## Criterion for significant runaway electron generation in activated devices A disrupting plasma in a high-performance device such as ITER and SPARC may generate large runaway electron (RE) currents that, upon impact with the tokamak wall, can cause serious damage to the device. To quickly identify regions of safe operation in parameter space, it is useful to develop reduced models and analytical criteria that predict when a significant fraction of the Ohmic current is converted into a current of runaway electrons. Such models have previously been developed for Dreicer [^1][^2] and hot-tail [^3] seed currents. In DT experiments however, the contributions from tritium decay and Compton scattering to the seed current may also be significant or even dominant. In this work, we extend previous work and develop a semi-analytic criterion that includes seed currents from tritium decay and Compton scattering. In addition, the avalanche multiplication factor includes effects of partial screening of heavy ions [^4]. The result is a semi-analytic model that can predict significant RE generation in the next generation of activated devices and is suitable for integrated modeling. The model is validated by fluid simulations in DREAM and is shown to delineate regions in parameter space of significant runaway generation. [^1]: P Helander, L-G Eriksson and F Andersson (2002). Runaway acceleration during magnetic reconnection in tokamaks. [Plasma Phys. Control. Fusion **44**, B247–B262](https://iopscience.iop.org/article/10.1088/0741-3335/44/12B/318) [^2]: H Smith, P Helander, L-G Eriksson, D Anderson, M Lisak and F Andersson (2006). Runaway electrons and the evolution of the plasma current in tokamak disruptions. [Phys. Plasmas **13**, 102502](https://pubs.aip.org/aip/pop/article-abstract/13/10/102502/936212/Runaway-electrons-and-the-evolution-of-the-plasma?redirectedFrom=fulltext) [^3]: T Fülöp, H M Smith and G Pokol (2009). Magnetic field threshold for runaway generation in tokamak disruptions. [Phys. Plasmas **16**, 022502](https://pubs.aip.org/aip/pop/article-abstract/16/2/022502/105556/Magnetic-field-threshold-for-runaway-generation-in) [^4]: L Hesslow, O Embréus, O Vallhagen and T Fülöp (2019). Influence of massive material injection on avalanche runaway generation during tokamak disruptions. [Nucl. Fusion **59**, 084004](https://iopscience.iop.org/article/10.1088/1741-4326/ab26c2)