ecchelmet Dealing with a 16 m tall challenge
The Hydro Technical Structures Project at KKNPP
The project team at the Kudankulam Nuclear Power Plant (KKNPP) Units 3–6, India’s largest nuclear power station, is constructing Hydro Technical Structures (HTS) involving inlet and outlet portal systems. Each unit of KKNPP has a 1,000 MWe capacity with a steam-driven turbo generator supplied with steam from a pressurizedtype reactor of Russian design. The HTS Project comprises both offshore-based and onshore-based construction, the latter having pump house areas where they have constructed thirty-eight RCC walls of 16 m height, casted in a single pour, one wall at a time.
Negotiating a steep climb
Falling in the project’s critical path, these walls are important further involving cross walls, liner erection, and erection of an embedded guiding system. “To improve our productivity and finish the work as committed, we cast the walls for their full height of 16 m, from raft top to bottom of the roof slab, in a single pour,” remarks Project Manager, Jayaprakash Tentu, who is delighted with the result that he attributes to the sustained efforts by the formwork design, execution, and project teams.
We organize rescue mock drills every six months to ensure that our people are familiar with the emergency response procedures, and the recorded observations & feedback at these mock drills help us maintain the resources in good condition for emergency management.
Jayaprakash Tentu
Project Manager
The challenges faced by Mathan Jayaraj, EHS In-charge and team were many. Workmen had to work parallelly for rebar, EP, grooves, and large-area formwork, with all of them requiring access to a confined workspace. “The larger pour height increased concrete pressure causing the concrete mass to generate terrible heat in a confined area where it was also difficult to make emergency rescues when tying rods,” he laments. They encountered difficulty to carefully lift and position the 16 m shutter board and had to work in extremely humid conditions.
Work at height is risky that demands extensive fall protection arrangements and rescue & relief measures and their first step was to form an Emergency Response Committee (ERC) comprising key site personnel, with each member assigned a deputy to replace them, if necessary, with the responsibility to manage orderly responses to emergencies. “We organize rescue mock drills every six months to ensure that our people are familiar with the emergency response procedures, and the recorded observations & feedback at these mock drills help us maintain the resources in good condition for emergency management,” comments Jayaprakash.
A well-thought-out procedure to rescue personnel from inside the 16 m high wall was prepared and demonstrated to the workmen, and an emergency rescue exercise conducted before the first pour for the wall. “Our emergency mock drill, conducted a day prior to the start of the pour, involved rescuing a ‘dummy’ victim from inside the wall frame with the help of a vertical stretcher,” elaborates Mathan Jayaraj, EHS Incharge. “The workforce both inside and outside were equipped with walkie talkies, a ‘C’ frame and evener beam was used to distribute the load, while a pick & carry crane held up one side of the 16 m shutter board during lifting and placing of formwork.”
Our emergency mock drill, conducted a day prior to the start of the pour, involved rescuing a ‘dummy’ victim from inside the wall frame with the help of a vertical stretcher.
Mathan Jayaraj
EHS In-charge
The end stopper shutter was fixed to the full 16 m only at one end while at the other end, it was fixed only to a height of 5.5 m with a heavy-duty air blower duct for ventilation. “Once the concreting was completed up to a height of 5.5 m, we shifted the air blower to the next 5.5 m level,” informs M Arumugakasi, Engineer (EHS), adding that intermediate platforms were laid inside the walls to do vibrating activity during concreting.
To ensure the well-being of the workmen, their blood pressure and pulse were checked before entering the concreting work area, and they were rotated every two hours. “An ‘In and Out’ register ensured that the workers got frequent breaks,” adds D Preston, Assistant Manager (EHS). “Buttermilk, ORS powders, and glucose were given to the workmen during concreting work to ensure that they stayed hydrated and alert.”
A tall task has been expertly completed by Jayaprakash and his team, and their milestone achievement was appreciated by senior officials of the client, Nuclear Power Corporation of India (NPCIL).