Posiva’s Spent Fuel Database

A spent fuel management system is imperative for the function of Posiva’s new final disposal site, which is to be a final disposal site for SNF from Olkiluoto and Loviisa Nuclear Power Plants in Finland. You can find more about our Posiva references here.

PATI

PATI is a sophisticated nuclear material management system including nuclear material bookkeeping and authority reporting, support services, and extra modules for fuel assembly handling among other functions. PATI is a safeguards solution that is fine-tuned and developed in co-operation with the customer. IAEA and national authorities set clear requirements for safeguards operations for nuclear facility operators. Fortum’s in-house expertise can respond to both the needed safeguards expertise and IT software delivery capability. 

PATI is used as a daily tool for managing tasks like nuclear material reception, planning of fuel transfers, planning for reloads, planning the use of spent fuel storage capacity and accountancy reporting to Authorities. Management of these tasks concerns many users at power plant. These users and their tasks may be following:

• Nuclear Material Responsible Person: Authority reporting
• Reactor Engineer: Management of fuel stores, planning of transfers, reloads and reporting
• Reactor Physicist: Information for planning of reactor reloads
• Fuel Procurement: Fresh fuel stock
• Fuel Manufacturing Surveillance: Fuel information for reactor reload license
• Fuel examinations: Fuel history, fuel damage information

Concise and valid data is needed to meet user requirements in a format that is easy to use and maintain. Fortum uses PATI to meet the need by main functions such as:

• Centralized storage for fuel life time data
• Import and operation license information of fuel assemblies
• Usage and movement history of fuel assemblies
• Mass changes of fissile Uranium and Plutonium isotopes during plant operating cycles
• Graphical maps of internal rod burn-up of fuel assemblies after any given plant cycle
• Graphical maps of fuel assembly locations on any given date
• Residual thermal power of fuel assemblies at any given date
• Planning of reactor reloading and transfer operations
• Generation of instructions for the fuel handling machine (FHM) operators
• Generation of fuel movement files for the FHM automation system.
• Authority reporting (PIL, ICR, MBR)

As mentioned PATI being a tried and trusted nuclear material management software it was seen as a natural basis on which Fortum could build a new case specific software for Posiva. Creating a new system based on prior experiences always enables a possibility for improvements. In the case of KAAPO, which in practice is a modified and upgraded PATI system, Fortum were able to provide Posiva with an existing software platform, good understanding of customer needs, as well as the capability to consult the customer with advanced solutions. Teollisuuden Voima Oy, the other Nuclear operator in Finland, has also been involved in the development of Kaapo.

The KAAPO software uses the collected fuel assembly data from the Finnish power companies and  not only performs nuclear material accounting, but also optimizes the best selection of fuel assemblies and their mutual configurations in the disposal canisters according to the set boundary conditions for safety. It was recognized that KAAPO provided a motivation to improve how we think of SNF management and functions of PATI were further developed and added to Posiva’s database system. These functions include most notably optimizing the loading and configuration of the nuclear fuel to further improve the efficiency and safety of the final disposal facility.  After starting a SNF disposal cycle, the software follows the fuel assemblies from their unloading from a transport cask, through the encapsulation and lastly to the final disposal in the tunnels about 450 meters deep in the Finnish bedrock. All the actions performed for the fuel assemblies, as well as the locations where they have been are logged into the database. The database has been built in a manner that it is able to provide the necessary nuclear safeguards reports for the state regulatory authority, the European Commission and the IAEA.

User cases where KAAPO can be utilized include:

• UC1, Decay heat production
• UC2, Nuclear criticality safety
• UC3, Transport and transfer planning
• UC4, Nuclear materials bookkeeping and reporting
• UC5, Loading optimization of the canister
• UC6, Nuclear waste bookkeeping
• UC7, Internal reporting
• UC8, Maintenance of the canisters
• UC9, Maintenance of the tunnel layout model

The Trial Run of Final Disposal started on 30^th of August 2024. This trial run functions as the final test for KAAPO, where the software will play a vital role in the testing procedures. The trial run is performed in an identical manner to how ONKALO® would during the operational phase with SNF, however the actual SNF assemblies  will be replaced with dummy assemblies. KAAPO functions as the main SNF database software during the test. 

KAAPO, as a unique project separated from the baseline PATI, works as a great reference on how a pre-existing system may be tailored to match the customer needs. Posiva is a very special customer for Fortum as the company aims to be the first operator of a final disposal site for spent nuclear fuel in the world. Thus the IT systems amongst other plans have to be reliable and proven. 

The spent fuel database system provided by Fortum could achieve, and even exceed the requirements, while Fortum continues to provide the support and maintenance of the system for Posiva in the future as the final disposal facility is commissioned for active use. 

This software is presumably one of the first of its  kind in the world, since a majority of countries within the nuclear industry are in the early stages of nuclear waste final disposal development. As a forerunner in this field, KAAPO will continue developing as it is used, and will function as a trailblazer for all similar solutions to come.