Nuclear power plants―Instrumentation important to safety―Radiation monitoring for accident and post-accident conditions―Part 2:Equipment for continuous off-line monitoring of radioactivity in gaseous effluents and ventilation air
GB/T 12726 "Nuclear Power Plants — Instrumentation Important to Safety — Radiation Monitoring for Accident and Post-accident Conditions" is comprised of 4 parts:
— Part 1: General Requirements;
— Part 2: Equipment for Continuous Off-line Monitoring of Radioactivity in Gaseous Effluents and Ventilation Air;
— Part 3: Equipment for Continuous High Range Area Gamma Monitoring;
— Part 4: Equipment for Continuous In-line or On-line Monitoring of Radioactivity in Process Streams.
This part is Part 2 of GB/T 12726
1 Scope
This part of GB/T 12726 provides general guidance on the design principles and performance criteria for equipment for continuous off-line monitoring of radioactivity in gaseous effluents and ventilation air used in nuclear power plants for accident and post-accident conditions.
General requirements for technical characteristics, test procedures, radiation characteristics, electrical, mechanical, and environmental characteristics are given in GB/T 12726.1-2013. These requirements are applicable in this part unless otherwise stated.
This part is applicable to:
— noble gas activity monitors intended to measure the volumetric activity of radioactive noble gases in gaseous effluents at the discharge point and the variation of volumetric activity with time during accident and post-accident conditions. The monitor may also be used for the determination of the total discharge of noble gas activity over a given period.
— noble gas, aerosol and specific nuclide (commonly iodine, in its different forms: inorganic iodine, organic iodine and iodine sticking on dust) monitors intended 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 during or after an accident.
This part is only applicable to continuous off-line measurement, i.e. monitors whose detector measures a representative proportion of the main effluent or ventilation stream at some remote location (sampling assembly). This part does not apply to monitors with the detector positioned in or adjacent to the effluent or ventilation stream, which are within the scope of GB/T 12726.4.
Sample extraction and laboratory analysis, which are essential to a complete program of effluent monitoring, are not within the scope of this part.
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2 Normative References
The following documents are indispensable for the application of this document. For dated references, only the dated editions apply. For undated references, the latest editions (including any amendments) apply.
GB/T 12726.1-2013 Nuclear Power Plants — Instrumentation Important to Safety — Radiation Monitoring for Accident and Post-accident Conditions — Part 1: General Requirements (IEC 60951-1:2009, IDT)
ISO 2889:2010 Nuclear Power Plants — Instrumentation and Control Systems Important to Safety — Classification of Instrumentation and Control Functions
IEC 61226 Sampling Airborne Radioactive Materials From the Stacks and Ducts of Nuclear Facilities
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 12726.1-2013 apply.
Foreword II
Introduction IV
1 Scope
2 Normative References
3 Terms and Definitions
4 Design Principles
4.1 General
4.2 Basic requirements related to functions
4.3 Sampling assembly
5 Functional Testing
5.1 General
5.2 Reference sources
5.3 Performance characteristics : response to other radioactive gases or particles
5.4 Air circuit performance test
Table 1 Standards of SAC/TC 30/SC 2/SC 3 V
Table 2 Additional Tests to Complement the General Tests Required in GB/T 12726.1-2013
