Method of analyzing the changes in geometry of an irradiated fuel

Patent metadata

Field	Value
Publication number	US-9733074-B2
Application number	US-201414452300-A
Country	US
Kind code	B2
Filing date	Aug 5, 2014
Priority date	Aug 7, 2013
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A method for analysing at least one fuel rod comprising a stack of nuclear fuel, a rod comprising packed zones completely filled with fuel and intermediate zones partially full of fuel, comprises: acquiring a count profile associated with a non-migrating isotope, a profile being made up of spectrometry measurements taken along the rod for this isotope; determining a set of at least one indicator K_i that makes it possible to quantify the reduction in material at an intermediate zone of index i, the said indicator being deduced from the count profile; detecting the change in geometry by comparing the set of at least one indicator K_i against a set of at least one reference value RK indicative of the initial geometry of the nuclear fuel stack.

First claim

The invention claimed is:

1. A method for analyzing at least one fuel rod comprising a stack of nuclear fuel, a rod comprising packed zones completely filled with fuel and intermediate zones partially full of fuel, the method being implemented by an analysis system comprising a gamma ray spectrometry device having a sensor and a spectrometry processing unit, the method comprising the following steps:
measuring gamma ray radiation emitted by the nuclear fuel with the sensor of the gamma ray spectrometry device to acquire spectrometry measurements of said at least one fuel rod;
acquiring a count profile with the spectrometry processing unit associated with a non-migrating isotope in said at least one fuel rod, a count profile being derived from the spectrometry measurements taken along the at least one rod for said non-migrating isotope with the sensor of the gamma ray spectrometry device;
determining with the spectrometry processing unit a set of at least one indicator K_i to quantify a reduction in material at an intermediate zone of index i, the said indicator being deduced from the count profile; and
detecting a change in geometry of said at least one fuel rod with the spectrometry processing unit by comparing the set of at least one indicator K_i against a set of at least one reference value RK indicative of the initial geometry of the nuclear fuel stack.

2. The analysis method according to claim 1 , comprising a step of estimating the location of the intermediate zones by analyzing the count profile with the spectrometry processing unit.

3. The analysis method according to claim 1 , in which the detecting the change in geometry is detected in at least one intermediate zone and deduced by statistical analysis of the indicators of K_i, a change in geometry being flagged when at least one value K_i is incompatible with a theoretical measurement spread that could be expected with no change in geometry.

4. The analysis method according to claim 1 , in which the detecting the change in geometry is detected for at least one intermediate zone by comparing K_i with a predefined reference value RK, a change in geometry being detected when the ratio between K_i and RK exceeds a previously-chosen comparison threshold k1 or lies below another previously chosen comparison threshold k2.

5. The method according to claim 4 , in which the reference value RK is determined statistically by the mean of the K_i values observed experimentally over a plurality of rods of the same type.

6. The method according to claim 4 , in which the reference value RK is determined by theoretical calculation for a given pellet geometry.

7. The method according to claim 1 , in which the rod is a rod or a section of rod of PWR type made up of a plurality of pellets, an intermediate zone corresponding to an inter-pellet zone.

8. The method according to claim 1 , in which a non-migrating isotope of Ru-136 type is used to determine the count profile.

9. A system for analyzing at least one nuclear fuel rod comprising the gamma-ray spectrometry device and the spectrometry processing unit implementing the method according to claim 1 .

10. A computer program stored on a non-transitory computer readable storage medium containing instructions for executing the method according to claim 1 when the program is executed by a processor of the analysis system.

Assignees

• Commissariat Energie Atomique

Inventors

• Loubet Laurent
• Lacroix Brigitte
• Noirot Jean
• Martella Thierry

Classifications

• G21C17/06 Primary

  Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination (G21C17/08, G21C17/10 take precedence; detecting leaking fuel elements during reactor operation G21C17/04) · CPC title

• G01T1/36

  Measuring spectral distribution of X-rays or of nuclear radiation {spectrometry (pulse selection circuits per se H03K; investigation of materials by radiation diffraction G01N23/20; spectrometer tubes H01J49/00)} · CPC title

• G01B15/06 Primary

  for measuring the deformation in a solid · CPC title

• Y02E30/30

  Nuclear fission reactors · CPC title