A motor stand of a primary motor-driven pump unit of a pressurized water nuclear reactor comprises an upper flange and fixing means suited to ensure the fixing of transverse holding means of the said primary motor-driven pump unit, the said primary motor-driven pump unit comprising an electric motor having a lower flange suited to be integrated with the said upper flange of the said motor stand. The motor stand is characterized in that the said fixing means comprise an annular element resting on the said upper flange of the said motor stand suited to be flanged between the said upper flange of the said motor stand and the said lower flange of the said motor, the said fixing means comprising at least one radial excrescence in which there is arranged a space suited to receive the said holding means.