Patent Number: 050135228
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The boiling water reactor shown in FIG. 1 has a reactor vessel 1 with fuel elements 2, control rods 3 and main circulation systems 4, of which one is shown in the figure. Each main circulation system has a pump 5. The main circulation pumps ensure that the reactor core is sufficiently cooled. The reactor vessel is part of a water circulation system 6, which also comprises a steam turbine 7, a condenser 8, a condensate cleaning filter 9, pumps 10 and 14 and a preheater 11. The cladding material of the fuel elements consists of a zirconium alloy, for example Zircaloy-2. Steam generated in the reactor core gives its energy to the rotor of the turbine and is condensed, after passage of the turbine, in the condenser with a coolant circuit 12 comprising a pump 13. The condensate from the condenser 8 is transported by the condensate pump 14 through the condensate cleaning filter 9 and the condensate cleaned therein is fed, after preheating in preheater 11, into the reactor vessel by the feed pump 10. In the exemplified case the condensate cleaning filter comprises an ion-exchange filter with an ion-exchange compound in the form of a mixture of an anion-exchange compound (polystyrene with quaternary ammonium groups cross-linked with divinyl benzene) and a cation-exchange compound (sulphonated polystyrene cross-linked with divinyl benzene). According to the invention, samples of the water 15, the reactor water (in the illustrated case in the form of feed water), are taken batchwise from the circulation system 6 via the conduit 16 with the valve 17 and a sampling system, as shown in FIG. 2. The sampling system exemplified in FIG. 2 includes a sealable container 19 of polytetrafluoroethylene with a volume of 25 ml. Only this part of the sampling system is shown in FIG. 1. The lower part of the container is provided with a filter 20 of polytetrafluoroethylene, the through-holes of which have a size of 0.45 .mu.m. Via a conduit 21 with a valve 22 the container is connected to a tank 23 with a pressure gas in the form of nitrogen gas of a pressure of around 0.5 MPa, via another conduit 24 with a valve 25 it is connected to a tank 26 with solvent in the form of a mixture of 4 part by volume concentrated hydrochloric acid and 1 part by volume thioglycolic acid, via a conduit 27 with a valve 28 it is connected to a tank 29 with high purity water, via a conduit 30 with a valve 31 it is connected to a discharge 32, via a conduit 33 with a valve 34 it is connected to an apparatus 35 for analysis of the solution of particulate compounds, dissolved on the filter, in the reactor water by ion chromatography, and via a conduit 36 with a valve 37 the container is connected to an apparatus 38 for analysis of ionic dissolved compounds in the reactor water, also by ion chromatography. All the valves, i.e., valves 17, 22, 25, 28, 31, 34 and 37, are openable and closable. The container 19 is placed in a microwave oven 40, which is schematically illustrated by dashed lines in FIG. 2. In the application of the method according to the invention in the exemplified case, a specified amount of the reactor water 15 is led via the conduit 16 to the container 19, through the filter 20 and via the conduit 30 to the discharge 32, particulate compounds present in the reactor water being collected on the filter. During this process the valves 17 and 31 are held open whereas the other valves are closed. The amount of reactor water or the time for its supply and passage through the container is adapted such that a quantity of particulate compounds, suitable for analysis, is collected on the filter. When the specified amount of reactor water has traversed the container, the valve 17 is closed and the valve 22 is opened to empty the container of all possibly remaining liquid with a flow of nitrogen gas from the tank 23. After closing the valve 22 and the valve 31, the valve 25 is opened and a specified quantity of solvent is supplied to the container 19 from the tank 26 via the conduit 24, so that most of the volume of the container is filled with solvent. The remaining volume, consisting of nitrogen gas, functions as a pressure-equalizing gas volume. After the supply of this quantity of solvent, the valve 25 is closed. Then the container is heated with the microwave oven 40 for a definite period of time to a temperature which is sufficient for the particulate compounds collected on the filter to be dissolved for certain. After this operation, the valves 22 and 34 are opened, the container 19 with gas pressure being emptied of the solution of the particulate compounds present therein while the solution is being transported to the apparatus 35 for analysis by ion chromatography. After emptying the container, the valves 22 and 34 are closed. In the ion chromatograph 35 a chromatogram is taken up in a conventional manner, which shows the nature and the content of the elements included in the particulate compounds and hence the quantity of these particulate compounds in the batch of the reactor water taken out via the conduit 16. After closing of the valves 22 and 34, the container 19 is washed with water from the storage 29 by opening the valves 28 and 31. After closing of the valve 28 and opening of the valve 17, the whole process described above is repeated, which is thus started by supplying a new batch of the reactor water to the container 19 while keeping the valves 17 and 31 open for a specified time and keeping the other valves closed. By repeatedly withdrawing batches of the reactor in the manner described, preferably with the same time intervals during operation of the reactor, it is possible continuously to follow the composition and content of the particulate compounds in the reactor water and then to determine whether changes of the reactor water have occurred which necessitate taking measures regarding the operation of the reactor to eliminate the cause of the changes. Opening and closing of all valves in the illustrated device, as well as the microwave heating, are controlled by automatic control, preferably by computer control comprising microprocessors. The exemplified device can also be used for analysis of ionic compounds in the reactor water. In such case the withdrawn sample of the reactor water, which has passed through the filter 20 in the container 19, is passed via the conduit 36 to the analysis apparatus 38 instead of via the conduit 30 to the discharge 32. During this process the valve 37 is kept open and the valve 31 is kept shut.