Drawing device for in-core instrumentation detector

One inlet pipeline is disposed on the side surface of a casing on the side of a reactor container. A plurality of exit pipelines are disposed on the opposing side surface while being distributed on a circumference of a circle having its center opposite to the center of the inlet pipeline. A fixed shaft is disposed on the side wall at which the exit pipelines are disposed. A cylindrical shaft is supported rotatably to the fixed shaft. A radial arm is disposed at the end of the cylindrical shaft on the side of the exit pipelines, and the arm has an opening for loosely engaging the other end of a rotatable guide tube rotated intermittently around an inlet pipeline as a center. A counter weight having the same weight as the arm protruding on the side opposite to the arm is disposed at the end of the cylindrical shaft to which the arm is disposed. A fine control weight is disposed in the vicinity of the top end. With such a constitution, imbalance upon rotation of the cylindrical shaft can be eliminated, each of the exit pipelines can be indexed accurately when the number of the exit pipelines is great. (I.N.)