Control rod drives

Control rod drives

Linear step drives – blocks of electromagnets

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.

Thirty-seven rack and pinion control rod drives are used in the VVER 440 reactor. The VVER 1000 reactor uses between 61 and 121 linear step drives, depending on the specific type of reactor. 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 since 1980 and continues to work on their development and further improvement. By way of continual development, we have managed to extended the guaranteed lifetime of linear step drives from the original 10 years to 40 years.

In 2004-2005, we completed the development of 3rd generation drives called LKP-M/3. Based on experience with the operation of first- and second-generation control rod drives, their development focused mainly on accurate indication of the actual position in the active core, reducing the time required for their insertion, easier assembly, increasing the range of travel, higher operating temperature of electromagnets, and increasing the lifetime of all components of the control rod drive to a minimum of 40 years.

In 2019, the development of the fourth generation of linear step drive LKP-M/4 designed for modern units with VVER type reactors was successfully completed, where the life tests of the prototype were completed with an excellent result.

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. 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. The original drive version had a lifespan of 10 to 11 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 movements of the control rod in case of looseness in the upper part of the drive

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 control rods through a reactor, which consists of the absorption and fuel parts. 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, Poland, 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. 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 control rod at the required speed in the power control mode
  • reaches the required position of the control rod
  • stops the control rod in the required position
  • indicates the actual position of the control rod with the required accuracy
  • drops the control rod at the required speed in the emergency shutdown mode
  • prevents the control rod from surfacing in the event of the shroud coming loose
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 comparing the last generation of CRDM type LKP-M/3.
  • Reduction of maintenance activities and time during unit regular 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 the requirement to supply nine sets of modernized SGIU-M electronics.

AZ/BSM control rod drive

In 2006, 58 control rod drives were produced for the RBMK-1500-type nuclear power unit at the Ignalina NPP in Lithuania.

The history of the project

pohony řídicích tyčí PRO

1980-1985 the first PRO control rod drives supplied to the Paks NPP, Hungary

lineární krokové pohony řídicích tyčí

1991the first linear step drives (type LKP-S) supplied to the Belene NPP, Bulgaria

lineární krokové pohony řídicích tyčí

1993the first linear step drives (type LKP-M) for the Temelín NPP

lineární krokové pohony řídicích tyčí

2011the first 3rd generation linear step drives (type LKP-M3) for the Temelín NPP

pohon regulačního orgánu PRO

2016delivery of 46 refurbished control rod drives for the Dukovany NPP, originally produced by ŠKODA JS for the Nord NPP in Germany

vložené tyče pro pohony regulačního orgánu

2018delivery of 49 intermediate rods for the Loviisa NPP in Finland

2019conslusion of the contract for the supply of 78 of PRO-M drives and 32 of intermediate rods were delivered for Rovno NPP


2019completed development of a new generation of drive – LKP-M/4

pohon regulačního orgánu PRO

2016-2021dodávka 160 pohonů řídicích orgánů pro JE Dukovany
(z toho 46 repasovaných – původně určených pro JE Nord)

Interesting numbers

1343 PRO control rod drives produced
1240 LKP linear step drives produced
1223 intermediate rods for VVER 440-type reactors supplied