atw 2018-05v6


atw Vol. 63 (2018) | Issue 5 ı May




Operating sequence in 2017











Electrical output in %

January February March April May June July August September October November December

During the reporting year 2017 the nuclear power plant Grohnde

was put off the grid for a 39,5-day revision with refuelling and

achieved an availability factor of 86.1 % The gross production

amounted to 9,684,880 MWh.

Opposite to the scheduled 33-day downtime the revision extended

by 159 hours due to the assembly of a pipe blend inside the secondary

cooling water system for secured intermediate cooling system, the

exchange of plate springs at the upper central framework, the

recovery of a missing fuel element centring pin on the placement

console as well as the repair on a input valve at the main steam valve


The plant was additionally taken off the grid for eleven days in

100 November due to the repair of a small leakage at the Δp- measurement

on one of the primary coolant pumps.


Planned shutdowns

460March to 12 April: 34 th Refuelling and revision:

Nuclear power plant Grohnde was shut down as scheduled after a



stretch-out operation on 4 March for the 34 th revision and



The main planned works during this year’s revision were:

• Refuelling and implementation of 60 fresh fuel elements.


• Complete inspection of 23 fuel elements.

• Eddy current testing of 37 control elements.

• Visual examination of 16 throttle bodies.

• Oxide layer thickness measuring on fuel elements.

• Pressure Positionierung:

testing on primary circuit.

• Secondary pressure testing on the steam generator.

Bezug, links, unten

• Ultrasonic testing of the reactor pressure vessel (RPV) and RPV

nozzles. X = 20,475 Y = 95,25 B = 173,5 H = 38,2 power plant Krsko (Slovenia).

• Change VGB: of HKS6K 28 hold down 30 spring % assemblies of the upper central


atw: 100 60 0 0

• Examination due to breakage of a fuel element-centring pin in the

lower central framework.

• Exchange of the motor on one of the primary coolant pumps.

• Exchange of the mechanical seal on two main coolant pumps.

• Revision of the axial bearings on a main coolant pump.

• Leakage testing of the containment vessel.

• Works and examination in the redundancies with the focus on the

tasks in the main redundancy 4/8 maintenance works on valves

and actuators as well as examination on vessels, batteries and

electronic junctions.

• Cleaning of nuclear intercooler.

• Revision of the turbine rotor low pressure-part 1 + 2 including

ultrasonic testing of the wheel discs.

• Reconstruction of a pump bow of the secondary cooling water

system for secure interim-coolant systems.

Due to a recognized and non-lockable leakage at the flanges of one of

the pre-control valve inside the valve station, during the short

starting process on 9 April a SCRAM was released at 18:05 at 8 % of

reactor capacity in order to shutdown the plant in subcritical cold

state for the repair.

Unplanned shutdowns and reactor/turbine trip

5 to 17 November: Downtime for repair of a small leakage.

Due to a small leakage at the Δp-measurement of main coolant pump

YD40 the plant was shut down on 5 November 2017. After the repair

of the defective pipe and non-destructive examinations as well as

on-site inspections of comparable small-bore pipes the plant was put

to operation on 17 November.

Power reductions above 10 % and longer than for 24 h

Load sequence operation was carried out in January due to the

requirements of the load distributor.

National Peer Review

In 2017 a National Peer Review on the issue “Risk Assessments” took

place at KWG.

WANO Review/Technical Support Mission

In 2017 KWG attended a technical support mission on the issue of

“Prevention of Contamination by Foreign Bodies“ at the nuclear

Delivery of fuel elements

In 2017 two fuel elements of the ANF GmbH Lingen and

28 Westinghouse fuel elements were delivered.

Waste management status

In 2017 no spent fuel casks were loaded.


Operating results 2017 – Part I*

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