Search Results

You are looking at 1 - 4 of 4 items for

  • Author or Editor: H. Nilsson x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The reaction calorimeter CAP202 (chemical process analyzer) determines thermal effects by measuring the true heat flow (THF) based on unique design principles. In particular, measurements can be performed without requiring any calibration procedures and the obtained results are most reliable and exhibit extremely stable baselines. The benefits in respect of experimental speed, data quality and long term performance are obvious. Due its broad dynamic range the instrument can be employed for measurements ranging from small physical heat to energetic chemical reactions. The CPA allows running experiments seamlessly with reaction volumes between 10 and 180 mL. This volume flexibility simplifies the investigation of multi-step operations and is the basis for various applications employing precious or highly energetic compounds. Due to the fact that calibrations are not required, altering conditions during a single experiment like changes in viscosities, liquid levels or stirring speeds do not affect the results of the measurements.

Restricted access

Abstract  

The age of plutonium is defined as the time since the last separation of the plutonium isotopes from their daughter nuclides. In this paper, a method for age determination based on analysis of 241Pu/241Am and 240Pu/236Pu using ICP-SFMS is described. Separation of Pu and Am was performed using a solid phase extraction procedure including UTEVA, TEVA, TRU and Ln-resins. The procedure provided separation factors adequate for this purpose. Age determinations were performed on two plutonium reference solutions from the Institute for Reference Materials and Measurements, IRMM081 (239Pu) and IRMM083 (240Pu), on sediment from the Marshall Islands (reference material IAEA367) and on soil from the Trinity test site (Trinitite). The measured ages based on the 241Am/241Pu ratio corresponded well with the time since the last parent-daughter separations of all the materials. The ages derived from the 236U/240Pu ratio were in agreement for the IRMM materials, but for IAEA367 the determination of 236U was interfered by tailing from 238U, and for Trinitite the determined age was biased due to formation of 236U in the detonation of the “Gadget”.

Restricted access

Abstract  

When chemical reactions are performed in semi-batch mode and the reaction rate is relatively low, the reactant added may be accumulated. The resulting thermal accumulation is of major concern regarding process safety, as a fault in the cooling system may lead to a run-away reaction. The feed rate in semi-batch processes is usually constant, but this paper discusses methods of optimizing the feed rate interactively, based on the measured heat flow and the calculated amount of compound that has actually reacted. The prerequisite of such procedures is to run the experiments in a reaction calorimeter in which the heat flows can be measured accurately and continuously. For this purpose a ChemiSens reaction calorimeter CPA202, which is calibration free and gives stable, flat ‘zero-line-type’ baselines, was employed.

Restricted access

Abstract  

A method has been developed for the determination of63Ni in environmental samples. The samples are ashed and leached with aqua regia whereafter hydroxides are precipitated with ammonia, leaving Ni in the aqueous phase. Nickel is extracted as dimethyl glyoxime complex by chloroform and back-extracted with HCl. Finially, Ni is electroplated onto a copper disc from an ammonium sulphate medium at high pH. The radiochemical yield is determined by atomic absorption measurements of stable Ni before and after electrodeposition.Nickel-63 on the discs is measured by beta spectrometry using solid state ion implanted detectors and by using a conventional windowless anti-coincidence shielded GM gas flow counter. Using a counting time of 3000 minutes, the minimum detection limits were 8 and 1 mBq, respectively.The method was applied to a series of macroalgae (Fucus vesiculosus) collected at different distances from a nuclear power plant. There was a correlation between distance to the power plant and the63Ni concentration in the algae. The relationship between63Ni and60Co, as well as that between63Ni and stable nickel, was also investigated.

Restricted access