**7. References**


Taking into account the WWER-1000 fuel assembly four-year operating period transposition algorithm, as well as considering the disposition of control rods, it has been obtained that the axial segment, located between z = 2.19 m and z = 2.63 m, is most strained and limits the

For the WWER-1000 conditions, the rapid creep stage is degenerated when using the Zircaloy-4 cladding corrosion models MATPRO-A and EPRI, at the correcting factor СOR = - 0.431. This phenomenon proves that it is possible, for four years at least, to stay at the steady creep stage, where the cladding equivalent creep strain and radial total strain do not

The WWER-1000 thermal neutron flux axial distribution can be significantly stabilized, at power maneuvering, by means of a proper coolant temperature regime assignment. Assuming the maximum divergence between the instant and equilibrium axial offsets equal to 2%, the regulating unit movement amplitude at constant average coolant temperature is 6%, while the same at constant inlet coolant temperature is 4%. Therefore, when using the method with < > *T* =const, a greater regulating unit movement amplitude is needed to guarantee the linear heat rate axial stability, than when using the method with *Tin* = const, on the assumption that all other conditions for both the methods are

The WWER-1000 average cladding failure parameter after 500 day cycles, for the most strained sixth axial segment, at power maneuvering according to the method with < > *T* =const, is 8.7% greater than the same for the method with *Tin* = const, on the assumption that the thermal neutron flux axial distribution stability is identical for both the

The physically based methods of WWER-1000 fuel cladding durability control include: optimal choice of the group of regulating units being used at reactor power maneuvering, balance of stationary and variable loading regimes, choice of fuel element consrtuction and fuel physical properties considering the most strained fuel element axial segment, assignment of the coolant temperature regime and the fuel assembly transposition

Bogachev, A.V. et al., 2005. Operating experience of system of the automated control of a

Kesterson, R. L. and Yueh, H. K., 2006. Cladding optimization for enhanced performance

Kim, J.H. et al., 2007. Deformation behavior of Zircaloy-4 cladding under cyclic pressurization. Journal of Nuclear Science and Technology 44, 1275–1280.

Structural Mechanics in Reactor Technology, Beijing, China. Bull, A., 2005. The future of nuclear power, Materials challenges, Birmingham, 21 pp.

margins. In: Proc. Int. Conf. TopFuel, Salamanca.

residual cyclic resource for RP with VVER-1000. In: Proc. 18-th Int. Conf. on

fuel cladding operation time at day cycle power maneuvering.

exceed 1-2%, on condition that the corrosion rate is sufficiently small.

**6. Conclusions** 

identical.

methods.

algorithm.

**7. References** 


**11** 

*Iran* 

*Aliabad Katoul*

**Improving the Performance of** 

**the Power Monitoring Channel** 

*2School of Mechanical Engineering, Shiraz University, Shiraz* 

*1Department of Engineering, Aliabad Katoul Branch, Islamic Azad University,* 

In this chapter, different methods for monitoring and controlling power in nuclear reactors are reviewed. At first, some primary concepts like neutron flux and reactor power are introduced. Then, some new researches about improvements on power-monitoring channels, which are instrument channels important to reactor safety and control, are reviewed. Furthermore, some new research trends and developed design in relation with power monitoring channel are discussed. Power monitoring channels are employed widely in fuel management techniques, optimization of fuel arrangement and reduction in consumption and depletion of fuel in reactor core. Power reactors are equipped with neutron flux detectors, as well as a number of other sensors (e.g. thermocouples, pressure and flow sensors, ex-vessel accelerometers). The main purpose of in-core flux detectors is to measure the neutron flux distribution and reactor power. The detectors are used for flux mapping for in-core fuel management purposes, for control actions and for initiating reactor protection functions in the case of an abnormal event (IAEA, 2008). Thus, optimization on power monitoring channel will result in a better reactor control and increase the safety

It is convenient to consider the number of neutrons existing in one cubic centimeter at any one instant and the total distance they travel each second while in that cubic centimeter. The number of neutrons existing in a cm3 of material at any instant is called neutron density and is represented by the symbol n with units of neutrons/cm3. The total distance these neutrons

A good way of defining neutron flux (߶) is to consider it to be the total path length covered by all neutrons in one cubic centimeter during one second. Mathematically, this is the

**1. Introduction** 

**2. Neutron flux** 

equation below.

Corresponding Author

 \*

parameters of reactor during operation.

can travel each second will be determined by their velocity.

M. Hashemi-Tilehnoee1,\* and F. Javidkia2

(1) ݒ݊ ൌ߶

