| SAFETY & SECURITY


The release of hazardous material from a nuclear emergency has the potential to cross international borders. Using the RASTEP method, with generic plant data to gain an early idea of the effect of different scenarios, might be sufficiently robust to give local and national authorities the necessary insight to implement protective actions, even if some of the details are unknown or yet to be realised


in many ways. For example, a lack of realistic estimates of frequencies of crucial events might have been one of the roots of the Fukushima accident, where assessments questioning the tsunami design basis existed long before the earthquake of 2011. After these assessments some countermeasures were put in place — but these obviously did not go far enough. We can take this to encourage the view that safety assessments contain useful information that we might be able to use, should we need it. Inspired by various research projects, we found that


Bayesian Belief Networks (BBN), which are applied for decision-support in a variety of fields, may offer a means of bridging the gap between day-to-day safety assessment and emergency response. Causal relationships between factors and outcomes are already explored within the nuclear power industry. However, the BBNs provide something that standard assessments of facilities typically disregard – live observations. All EP&R protocols take in factors unique to a particular


site, such as design specifics and the local population, so no two emergency response plans are ever the same. This requires any commercial decision-support tool to be flexible. Our efforts led to the development of the RASTEP (Rapid


Source Term Prediction) methodology. It aims to have this flexibility, while being able to take compiled information, in the form of probabilistic data and deterministic source term analyses, from the level 1 and 2 PRA and supplement it with real-time information on plant conditions (also following the IAEA standards).


RASTEP has been designed to support decision-making during infrequent events, but we believe that the principle of using BBNs in this way can be translated into other uses and industries. This will give emergency decision- makers more insight, time, and resources to make the most appropriate call with the information currently at their disposal. Information derived from a BBN may, at least, provide another level of robust protection against information deficiencies. This could be vital in scenarios where seconds matter. The release of hazardous material from a nuclear


emergency has the potential to cross international borders. Using the RASTEP method, with generic plant data to gain an early idea of the effect of different scenarios, might be sufficiently robust to give local and national authorities the necessary insight to implement protective actions, even if some of the details are unknown or yet to be realised. Such tools may be especially fruitful countries with no or small- scale nuclear power programmes. Sharing information regarding a nuclear incident should


be as instant as possible and give the clearest possible picture. Taking the Fukushima accident as example, in emergency response outside Japan there were large differences between countries. Information sharing was limited, possibly held back by the extreme uncertainties of the situation and lack of insight in typical safety assessment results.


With the increased focus on fossil-free energy, this is


a time to strengthen our designs and methods further and to make full use the vast bodies of safety assessment information that have already been accumulated. We hope that our method of building such information into a BBN model for EP&R applications can serve as an interesting and inspiring example here. The success of nuclear in mitigating climate change and air pollution, as well as its potential to contribute to society in other sectors (hydrogen, heating, propulsion, production of medical isotopes) will be a question of performance and safety. We have both the responsibility and possibility to use the huge amounts of information already at our disposal to increase our chances. ■


Vysus Group’s whitepaper, ‘Aiding decision making


for accidents at nuclear power plants and wider markets’ is available for download at: www.vysusgroup.com/whitepapers/the-rastep- methodology-aiding-decision-making-for-accidents- at-nuclear-power-plants-and-wider-markets


www.neimagazine.com | January 2022 | 37


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45