Control rod drives

Control rod drives are the active element of the reactor instrumentation and control system (I&C system). They move the control rods through the reactor, reposition them, stop them in the required position, detect their position and last but not least, they ensure that control rods are inserted at the required speed in the emergency shutdown mode.

The drives can be controlled independently or simultaneously – depending on the signals sent from the I&C system.

ŠKODA JS has been producing control rod drives for the type VVER 440 and VVER 1000 reactors since 1980, and continues to work on their development and further improvement.

Modernized PRO-M control rod drive

Pohon regulačního orgánu PRO-M pro reaktory VVER 440

The modernized PRO-M control rod drive is the active part of the instrumentation and control system for the VVER 440 reactor. Thirty-seven rack and pinion control rod drives are used in the VVER 440 reactor. This type of drive, including the electronic control system and position indicator, was developed to improve operational characteristics and reduce the probability of failure. Owing to this improvement, the lifespan of the mechanical parts was gradually extended up to the current 25 years compared to the original drive version with the lifespan of 10 years.

Since 1980, we have produced more than 1,300 various versions of the PRO type control rod drive and supplied them to twenty units at nuclear power plants in the Czech Republic, Slovakia, Ukraine, Hungary, Poland and Germany.

The PRO-M drive, together with the position indicator, performs the following functions:

moves the VVER-440/V 213 type control rod
stops the control rod in extreme positions and in between them
indicates the control rod position gradually and independently every 10mm and 250 mm, and the extreme positions
drops the control rod in the emergency shutdown mode
prevents spontaneous lift-off of the control rod in case of leakage in the upper part of the drive

The shape and size of the PRO-M control rod drive by ŠKODA JS is identical to the original PRO drives, thanks to which it is used to replace the currently operated VVER 440 type control rod drives.

Intermediate rods for PRO control rod drives

vložené tyče pohony regulačních orgánů PRO

The PRO drive moves the reactor control rod, which consists of the absorption and fuel parts in tandem. The control rod and the drive are connected by an intermediate rod. Since 1980, ŠKODA JS has produced more than 1,200 intermediate rods for nuclear power units in the Czech Republic, Slovakia, Hungary, Ukraine and Finland.

Modernized LKP-M linear step drives

The modernized LKP-M linear step drive is the principal part of the control and safety system of the VVER 1000 reactor. 61 or up to 121 linear stepping drives work in the VVER 1000 reactor, based on the type of reactor. Depending on commands from the SGIU-M reactor control and safety system, which is also supplied by ŠKODA JS, each LKP-M drive is capable of working on its own, independently of other drives, or simultaneously with them. We continually modernize and further develop this equipment. The lifetime of our latest, third generation of the drive is almost 40 years, which essentially corresponds with the lifetime of a nuclear power plant.

The LKP-M drive performs the following functions:

lineární krokový pohon regulačních orgánů LKP-M

integrity of the primary circuit
repositions the rod cluster control assembly at the required speed in the power control mode
reaches the required position of the rod cluster control assembly
stops the rod cluster control assembly in the required position
indicates the actual position of the rod cluster control assembly with the required accuracy
drops the rod cluster control assembly at the required speed in the emergency shutdown mode
prevents the rod cluster control assembly from lift-off in the event of the housing leackage

In 2004-2005, we completed the development of the 3rd generation of drives designated as LKP-M/3 type. After experience with the operation of the first and second generation drives, the development was mainly focused on making the monitoring of the position of the rod cluster control assembly in the core more accurate, shortening the drop time of the rod cluster control assembly, simplifying installation, increasing the working stroke, increasing the permitted operating temperature of the electromagnets and extending the service life of all drive components to min. 40 years.

In 2019, the development of the fourth series of the LKP-M/4 linear stepping drive of rod cluster control assembly, intended for the latest units with VVER-type reactors, was successfully completed, where the lifetime resource tests of the prototype were completed with an excellent result.

Main goals of modernized LKP-M/4 drive:

Full compatibility of new evolutionary generation of CRDM type LKP-M with VVER 1200 and former VVER 1000 units (reactor and cable routes).
Lifetime extension by increase of mechanical wearing resistance compared to the last generation of CRDM type LKP-M/3.
Reduction of maintenance activities and time during unit planned outage.
Modernize solution of power and control electronics with state-of-the-art solution.

Since 1990, ŠKODA JS has manufactured more than 1,200 drives for VVER 1000 units in the Czech Republic, Bulgaria and Ukraine. As part of the contract, there was also supply of nine sets of modernized SGIU-M electronics.