## 1 Introduction  
The Joint European Torus (often referred to as just the JET) is the biggest tokamak experimental device ever operated, and it is one of only two devices to employ a deuterium/tritium mixture as fuel, the other being TFTR, which was discontinued in the late 1990s. The JET's operations began in 1983, with the initial tritium experiment conducted in 1991 (the first time tritium was used in a tokamak for a fusion reaction), followed by DTE1 in 1997, and the trace tritium experiment in 2003. At the moment, the JET is in its decommissioning stage after the successful completion of DTE2 and DTE3, which included a long period of deuterium and tritium operations carried out between 2018 and 2023. The experimental campaigns conducted will significantly contribute to the development of the ITER project. The JET will provide crucial experimental data for formulating ITER's operational strategies and advancing early designs for its optimal performance. The focus of the JET's DT operation and the use of its data will be dedicated to supporting efforts toward achieving ITER's research goal [1; 2]. The following paragraph provides a summary of the JET's experiment global technical parameters. The most crucial technical data are composed of numerous fundamental components. The first wall is made of solid tungsten (the divertor), tungsten-coated carbon fiber composites (CFCs) (also in the divertor's construction), and Be (the main chamber). The JET employs 16 toroidal field coils and 12 poloidal field coils, producing a maximum magnetic field of 3.45 T (normal) and 3.9 T (exceptional). The plasma current ranges from 1.0 MA to 4.0 MA, with pulse durations of \(<\)10-40 s, depending on TF, heating, and other factors. The JET can achieve plasma heating of up to \(\sim\)40 MW with neutral beam injections of 32 MW of deuterium, 36 MW of tritium, and 14 MW of helium, with pulse times as short as \(\sim\)30 min. The injection energy can reach 125 kV, and the ion cyclotron heating can be as much as 5 MW at 25-55 MHz [2; 3]. JET tests using a deuterium and tritium (D-T) fuel combination, which is intended for fusion power plants, offer a rare chance to verify current D-T fusion power prediction techniques in support of developing future fusion reactor machines and operation preparedness. To improve the D-T operating scenarios and develop future D-T fusion reactors, reliable predictions of deuterium and tritium (D-T) neutronics and radiological characteristics are essential. The second JET D-T experimental campaign was conducted by EUROfusion in 2021 using optimized operating scenarios. Under ITER-relevant conditions, i.e., operation with a baseline or hybrid scenario in the complete metallic wall, D-T fusion power sustained for over 5 s was attained [2; 3]. Many assumptions based on D discharges were used in D-T prediction modeling, which was carried out in advance of the 2021 JET D-T experimental program. It is crucial to indicate the accuracy of D-T neutron predictions, together with the experiments, and to apply the simulation input data from the 2021 JET D-T discharges to current radiological characteristic modeling in order to increase the validity of ITER D-T predictive modeling in the future [2; 3]. It is crucial to analyze in detail the models and simulation settings used in inventory modeling to indicate additional improvements needed in current nuclide pathway estimation tools and to indicate the accuracy of D-T fusion neutronic predictions with respect to measured values in 2021 JET D-T discharges in order to increase the validity of deuterium-tritium neutron source modeling. The neutron energy from D-T fusion reactions scales higher than it does for DD reactions. Therefore, this calls for complex integrated modeling that accurately forecasts radiological properties through the simulation of neutron transport, decay heat, activation, and dose rate.