The limitation of chemical fixation methods for EM specimen preparation seems to be successfully solved by rapid freezing methods.Heuser's technique for quick freezing of unfixed cells and tissues in contact with highly polished ultrapure cooper block cooled with liquid helium (1) has been proved to be a useful technique for cell membranes and cytoskeleton studies.Using a Polaron made quick freezing slammer, we met some technical difficulties and subsequently we redesigned two important parts of the machine -the specimen freezing head and the cold block chamber -as described below (Pig. 1.).The specimen freezing head [61 as designed by Polaron is attached to the dropping guide rod by six pins which fit in six head pins into the connector head is very uncomfortable, this handling being made above the cold gas stream of the cooling agent. On the other hand, during this laborious handling, an accidental prefreezing of the specimen may occur. In order to avoid these disadvantages, we designed a connecting device The second modificaton involved the cold block chamber. In order to avoid the ultrastructural distortions of the biological specimens caused by specimen impact against the cooper block (2), the cold block chamber was modified as illustrated in fig. 1. The chamber [13] was mounted through the base plateau 1161 on six springs [14] and other six springs I151 were mounted under the plateau.When the upper springs are compressed during specimen impact against the cooper block, the bottom springs are relaxed followed by their recontraction and the relaxation of the upper springs. This system proved to absorb the shock waves more efficiently.The modified quick freezing slammer is currently in use, with good results, in our laboratory, working with liquid nitrogen as collant agent.

Uranium prospecting in Romania has started some 50 years ago, when a bilateral agreement between Romania and the former Soviet Union had been concluded and a joint Romanian-Soviet enterprise was created. The production started in 1952 by the opening of some deposits from western Transylvania (Bihor and Ciudanovita). From 1962 the production has continued only with Romanian participation on the ore deposit Avram Iancu and from 1985 on the deposits from Eastern Carpathians (Crucea and Botusana). Starting with 1978 the extracted ores have been completely processed in the Uranium Ore Processing Plant from Feldioara, Brasov. Complying with the initial stipulations of the Nuclear National Program launched at the beginning of the 1980s, the construction of a nuclear power station in Cernavoda has started in Romania, using natural uranium and heavy water (CANDU type), having five units of 650 MW installed capacity. After 1989 this initial Nuclear National Program was revised and the construction of the first unit (number 1) was finalized and put in operation in 1996. In 2001 the works at the unit number 2 were resumed, having the year 2005 as the scheduled activating date. The future of the other 3 units, being in different construction phases, hasn’t been clearly decided. Taking into consideration the exhaustion degree of some ore deposits and from the prospect of exploiting other ore deposits, the uranium industry will be subject of an ample restructuring process. This process includes workings of modernization of the mines in operation and of the processing plant, increasing the profitableness, lowering of the production costs by closing out and ecological rehabilitation of some areas affected by mining works and even new openings of some uraniferous exploitations. This paper presents the actual situation and the prospects of uranium mining industry on the base of some new technical and economical strategic concepts in accordance with the actual Romanian Program for Nuclear Energetics.

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