BS IEC 60951-4 pdf – Nuclear power plants – Instrumentation important to safety – Radiation monitoring for accident and post-accident conditions — Part 4: Equipment for continuous in-line or on-line monitoring of radioactivity in process streams

BS IEC 60951-4 pdf – Nuclear power plants – Instrumentation important to safety – Radiation monitoring for accident and post-accident conditions — Part 4: Equipment for continuous in-line or on-line monitoring of radioactivity in process streams
1 Scope
This part of lEC 60951 provides general guidance on the design principles and performancecriteria for equipment for continuous in-line or on-line monitoring of radioactivity in processstream 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 lEC 60951-1.Theserequirements are applicable in this part unless otherwise stated.
IEC 60951-4 is only applicable to continuous in-line or on-line measurement,i.e. monitors forwhich the detector measures radioactivity by being positioned in the process stream (i.e.immerged in) or adjacent to the process stream (i.e. viewing straight through a pipe or tank).lt does not apply to monitors for which the detector measures a representative proportion ofthe stream at some remote location (sampling assembly),which are within the ‘scope oflEC60951-2.
IEC 60951-4 is only applicable to monitors for accident and post-accident conditions. Processstream radiation monitoring equipment for normal and incident conditions are within the scopeof lEC 60768.
Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies. For undated references, the latest editionof the referenced document (including any amendments) applies.
IEC 60068-2-30;2005,Environmental testing – Part 2-30:Tests – Test Db: Damp heat, cyclic(12 h + 12 h cycle)
IEC 60068-2-78:2001，Environmental testing – Part 2-78: Tests – Test Cab: Damp heat,steady state
IEC 60951-1:2009，Nuclear power plants – Instrumentation important to safety – Radiationmonitoring for accident and post-accident conditions – Part 1: General requirements
3Terms and definitions
For the purposes of this document, the terms and definitions given in lEC 60951-1 apply.
4.1General
Except where otherwise specified,all the requirements specified in Clause 4 of lEC 60951-1shall be carried out，unless otherwise stated.
4.2Basic requirements related to functions
The main purpose of equipment for continuous in-line or on-line monitoring of radioactivity inprocess streams is to continuously measure radiation levels in appropriate pipes or tanks,either by being positioned in them (i.e. immerged in the process stream) or adjacent to them(i.e. viewing “straight through the process stream). These radiation measurements aredisplayed locally and/or in control rooms to keep plant operators aware of current radiologicalconditions.This information is used for control purposes and/or initiation of protective actions.Therefore，the equipment concerned by this standard is capable of actuating alarms andproviding inputs to other plant systems and processes in order to isolate processes atabnormal radiation levels.
The basic requirements for the design, selection, testing, calibration and functional location ofequipment for continuous in-line and on-line monitoring of radioactivity in process streams areplant specific.Process radiation monitors within the scope of this standard can be classifiedinto two basic types:
– in-line monitors: the detector is located directly in the process stream (pipe, tank, duct),- on-line monitors: the detector faces directly the process stream.
For the purpose of critical data collection，these monitors may be designed to withstandadverse environmental and seismic conditions, during and after an accident.
ln addition to the basic requirements of lEC 60951-1,the specification procedure shouldinclude the following:
– Establish the required measurement characteristics (purchaser): Determine the stream
characteristics (physical,chemical and dynamic characteristics of the stream to bemonitored) such as: type of fluid，thermodynamic state，temperature range and rate ofchange, pressure range and rate of change, radiochemical properties,etc.
4.3Range of measurement
ln addition to 4.2 of lEC 60951-1, the following requirements shall apply:
The effective range of measurement should be at least six decades.4.4ln-line detectors mechanical features
4.4.1General requirements
Whenever in-line detectors are located in a sleeve or a piping system implanted as part of apipe or tank under pressure or carrying hot or corrosive fluid，specific ‘requirements shallapply to ensure thermodynamical and mechanical conditions are taken into account.