Search Results

You are looking at 1 - 9 of 9 items for

  • Author or Editor: L. Koch x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The established reprocessing input analysis methods (Pu/U ratio- and volume/concentration methods) are compared with two isotope correlation techniques based on heavy isotopes and fission gas nuclides. The potential of the latter for the verification of reprocessing input data is demonstrated covering various aspects such as accuracy, intrusiveness, additional effort, independence of plant operations, reliability etc.

Restricted access

Abstract  

The burn up determination of fast reactor fuel is more difficult than for thermal reactors, because a greater number of isotopes fissions. The burn up measurement by fission products needed the determination of fission yields in a fast flux of isotopes contributing considerably to fission. To ease the analysis the sample conditioning was eliminated if applicable. The measurement techniques and the evaluation was automatised. A isotope correlation to check the analysis is mentioned.

Restricted access

Abstract  

Plutonium, seized from illicit trafficking in nuclear materials, can originate from several, distinct sources. The primary focus of nuclear-forensics investigations of confiscated Pu is to specify correctly its origin. We demonstrate that such specification is possible by means of accurate determination the Pu isotopic composition. In this study, five Pu samples of different origins were analysed by thermal-ionisation mass spectrometry. The source (i.e., the type of production reactor) of each sample was determined by comparing the measured Pu isotopic composition with that calculated by one of two reactor-production computer codes, ORIGEN2 and SCALE. These results, in conjunction with the age determination of each sample, allow us to deduce the origin of each.

Restricted access

Abstract  

A combined -spectrometric and mass-spectrometric determination of237Np in spent nuclear fuels using239Np as an inherent spike has been developed. In spent fuel239Np is in radiochemical equilibrium with243Am. Neptunium in the tetravalent state is separated by TTA solvent extraction from the other actinides and most of the fission products and the -activity ratio of237Np to239Np is measured. The237Np activity is via239Np directly linked to the243Am mass in a sample, which is determined by mass-spectrometric isotope dilution analysis.

Restricted access

Consider a family of closed unit circular discs in the plane. Two discs are called neighbours if they have a point in common. Let N(d) denote the maximum possible number of neighbours of one disc in a family of unit circular discs, where the distance between any two circle centers is at least d. HereN(d) is determined for 1  between any two circle centers is at least d. HereN(d) is determined for 1

Restricted access

Abstract  

The effects of flame retardants such as hydrated aluminium oxide, antimony trioxide and chloroparaffin on the thermal properties and flammability of sulphur vulcanizates of butyl and halogenated butyl elastomers were studied. The thermoanalytical curves of the elastomers were interpreted. Greater tendencies to thermal degradation were observed for halogenated butyl elastomers than for the original butyl rubber elastomer. This was confirmed by elastomer combustibility studies. The use of these flame retardants allowed the formation of self-extinguishing vulcanizates of the investigated elastomers.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
J. Garcia Alonso
,
D. Thoby-Schultzendorff
,
B. Giovannone
, and
L. Koch

Abstract  

Inductively Coupled Plasma Mass Spectrometry ICP-MS has been applied to the characterisation of various nuclear waste forms. Long-lived radionuclides can be determined with similar sensitivities. The installation of an ICP-MS in a glove box and applications and limitations of the methods to nuclear materials, with especial emphasis on isobaric interferences are described.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
J. Glatz
,
I. Garcia-Alonso
,
T. Kameyama
,
L. Koch
,
G. Pagliosa
,
T. Tsukada
, and
H. Yokoyama

Abstract  

In order to study the dissolution behavior of a highly burnt LWR fuel, a fuel pin irradiated in the DR3 test reactor in Risoe National Laboratory, has been characterized by microstructural examination and then dissolved under PUREX type conditions. The dissolution behavior was investigated and the residues analyzed by scanning electron microscopy and by ICP-MS and IDMS after dissolution.

Restricted access

The pathogenesis of chicken infectious anaemia virus (CAV) infection was studied in 6-week-old and one-day-old SPF chickens inoculated intramuscularly with graded doses of Cux-1 strain (106−102 TCID50/chicken). Viraemia, virus shedding, development of virus neutralizing (VN) antibodies and CAV distribution in the thymus were studied by virus isolation, polymerase chain reaction (PCR), immunocytochemistry (IP) and in situ hybridization until postinfection day (PID) 28. In 6-week-old chickens infected with high doses of CAV, viraemia and VN antibodies could be detected 4 PID and onward without virus shedding or contact transmission to sentinel birds. However, virus shedding and contact transmission were demonstrated in one-day-old infected chickens. In the 6-weekold groups infected with lower doses, VN antibodies developed by PID 14, transient viraemia and virus shedding were detected. The thymus cortex of all 1-dayold inoculated chickens stained with VP3-specific mAb. Cells with positive in situ hybridization signal were fewer and scattered throughout the thymus tissue of the one-day-old inoculated chickens as compared to IP-positive cells. These results suggest that early immune response induced by high doses of CAV in 6-week-old chickens curtails viral replication and prevents virus shedding.

Restricted access