International Society for Industrial Process Tomography

The Design of Electrical Impedance Tomography
Detectors in Nuclear Industry

Mathieu Darnajou^1,2*, Chunhui Dang^1,2, Guillaume Ricciardi¹,

Salah Bourennane², Cédric Bellis³ and Holger Schmidt⁴

¹CEA Cadarache, 13115 Saint-Paul-lez-Durance, France

²École Centrale de Marseille, 38 Rue Frédéric Joliot Curie, 13013 Marseille, France

³Laboratoire de Mécanique et d’Acoustique, 4 impasse Nikola Tesla, 13013 Marseille, France

⁴Framatome GmbH, Paul-Gossen- Str. 100, 91052 Erlangen, Germany

^*Email: mathieu.darnajou@cea.fr

ABSTRACT

The Electrical Impedance Tomography detector designed to measure the flow pattern in the primary circuit of nuclear plants is a cylinder that includes one or several rings of electrodes. This paper aims at determining the requirement on the design of the electrodes, the diameter and length of the cylinder being constrained by the circuit pipe. Since the electric potential is imposed during measurements, the image reconstruction quality of the images is optimised for the largest area of the electrodes. The angular size is maximised, respecting a minimal gap of 1mm due to technical constraints. The axial size has to be maximised as well, nevertheless, the pipe elements upstream and downstream the detector being made in conductive stainless steel, a leakage of current is expected if the isolation layer to the electrodes is thin.

This paper presents the results of a simulation campaign, where the C++ software FreeFem++ were used to quantify the leakage that depends on the electrode area and the isolation layer thickness between the conductive pipes and the electrodes. Another interest, is the counterintuitive behaviour of the sensitivity map of measurements. The sensitivity function relates the magnitude of an internal change in voltage measured between electrodes to the change in resistivity which has given rise to it. To validate this behaviour, numerical and experimental research axis are considered at the CEA Cadarache, France.

Keywords LOCA, Current Leakage, Sensitivity, FreeFem++

Industrial Application Nuclear Industry and general industrial EIT