IEC 61468:2000 pdf download

IEC 61468:2000 pdf download.Nuclear power plants – In-core instrumentation – Characteristics and test methods of self-powered neutron detectors.
3 Definitions and abbreviations
3.1 Definitions
For the purpose of this publication, the following definitions apply:
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 is usually 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 number Z changes. Processes include electron emission ( decay), electron capture, and positron emission decay)
3.1.3
burn-up
depletion or reduction of target atoms when exposed to a thermal neutron fluence rate over time, 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 material will be consumed to such an extent that the detector characteristics exceed the specified tolerances for a specified purpose [1EV 394-18-30J
3.1.5
capture cross-section
measure of the probability of a particular collision or interaction process, stated as the effective area 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 E0 = hv0 strikes a target electron causing the electron to recoil with energy E = 112mv2. The photon itself is scattered at an angle O and energy E.
3.1.7
cross-section, a
area within a target nucleus, which if struck by an incident particle will lead to a reaction taking place. The number of particles undergoing interaction (ar) is equal to the number of incident particles (n1) times the cross-section times the total number of target nuclei per target volume times the target thickness (t).
3.1.8
decay constant (A.) disintegration constant radioisotope decay constant proportionality constant
for each radioisotope. A is derived by dividing the natural logarithm of 0.5 by the half-life (in seconds), and expressed in s1
A — (ln0,5)/t112 — 0,693/f112
3.1.9
delayed response
time delay or lag in signal generation after exposure to a step change in neutron fluence rate. The mean lag time is (t1121ln2) where f112 is the half-life of the radioisotope which produces the signal. The signal reaches equilibrium after a period of about five times p1,2 following the step change
3.1.10
equilibrium response
for beta-decay self-powered neutron detectors, the response (signal) generated once the rate of neutron capture in the emitter equals the decay rate of radioisotopes in the emitter
3.1.11
halt-life (t112)
time required for the number of atoms or the activity of a radioactive element to decrease from a particular value to half that value
3.1.12
in-core neutron detector
detector, fixed or movable, designed for the measurement of neutron fluence rate (flux) or neutron fluence at a defined point or in a region of a reactor core or primary envelope
3.1.13
integral self-powered neutron detector
self-powered neutron detector assembly in which the lead cable section is an extension of the detector section, i.e. the emitter is directly attached to the core/signal wire; both sections share common insulation, and the collector of the detector section is also the outer sheath of the lead cable section (see figure 1)
3.1.14
modular self-powered neutron detector
self-powered neutron detector assembly made by mechanically joining, welding or brazing a detector (emitter, insulator, collector) to a length of lead cable (core/signal wire, insulator, outer sheath) (see figure 2)
3.1.15
photoelectric effect
photon collision in which the energy of the incident photon is absorbed by the target atom, causing an electron to be emitted with energy E = hv — Be, where hv is the energy of the incident photon and B8 is the binding energy of the emitted electron
3.1.16
prompt response
signal generation from a self-powered neutron detector based on the (n, y, e) reaction.