Lisp at CORAPS

Doel 2


CORAPS  (Core refuelling automatic planning system)

What is it ?

CORAPS is a computer application for planning fuel reshuffling in PWR nuclear power plants. It is aimed at generating an optimal sequence of operations and assisting the supervisor during the reshuffling process.

For whom ?

CORAPS is designed to assist engineers in charge of planning and supervising the reshuffling process.

It provides an easy to use environment in which the user can accomplish the following tasks :

  • elaboration of the refuelling sequence;
  • visualisation, modification and checking of the refuelling sequence;
  • document printing, meeting QA requirements.

 What are its advantages ?

Its main advantages are :

  • increased safety;
  • time and cost saving;
  • improved plant availability, cost effectiveness;
  • fast response time in case of problem during refuelling (e.g. damage to a fuel assembly).

Main functionality

The main features are the following :

  • optimality of the sequence;

  • satisfaction of constraints;

There exists a large diversity of constraints due to plant particularities and the differences in user strategies. CORAPS is able to take this variety into account.

  • speed of sequence generation (with CORAPS 2 or 3 days, manually 2 weeks);

  • assistance to user for :
    • visualising and modifying the program's output both before and during the reshuffling operations;
    • validation of user modifications.

  • reliability of printed sequence documents;

  • easy interfacing with local databases and applications (fuel management).

How does it work ?

The greatest challenge is to mimic the human expert, and take advantage of the expertise that is already available, while exploiting the computer's searching power. The main objective of CORAPS is to automate and speed up the generation of an optimal sequence, in accordance with both physical and user constraints. To achieve this objective, a number of search algorithms have been implemented. The searches are exhaustive when feasible, or guided by a right set of heuristics that can limit the search space without missing optimal solutions.

Site customisation

A large variety of constraints and strategies are already implemented within CORAPS. Thanks to this flexibility, CORAPS can be quite easily adapted to other PWR nuclear installations, using the same kind of equipment or following similar strategies.

Computer environment

CORAPS is developed in LISP + CLOS (Franz Allegro Common Lisp), making extensive use of object-oriented programming facilities for the development of the user interface. It runs under Windows NT on a Pentium based PC equipped with 64 MB of memory.


CORAPS has been developed since 1987 and is fully operational since 1990. It is now the standard tool for the seven Belgian PWR plant reshufflings (more than 80 refuelling sequences have been generated with CORAPS).

Flow chart of the CORAPS computer application

A graphic display screen of the reactor building
This interface allows step by step visualisation of the refuelling sequence (top window).
At each stage, the content of the containment and the fuel buildings is presented (left window).
A dedicated editor (right window) enables the user to delete,
move or modify any operation generated by the planning module.

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Last update : 22/11/2001