Nuclear power plant operators are under constant pressure to reduce the operating cost of their assets. PWR operators are no exception, they are continuously looking for cost reduction in loading the reactor core together while at the same time satisfying challenging safety requirements. Finding the best PWR reload pattern fulfilling all the limiting criteria is a very complex task. The LPOpt software developed by UJV helps to solve this problem.

LPOpt main features:

• LPOpt is the software developed by UJV for fast, robust, flexible and reliable PWR core loading pattern optimization maximizing fuel utilization and fulfilling operational and safety requirements in the best possible way.
• LPOpt is based on the current state of the art combinatorial Estimation Distribution Algorithm (EDA) combined with a unique multi-objective pareto- optimality search concept developed at UJV to find suitable (sub-optimal or the best possible) loading patterns for user-predefined fuel assembly assortment. LPOpt is extremely robust, as it is designed to use a very small number of optimizer internal control parameters. Once defined by the user for a given optimization task (selected PWR core response parameters, fuel assembly assortment, and constraint conditions), they remain the same for all subsequent optimizations.
• LPOpt is very flexible, since it allows users to define very general constraints (restrictions) on core response parameters, possible positions - fuel assembly types - fuel assembly rotations, and it also allows for a set of user-defined starting loading patterns (based on user expertise), which significantly speed up the convergence rate of the optimization process.
• LPOpt is an extremely powerful and simple to use multi-parameter optimizer connected to an external PWR 2D-3D core simulator working as a black-box in stand-alone regime for parallelized, fast and accurate evaluation of user-selected core cycle response parameters.
• LPOpt is extremely reliable, as it is able to find optimized fuel cycle patterns satisfying safety margins and additional user-specified constraints by evaluating up to millions of loading patterns per hour.
• LPOpt is able to search for sub-optimal loading patterns in two basic regimes: fixed search – the number of available fuel assemblies is equal to the number of in-core positions; expanded search – the number of available fuel assemblies is greater than the number of core positions.
• LPOpt was developed by UJV to provide a unique in-core fuel management tool with a simple and effective user interface, giving the user an immediate benefit.

• Find loading patterns in 5 minutes or up to a day
• Next cycle design + support for complete reload safety evaluation Finding suitable fuel assembly assortments (via the expanded search regime!)
• Emergency loading pattern design (contingency plan)
• Multi-cycle analysis
• Fuel-Operational economic evaluations
• Strategic “what-if” scenarios
• Specific loading pattern search and cycle-core prediction

• LPOpt is a heuristic and stochastic evolutionary algorithm
• Simultaneous search for proper fuel assembly positions and their rotations.
• Highly flexible ways to incorporate user knowledge or experience to control the optimization process:
  • Highly flexible and general constraints on fuel assembly position – type – rotation
  • Fully stochastic loading pattern search or search starting from user-predefined set of
• loading patterns
• Fuel assembly assortment may be bigger than number of in-core positions (fixed vs expanded search regime!)
• LPOpt utilizes a completely new stochastic sampling algorithm (developed by UJV) for effectively generating new reliable loading patterns by continuously updating the probability distribution of loading patterns corresponding to the best pareto-optimal core responses. LPOpt utilizes a fully multi-objective + constrained optimization. Each evaluated core response parameter can be either constrained or both constrained and optimized (minimized or maximized) at the same time.
• LPOpt utilizes a unique (multiplicative) multi-objective penalization algorithm to reliably and effectively handle all constraint conditions on core response parameters.
• LPOpt is fully functional and implemented to optimize loading patterns for WWER energetic reactors (WWER-1000 and WWER-440)
• Utilization of UJV’s ANDREA 2D-3D core simulator:
  • very fast 2D responses ~ 0.2sec/LP/cpucore, highly accurate 3D responses ~ 100 sec/LP/cpucore (2D-3D core response corrections are applied effectively during optimization process!)
  • 1/6 symmetry core (WWER) evaluation (no need to apply 1/12 sub-symmetry on WWER- 440!)
  • well scaled core response evaluation task distribution (via parallelization) on available computing resources utilizing high-speed I/O communication through the network (multi- core computing servers or multi-node computing clusters).
  • Typical computing time of optimization task (depending on user computing resources and task definition!): from 10 minutes to 1 day.
  • General possibility to utilize any other (user-preferred) stand-alone core simulator (This solution is not so effective as a solution based on ANDREA core simulator!)
• Very simple preparation of optimization tasks and corresponding input data
• Fully scriptable command-line interface
• Wide range of output data format and result content specifications
• General compatibility with many Linux OS distributions (RHEL, Dabian, Ubuntu, etc.) Windows or UNIX operating systems are not supported!

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