MZFR reactor

HWRs of the pressure vessel type have been designed and constructed in Sweden, Germany, and Argentina. The main references of this line are the Agesta reactor in Sweden (shutdown), the MZFR reactor in Germany, and the Atucha-1 and Atucha-2 reactors in Argentina. 

The 57-MWe MZFR reactor was built by Siemens-KWU at the Karlsruhe Research Center for limited electricity supply and district heating. It was the prototype for the Atucha-1 and Atucha-2 reactors built in Argentina. The principal features are similar to those incorporated in Atucha-1. 

Use of well-proven special heavy-water equipment and systems from the heavy-water reactor power plants MZFR (multi-purpose-research reactor, Karlsruhe, FRG, 58 MW) and Atucha I (Argentina, 367 MW(e)). 

KWU PHWR plants have accumulated 30 reactor years of experience. MZFR (PHWR) has accumulated load factor of 62.6% until the end of 1983. ATUCHA-I is connected to the grid since 1974-06. It has accumulated 9 years of reactor years with a cumulative load factor of 78.4% until the end of 1983. 

The heavy water pressure vessel reactor MZFR, the prototype of the plant ordered for the Argentine, has been on power since March, 1966 (ref. 1). The reactor went critical in September, 1965 and commenced power production 6 months later. Its gross electrical output is... 

THE MZFR TYPE HEAVY WATER REACTOR OF ECONOMIC SIZE... 

The experience gained with the MZFR and the most remarkable success of H2O pressurized water reactors provided a strong Inducement to develop the MZFR concept of a natural uranium fuelled D2O-PWR up to an economic size. This had been achieved when we tendered for the 320 MW Atucha unit in the Argentine last year. 

When the MZFR core was about to be designed, small fuel rod diameters were chosen, because, for a given moderator to fuel ratio, they will result In a high power density and a small core. Today, the limitations on vessel size are no longer so severe, but, it is the capital investment, particularly due to the heavy water Inventory, as well as to some extent to the price of the reactor vessel and the fuel which favour a core of high specific power. The most effective means to achieve this are 37-rod bundle clusters and fuel rods of small diameter. 

The production costs of a MZFR type fuel element which also apply to the fuel of the Atucha reactor amount at the present to approximately 55 of the total costs, with the balance of 4-5 for uranium and Zlrcaloy. It is thought that a significant reduction In future production costs is possible by rationalized manufacturing methods and standardized test procedures which go hand in hand with Increased production capacities. The uranium costs may be assumed to remain constant in the period under review. In the long run it is therefore advisable to choose that fuel element design which will benefit most by the expected production cost reduction. 

On their way from the reactor to the cooling pond and vice versa the fuel elements must be dried so as to prevent the mixing of D2O and HgO. As an improvement over the MZFR design a drying station of significantly shorter drying periods has... 

Arranging the control rod drives above the reactor vessel offers important technical advantages. The design principle, which proved successful with the MZFR, has therefore been retained without alteration. Twenty-nine control and shutdown rods are inserted at an angle into the pressure vessel from its periphery. It has been verified by calculations that undamped local power oscillations cannot occur in the core of the size of a 300 MW reactor, so that the reactor can be kept under control by two rods when operating at full power. 

The core dimensions characteristic of natural uranium reactors require pressure vessels of large diameter. Six years ago, when the design of the MZFR vessel was established, Its parameters corresponded to the production capabilities at that time. Those limitations have meanwhile been transgressed and are no longer valid. The Steel vessel for the Atucha power plant corresponds to an electrical output of... 

The MZFR prototype reactor has now been operating for about two years. Could the Authors please indicate (a) the observed rate of loss of heavy water from the circuit (b) the resultant irrecoverable loss of heavy water (c) the amount of heavy water which is Isotoplcally diluted ... 

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