Reactor pressure-relieving filter system, comprising • an interior space hermetically enclosed by a pressure-resistant reactor casing, • at least one pressure-relieving opening through the reactor casing, • a dry filter for a gas mass flow (20, 46, 48) emerging from the pressure-relieving opening when there is excess pressure in the interior space, • the dry filter being a molecular sieve for the separation of iodine in gas form, • the filtering efficiency depending both on the average dwell time of the gas mass flow (20, 46, 48) in the dry filter and on the temperature difference between the gas mass flow (20, 46, 48) and the respective dew point, and • a flow channel (22, 44) for connecting the pressure-relieving opening and the dry filter, characterized in that • the dry filter is a molecular sieve for the separation of iodine in gas form, the filtering efficiency depending both on the average dwell time of the gas mass flow (20, 46, 48) in the molecular sieve and on the temperature difference between the gas mass flow (20, 46, 48) and the respective dew point, • a passive orifice plate (24, 42) is provided directly upstream of the molecular sieve in the flow channel (22, 44), whereby an overheating of a gas mass flow flowing through the molecular sieve at the beginning of a pressure relief is achieved, and • the passive orifice plate (24, 42) and the molecular sieve are dimensioned in such a way that the effect of an increased filtering efficiency as a result of an overheating of a high gas mass flow (20, 46, 48) and the contrary effect of an increased filtering efficiency as a result of a longer dwell time with a low gas mass flow (20, 46, 48) are compensated in such a way as to ensure an approximately constant filtering efficiency over the time period of a pressure relief with decreasing gas mass flow (20, 46, 48). • an interior space hermetically enclosed by a pressure-resistant reactor casing, • at least one pressure-relieving opening through the reactor casing, • a dry filter for a gas mass flow (20, 46, 48) emerging from the pressure-relieving opening when there is excess pressure in the interior space, • the dry filter being a molecular sieve for the separation of iodine in gas form, • the filtering efficiency depending both on the average dwell time of the gas mass flow (20, 46, 48) in the dry filter and on the temperature difference between the gas mass flow (20, 46, 48) and the respective dew point, and • a flow channel (22, 44) for connecting the pressure-relieving opening and the dry filter, • the dry filter is a molecular sieve for the separation of iodine in gas form, the filtering efficiency depending both on the average dwell time of the gas mass flow (20, 46, 48) in the molecular sieve and on the temperature difference between the gas mass flow (20, 46, 48) and the respective dew point, • a passive orifice plate (24, 42) is provided directly upstream of the molecular sieve in the flow channel (22, 44), whereby an overheating of a gas mass flow flowing through the molecular sieve at the beginning of a pressure relief is achieved, and • the passive orifice plate (24, 42) and the molecular sieve are dimensioned in such a way that the effect of an increased filtering efficiency as a result of an overheating of a high gas mass flow (20, 46, 48) and the contrary effect of an increased filtering efficiency as a result of a longer dwell time with a low gas mass flow (20, 46, 48) are compensated in such a way as to ensure an approximately constant filtering efficiency over the time period of a pressure relief with decreasing gas mass flow (20, 46, 48).