IEC 61468:2000 pdf free download – Nuclear power plants -ln-core instrumentation – Characteristics and test methodsof self-powered neutron detectors
1 Scope and object
This International Standard applies to in-core neutron detectors and instrumentation which aredesigned for purposes important to safety: protection, control and information. lt is restricted tocharacteristics and test methods for self-powered neutron detectors (SPNDs). Self-poweredneutron detectors can be used for neutron fluence rate(flux) measurements and spatial powermeasurements in nuclear reactors. This standard gives requirements，recommendations andguidance on selection of the type and characteristics of SPNDs for different possibleapplications 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 IAEA Codes and Safety Guides and lEC 61513.
2 Normative references
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.For undatedreferences, the latest edition of the normative document referred to applies. Members of lECand 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 nuclear reactors;characteristics and test methods
IEC 60568:1977, In-core instrumentation for neutron fluence rate (flux) measurements in powerreactors
IEC 61226:1993, Nuclear power plants – Instrumentation and control systems important forsafety – Classification
IEC 61513,Nuclear power plants – lnstrumentation and control for systems important to safety-General requirements for systems 1)
3.1.1 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-core assembly,or by using detectors with an internal compensating lead wire (see figure 3)
3.1.2 beta decay
radioactive decay process in which mass number A remains unchanged but the atomic numberZ changes.Processes include electron emission (- decay),electron capture，and positronemission(β+ decay)
3.1.3 burn-up
depletion or reduction of target atoms when exposed to a thermal neutron fluence rate overtime, due to conversion to other radioisotopes
3.1.4 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]
3.1.5 capture cross-section
measure of the probability of a particular collision or interaction process,stated as the effectivearea which target particles present to incident particles for that process
3.1.6 Compton effect
ordinary elastic collision in which an incident photon of energy Eo = hvg strikes a target electroncausing the electron to recoil with energy E= 1/2mv2.The photon itself is scattered at an angleand energy E = hvo- E
3.1.7 cross-section
area within a target nucleus,which if struck by an incident particle will lead to a reaction takingplace.The number of particles undergoing interaction (n,) is equal to the number of incidentparticles (n) times the cross-section(o) times the total number of target nuclei per targetvolume (N)y times the target thickness (t).