3D Laser scanning to measure thermal sleeve misalignment in PWR vessel head

Cuevas, Esmeralda; TECNATOM, SA; Spain

Garrido, A.R.; Tecnatom S.A.; Spain
Montero, S.H.; Tecnatom S.A.; Spain

ID: ECNDT-0482-2018
Session: Nuclear Industry 1
Room: H2
Date: 2018-06-13
Time: 11:10 - 11:30

Under certain conditions, a wearing process occurs on the support flange of the thermal sleeves of the PWR reactor vessel head penetrations. This mechanical wear is due to the water flow turbulences into the vessel which make movements on the sleeves which affect to the support flange of the thermal sleeve and the surface of the control rod drive mechanism housing (CRDMH) where the sleeve flange is seated, lowing the thermal sleeve from its initial position. This issue is named misalignment.
Due to the interesting area, has limited access to perform a visual inspection, even remote, TECNATOM has solved this matter taking measures of the distance between the lower edge of the thermal sleeve funnel and the lower edge of the associated CRDMH. These measures are taken by laser scanning techniques from the inside of the head.
Tecnatom has developed a specific end-effector to carry out the laser scanning inspection as a part of the Tecnatom vessel inspections system, which is able to perform Visual, Ultrasonic and Eddy Current examinations in the reactor vessel head penetrations. The laser scanning end-effector is formed by a 3D laser scanner attached to a rotatory device which allows to get the distance all around the 360º of the thermal sleeve. The 3D laser scanner records simultaneously the edge of the thermal sleeve funnel and the lower Edge of the CRDMH, obtaining the vertical distance between both parts and checking if any variation on the vertical position has happened.
3D laser scanning dedicated software allows to compare the measures obtained with theoretical or historic data, to identify any variation of the values.
The 3D laser scanning inspection system has reached the accuracy target required and has been applied in a vessel head in service inspection last 2017 May, during the outage of a Spanish nuclear power plant.