High-grade welding technique for Urenco14-04-2009
At Urenco in Almelo uranium is enriched for use as fuel for nuclear plants. This enrichment has a nuclear basis and therefore sets high demands for safety precautions in the production process. Part of this process are the pipelines for the supply and drainage of uranium. For the engineering, production and mounting of crucial parts of this piping Urenco, makes use of Vos Mechanical Solutions.
Photo: Frank Borggreve, Manager Special Solutions
Paul Israel and Arno Voorhuis work as construction manager and construction engineer respectively at Enrichment Technology Company Limited (ETC), an independent part of Urenco: “ETC is an international high-tech company with plants in the Netherlands, the United Kingdom and Germany. In Almelo gas centrifuges are produced. The development of centrifuges takes place in Jülich while the piping for cascades are manufactured in Gronau. In Capenhurst enrichment installations are designed. ETC also provides project management for the construction of these plants. In 2006 ETC became a independent company as a result of a joint venture between URENCO and Areva.
The process of enrichment in a nutshell
URENCO Nederland B.V. in Almelo is the operating company of URENCO Limited.
The company enriches uranium by means of gas centrifuges for use as fuel
in nuclear plants all over the world.
Uranium enrichment is necessary because natural uranium consists of only 0,7% of fissionable material (the so-called U235-atoms), with which nuclear energy is generated. By enriching uranium URENCO enlarges the fissionable atoms in the uranium by 4%. How does this enrichment work? Paul Israël and Arno Voorhuis: “Uranium is led in gas form via a pipeline into a fast-spinning centrifuge.
Here the non-fissionable uranium atoms are separated from the fissionable atoms. The former are heavier and because of this move easier to the outer area in the fast-spinning centrifuge than the lighter U-235 atoms. The latter stay in the centre of the centrifuge and are drawn-off and transferred to the next centrifuge. URENCO aims at approximately 4% enriched uranium. This cannot be achieved in a single centrifuge. The enrichment process is repeated several times in a group of coupled centrifuges. At URENCO these coupled centrifuges are called cascades. URENCO’s gas centrifugal enrichment technique has been the best in the world for years. It was developed by a consortium of specialist from England, Germany and the Netherlands. Because of renewed interest in nuclear energy, uranium enrichment is becoming important again.
In the plants of URENCONederland there are more than 100.000 centrifuges employed of consecutive generations. High-tech installations where safety is a top priority. This is obvious because it involves nuclear materials. URENCO has a permit to manufacture 4500 ton SWU enriched uranium per annum. ”Gas centrifuge is known as the most efficient technology for uranium enrichment. Through continuous research and development, improvements are applied continuously to make the process more dependable and safe.” according to Paul Israël and Arno Voorhuis.
Responsible for high-grade piping
Vos Mechanical Special Solutions is involved in a part of the construction of successive production facilities where centrifuges operate. Paul Israël and Arno Voorhuis: “During several years URENCO in Almelo has constructed production facilities for the centrifugal process. We are now ready for SP5 and hall 6. Vos Mechanical Special Solutions has received the assignment for the take-off in hall 6 for the engineering, manufacture, assembly and testing of the uranium system. Take-off is the area where the non-enriched uranium (Feed) is transported via the UF6-piping to the gas centrifuges and returns as impoverished uranium (Product). Feed, Tails as well as Product are stored in special transport containers. The piping to and from the cascades is of crucial importance within the total process. The piping is supplied by Special Solutions and will also be installed by them. The necessary engineering is executed by Special Solutions with their own 3D System Inventor. The manufacture of the piping including the high-grade welding will be executed in our own cleanroom in Klazienaveen. Safety precautions are an important part in the manufacture. At the start of the project, the Special Solutions Team will be extensively instructed by ETC.”
Extreme high demands to welding process
Paul Israël and Arno Voorhuis: “Our demands to the welding process are extremely high at Vos Special Solutions. It is carried out at the highest level on the basis of TIG-welding. The leak proof of the aluminium piping must be tested and guaranteed. This work is their responsibility – after all it is used for uranium transport so the piping must be fully leak proof. At the same time there may not be any impurities in the pipeline. That is why all welding processes are done in a special cleanroom at Special Solutions in Klazienaveen - obviously within certain temperature ranges and fixed humidity. This project consists of 700 meter piping. This does not seem much but it must be extremely safe and leak proof. The production times are also getting shorter. This means that Special Solutions must weld and assemble at the highest level but within shortening production times. They have, as one of a few companies, qualified and experienced welders. Special Solutions also has insight in the processes we use. This results in very efficient cooperation. Vos Special Solutions makes a difference because the company is solution-aimed. If, during the process, an adjustment to the design is necessary, we can switch quickly and efficiently. We will have a clear 3D-drawing ready the following day. They react quickly to our questions. In addition to this the company is also employable in dismantling production halls. Because of safety risks, this must also be done scrupulously. Vos Special Solutions does the dismantling of the piping and URENCO takes care of the removal.”
SWU, the abbreviation of Separate Work Unit, is the unit in which uranium enrichment is measured world-wide.