Method for calculating a PCI margin associated with a loading pattern of a nuclear reactor, associated system, computer program and medium

Patent metadata

Field	Value
Publication number	US-11670429-B2
Application number	US-202217697887-A
Country	US
Kind code	B2
Filing date	Mar 17, 2022
Priority date	Jun 22, 2016
Publication date	Jun 6, 2023
Grant date	Jun 6, 2023

Abstract

A method for calculating a PCI margin associated with a loading pattern of a nuclear reactor including a core into which fuel assemblies are loaded according to the loading pattern is implemented by an electronic system. The fuel assemblies include fuel rods each including fuel pellets of nuclear fuel and a cladding surrounding the pellets. This method includes calculating a reference principal PCI margin for a reference loading pattern of the fuel assemblies in the core; calculating a reference secondary PCI margin for the reference pattern; calculating a modified secondary PCI margin for a modified loading pattern of the fuel assemblies in the core, and calculating a modified principal PCI margin for the modified pattern, depending on a comparison of the modified secondary PCI margin with the reference secondary PCI margin.

First claim

What is claimed is:

1. A method for calculating a pellet-cladding interaction margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets,
the method being implemented by a computer and comprising the following steps:
b) calculating a reference principal pellet-cladding interaction margin for a reference loading pattern of the fuel assemblies in the core,
c) calculating a reference secondary pellet-cladding interaction margin for the reference loading pattern,
d) calculating a modified secondary pellet-cladding interaction margin for a modified loading pattern of the fuel assemblies in the core,
e) calculating a modified principal pellet-cladding interaction margin for the modified loading pattern, depending on a comparison of the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin;
the method further comprising controlling, by the computer, the state of the power balance of the nuclear reactor by using the calculated principal pellet-cladding interaction margin for a considered loading pattern of the fuel assemblies in the core to avoid rupture by pellet-cladding interaction of the claddings present in the core,
wherein when the modified secondary pellet-cladding interaction margin is greater than or equal to the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is equal to the reference principal pellet-cladding interaction margin, and
when the modified secondary pellet-cladding interaction margin is less than the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is less than the reference principal pellet-cladding interaction margin.

2. The method according to claim 1 , wherein, when the modified secondary pellet-cladding interaction margin is less than the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is equal to the reference principal pellet-cladding interaction margin reduced by a corrective factor depending on the deviation between the modified secondary pellet-cladding interaction margin and the reference secondary pellet-cladding interaction margin.

3. The method according to claim 2 , wherein the corrective factor depends on a ratio between the modified secondary pellet-cladding interaction margin and the reference secondary pellet-cladding interaction margin and is strictly between 0 and 1.

4. The method according to claim 1 , wherein step b) comprises the following sub-steps:
b1) simulating at least one operating transient of the nuclear reactor,
b2) calculating the value reached by at least one physical quantity during the operating transient in at least part of a cladding of a fuel rod, and
b3) determining, as reference principal pellet-cladding interaction margin, the deviation between the maximum value reached by the value calculated in sub-step b2) during the transient and a technological limit of the fuel rod.

5. The method according to claim 4 , wherein the transient simulated in sub-step b1) is a transient chosen from among the group consisting of:
an excessive load increase,
an uncontrolled withdrawal of at least one group of control clusters,
a fall of one of the control clusters, and
an uncontrolled boric acid dilution.

6. The method according to claim 4 , wherein the method comprises, before step b), the following step:
a) determining a rupture value of the physical quantity characterizing a rupture of the cladding.

7. The method according to claim 6 , wherein step a) includes:
subjecting previously irradiated fuel rods to experimental nuclear power ramps,
calculating the values reached by the physical quantity in at least one cladding broken during a power ramp, and
selecting the rupture value as being the minimum value from among the calculated values reached.

8. The method according to claim 1 , wherein the method further comprises the following step:
f) determining a limit value to trigger an emergency stop and/or an alarm from the calculated principal pellet-cladding interaction margin and for the considered loading pattern of the fuel assemblies in the core.

9. The method according to claim 4 , wherein the physical quantity is chosen from among the group consisting of:
a constraint or a constraint function in the cladding; and
a deformation energy density in the cladding.

10. A non-transitory computer-readable medium including a computer program comprising software instructions which, when executed by a computer, carry out the method according to claim 1 .

11. An electronic system for calculating a pellet-cladding interaction margin associated with a loading pattern of a nuclear reactor comprising a core in which fuel assemblies are loaded according to the loading pattern, the fuel assemblies comprising fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets, the electronic system comprising:
a first calculating module configured to calculate a reference principal pellet-cladding interaction margin for a reference loading pattern of the fuel assemblies in the core;
a second calculating module configured to calculate, on the one hand, a reference secondary pellet-cladding interaction margin for the reference loading pattern, and on the other hand, a modified secondary margin for a modified loading pattern of the fuel assemblies in the core; and
a comparison module configured to compare the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin,
the comparison module further being configured to calculate a modified principal pellet-cladding interaction margin for the modified loading pattern, depending on the comparison of the modified secondary pellet-cladding interaction margin with the reference secondary pellet-cladding interaction margin,
wherein when the modified secondary pellet-cladding interaction margin is greater than or equal to the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is equal to the reference principal pellet-cladding interaction margin, and
when the modified secondary pellet-cladding interaction margin is less than the reference secondary pellet-cladding interaction margin, the modified principal pellet-cladding interaction margin is less than the reference principal pellet-cladding interaction margin.

Assignees

• Framatome Sa
• Schaeffler Technologies Ag

Inventors

• Andre Poyaud Gilles
• Galland Isabelle

Classifications

• G21C17/00

  Monitoring; Testing (measuring in general G01); {Maintaining} · CPC title

• Y02E30/30

  Nuclear fission reactors · CPC title

• G21D3/004

  Fuel shuffle simulation; fuel shuffle optimisation · CPC title

• G21D3/001 Primary

  Computer implemented control · CPC title

• G21C7/00

  Control of nuclear reaction · CPC title