**3. Results**

In this simulation the input parameter value (*H*) is attributed to arbitrary Keff. So if the favorite Keff is: 1 then the value of *H* will be defined: 100 and it is also for Set point (reference Keff). So Set Point: 50 means the reference Keff is: 0.50 and in this situation this Keff is enumerated as the arbitrary and favorite Keff that stability of reactor in this situation is based on it. This arbitrary Keff with output of Zero-Order Hold block is compared for performance of simulation by SIMULINK software. Also for example velocity: 3 means the velocity of control rod in this simulation is: 3 units per second (for example: 3mm/s). In this state the velocity of control rod is increased comparing to the last stage which was: 1 unit per second. The velocity of control rod belongs to Speed block which is an input to Tsp Sum block in the block diagram.

By changing the values of the cited parameters (which were: Set Point, the velocity of control rod (*v*), *H* and the delay time), the different states of the graphs can be shown according to Figs.4, 5, 6 and 7:

Fig. 4. Without oscillation for: Set Point: 100, *v*: 1, H: 50, delay time: 10 ms

Because of the control rod movement is steady, in order to calculate the total amount of the discrete movements of control rod, the Discrete-time Integrator block has been used. The *Fcn* produced function has been transferred to Zero-Order Hold block which plays logic converter role. In addition the Transport Delay block is related to the inherent delay time that is: *tD*. The parameters which must be adjusted are: Set Point that is: the default amount of Keff as reference Keff and the meaning of the Set Point=100 is: Keff=1, the velocity of control rod (*v*), recent Keff (block H) and the stop time that is: the innate delay time or *tD*. The graphs

In this simulation the input parameter value (*H*) is attributed to arbitrary Keff. So if the favorite Keff is: 1 then the value of *H* will be defined: 100 and it is also for Set point (reference Keff). So Set Point: 50 means the reference Keff is: 0.50 and in this situation this Keff is enumerated as the arbitrary and favorite Keff that stability of reactor in this situation is based on it. This arbitrary Keff with output of Zero-Order Hold block is compared for performance of simulation by SIMULINK software. Also for example velocity: 3 means the velocity of control rod in this simulation is: 3 units per second (for example: 3mm/s). In this state the velocity of control rod is increased comparing to the last stage which was: 1 unit per second. The velocity of control rod belongs to Speed block which is an input to Tsp Sum block in the

By changing the values of the cited parameters (which were: Set Point, the velocity of control rod (*v*), *H* and the delay time), the different states of the graphs can be shown

Fig. 4. Without oscillation for: Set Point: 100, *v*: 1, H: 50, delay time: 10 ms

can be observed by the oscilloscope.

**3. Results** 

block diagram.

according to Figs.4, 5, 6 and 7:

Fig. 5. The low oscillation for: Set Point: 100, *v*: 1, H: 100, delay time: 15 ms

Fig. 6. The medium oscillation for: Set Point: 100, v: 5, H: 100, delay time: 15 ms

The Theoretical Simulation of a Model by SIMULINK for

University-South Tehran Branch has been carried out.

(November 2009), 2311-2316.

(January 2004), 195-207.

March 2011), 307-330.

Chapter 5.

184–193.

Springer Pub, 30-75.

*Energy*, Vol. 13, No.4, 203–207.

*and Technology*, Vol. 29, No.6, 530–546.

**5. Acknowledgment** 

**6. References** 

321-327.

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act in the same way as the cluster at fuel assembly at core of nuclear power reactors though

This book chapter is related to a research project entitled: "The Simulation of a Model by SIMULINK of MATLAB for Determining the Best Ranges for Velocity and Delay Time of Control Rod Movement in LWR Reactors" that by financial supporting the Islamic Azad

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Fig. 7. The large oscillation for: Set Point: 100, v: 7, H: 100, delay time: 10 ms

The Figs.4, 5, 6 and 7 show if the velocity of control rod for upward and downward movements is increased then the Keff will be pendulous surrounds of defined Set Point (reference Keff) and also the oscillation amplitude will be more than lower velocity situations. For low velocities the oscillation amplitude is slight and acceptable. Another effective factor is inherent delay (such as derived delay of control rod mechanism) and its inordinate increasing can cause unstable states.
