Diamond Cutting and Drilling at Operating NPPs: Impact-Free Demolition and Reconstruction

This article examines the use of diamond cutting and diamond drilling technologies in construction, demolition, and reconstruction works at facilities using nuclear energy (FUNE). It analyzes the advantages of these methods compared with traditional methods such as jackhammers, rotary hammers, and gas cutting in terms of vibration, noise, dust generation, and preservation of surrounding structures. Typical tasks are presented: cutting openings in reinforced-concrete walls and slabs, dismantling building fragments, and drilling holes for utilities. The equipment used (wire, wall-saw, chain-saw units, and diamond core bits) and requirements for organizing work at restricted-access facilities are described.



At nuclear power plants and nuclear-industry enterprises, there is often a need to change layouts, replace equipment, modernize engineering systems, or partially dismantle structures. Traditional methods, including jackhammers, hydraulic breakers, oxy-fuel cutting, and rotary hammers, are unacceptable for several reasons: high vibration can damage neighboring critical structures, up to loss of tightness; impact loads are unacceptable near operating equipment; open flame and sparks are prohibited in zones with explosive media or hydrogen hazard; and heavy dust generation complicates decontamination and radiation control.



Diamond cutting and diamond drilling are technologies based on the use of diamond-coated tools such as segments, core bits, and wires. They make it possible to perform precise, controlled cuts and holes without impact effects, with minimal vibration, low noise, and simultaneous water cooling that suppresses dust. At facilities using nuclear energy (FUNE), these methods are widely used for building reconstruction, opening creation, demolition of large equipment, and removal of concrete-structure fragments.



Regulatory and Restricted-Access Constraints at NPPs

The use of diamond cutting technologies at facilities is governed by:



• NP-041-22 - requirements for maintaining the load-bearing capacity of structures when making openings and cutouts.

• Safety rules for working with tools (internal NPP regulations) - prohibition of impact tools in controlled-access zones and requirements for spark safety.

• Sanitary standards for vibration and noise (SanPiN) - at operating units, noise from work must not exceed 80 dBA to ensure personnel communication.

• Radiation-safety rules - organization of the work zone and control of aerosol release of radioactive dust; diamond cutting with water cooling reduces dust generation by 95-98%.



Before work begins, a work permit is issued, a work execution plan (WEP) with a diamond-cutting section is prepared, and the method of dust suppression and slurry collection is determined, including slurry containing radioactive particles when work is performed in the controlled access zone (CAZ).



Types of Work Performed by Diamond Cutting at FUNE

1. Diamond Core Drilling of Holes

• Diameter: from 8 mm to 1000 mm (standard core bits up to 200 mm, large drilling rigs up to 1000 mm).

• Depth: up to 2-3 m (with rod extension).

• Tasks: drilling holes for engineering utilities (pipes, cables, air ducts) in walls and slabs; taking concrete samples (cores) for quality control and residual-life assessment; making anchor holes for equipment fastening; ventilation, drainage, and process channels.

• Advantages: perfectly round hole without chipping (reinforcement is cut through), ability to drill at an angle, and work in confined spaces.



2. Diamond Cutting with Wall Saws

• Cut thickness: up to 500-1000 mm in one pass (blades 800-1600 mm).

• Purpose: straight-line cutting of openings in walls and slabs, cutting reinforced-concrete structures into blocks (block demolition), and removal of slab, beam, and column sections.

• Features: high cutting speed (up to 0.5-1 m²/hour of B25-B40 concrete), smooth edge, and ability to cut reinforced concrete (diamond segments cut reinforcement).



3. Diamond Wire Cutting

• Wire diameter: 8-11 mm (with diamond beads).

• Purpose: cutting massive structures of great thickness, such as walls up to 2-3 m, foundations, and shells; dismantling large equipment by cutting frames, housings, and thick-walled pipes.

• Advantages: unlimited cutting depth, ability to cut along a curved contour (for example, removing a wall fragment of complex shape), and low vibration.



4. Chasing and Chain Cutting

• Narrow slots: width 30-50 mm, depth up to 400 mm.

• Tasks: chases for wiring, pipes, safety systems, and installation of flexible cable ducts.



Organization of Diamond-Cutting Works at Restricted-Access Facilities

Because works are often performed at operating power units or in zones under partial radiation control, the process is strictly regulated:



1. Preparatory stage: radiation survey of the cutting zone (for CAZ), marking, installation of barriers, supply of water and electricity (3x380 V, 16-32 A). For wire and wall-saw equipment, a cooling system with water supply up to 20 L/min is required.

2. Equipment fastening: drilling rigs and cutters are fixed to concrete with anchors (with pull-out verification) or vacuum plates to prevent displacement due to vibration.

3. Cutting process: continuous monitoring of current, feed rate, and water flow. In the CAZ, spent water (slurry) is collected and sent for analysis as potential radioactive waste.

4. Removal of the cut fragment: winches, jacks, and cranes are used for dismantling large blocks, with preliminary calculation of block weight. The opening edges are cleaned and the reinforcement is checked for preservation of load-bearing capacity.

5. Completion: water pumping, packaging of slurry in containers, and cleanliness control of the surface before sealing the opening, if necessary.



Advantages of Diamond Cutting over Traditional Methods at NPPs

Examples of Diamond-Cutting Applications at FUNE

• Creating a technological opening in a reactor-hall wall: thickness 1 m, B40 concrete, three-row reinforcement. Diamond wire cutting with water cooling is used. The opening is completed in two shifts without vibration, and reinforcement of adjacent areas is not required.



• Drilling 200 holes for pipes of an emergency cooldown system: diameter 150 mm, depth 500 mm, reinforced concrete. With diamond core bits, one hole takes 15-20 minutes versus 1.5 hours using a rotary hammer with a conventional concrete core bit (without diamonds).



• Dismantling the lining of a spent-fuel pool: cutting acid-resistant brick and concrete base with diamond blades with a high service life (polishing diamond segments). Dust and slurry are collected in a closed-loop system with purification, preventing spread of radioactive particles.



Quality Control and Safety

• Control of cutting parameters: deviation from the cutting line must not exceed 5 mm over 10 m of length, and there must be no uncut sections.

• Inspection of cutting tools: diamond segments are checked for wear; wire is replaced after 30-50 m² of cutting depending on concrete class.

• Radiation control: in strict-regime zones, every core and all slurry are checked, and equipment is decontaminated after work.

• Electrical safety: equipment is connected through an RCD (30 mA); water cooling prevents water from entering electronics (built-in IP54 systems).



Conclusions and Recommendations

The use of diamond cutting and drilling at facilities using nuclear energy is technically justified and economically efficient for demolition, reconstruction, and modernization tasks. It is recommended to:



1. Use only diamond cutting for all openings in load-bearing structures (walls, slabs) at NPPs, without transferring impact loads to the structures.

2. When dismantling large fragments (blocks), use wire cutting with selection of wire diameter depending on reinforcement and concrete strength.

3. For drilling holes for utilities and anchoring, use diamond drilling rigs fixed to the surface by vacuum or anchors to ensure accuracy.

4. Mandatory design of water cooling and slurry collection in the CAZ, followed by disposal as potentially radioactive material.

5. Include in the as-built documentation reports on opening-geometry control and certificates of inspection for hidden works (reinforcement, strength of opening edges).



To obtain a commercial proposal for diamond cutting and drilling at your facility, including drilling holes for utilities, creating openings, block demolition by wire cutting, and collection and disposal of slurry, send a technical specification indicating material type, thickness and reinforcement, required accuracy, and room safety class to the commercial department of TechAtomStroy LLC through the feedback form on the website. A cost and schedule calculation will be prepared with the restricted-access requirements of the site taken into account.



*This material was prepared on the basis of NP-041-22, Rostechnadzor requirements for reconstruction at operating NPPs, and safety standards for diamond cutting (EN 13236, GOST R IEC standards).*