MARLA is an easy-to-use tool for planning and optimizing BWR fuel shuffles. MARLA addresses the industry need for licensing-grade reactivity analysis in support of core alterations by fully analyzing each intermediate core configuration for shutdown margin.

Automated Shuffle Design

Design and optimize your fuel shuffle better than ever before with maintenance and cask load planning.

Licensing-Grade SDM Analysis

MARLA automatically analyzes all intermediate core configurations for shutdown margin using a full 3D SIMULATE solution.

Streamlined Core Reload

MARLA allows core designers and reactor engineers to work on the same platform to efficiently prepare for an outage.

Automated Shuffle Design

MARLA is capable of planning an entire fuel shuffle, including design and optimization of the fuel movement schedule, analysis of core shutdown margin, and generation of the Fuel Movement Checklist for operations. Point-and-click graphics allow the user to easily and quickly define all maintenance work scheduled to take place during the refueling outage, including:

  • Control blade and/or drive replacement
  • Detector replacement or inspection
  • Bundle inspection, sipping, or re-channeling
  • IVVI work

MARLA automates shuffle design by splitting it into two phases: Phase I shuffles the core to open the maintenance window and Phase II shuffles the core out of the maintenance window to reach the new reference loading pattern.

Each phase is designed independently, so that engineers can plan maintenance work without sacrificing core reload efficiency. MARLA also allows the user to define a separate type of shuffle in each phase to accommodate demanding outage schedules and provides automation to perform a full core offload of all bundles at any point during the shuffle plan.

All BWR containment designs are supported, including GE Mark-III containment with dual bridges and a fuel transfer tube between buildings.

Licensing-Grade Shutdown Margin Analysis

MARLA executes a series of parallel SIMULATE cases to fully analyze each intermediate core configuration for shutdown margin, based on a dynamic process that determines the extent to which cells surrounding an inserted bundle are influenced. Shutdown margin is analyzed as the shuffle design progresses to ensure that each step provides the desired margin, as defined by the user.

Existing shuffle plans can be re-analyzed at any time and all calculations are performed using the 3D, licensing-grade nodal methods used in SIMULATE. There are no additional geometry or spectral approximations used. Shutdown margin calculations are entirely controlled by MARLA and require no working knowledge of SIMULATE.

Cask Loading Campaigns

MARLA can be used to determine the bundles that should be loaded into dry storage casks to meet future storage needs. After the user inputs future cask loading dates, MARLA finds bundles in the storage pool that will meet target heat loads and constraints imposed by the cask vendor.

MARLA contains an internal library of cask designs and plans the loading of bundles into casks well into the future in order to ensure that the plant will be able to fully load all casks safely without violating heat load limits.

Fuel Pool Management

MARLA calculates decay heat load of each bundle in the core and of each bundle in the fuel storage pool. Decay heat loads can be calculated on a step-by-step basis throughout the shuffle as bundles are moved from core to pool or from the pool to the core.

The user can easily re-arrange the contents of the pool or sub-divide the pool for different storage zones. MARLA features an automated implementation of B.5.b guidelines for spent fuel storage; automatically arranging the pools to open holes in a 1-in-5 pattern using cooling times to define hot and cold bundles.

Streamlined Core Reload

MARLA works with any existing CASMO/SIMULATE core model, allowing engineers and core designers to simultaneously prepare for a refueling outage.

After the user inputs shuffle design constraints, MARLA can re-design and re-analyze the shuffle in real-time, removing the need to build time-consuming contingencies into the shuffle plan. By providing superior reactivity management and increased shuffle efficiency, MARLA protects against reactivity surprises during the refueling outage, dramatically reducing planning time and outage costs.

With tools to manage fuel pools and nuclear components as well as automate the choice of bundles to be loaded into dry storage casks, MARLA replaces many task-specific and in-house software programs currently in use at many nuclear plants.

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