BS IEC 60951-3 pdf download – Nuclear power plants – Instrumentation important to safety – Radiation monitoring for accident and post-accident conditions — Part 3: Equipment for continuous high range area gamma monitoring

BS IEC 60951-3 pdf download – Nuclear power plants – Instrumentation important to safety – Radiation monitoring for accident and post-accident conditions — Part 3: Equipment for continuous high range area gamma monitoring
1 Scope
This part of lEC 60951 provides general guidance on the design principles and performancecriteria for equipment for continuous high range area gamma monitoring in nuclear powerplants 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.
This standard is applicable to installed dose rate meters that are used to monitor high levelsof gamma radiation during and after an accident. It covers equipment intended to isotropicallymeasure air kerma,ambient dose or other exposure quantities due to gamma radiation ofenergy between 80 keV and 7 MeV.The equipment is intended primarily for the purpose ofnuclear plant safety.
Portable instruments for emergency purposes and installed area radiation monitors used todetermine continuously the radiological situation in working areas during normal operation arewithin the scope of lEC 60532.
2Normative 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.
lEC 60951-1:2009，Nuclear power plants – Instrumentation important to safety – Radiationmonitoring for accident and post-accident conditions – Part 1: General requirements
IEC 60780,Nuclear power plants – Electrical equipment of the safety system – Qualification
IEC 61226,Nuclear power plants – Instrumentation and control systems important to safety -Classification of instrumentation and control functions
ISO 4037 (all parts)，X and gamma reference radiation for calibrating dosemeters anddoserate meters and for determining their response as a function of photon energy
Iso 6980 (all parts)，Nuclear energy – Reference beta-particle radiation
ISO 8529(all parts)，Reference neutron radiations
3Terms and definitions
For the purposes of this document, the terms and definitions given in lEC 60951-1 apply.
4Design principles
4.1General
The general requirements of lEC 60951-1 are applicable to all types of monitors within thescope of the present standard, unless otherwise stated.
4.2Range of measurement
The purchaser shall specify the required effective range of measurement and the radiationsources specific to the plant design. The range shall be suitable for the level of and thevariation in radiation in the area during accident and post-accident conditions. lt shall be atleast six decades. The low end of the required range shall overlap the highest decade of doserate monitors designed for normal operation conditions.
The energy response of the detector in relation to the expected radiation energy spectrumshall also be specified. Typically detectors should respond to gamma radiation within anyenergy range from 80 kev to 7 Mev.
4.3Accuracy (relative error)
ln addition to 4.6 of lEC 60951-1, the following requirements shall apply.
When a detector assembly utilizes more than one radiation detector to cover the full range ofdose equivalent rates indicated by the detector assembly,these requirements apply to therelevant ranges for each detector separately.
4.4Location of sensors
The requirements for such equipment are plant specific. Therefore, the locations in which themonitoring equipment is required shall be determined according to the plant design.
Usually equipment is located within the reactor containment. lt shall be located to providemaximum coverage of the areas being monitored and to minimize shielding effects from otherequipment or structures.As far as is practical, locations should be selected so as to facilitatemaintenance and calibration operations.
Because of the high level of radiation,the equipment is usually designed with a detectorassembly located remotely from any processing assembly (electronics), taking into accountthe length of the cable between detector and remote electronics which should be minimized.
4.5Detector radiation response characteristics
The detector assembly shall be designed to be effectively insensitive to beta and neutronradiation (compared to its gamma sensitivity) expected to be present during the accidentconditions for which the equipment is intended to operate.
4.6Requirements related to accident conditions
In addition to 4.11 of lEC 60951-1, the following requirements shall apply.
The type of equipment covered by this standard is typically regarded as essential safetyrelated equipment. lt shall be therefore classified according to IEC 61226 guidance andenvironmentally qualified in accordance with the requirements of iEC 60780.