NDTnet 1998 Aug, Vol.3 No.8

Abstract

ENUSA equipments called Gamma Scanner are a combination of different detector of gamma radiation to control uranium enrichment and gaps and electromagnetic detectors to control fuel rods internals and rod surface. Tree different equipments are used.

Eddy Current differential coil to inspect surface defects in fuel rods. System are working at 3Mhz with alarm box and are ready to detect big scratches of 0,10 mm depth and holes of 0,5 mm of diameter and 0,2 mm dept.

Active Gamma scanner consists mainly in a neutron source of 1,5 mg maximum of ²⁵²Cf and three scintillator of INa(Tl) with four photomultipliers by scintillator to check fissile content. A source of ²⁴¹Am is used to control the fuel stack gaps and plenum length by gamma transmission. This system is controlled by two computers that automatically calculate parameters of inspection according to fuel rod design and basic equipment conditionsDetection capability of the system for individual deviant pellets of 10 mm length is 8 % relative to nominal value with 70 % of confidence and a false reject lower than 5 %. Length precision are in the order of 1,0 mm or better (rod, plenum, enriched zones, gaps).The Passive Gamma Scanner & Gd Detector have been developed to check variations of Gd and ²³⁵U in gadolinium fuel rods. It is equipped with 32 BGO detectors for enrichment control; a densitometer of slam to control pellets stack, plenum length and gaps; and a magnet with coils to control % of Gd₂O₃ by the use of eddy current technology. This detector will detect gaps and diameter variations and modifications in pellets and that permit to control density, diameter and integrity of fuel pellets column inside fuel rod assembly. The system is controlled by a VAX computer that processes all the signals and generates control parameters.Using a scanning speed of 1 m/min, the following system capabilities are obtained: a) Length (fuel stack, rod, plenum ) < 1.0 mm with 95 % confidence. b) A single 10 mm length enrichment deviant pellets of < 10 % relative to nominal with 70 % confidence, and c) A single 10 mm length gadolinium deviant pellet of < 0.5 weight percent of Gd with 70 % confidence.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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