Indigenous Development of In-core Thimble Cleaning System at C-1

Equipment for In-core thimble cleaning of a PWR nuclear power reactor has been designed and fabricated indigenously at Chashma Nuclear Power Plant-1. This facility will not only meet the demands of C-1 but it can also be used in future PWRs in Pakistan. 

In-core thimbles are installed in a PWR reactor core to facilitate inward and outward movement of nuclear/radiation detectors used for the measurement of fuel burn up, reactor activity and other nuclear parameters during plant operation. Periodic cleaning of these In-core thimbles is mandatory to facilitate Eddy Current Testing and smooth detector movement during operation. This equipment is interfaced with reactor core from the apertures of bottom mounted In-core thimbles which are present beneath the reactor pressure vessel. Cleaning process includes chemical cleaning, air drying, water flushing, vacuum drawing and lubrication of bottom mounted 16 meter high thimbles. As this activity is prone to industrial, chemical and nuclear hazards for reactor core as well as for working personnel, therefore, a closed loop system is required to carry out the job safely and efficiently.

A team led by Hussain Kamran Gardezi, SE started work on the indigenous development of this system in August, 2009 as a part of wider indigenization plan. Target date of tested product was set as first week of April, 2010, in time for deployment in RFO-6. 

This work was completed on 6th of April, 2010 and the equipment was tested on a mock up fabricated for this purpose. On 14th of April 2010 cleaning was performed on In-core thimbles of C-1 reactor successfully.

In-Core thimble cleaning task has a lot of technical and safety related issues and intricacies, due to which there are very few companies in the world which 

Indigenously developed thimble cleaning equipment.

DG (CNPGS) visits during final testing.

Equipment connected with the In-core thimbles.

Team members at work in reactor building.

provide this equipment and services albeit at a very high cost. Therefore indigenous development of this equipment and services will not only save national exchequer and reduce dependency on import for C-1 and the future NPP's of Pakistan, but also after refinement, this equipment and service can be exported to other PWRs of the world.