Quality evaluation of domestically manufactured zircaloy tubing for nuclear fuel cladding was carried out in 1972, with the view to utilizing the material in part of the reloading fuel assemblies for the Tsuruga Power Station of the Japan Atomic Power Co., on which occasion, some discrepancies were found among the test results obtained by several investigators who had contributed to the project. Consequently, a cooperative study was carried out for the purpose of standardize the testing procedures.
As a first step, the subjects of examination were limited to tensile and burst tests, and to measurements of grain size and hydride orientation. The tests were repeated several times and the results obtained were compared.
As a result, the test data obtained by the different investigators could be brought into satisfactory agreement and adopted as reliable practical criteria.

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The two-phase discharge coefficient C_D of a large sharp-edged orifice was derived experimentally from the ROSA-I data of the Japan Atomic Energy Research Institute. These orifices are used for predicting the discharge flow rate in the event of a loss-of-coolant accident occurring in a light water nuclear reactor. In this analysis, x₀ the transient value of the quality of the discharged fluid in the high pressure reservoir, is calculated from the reservoir pressure P₀ and the weight w of the residual fluid, using the "depressurization rate method", proposed in the 2nd report of the present series. Furthermore, the standard value of the two-phase critical weight velocity G_C is obtained with use of the author's theory presented in the 1st report.
The relation between C_D and x₀ varies markedly according to the quality. When x0 is not so small, C_D is determined only by the orifice diameter D, and does not vary with x₀ or P₀. When x₀ approaches zero, C_D increases sharply, reaching a value of 1.5. At the same time it increases slightly with decreasing P0 and with decreasing D.
The physical meaning of this behavior of C_D is considered as follows. When x₀ is not very small, flow contraction occurs immediately downstream of the orifice, and at the same time there take place the severe supercooling of the steam phase pointed out in the 2nd report. The value of C_D diminishes below unity, for these two reasons, the latter being probably more important. On the other hand, when x₀ is close to zero, the rapid depressurization of the fluid causes a shortage of bubble nuclei, which prevents vaporization from proceeding at the rate dictated by the depressurization, and this raises C_D above unity.

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A method of calculation is proposed for finding the flow rate at each stage in an asymmetric ideal cascade for the case where α=β^s/t, α and β being the head and tail separation factors, respectively, while s and t are integers. Using this method of calculation, the values of the flow rate at each stage in the asymmetric ideal cascade for α=β⁵ and α=β^3/2 are calculated.

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