Plasma parameters, like the internal inductance li and the diamagnetic poloidal beta βDIA, are of particular relevance for a reliable real-time control system of next step Tokamaks. These and other quantities have been obtained at JET (Joint European Torus) with a method that uses the Shafranov integrals S1, S2 and S3. Indeed they allow the direct calculation of the Shafranov parameter Λ = βMHD + li/2 and of βDIA. Moreover, in discharges with a sufficiently high elongation (k > 1.3 typically), the internal inductance can be separated from the MHD poloidal beta βMHD and calculated independently, through the Shafranov integrals, with a precision which is more than satisfactory for real-time applications. It is worth mentioning that, since S1, S2 and S3 are integrals defined on the plasma boundary, a specific algorithm, depending on the fast code XLOC, has been expressively developed to determine this quantity. The method to determine the plasma parameters has been verified off-line, benchmarking its outputs with the estimates of the most sophisticated equilibrium codes available. The results of this systematic comparison have been very encouraging both in the limiter and x-point phases of the discharges and on all the investigated plasma configurations. The computational time, necessary to determine the plasma boundary and about 50 signals, is only about 1.5ms on a PC equipped with a 400MHz Pentium II, well below the 10ms constraint of JET real-time applications. The code has therefore been implemented on-line and its outputs have already been exploited to achieve the feedback control of some plasma parameter