Radiological characterisation in view of nuclear reactor decommissioning: On-site benchmarking exercise of a biological shield

Nearly all decommissioning and dismantling (D&D) projects are steered by the characterisation of the plant being dismantled. This radiological characterisation is a complex process that is updated and modified during the course of the D&D. One of the tools for carrying out this characterisation is the performance of in-situ measurements. There is a wide variety of equipment and methodologies used to carry out on-site measurements, depending on the environment in which they are to be carried out and also on the specific objectives of the measurements and the financial and personnel resources available. The extent to which measurements carried out with different types of equipment or methodologies providing comparable results can be crucial in view of the D&D strategy development and the decision-making process. This paper concerns an on-site benchmarking exercise carried out at the activated biological shield of Belgian Reactor 3 (BR3). This activity allows comparison and validation of characterisation methodologies and different equipment used as well as future interpretation of final results in terms of uncertainties and sensitivities. This paper describes the measurements and results from the analysis of this exercise. Other aspects of this exercise will be reported in separate papers. This paper provides an overview of the on-site benchmarking exercise, outlines the participating organisations and the measurement equipment used for total gamma, dose rate and gamma spectrometry measurements and finally, results obtained and their interpretations are discussed for each type of measurement as a function of detector type. Regarding the dose measurements, results obtained by using a large variety of equipment are very consistent. In view of mapping the inner surface of the biological shield the most appropriate equipment tested might be the organic scintillator, the BGO or even the ionisation chamber. In addition, for mapping this surface, the most appropriate total gamma equipment tested might be the LaBr$_{3}$(Ce), the thick organic scintillator or the BGO. These measurements can only be used as a secondary parameter in a relative way. Results for the gamma spectrometry are very consistent for all the equipment used and the main parameters to be determined

Natural Virus Infection of Hedge Bindweed (Calystegia sepium)

Virus symptoms were observed on Hedge bindweed (Calystegia sepium) a well known plant in Hungary. In the literature there is no record of virus infection on Hedge bindweed, therefore, investigations were carried out to determine the causal agent. Sap from leaves showing virus-like symptoms was inoculated onto test plants inducing systemic infection on Nicotiana clevelandii, N. benthamiana, local lesions on Chenopodium quinoa and no infection on Datura stramonium and Cucumis sativus. Sap of N. clevelandii was examined by electron microscopy, showed the presence of long flexous particles. The biological and other properties of the virus have also been studied. Properties of particles in sap were as follows: TIP (thermal inactivation point): 78 °C, LIV (longevity in vitro): 26 days and DEP (dilution end point): log 10 minus 5. The size of coat protein is 36 kDa, and the genome consists of 7-8000 nt RNA. Double-stranded cDNA were produced using random hexanucleotide primers, cloned and sequenced. BLAST search of sequence databases revealed nucleotide sequence identity with carlaviruses. Further investigations are needed to decide whether the virus isolated from Hedge bindweed is a new carlavirus or a new strain of an existing carlavirus

Host range and number of generations of pea thrips (Kakothrips pisivorus westwood, 1880) (Thysanoptera: Thripidae) in Hungary

The Fabaceae species Lathyrus tuberosus, Vicia species and Coronilla varia, all of which have an extended flowering period, provide the larvae food and shelter long enough for the pea thrips Kakothrips pisivorus to complete its development, and to have two generations yearly. Although flowers of pea cultivars also confer suitable conditions for egg laying, their flowering period is rather short. Therefore, the larvae are forced to move to developing pea pods in damaging numbers, resulting in the development of only one generation yearly on pea. However, specimens of K. pisivorus are able to colonize pea cultivars that have a similar phenology as Lathyrus tuberosus. Here we show that Hungarian pea thrips populations having either one or two generations are genetically identical

Velocity matching by pulse front tilting for large-area THz-pulse generation

We propose a generally applicable velocity matching method for THz-pulse generation by optical rectification in the range below the phonon frequency of the nonlinear material. Velocity matching is based on pulse front tilting of the ultrashort excitation pulse and is able to produce a large-area THz beam. Tuning of the THz radiation by changing the tilt angle is experimentally demonstrated for a narrow line in the range between 0.8-0.97 times the phonon frequency. According to model calculations broad-band THz radiation can be generated at lower frequencies. Advantages of the new velocity matching technique in comparison to the electro-optic Cherenkov effect and non- collinear beam mixing are discussed. (C) 2002 Optical Society of America

Differences in the vector efficiency of Thrips tabaci in Europe and North America

Although Thrips tabaci is a well-known vector of Tomato spotted wilt virus (TSWV) it does not belong to the spreaders of this dangerous pathogen in North America. The possible explanation of the differences in its vector efficiency in Europe and in North America is rooted in the fact that out of the two subspecies of T. tabaci, i.e. T. tabaci tabaci and T. tabaci communis only the specimens of the latter were introduced from Europe into North America. To support our hypothesis we have used a molecular marker that detects intraspecific ribosomal DNA sequence variations between the two subspecies of T. tabaci