27. The role of nuclear energy in the carbon neutrality goal

Limin Liu a, Hui Guo a, Lihong Dai b, Maolong Liu a, Yao Xiao a, Tenglong Cong a, Hanyan Gu a 

aSchool of Nuclear Science and Engineering, Shanghai Jiao Tong University, China

bChina Ship Development and Design Center, China

More than 100 countries around the world have pledged to achieve carbon neutrality, and nuclear energy has attracted significant attention from both academia and industry as a low-carbon energy source. This paper explores the role of nuclear energy in achieving carbon neutrality and the development of related technologies. It first summarizes the contribution of nuclear energy to electricity generation and thoroughly reviews its non-electric applications, particularly in heat generation, hydrogen production, and seawater desalination. Furthermore, it introduces the development trends of next-generation nuclear technologies, such as the 4th generation reactors and small modular reactors (SMRs), highlighting their advantages in terms of safety, economics, sustainability, and the provision of non-electric services. Finally, it discusses major challenges facing the utilization of nuclear energy, including the aging of nuclear plants, safety concerns, unfavorable governmental policies, and negative public perception. In conclusion, nuclear energy has played a key role in low-carbon electricity generation for decades and shows great potential for expansion into non-electric applications such as district heating, hydrogen production, and seawater desalination. Particularly, nuclear power plants, as low-carbon baseload energy sources, are highly compatible with renewable energy and can enhance the flexibility of energy systems. The development of 4th generation reactors and SMRs offers opportunities to improve the economics, sustainability, safety, and flexibility of nuclear energy, making them promising options for achieving carbon neutrality. However, various technical and non-technical challenges, such as plant aging, declining economic competitiveness, safety issues, and unfavorable public support, still need to be addressed. Continuous efforts are essential to overcome these challenges and to strengthen the role of nuclear energy in reaching the goal of carbon neutrality.

26. Laser weldability of cast and rolled high-entropy alloys for cryogenic applications

Hyunbin Nam a, Chulho Park a, Jongun Moon c, Youngsang Na b, Hyoungseop Kim c, Namhyun Kang a 

aDepartment of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea

bTitanium Department, Korea Institute of Materials Science, Gyeongnam 51508, Republic of Korea

cDepartment of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea

In this study, similar welding of cast and rolled Co₀.₂Cr₀.₂Fe₀.₂Mn₀.₂Ni₀.₂ high-entropy alloys (HEAs) was performed using a laser beam welding (LBW) process. Both cast and rolled HEAs were successfully welded without macroscopic defects such as cracks or pores under identical welding conditions.

The welded metal (WM) and base metal (BM) maintained a face-centered cubic (FCC) phase structure regardless of the welding speed. As the welding speed increased from 6 to 10 m/min, the primary dendrite arm spacing (DAS), dendrite packet size, and the volume fraction of shrinkage voids decreased, resulting in finer microstructures and improved mechanical properties. Notably, the cast HEA welds exhibited larger DAS and dendrite packet sizes compared to the rolled HEA welds, which was attributed to the larger grain size of the cast BM.

The hardness distribution revealed a sharp variation between the BM and WM in the cast HEAs due to the significant difference in dendrite size (approximately 200 times smaller in the WM). In contrast, the rolled HEA welds exhibited minimal hardness variation because the DAS of the BM and WM were similar.

Tensile testing showed that the cast HEA welds had comparable tensile properties to their BMs, and fractures occurred near the heat-affected zone (HAZ) or within the BM. However, the tensile strength of the rolled HEA welds was approximately 90% of the BM strength, with fractures occurring within the WM. This reduction in tensile strength was attributed to the relatively larger dendrite packet size in the WM compared to the finer grain size of the BM.

Furthermore, all specimens demonstrated superior tensile properties at cryogenic temperatures (77 K) compared to room temperature (298 K). This enhancement was due to the predominance of deformation twinning and dislocation formation at lower temperatures.

In conclusion, the laser similar welds of the cast and rolled Co₀.₂Cr₀.₂Fe₀.₂Mn₀.₂Ni₀.₂ HEAs developed in this study exhibited excellent mechanical performance at cryogenic temperatures, indicating their high potential for application in offshore structures and vessels operating under extreme environmental conditions.

25. Decontamination of uranium-contaminated concrete

Kim, S. S., Kim, W. S., Kim, G. N., Park, H. M., Park, U. R., & Moon, J. K.

Decontamination and Decommissioning Research Division, Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yusong-gu, Daejeon 305-353, Republic of Korea

This study investigated a decontamination method using nitric acid washing for uranium-contaminated concrete pieces from a decommissioned uranium conversion plant. The concrete was classified into epoxy-coated and non-coated groups due to their differing radioactivity levels. For non-coated concrete, separating cement paste from aggregates after washing with 0.1 M sulfuric or nitric acid was more effective than direct uranium leaching, offering a simpler decontamination process. In epoxy-coated concrete, uranium was concentrated in a mortar layer beneath the epoxy. Heating at 400 °C for 2 hours, followed by pulverization and sequential washing with nitric acid (0.1, 2.0, and 1.0 M), successfully reduced uranium levels below the self-disposal limit, though it generated radioactive sludge weighing half of the initial concrete mass.

Additionally, the study compared uranium extraction efficiencies of carbonate, nitric, and sulfuric acid solutions. Unlike previous research by Rahmati, uranium dissolved in 0.1–2.0 M sulfuric acid was not effectively removed by strong anion exchange resins (IRA 910 and Ag1×8), likely due to limited formation of uranium-sulfate complexes and sulfate ion interference. These findings provide insights into optimizing decontamination processes for uranium-contaminated concrete.

24. Effect of μ-precipitates on the microstructure and mechanical properties of non-equiatomic CoCrFeNiMo medium entropy alloys

Jae Woog Bae, Jeong Min Park, Jongun Moon, Won Mi Choi, Byeong-Joo Lee, Hyoung Seop Kim

a. Department of Materials Science and Engineering, Center for High Entropy Alloys, POSTECH (Pohang University of Science and Technology), Pohang 37673, South Korea 

This study investigates non-equiatomic CoCrFeNiMo medium-entropy alloys (MEAs) with varying Mo contents (Mo5 and Mo7.5) after cold rolling and annealing at different temperatures. The microstructural analysis reveals that these alloys consist of a face-centered cubic (fcc) matrix and Mo-rich μ-phase precipitates. Increasing the Mo content and lowering the annealing temperature enhance μ-phase formation, consistent with thermodynamic predictions. In the Mo7.5 alloy, μ-phase particles act as barriers to grain growth and recrystallization due to the Zener pinning effect. This leads to improved mechanical properties, with a tensile strength of up to 1100 MPa and significant ductility. The findings highlight the potential of μ-phase strengthening in fcc-structured alloys and contribute to the development of high-performance MEAs. 

23. Laser decontamination for radioactive contaminated metal surface: A review

Qian Wang (a), Feisen Wang (a), Chuang Cai (a), Hui Chen (a), Fei Ji (a), Chen Yong (b), Dasong Liao (a) 

a. Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, China

b. AVIC Chengdu Aircraft Industrial (Group) Co., Ltd., Chengdu, 610073, China

With the development of laser technology, the strategic need for efficient and accurate decontamination of various components of nuclear application devices can be met by laser decontamination. Recontamination is essential for ensuring the safety of workers and reducing the cost of waste disposal for nuclear power plant decommissioning. Lasers have several advantages in nuclear power plant decommissioning, and with the development of technology, they have reached a level where they can be used for nuclear power plant decommissioning. The surface contamination radioactive materials of nuclear power plants mainly exist as loose contamination layers and fixed oxide layers. The types of radionuclides and the thickness of the contamination layer are closely related to the operating conditions of nuclear facilities, and they have a significant impact on the process as they are the targets to be removed in laser decontamination. In this study, the effects of laser surface treatment mechanism and laser process parameters on the decontamination thickness, decontamination coefficient, decontamination efficiency, and aerosol particle distribution were examined. Although many studies have been conducted on the laser treatment mechanism and laser decontamination process, little research has been done on the microscopic process mechanism of laser decontamination and the effects of laser decontamination on surface characteristics. In particular, the interaction between laser and radioactive contaminants requires further study.

20. Comparative study of laser-induced spalling behavior on concrete blocks with different water/binder ratios

Seong Y. Oh * , Gwon Lim , Sungmo Nam , Byung-Seon Choi , Taek Soo Kim , Hyunmin Park

Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea

To investigate the effect of the water/binder (W/B) ratio on laser-induced explosive spalling, laser scabbling experiments on concrete blocks were performed. The level of porosity in concrete, which is significantly influenced by the W/B ratio, affects the possibility of laser-induced explosive spalling driven by the rapid increase in pore pressure. Two types of concrete blocks were prepared with W/B ratios of 34.3 % and 60 %. A 5 kW laser coupled with an optical fiber was used to induce spalling in both concretes. The low-W/B concretes exhibited vigorous explosive spalling, while the high-W/B concretes showed less vigorous explosions or more pronounced vitrification. These findings demonstrate a distinct difference in laser-induced spalling behavior between low- and high-W/B concretes. 

19. Laser scabbling of mortar

B. Peach (a), M. Petkovski (a), J. Blackburn (b), D.L. Engelberg(c)

a.Department of Civil and Structural Engineering, Sir Frederick Mappin Building, Mappin Street,,University of Sheffield, Sheffield S1 3JD, UK

b. TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK

c. Research Centre for Radwaste & Decommissioning, School of Materials, The University of Manchester, Manchester M13 9PL, UK

Laser scabbling of concrete is the process of removal of surface material using a high power laser beam. The main aim of this investigation was to establish an experimental procedure for assessing the effects of various parameters that may be critical for the effectiveness of the process, such as material composition and initial moisture content. The study shows that the key characteristics of the process can be detected by monitoring surface temperature variations. This experimental procedure is used to provide data on the effects of each parameter to explain the mechanisms that drive the process. The results suggest that scabbling is mainly driven by pore pressures in the cement paste, but strongly affected by other factors. Reducing permeability by adding PFA to the cement paste resulted in significant increase in volume removal; but reducing moisture content by air-drying of the material did not result in the expected reduction in volume removal. 

18. Laser decontamination for radioactive contaminated metal surface: A review

Qian Wang ¹, Feisen Wang¹ , Chuang Cai ¹, Hui Chen¹,FeiJia¹, Chen Yong², Dasong Liao¹

1. Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 610031, China

2. AVIC Chengdu Aircraft Industrial (Group) Co., Ltd., Chengdu, 610073, China

With the development of laser technology, the efficient and accurate decontamination of nuclear applications can be met. The surface of nuclear facilities exists as loose contamination layers and fixed oxide layers. The contamination thickness is related to the operating conditions, which affects the laser parameters.

The procedure for studying laser decontamination is mainly through cold and hot tests of simulated samples. There are various laser parameters that affect the decontamination efficiency. The process parameters should be consistent with the characteristics of the contaminants present on the contaminated surfaces of nuclear facilities. In order to reuse the decontaminated metal components, the effects of various laser parameters on the surface corrosion and fatigue performance of the metal should be further investigated.

17. A State-of-the-Art Review of Radioactive Decontamination Technologies: Facing the Upcoming Wave of Decommissioning and Dismantling of Nuclear Facilities

 Shengyong Liu 1,Yingyong He 2,Honghu Xie 2,*,Yongjun Ge 2,Yishan Lin 2,Zhitong Yao 3,*,Meiqing Jin 3,Jie Liu 3,Xinyang Chen 3,Yuhang Sun 3 andBinhui Wang 3

1Daya Bay Nuclear Power Operations and Management Co., Ltd., Shenzhen 518124, China

2State Key Laboratory of Nuclear Power Safety Monitoring Technology and Equipment, China Nuclear Power Design Co., Ltd. (Shenzhen), Shenzhen 518172, China

3College of Materials Science and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China

The average share of nuclear energy in electricity generation is expected to increase. Due to the aging of existing nuclear power plants and the increasing demand for nuclear power plants, decommissioning (D&D) of nuclear power plants has become very important. Decontamination is a prerequisite for D&D, which can make it easier to make and reduce the amount of radioactive waste. However, there is no comprehensive study on decontamination methods, which is not helpful for the sustainable development of nuclear energy and environmental protection. Therefore, this study first analyzes the current status and future trends of global energy and nuclear energy. Then, various decontamination approaches are compared and studied, including cleaning mechanisms, application targets, and intrinsic advantages and disadvantages. Finally, criteria and factors for selecting a decontamination process, challenges, and future research are indicated. Among mechanical methods, laser-based cleaning is promising because it has the ability to be automated and is fast, but it generates the risk of dust and airborne contaminants. Further studies can investigate factors such as selecting appropriate laser facilities, optimizing operating parameters, and designing high-efficiency dust collection systems. Regarding chemical methods, chemical gels are suitable for decontaminating complex shapes and vertical and overhead surfaces. In addition, the efficiency of other decontamination agents can be improved by improving the contact time. However, the formulation of colloidal gels is complex, and there is no gel type that is useful for all contaminants. Therefore, new and versatile gels should be developed to expand the application field. Combining various decontamination methods often leads to better results, so rational and effective combination of these decontamination methods has become a major direction.

16. SOLAR SINTERING ON LUNAR REGOLITH SIMULANT (JSC-1) FOR 3D PRINTING.

Avishek Ghosh¹ , Prof. Jean Jacques Favier² , Mackenzie Casey Harper³

1.  International Space University, 1 Rue jean Dominique Cassini, Parc. D innovation, Illkirch Graffenstaden, 67400. Strasbourg France.avishek.ghosh@community.isunet.edu

2. International Space University, 1 Rue jean Dominique Cassini, Parc. D innovation, Illkirch Graffenstaden, 67400. Strasbourg France. jean-jacques.favier@isunet.edu

3. Skycorp Incorporated, Nasa Ames Research Center, 3301 Lyon St. San Francisco, CA 94123 

There are many efforts for lunar exploration and the construction of a habitable zone. Among them, additive manufacturing (AM) using in situ natural resources (ISRU) is an economically effective method because it does not require the transportation of resources from the Earth. Various studies are needed for this purpose.

Fresnel lenses can focus solar energy to create high energy. In this study, we aim to laminate Moondust simulant (JSC-1).

As a result of the study, the Fresnel lens induced a temperature of over 1100⁰C, and as a result, a fused metal glass object was created from the simulant, proving the possibility of additive manufacturing.

However, more evaluations are needed to analyze the structural strength, adhesion, and bonding of the specimens manufactured through this study.

The next goal of this study is to further develop the solar sintering 3D printer to manufacture large-sized specimens and study various physical and mechanical characteristics.

15. Regolith sintering and 3D printing for lunar construction: An extensive review on recent progress

Muhammad Shazwan Suhaizan a, Phuong Trana, Ash Exnera, Brian G. Falzona

aDepartment of Decommissioning and Waste Management Japan Atomic Energy Research Institute Tokai-mura, Naka-gun, Ibaraki-ken 319-1995, Japan

a. School of Engineering, RMIT University, Melbourne, Australia

In-Situ Resource Utilisation (ISRU) is increasingly being seen as a viable and essential approach to constructing infrastructure for human habitation on the moon. Transporting materials and resources, from Earth to the Moon, is prohibitively expensive and not sustainable for long-term, large-scale development. Various fabrication technologies have been investigated in recent years, designed for extra-terrestrial exploration and settlement. This review presents a comprehensive study on the develop- ment of several sintering techniques of lunar regolith simulant to demonstrate its feasibility for ISRU on the moon. Various critical processing parameters are evaluated in pursuit of creating a structural material that can withstand the extreme lunar environment. Key outcomes are summarised and assessed to provide insight into their viability. Finally, current challenges are addressed and potential improvements, and avenues for further research, suggested.

Bulk sintering

• Sintering studies traditionally used pre-compressed or loose regolith powders at high temperatures to densify 

the powders into building elements.

• A more recent technique is spark plasma sintering which employs both heating and pressure to achieve higher den- 

sification.

• These methods would require large and immobile equip- ment with slow processing times and high energy con- 

sumption.

Focused sintering

• In contrast to bulk sintering, focused sintering entails fusing successive layers of lunar soil, enabling the in-situ 

sintering of the lunar surface or as a powder-bed method.

• Laser sintering is energy intensive even for moderately sized parts. Solar sintering applies concentrated energy 

from the Sun, eliminating the need for external power sources.

•   Residual/thermal stresses may limit their strength.

 3D‑printing  technologies

• Advances in Additive Manufacturing (AM) technologies are critical for the future development of space explora- 

tion and construction, as various techniques can be uti- lised according to specific requirements.

• Applications of 3D printing by solar sintering and Selec- tive Laser Melting (SLM) are capable of printing detailed 

high-precision parts as tools or building elements.

• Direct Ink Writing (DIW) technology is suited for fabri- cating larger architectural constructions, though is lim- 

ited in mechanical strength.

• Transportation of additives and additional materials to accommodate certain 3D-printing techniques, such as 

DIW, presents an impediment to adoption.

13. Analysis of nano-particle release from the surface of syructural concrete members by ablation using soft computing

Zibing Su a, Rui Wang b, Dalibor Petković c, Nebojsa Denic d, Riadh Marzouki e, Mohamed Amine Khadimallah f g 

aArt College of Chongqing Technology and Business University, Chongqing 400067, China

bSchool of Smart City Design, Chongqing Jianzhu College, Chongqing 400072, China

cUniversity of Niš, Pedagogical Faculty in Vranje, Partizanska 14, 17500 Vranje, Serbia

dUniversity of Priština in Kosovska Mitrovica, Faculty of Sciences and Mathematics, Serbia

eChemistry Department, College of Science, King Khalid University, Abha 61413, Saudi Arabia

fPrince Sattam Bin Abdulaziz University, College of Engineering, Civil Engineering Department, Al-Kharj, 16273, Saudi Arabia

gLaboratory of Systems and Applied Mechanics, Polytechnic School of Tunisia, University of Carthage, Tunis, Tunisia

Optical & Laser Technology (ELSEVIER) IF : 4.6 (2023)  

The paper is concerned with the evaluation of laser-treated cementitious surfaces. It is part of a bigger investigation into the laser cleaning procedure and its impact on the change of the Nano particles of cementitious composites and concrete member structures. Because of the wide range of absorptivity of highly developed surfaces of concrete members and cementitious materials, their reactions to laser irradiation varied significantly. Even while laser could effectively remove the particles from the surface of concrete members, there are usually some residual surface modifications related with mortar removing, fracture development, and glazing (melted mortar). In this study, a large amount of thermal stress is created with low power densities (300 W/cm2) and large spot sizes (50 mm) that promote structural concrete member cracking. By raise of power density, the cement matrix material melts make the thermal ablation mode ineffective. This procedure is also heavily influenced by the beam diameter to aggregate size rate. As a result, due to stable size of aggregate, the procedure is not scalable. In this study, the findings of ablation experiments on cement and concrete member specimens performed with a Yb-fiber laser with a power of 1 kW and a focused beam width of 800 m have been delivered through fiber optic beam delivery. In order to know the influence of substrate composition on ablation ratio and processes, the laser–surface interaction was examined on type I Portland cement with varying amounts of sand or fine silica. The primary objective is to maximize the material removal rate (MRR) and aspect proportion of alumina, stainless steel, and chromium (Cr). The goal of this study is to use an adaptive neural fuzzy inference system (ANFIS) to categorize the multiple input variables for MRR and ratios based on process variables. Scanning speed, annealing temperature, laser power, and laser frequency are all input parameters. The prediction might be crucial in determining the ideal circumstances for micro and Nano architectures of concrete members created by laser ablation. According to the data, annealing power has the greatest impact on aspect ratio, whereas micro structure width has the most effect on MRR. Analysis revealed that contaminants of alumina, stainless steel, and chromium (Cr) were highly segregated into distinct areas of the aerosol's particle size distribution. 

12. Determination of chloride content in concrete structures with laser-induced breakdown spectroscopy

G. Wilsch *, F. Weritz, D. Schaurich, H. Wiggenhauser

An important criterion for the evaluation of reinforced concrete structures is the measurement of the chloride content. This will normally be done by time consuming standard chemical methods. We propose the application of a spectroscopic technique, the laser-induced breakdown spectroscopy (LIBS), which provides the advantages of a fast measurement, the potential for on-site application and the possibility to investigate a wide range of different measuring points. The surface can be scanned, or depth profiles are available from cores. Measurements can be performed directly on the sample surface and the results are available in near real time. We present LIBS results measured on concrete cores as well as on grinded and pressed material in comparison with the results of standard chemical methods. The optimum LIBS set-up and the experimental conditions to detect and measure chlorine in building materials are reported. The limits of detection were determined and calibration curves were measured. 

11. Laser Radiation CO2 Effects in Cement Paste at Different Hydration Stages after Preparation

Moreno–Virgen M.R.1, Soto–Bernal J.J.2, Ortiz–Lozano J.A.3, Frausto–Reyes C.4, Bonilla–Petriciolet A.5, González–Mota R.6, Rosales–Candelas I.7 and Pineda–Piñón J.8

1 CICATA. Querétaro, Qro. México Instituto Tecnológico de Aguascalientes. E–mail: moreno_virgen@yahoo.com.mx

2 Instituto Tecnológico de Aguascalientes. E–mail: j2sb@cio.mx

3 Universidad Autónoma de Aguascalientes. E–mail: aortiz@correo.uaa.mx

4 CIO, Unidad Aguascalientes. E–mail: cfraus@cio.mx

5 Instituto Tecnológico de Aguascalientes. E–mail: petriciolet@hotmail.com

6 Instituto Tecnológico de Aguascalientes. E–mail: Rgmota73@yahoo.com.mx

7 Instituto Tecnológico de Aguascalientes. E–mail: ilianaroca@yahoo.com

8 CICATA. Querétaro, Qro. México. E–mail: arqjpp@yahoo.com

In this work the changes occurring in cement pastes irradiated by 10.6¡mi CO2 laser at different stages of hydration after preparation are presented. Raman spectroscopy, X–ray diffraction and Scanning Electronic Microscopy (SEM) techniques were used to observe molecular structural changes. Intensity of cement paste Raman peaks after laser irradiation was monitored in samples irradiated 2, 3, 4, 5, 6, 7, 8, 9,10 and 11 days after their preparation. Applied laser power changed Raman peaks intensity at 187.5cm–1,563cm–1, 695cm–1, 750cm–1, 897cm–1,1042cm–1 and 1159cm–1 that correspond to compounds already present in cement pastes. X–ray diffraction, SEM images and changes in the Raman peaks confirm the recrystalization of cement paste compounds into new phases (alite and belite) after irradiation. The produced changes show a clear dependence on the applied laser power density and age of samples. 

10.The effect of ageing and drying on laser scabbling of concrete

B. Peach (a), M. Petkovski (a), J. Blackburn (b), D.L. Engelberg(c)

a.Department of Civil and Structural Engineering, Sir Frederick Mappin Building, Mappin Street,,University of Sheffield, Sheffield S1 3JD, UK

b. TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK

c. Research Centre for Radwaste & Decommissioning, School of Materials, The University of Manchester, Manchester M13 9PL, UK

Laser scabbling of concrete is a process by which the surface layer of concrete is removed through the use of a high power (low power density) laser beam. In order to understand how the age and treatment of structures may affect the laser scabbling process, the aim of the research presented in this paper was to establish a relationship between laser interaction time, surface temperature and volume removal for cementitious materials of different ages and different degrees of saturation. The investigation focussed on (i) the effect of age on saturated specimens and (ii) the effect of prolonged drying. The results show that drying of specimens had the largest effect on scabbling. The effect of age on saturated specimens was small for PFA + OPC pastes, mortars and concretes, but significant for OPC pastes, where the volume of scabbling dramatically reduced with age. 

9. Laser scabbling of mortars

B. Peach (a), M. Petkovski (a), J. Blackburn (b), D.L. Engelberg(c)

a.Department of Civil and Structural Engineering, Sir Frederick Mappin Building, Mappin Street,,University of Sheffield, Sheffield S1 3JD, UK

b. TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK

c. Research Centre for Radwaste & Decommissioning, School of Materials, The University of Manchester, Manchester M13 9PL, UK

Laser scabbling of concrete is the process by which the surface layer of concrete may be removed through the use of a low power density laser beam. Previous research has suggested that the driving force responsible for laser scabbling is developed within the mortar. The aim of this investigation was to establish the key parameters that influence laser scabbling of mortars. The results show that the removal of free water from mortars prohibits scabbling, but resaturation allows mortar to scabble. A reduced permeability, either due to a reduction in the water/binder ratio or the use of 25% PFA replacement, enhances the scabbling. A higher fine aggregate content increases volume removal and fragment sizes during laser scabbling. 

8. The effect of concrete composition on laser scabbling

B. Peach (a), M. Petkovski (a), J. Blackburn (b), D.L. Engelberg(c)

a.Department of Civil and Structural Engineering, Sir Frederick Mappin Building, Mappin Street,,University of Sheffield, Sheffield S1 3JD, UK

b. TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK

c. Research Centre for Radwaste & Decommissioning, School of Materials, The University of Manchester, Manchester M13 9PL, UK

Laser concrete scabbling is the process by which the surface layer of concrete may be removed through the use of a low power density laser beam. The main aim of this investigation was to establish relationships between laser interaction time and volume removal for a wide range of material compositions, including different w/b ratios, binder compositions (OPC/PFA), aggregate/binder ratios and coarse aggregate sizes. The results show that 25% replacement of ordinary Portland cement with pulverised fuel ash and/or a reduced water/binder ratio improves the efficiency of scabbling of cement pastes. Mortars and cement pastes were seen to scabble at a constant rate, whereas concretes experienced a peak rate, after which volume removal reduced dramatically. Basalt aggregate concrete was less susceptible to laser scabbling than limestone aggregate concrete. The effects of composition on the mechanisms which drive laser scabbling are discussed. It is suggested that pore pressure spalling governs behaviour in cement pastes, and thermal stress spalling is more dominant in mortar specimens. The driving force responsible for laser scabbling of concretes is developed within the mortar. 

7. Using a High-Power Fibre Laser to Cut Concrete

Kaori Nagai, Kazuki Shimizu

Department of Architecture and Architectural Engineering, College of Industrial Technology, Nihon University, Chiba 275-8575, Japan 

Concrete cutting at construction sites causes problems such as noise, vibration, and dust. In particular, during the demolition and renovation work on buildings in urban areas, protection against noise, vibration, dust, etc., is needed. Concrete cutting using a CO2 laser was investigated 20 years ago. However, this method had never used because the equipment is difficult to carry. In this study, we used a portable fibre laser, which is convenient to carry. Two types of concretes with different strengths were prepared for the experiment. High-strength concrete has never been used in similar research before. High-strength concrete is just only used for skyscrapers because of its high quality and costs. Furthermore, it has already been used for skyscrapers in Japan. It is for this reason that we chose to use it in this study. Irradiation measurements were conducted under various conditions using laser powers of 6 and 9 kW. It was confirmed that the cutting effectiveness of CO2 and fibre lasers was approximately identical for concretes with a thickness of 200 mm. Furthermore, the cutting effectiveness for the two concretes with different densities was almost the same. However, the situation after cutting was different because the vitrification of the cutting and glass formation progressed in low-density concrete and an explosion phenomenon occurred in high-density concrete, simultaneously. This study suggests that laser concrete cutting can be used as a solution when noise and dust are major problems. 

6. A laboratory study about laser perforation of concrete for application in oil and gas wells

Hasan  Kariminezhad  , Hossein Amani b, Mobarakeh Moosapoor a

a  Department of Physics, Babol University of Technology, Babol, Iran 

b Faculty of Chemical Engineering, Babol University of Technology, Babol, Iran 

Laser perforation is the application of light to make a flow path between wellbore regions through the casing wall and cement layer all the way to reservoir production zone. Due to significant losses of laser power at long distances, introducing a novel method in order to facilitate laser perforation in oil and gas reservoirs is necessary. This paper aims to study on concrete perforation using a continuous 240 W/cm2 CO2 laser. In this research, the effect of water on the parameters of laser perforation such as rate of perforation (ROP), specific energy (SE) and dominant mechanisms was investigated. For this, two groups of concrete samples (dry and wet) were illuminated at 2, 6, 15, 30 and 60 s by the laser. Our results showed evaporation was main mechanism for dry samples at exposure times above 15 s, while spallation was the dominant mechanism for the wet samples at all exposure times. ROP and SE were significantly increased and decreased in the presence of moisture, respectively. Maximum ROPs obtained 2.26 mm/s and 0.45 mm/s for wet and dry samples, respectively. Also, minimum of SEs for wet and dry samples obtained 1.05 J/mm3 and 4.3 J/mm3, respectively. Finally, our experimental results were justified using a simplified heat conduction model. All these characteristics demonstrate presence of water in concrete possesses an important role to improve rate of laser perforation. Therefore, the results of this research could significantly reduce time and cost of laser perforation for application of oil recovery. 

5. Development of Concrete Building Cutting Technology Using High-Power Laser

Goya, S., Mori, H., Okuda, T., Fujiya, Y., Shimonabe, N., & Akaba, T. 

With the increasing power and better quality of laser oscillators, laser processing, which has not been applied to thick concrete, has been increasingly used in recent years. In this report, we describe laser cutting of thick concrete columns (with a maximum thickness of 1200 mm) by using high-power fiber laser of over 20 kW and an ultra-long focus optical system, aiming at establishing a remote demolition technology for nuclear plant buildings that are high radiation areas. This report also describes a new beam laser damper system using water that was developed as a technology for receiving the high-power laser beam passing through a cutting object, which has been an issue in high-power laser processing. 

4.  An experimental investigation of laser scabbling of concrete

B. Peach*, M. Petkovski*, J. Blackburn**, D.L. Engelberg***

*Department of Civil and Structural Engineering, Sir Frederick Mappin Building, Mappin Street, University of Sheffield, Sheffield S1 3JD, UK

**TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK

***Research Centre for Radwaste & Decommissioning, School of Materials, The University of Manchester, Manchester M13 9PL, 

UK

Concrete is widely used in the nuclear industry, often in direct contact with radioactive materials.

Concrete contamination tends to extend 8–12 mm from the surface

Mechanical scabbling has flaws, but lasers have the advantage of being remote.

Laser scabbling and surface glazing, with subsequent surface removal, was used successfully in the decommissioning of the Japan Atomic Energy Research Reprocessing Test Facility

Laser scabbling is comparable to explosive spalling exhibited in concrete exposed to fire conditions, but the large difference in heating rates would be expected to produce different mechanisms driving the two processes.

The aim of this research was to establish an experimental methodology for detecting the mechanisms responsible for laser scabbling of concrete.

The results of this study show that the scabbling behaviour of each material can be characterized by time histories of average surface temperature of the exposed area of the specimens.

The results show that the laser scabbling process is significantly affected by the material composition, with clear differences between cement pastes with different binder mixes; between cement pastes, mortars and concretes; and between concretes with the two different types of aggregates used in this study.

The results of this study showed that the size of fragments was generally smaller, and vitrification was more prominent, for saturated specimens compared to air dried specimens, but the higher degree of saturation did not lead to increased volume removal. This indicates that the presence of free water does affect the process, but is not a key factor controlling its effectiveness.

3.   Performance comparison of CO2 and diode lasers for deep-section concrete cutting

Philip L. Crouse , Lin Li *, Julian T. Spencer a a, b 

a . Sackville Street, Manchester M60 1QD, UK 

b. BNFL, R&T, Rutherford House, Risley, Warrington, WA3 6AS, UK 

Layer-by-layer laser machining with mechanical removal of vitrified dross between passes is a new technique with a demonstrated capability for deep-section cutting, not only of concrete, but of ceramic and refractory materials in general. For this application fairly low power densities are required. A comparison of experimental results using high-power CO2 and diode lasers under roughly equivalent experimental conditions, cutting to depths of >100 mm, is presented. A marked improvement in cutting depth per pass is observed for the case of the diode laser. The increased cutting rate is rationalized in terms of the combined effects of coupling efficiency and beam shape.

2. Effect of moisture content and mix proportion of concrete on efficiency of laser scabbling 

Seong-Uk Heo a , Ji-Hyun Kim b , Seong Yong Oh c , Gwon Lim c , Sungmo Nam c , TaekSoo Kim c , Hyunmin Park c , Chul-Woo Chung a,* 

a . Division of Architectural and Fire Protection Engineering, Pukyong National University, Yongso-ro 45, Nam-gu, Busan 48513, Republic of Korea 

b. Multidisciplinary Infra-Technology Research Laboratory, Pukyong National University, Yongso-ro 45, Nam-gu, Busan 48513, Republic of Korea 

c. Laser Application Research Team, Korea Atomic Energy Research Institute, Daedeok-daero 989beon-gil 111, Yuseong-gu, Daejeon 34057, Republic of Korea 

With the decision to permanently shut down Kori Unit 1, the importance of domestic nuclear power plant decommissioning technology has been strengthened, and the size of the domestic decommissioning market is expected to grow to about $7 billion by 2080. Concrete accounts for more than 70% of nuclear power plant facilities as a major construction material. Therefore, removing contaminated concrete is key to reducing the cost of decommissioning nuclear power plants. There are various removal methods, but all of them have disadvantages, and a method that came out to compensate for this is laser scalable. In this study, the effects on the moisture content and mixing ratio of concrete during laser scapular were investigated.

The mixing ratio of the concrete used in the experiment is shown in Table 2.

The specimens were divided into three conditions: OD (Oven dry), AD (Air dry), and SSD (Saturated surface dry).

Each specimen was prepared as follows. First, after concrete is poured, it is cured for 1 day. After that, it is left in a saturated lime solution for the remaining 27 days until the compressive strength test on the 28th.

after

OD: dried in an oven at 105°C for 60 hours

AD: It dried for 7 days at room temperature.

SSD: Only the surface water was removed with a dry towel.

The experimental results according to moisture are shown in Table 3.

The experimental results according to the composition are shown in Table 4.

Fig. 4 shows thermal images during the scheduling process in AD and SSD states.

Fig. 5 is a thermal image during the scaffolding process in the OD state.

The phenomenon of temperature drop in Figure 4 is caused by spalling, and as a result, as shown in Table 4, OD and SSD have better scheduling efficiency than AD. The phenomenon of temperature drop in Figure 4 is caused by spalling, and as a result, as shown in Table 3, OD and SSD have better scheduling efficiency than AD. The change in efficiency according to the composition was not large as shown in Table 4.