Simulations of massive noble gas (NG) injection into the JET plasma have been performed using the TOKES code. The results of these simulations have been verified by comparison with JET experiments. Further simulations performed showed that the amount of NG for triggering the thermal quench can be reduced 40 times. Such small amount of injected NG should generate runaway electrons (RE) with rather large probability. For mitigation of the wall damage with these RE a special sacrificial diaphragm, consisting from several W 'nails' with the characteristic thickness of 2cm has been proposed. The diaphragm erosion with RE beam has been roughly estimated from above as less than 0.5cm per disruption. Taking into account the plasma shielding may decrease erosion ~10 times.