H. Bruchertseifer

On the Radiolytic Decomposition of Colloidal Silver Iodide in Aqueous Suspension

The decomposition of aqueous colloidal suspensions of AgI induced by ionizing radiation was investigated under various conditions using 188Re as an in situ beta-radiation source. The suspensions were stabilized by an initial excess of either I- or Ag+ ions. Although the results were somewhat scattered, the following trends were observed. With an initial excess of I- and under strong oxidizing conditions (N2O sparging) at pH 2, ˜65% AgI was decomposed into nonvolatile and volatile iodine (ratio 2:1) for doses of ˜20 kGy, and up to ˜80% was decomposed (mostly nonvolatile iodine) at pH 5. Chloride ions greatly enhanced the volatile and lowered the nonvolatile fractions. Little decomposition (<10%) was obtained with air sparging at both pH 2 and pH 5. Chloride ions increased the maximum decompositions to ˜60% (˜47% volatile) and ˜20% (mainly nonvolatile iodine), respectively. With an initial excess of Ag+ with N2O sparging and at pH 2 and pH 5, very little volatile iodine was produced. The maximum decomposition was ˜20% after ˜20 kGy. Chloride ion addition at pH 2 had greatly enhanced the volatile iodine yield. The relevance of these results to the possible release of iodine to the environment following a nuclear reactor accident is discussed.

Ion-exchange separation of Zr and Hf microamounts in dilute HCl/HF solutions: A model system for chemical identification of Rf and study of its properties

A procedure was developed for selective separation of Group IV elements from Sr and Lu, followed by rapid separation of Zr and Hf by cation-exchange chromatography in dilute HCl/HF solutions. The possibility of using this procedure for chemical identification and determination of decay parameters of the new isotope 267Rf was demonstrated.

Ion chromatographic analysis of aqueous iodine species by conductivity and radioactivity measurements

Summary A new device was developed for the identification of several iodine species in aqueous solution using ion chromatography. Iodide, iodate and molecular iodine can be determined. (The equipment allows both conductivity and radioactivity detections.) The method is applicable for the determination of radioactive iodine contaminations in the cooling water of nuclear power plants.

Iodine behaviour during a severe accident in a nuclear power pPlant

Iodine is a main fission product of the fuel generated during power operation in nuclear power plants (NPPs). A severe NPP accident can cause fuel, containing fission products (FPs), control rod assemblies and core structures to melt and then release into the containment. The key signatures of iodine behaviour during a NPP severe accident are reviewed, i.e. its release from the molten core in the reactor pressure vessel and transfer via the primary coolant system into the containment. Containment or filter failure would disperse radioactive iodine into the environment. The iodine radioisotopes, 1 3 1 I (T 1 / 2 ca. 8 d) in particular, in sufficient concentrations can pose a health hazard. The overview focuses on the current state of knowledge on iodine behaviour in containment. The formation of volatile iodine species (molecular iodine and organic iodides) by FP-radiation and recent efforts at PSI to suppress their release by reduction to non-volatile iodide for engineered systems are described. Despite extensively available data, further experimental studies are needed to reduce the significant uncertainties in model development. In particular, additional studies on organic iodide formation are required, since these species form the major volatile fraction under certain conditions. Gas phase reactions and the potential effects of many other sump constituents are also important.

Cation-exchange separation of Group V elements: Model experiments on isolation and chemical identification of Db

A cation-exchange procedure was developed for separating Nb from Ta, Pa from Ta, and Nb, Pa, and Ta from Zr, Hf, and lanthanides in dilute HC1/HF solutions. The stability of the fluoride complexes of Group IV and V elements decreases in the following order: Nb ∼ Pa > Zr > Hf > Ta. This procedure can be used in experiments on synthesis of superheavy nuclei for isolation of Db from the reaction products and for its chemical identification.

Relatively Long‐Lived Dubnium Isotopes and Chemical Identification of Superheavy Elements

The present study has been performed within the framework of experiments aimed at the investigation of chemical properties of long‐lived Db isotopes in aqueous solutions. The isocratic anion exchange separations of group V elements in the solutions containing HF have been considered. Parameters of separation of dubnium homologues (Pa, Nb and Ta) in HF/HNO3 mixed solutions have been optimized. The procedure of separation of group V elements from multicomponent system has been suggested.

Radiochemical Separation of Group 5 Elements. Model Experiments for Investigation of Dubnium Chemical Behaviour

Chemical behaviour of group 5 elements in the aqueous hydrofluoric acid solutions was studied. The radiochemical method for the cation exchange separation of Nb (Pa) and Ta from Zr, Hf and lanthanides is presented. The developed scheme allows excluding of the presence of SF heavy actinides in fractions of separated elements. On the basis of the data of the present work, it is possible to suggest the following order of the stability of the fluoride complexes of group 4 and 5 elements: Nb ≈ Pa > Zr > Hf > Ta. The order of the complex formation is in agreement with theoretical predictions. This analytical procedure can be used in future heavy nuclei synthesis experiments for the separation of dubnium (Db) from other reactions products and for its chemical identification.