Dynamic HRA in outage from literature and outage personnel interview perspectives

In 2021, the goal of the SAFIR2022 project NAPRA task T3.2 was to provide an overview of an outage of a nuclear power plant from the perspective of human reliability analysis (HRA). The general features of the outage as well as the specific matters related to human reliability and dynamism in the outage context were studied from literature and outage personnel interview perspectives.The safety-critical nature of an outage is well recognized, and there is a wealth of literature on the specifics of outage and the challenges associated with the successful completion of work. HRA methods have mostly been developed for full power conditions where the operator’s actions are well trained and laid down in procedures, in time frames typically less than 60 minutes. In the planned shutdown the work concentrates outside the control room, is less in procedures and less trained and the time frames may be much longer. The environment is continuously changing, there are huge number of workers, large variety of work activities, tight schedule and the requirements are high concerning both safety and productivity. The key issues that should be considered in the HRA are errors of commission (EOCs), dependencies between human actions and the dynamism of the operating environment.One practical objective of this report was to identify a scenario to focus on in further work related to dynamic modelling. Based on interviews, heavy loads were identified as critical but also mentally and physically loaded. They also include features identified safety critical in scientific literature. This scenario will be studied in more detail in 2022. Work analysis will be performed with special emphasis on applying a combination of methods to elicit the key dynamic features from the HRA perspective

Effect of sprinklers on the patient's survival probability in hospital room fires

The effectiveness of sprinklers in protecting a patient in a hospital room fire was investigated by performing 26 sprinklered and four free-burn experiments in real hospital rooms equipped with water-based automatic suppression system. Three different fire loads were used: UL 1626 corner test fire and two different textile fires. The measurements included temperatures, pipe pressure, and concentrations of about 20 different gas compounds. Based on the measurement results, we calculated the Fractional Effective Dose (FED) and Fractional Irritant Concentration (FIC) –values, and estimated the likelihood of incapacitation as a function of time. The results showed that sprinklers maintained temperatures at low level and reduced toxicity, mainly through fire development control. In UL1626 and large textile fires, sprinklers decreased the patient's incapacitation probability from 0.9 or above to the level of 0.4. In small textile fires, the difference between the incapacitation probabilities of sprinklered fires and free-burns was less than the measurement uncertainty. FED results were sensitive to the calculation method due to the different treatment of NOx –gases.Peer reviewe