A11-4 Using the program

The program CSPSen.xls is available on the companion website. On running the program the initial page of the spreadsheet is displayed with the cells A1 A11 filled with the input data of a sample case. The numerical data of the sample case have to be replaced by the data of the case to be studied. 

The spreadsheet program calls macro SP and the calculation proceeds automatically. Initially the input data is printed and then results populate the cells. Usually at least 500 steps are necessary for a transient duration of ten hours. Once the calculation has been performed, it is advised to answer No to the question Salvare le modifiche ( Save the modifications ) in order to preserve the sample opening page for future use. 

It is advised to choose, for the transients with liquid efflux, a DPI of 5 (kg cm ) and an initial DPI of 0.5 (kg cm ). If the calculated DT is in any case too long (indicatively higher than 1000 s) the calculation should be repeated with a lower DPI, down to 0.3-0.2 (kg cm ). It is advisable not to leave zeros in the input data and to replace them with very small, mutually consistent, numbers. 

The version of the program described here does not foresee the study of Anticipated Transients Without Scram (ATWS) or the calculation of the pressure in a water tank where the primary liquid from the depressurization system is discharged. For additional calculations of this type, the following notes and formulae may be useful. 

For calculations of this type, the evaluation of the shutdown effect of the depressurization is interesting. The depressurization, in fact, causes a loss of primary liquid and a pressure decrease which increase the steam volume in the core (the void content of the core is increased) with consequent introduction of negative reactivity and shutdown of the chain reaction. These evaluations can be done taking into account that results consistent with refined calculations are obtained by assuming that the core shutdown occurs for an average void ratio a in the primary system of 30 per cent. The value of a can be calculated by the following formulae  

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