METHOD AND DEVICE FOR PRODUCING GUIDE PIPE FOR MEASURING ELEMENT OF NUCLEAR REACTOR

摘要

PURPOSE:To form efficiently a uniform nitrided layer and to obtain a guide pipe having high reliability by heating the guide pipe consisting of a stainless steel to high temp. while introducing gaseous ammonia therein. CONSTITUTION:A guide pipe 18 for a measuring element of a nuclear reactor consisting of a stainless steel and having a small diameter and long length is heated to a prescribed high temp. Gaseous ammonia is introduced into the pipe 18 heated to the high temp. from one of the two open ends to the other alternately plural times by changing the flowing direction to form a nitride layer 19 in the pipe. The treatment is accomplished in this stage by controlling the degree of dissociation of the gaseous ammonia to 20-45%. The nitrided layer 19 having a desired thickness and uniform quality is thus formed on the inside surface of the pipe 18 by which the pipe 18 having high reliability is obtd.