BS IEC 61468 pdf download Nuclear power plants — In-core instrumentation — Characteristics and test methods of self-powered neutron detectors
1 Scope and object
This International Standard applies to in-core neutron detectors and instrumentation whichare designed for purposes important to safety: protection，control and information. lt isrestricted to characteristics and test methods for self-powered neutron detectors(SPNDs).Self-powered neutron detectors can be used for neutron fluence rate (flux) measurementsand spatial power measurements in nuclear reactors. This standard gives requirements,recommendations and guidance on selection of the type and characteristics of SPNDs fordifferent possible applications of SPNDs.
For the principles of overall plant and l&C system design and the purpose of neutron fluencerate measurements，reference should be made to general principles of nuclear reactorinstrumentation according to lAEA Codes and Safety Guides and lEC61513.
The following normative documents contain provisions which, through reference in this text,constitute provisions of this International Standard. For dated references,subsequentamendments to, or revisions of,any of these publications do not apply.However, parties toagreements based on this International Standard are encouraged to investigate the possibilityof applying the most recent editions of the normative documents indicated below. Forundated references，the latest edition of the normative document referred to applies.Members of lEC and lS0 maintain registers of currently valid International Standards.
IEC 60050(394):1995,International Electrotechnical Vocabulary (IEV) Chapter 394: Nuclearlnstrumentation: Instruments
IEC 60515:1975, Radiation detectors for the instrumentation and protection of nuclearreactors; characteristics and test methods
IEC 60568:1977, In-core instrumentation for neutron fluence rate (flux) measurements inpower reactors
IEC 61226:1993, Nuclear power plants – Instrumentation and control systems important forsafety – Classification
IEC 61513，Nuclear power plants – Instrumentation and control for systems important tosafety – General requirements for systems 1)
3 Definitions and abbreviations
For the purpose of this publication, the following definitions apply:
background or lead-compensation (of a self-powered detector signal)
a method employed to correct the current from a SPND for background contribution.This isusually accomplished by placing an “emitterless” background detector in the in-coreassembly, or by using detectors with an internal compensating lead wire (see figure 3)
radioactive decay process in which mass number A remains unchanged but the atomicnumber Z changes.Processes include electron emission (8- decay), electron capture,andpositron emission(+ decay)
depletion or reduction of target atoms when exposed to a thermal neutron fluence rate overtime, due to conversion to other radioisotopes
burn-up life (of a neutron detector)
estimated fluence of neutrons of a given energy distribution after which the sensitive materialwill be consumed to such an extent that the detector characteristics exceed the specifiedtolerances for a specified purpose [IEV 394-18-30]
measure of the probability of a particular collision or interaction process, stated as theeffective area which target particles present to incident particles for that process