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Collaborative Web Application to Support Source Term Assessment

Introducing TIUKU system, a collaborative web application for analyzing radiological emergency situations. It includes features such as dispersion and dose calculation models, viewing radiation measurements and weather data, inputting nuclear power plant status, exporting results, and preparing situational reports.

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Collaborative Web Application to Support Source Term Assessment

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  1. Collaborative Web Application to Support Source Term Assessment Tuomas Peltonen, Thomas Lehtomäki STUK - Radiation and Nuclear Safety Authority NERIS Workshop 2019, Roskilde, Denmark 5.4.2019 [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  2. Outline • Introduction to TIUKU system • Source term input form and source term database • Source term exchange in IRIX format • Nuclear power plant status form • Automatic NPP parameter transfer • Examples of releases • Challenges in source term assessment [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  3. Introduction to TIUKU system • TIUKU (From Finnish ”TIlanne- ja UhkaKUvajärjestelmä”, In English ”Situation awareness and threat analysis system) • Developed at STUK since 2006 in co-operation with Finnish Meteorological Institute FMI (pre-study in 2004). Accessible from STUK and FMI. Formerly known as KETALE. • TIUKU system is a collaborative web application that provides a single user interface for all tools needed in analysing radiological emergency situations. • TIUKU has been developed using open source software • Web application Pyramid (Python Web framework) • UI has been developed using plain HTML and jQuery • MongoDB NoSQL database • Mapserver WMS/WFS Service [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  4. Introduction to TIUKU system: Key features • Running of dispersion and dose calculation models and viewing the results • Viewing of observations like radiation measurement results and weather data • Input and display of nuclear power plant status (main safety functions) • Exporting of results to other systems and PDF printing • Preparing situational reports and countermeasure recommendations • Flexible content management system [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  5. Introduction to TIUKU system MEASUREMENTS (simulated) DISPERSION RECOMMENDATIONS REPORTING [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  6. Source term input form and database • In TIUKU source terms are harmonized so that they can be used by different software i.e. from database it is possible to produce source term in different formats. • Some pre-defined source terms are stored in a database, and they can be used if source term assessment is unknown. • Source terms can be input either as percentages of reactor inventory per time period or as Bq’s per time period. • Inventories of domestic NPPs are up-to-date in TIUKU • Different ways for grouping of nuclides and also input of single nuclides. • Source terms are then saved into database including version history. • Further source terms are used as an input for dispersion calculations either by making a Web service request via TIUKU system or by exporting the source term to other software. • It is significantly better to exchange information electronically between different software due to complex input and to minimize typing errors. [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  7. Source term input form and database [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  8. Source term exchange in IRIX format • TIUKU source term handling fully supports IAEA’s radiological information exchange format IRIX. • Both importing and exporting of the source term is possible in the system. This makes it possible to import source terms to TIUKU generated by third-party software and also to use exported source terms in JRODOS decision support system for example. • TIUKU IRIX files have been tested against IRIX XML schemas. 3rd party sourcetermassessmentcode JRODOS IRIX import Model result IRIX export IRIX import STUK’sother dispersion and dosecalculation software Source term TIUKU [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  9. Nuclear power plant status form • Reliable data of the status of the nuclear power plant’s safety systems is needed in order to estimate the source term. • There is an automatic data transfer and display system from the power plant's process computer to STUK. • Situational information is also gathered from other available sources. For maintaining situational awareness during an emergency TIUKU has a form for reactor safety assessment. • In the form users define the current status of safety functions and other relevant information. The assessment can be exported as a report including a layout of the nuclear plant with status of safety functions (color coding). [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  10. Nuclear power plant status form Status of safety functions Web form Status of safety functions visualised in schematic nuclear power plant figure Edit status of individual safety function [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  11. Automatic NPP parameter transfer • reactor main parameters • primary circuit main parameters • secondary circuit main parameters (pressurised water reactor) • make-up water and emergency cooling systems • decay heat removal systems • containment main parameters • the most important reactor and plant protection signals • the most important electrical systems • radiation situation at the plant unit • radiation situation at the site area • radiation situation in the vicinity • meteorological data. [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  12. Examples of releases (median and 95 % percentile) • PRA sequences work well early in the accident when there are many uncertainties • The probabilities and source term distributions give a rough estimation for possible scenarios • It’s important to understand the assumptions behind the PRA level 2 sequences! [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

  13. Challences in source term assessment • The main challenge of estimating the source term are the uncertainties related to the plant parameters, inconsistency of data and hidden or unknown failures in important safety systems. • In STUK a spectrum of pre-calculated accident scenarios derived from PRA level 2 are used to provide a base source term. • The accident timing is adjusted by using expert judgement. • When a source term is estimated before the release, it is not known if the operators will succeed with all the critical operator actions. • There is also always a risk that the containment fails in an unexpected way. Therefore the estimation of the source term boils down to confidence levels: • How much confidence is needed to estimate a small source term when severe accident systems work and are operated as designed. [Collaborative Web Application to Support Source Term Assessment, Tuomas Peltonen

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