and tempered at 650°C, then irradiated in the JMTR reactor at 65°–75°C to a neutron dose of 1.4–1.7×10²⁰ n/cm² (E _n >1MeV).

Peaks were observed on the internal friction curves from unirradiated specimens. These peaks disappeared upon irradiation, but reappeared with annealing treatment at 150°C.

Radiation-anneal hardening was observed at 250°C. The recovery of radiation hardening begins at a temperature between 250° and 350°C, but is not completed even at 550°C.     

Effect of Gamma-Ray Irradiation,on Cellulose Nitrate Track Detector

The influence of γ-irradiation on the bulk etching rate of cellulose nitrate is described. The increase in bulk etching rate induced by γ-ray from ⁶⁰Co has been measured at different irradiation doses and at different etching temperatures. From this temperature dependence the activation energy for the etching reaction is obtained. Some conclusions derived from experimental results are discussed in relation to a criterion for track registration.     

Photochemical Reactions of Uranium(VI) in Aqueous Phosphoric Acid Solutions

Photochemical reactions of U(VI) ion with halogen and pseudohalogen anions. I^?, Br^?, Cl^? and NCS^?, were studied in aqueous phosphoric acid solutions under irradiation of nitrogen laser. The formation of U(IV) was observed in the reactions with I^?, Br^? and NCS^?, but not with CI^?. The yield of U(IV) increased in the order Br^?<NCS^?<I^?. This order was the same as the quenching rate constants of the excited U (VI) ion with these anions, but the reverse of their standard redox potentials. These facts are consistent with the electron transfer mechanism between excited U (VI) and these anions. The rates of the formation of U (IV) in the presence of Br^? were measured by the spectrophotometric method. It was found that the rate equation was first order in both U (VI) and Br^?. The results were reasonably interpreted by a series of reaction processes involving U(V) and Br radical. The photo-oxidation of tris(1, 10-phenanthroline)-Fe (II) ion by U (VI) was also studied in the same procedures. Based on the rate law, we proposed a one-electron transfer mechanism involving U(V) as an intermediate.