BS IEC 61559-1 pdf download – Radiation protection instrumentation in nuclear facilities — Centralized systems for continuous monitoring of radiation and/or levels of radioactivity — Part 1 : General requirements

BS IEC 61559-1 pdf download – Radiation protection instrumentation in nuclear facilities — Centralized systems for continuous monitoring of radiation and/or levels of radioactivity — Part 1 : General requirements
lf a safety classification applies，appropriate requirements shall apply concerningspecification, design，manufacturing, installation and operation of the equipment with respectto the necessary quality of computer hardware and software.The requirements shall beagreed between manufacturer and purchaser. In particular the purchaser (operator) shalldecide the appropriate safety standard applicable to the site in which the system will function.The basic safety standards IEC61508 series apply.
When IEC 61508 is selected，then the requirements of that standard shall apply asappropriate to the required safety integrity level specified for the system.
Compliance with IEC 61513 facilitates consistency with the requirements of lEC 61508 seriesas they have been interpreted for the nuclear industry.
4.1.3System configuration
The type of equipment defined in this standard generally comprises up to four types ofassemblies，which may be interconnected in a number of configurations and to the centralcomputer(ccy(see Figures 1 to 4).
These assemblies are:
detector assembly (DA);processing assembly (PA);allarm assembly(AA);
monitoring assembly (MA).
The monitoring assembly is an integrated assembly consisting of combinations of processing,alarm，and detector assemblies.These assemblies may be located in a single package(instrument), or as individual assemblies.
Each installation is unique; some typical examples are illustrated.
Figure 1 shows a monitoring assembly located within the monitoring area.
Figure 2 shows an example where the detector assembly is located within the monitored area,whilst the processing assembly is located in an area of lower radiation or volumetricradioactive contamination in air. In this example,the alarm assembly must be located withinthe monitoring area to warn personnel. The detector assembly measuring volumetricradioactive contamination in air may be located outside the monitoring area，but the airsample must be drawn from within the area. The need to position a second alarm unit at theentry point to prevent access，should be considered. Further alarm assemblies triggered bythe processing assembly may be required to adequately cover the geographical area.
The links from detector assembly to processing assembly and processing assembly to alarmassembly shall be standardized and ideally independent of assembly type.
The elements forming a monitoring assembly shall have the ability to be grouped,and tooperate in autonomous mode.The monitoring assembly to CC link shall be standardized.
The central computer has to collect the data transmitted from the various monitor units datalinks.Additionally diverse digital alarm status inputs may also be accepted.
All data links shall be a good quality，commercially available protocol. Additionally theinstallation of the detector assembly to processor unit link and processing unit to alarm unitlink and links to the central computer，shall follow the electromagnetic compatibilityrequirements of lEC 61000-5-1.
The monitoring assembly or processing assemblies can be linked to the central computer invarious ways:
– either all are linked directly to the central computer, that is a centralized configuration;- or are linked via a CC outstation. Such a configuration reduces the length of the cables.
Figures 1 to 4 detail such arrangements.
4.1.4 Location of detector assemblies
The design and location of detector assemblies and/or monitoring assemblies shall beconsidered in relation to the radiological protection requirements of the particular plantconcerned.Generally, the extent of the provision shall be related to the type and degree ofhazard,and the extent of occupancy by plant personnel.Guidance on the criteria which maybe used is given in Annex B.
4.2Design requirements for the assemblies4.2.1 Detector assembly
The monitoring sensors are specified for the quantity and radiation type they have to detect(electron,photon，and neutron radiations，gas contamination，alpha and/or beta aerosolcontamination), and they shall meet therelevant lEC standards applicable to themeasurement being carried out. In some cases, there are directly applicable standards，forexample,lEC 60532 for gamma radiation monitors, and lEC 61322 and lEC 61005 for neutronmonitors. ln other cases,relevant requirements may be identified in standards dealing withequipment specifically designed for other，technically similar applications.(For example,IEC 60761 series dealing with gaseous effluent monitors.) ln such cases， the applicability ofthe standards shall be agreed between manufacturer and purchaser.
lt is intended that this standard should allow interchangeability of detector assemblies fromdifferent manufacturers. To facilitate this，regardless of the quantity being measured，whenthe detector assembly is separate from the processing unit, the attributes of the output signalfrom the detector assembly shall be agreed between manufacturer and purchaser.
The output of the detector assembly shall be made directly proportional to the activity beingmeasured.
4.2.2 Processing assembly4.2.2.1General
The processing assembly converts the output signal from the detector assembly into datarepresenting the quantity to be measured. lt also activates the alarm assembly, if the quantityto be measured exceeds preset thresholds.