IEC 62705-2014 pdf Nuclear power plants – Instrumentation and control important to safety – Radiation monitoring systems (RMS): Characteristics and lifecycle

5 RMS categorization and classification 5.1 Function categorization for RMS RMS in nuclear power plants provides continuous information about the radiological conditions in NPP by measuring the radiation levels in specific areas, on certain process lines and at gaseous and liquid release points. It provides alarms and can initiate automatic actions when the monitored radioactivity reaches levels that have been determined to be abnormal. The plant safety design base assigns the individual RMS functions important to safety into one of three categories A, B or C, considering the relationships to other systems to be connected. The main design requirements for the systems and equipment associated with these categories are consistent with those of Clause 7 of IEC 61 226:2009. The category shall be assigned during system requirement specification phase. 5.2 System classification for RMS RMS shall be classified according to its suitability to implement I&C functions up to a defined category during the system specification phase as shown in 6.2.3 of IEC 61 51 3:201 1 . Examples of the classification for RMS installed in PWR and BWR plants are shown in Annex A.
6.3 Radioactive aerosol off-line monitoring RMS for radioactive aerosol off-line monitoring is used for the following purposes: – to measure the volumetric activity of radioactive aerosols in gaseous effluents at the discharge point and the variation of volumetric activity. The monitor may also be used for the determination of the total discharge of radioactive aerosol over a given period; – to measure the volumetric activity in air or gas systems (control room ventilation, reactor leakage collection, drywell ventilation exhaust, fuel handling building ventilation exhaust, reactor building ventilation purge exhaust) and detect any significant increase of radioactivity. For RMS designed only for normal operation condition, the design and testing of RMS shall be performed in accordance with IEC 60761 -1 and IEC 60761 -2. For RMS designed for accident conditions, the design and testing of RMS shall be performed in accordance with IEC 60951 -1 and IEC 60951 -2. Sampling assembly for RMS used for this monitoring shall be designed and tested in accordance with ISO 2889. 6.4 Radioactive iodine off-line monitoring RMS for radioactive iodine off-line monitoring is used for the following purposes: – to measure the volumetric activity of radioactive iodines in gaseous effluents at the discharge point and the variation of volumetric activity. The monitor may also be used for the determination of the total discharge of radioactive iodine over a given period; – to measure the volumetric activity in air or gas systems (control room ventilation, reactor leakage collection, drywell ventilation exhaust, fuel handling building ventilation exhaust, reactor building ventilation purge exhaust) and detect any significant increase of radioactivity. For RMS designed only for normal operation condition, the design and testing of RMS shall be performed in accordance with IEC 60761 -1 and IEC 60761 -4.