All kinds of risk events will be encountered in the implementation of nuclear power projects, among which construction risk is a risk event that mainly occurs in the construction site and needs to be paid attention to. For construction risk events, measures of prevention first and combining prevention with control can be taken to prevent risks. At the same time, by combining the reasonable and feasible construction scheme, we can ensure to meet all construction requirements, rationally allocate construction resources, accumulate construction experience, contract risk management responsibilities, and realize closed-loop control of risk event transfer, avoidance and resolution.
Paper Keywords: nuclear power engineering; Construction risk; Risk factors; Risk response
First, the characteristics of nuclear power engineering
Nuclear power project is a super-large project, which has the characteristics of long project cycle (the construction period is generally about 5 years), huge investment (generally 15002000 USD/kWh installed capacity), complex technology, high safety requirements, intensive logistics, involving many units, complex interfaces, and concentrated venues. In the process of project implementation, there are various risks: external risks, design risks, procurement risks, construction risks, commissioning risks, management risks, contract risks, financial risks and so on. These risks have an important impact on the implementation of nuclear power projects. Some risks may cause the project to be delayed, and some risks may cause the project to be too heavily in debt, causing difficulties in capital turnover, making the project unable to achieve the expected goals, thus affecting the overall economy of nuclear power projects.
Second, the construction risk factors
According to the frequency and field of problems in site construction, combined with the characteristics and workflow of nuclear power project construction risks, the construction risks of nuclear power projects are divided into five categories.
1. Risk factors of construction technology
(1) design factors. 1) Accuracy of basic data. The basic design data and engineering investigation documents may be limited by technical and economic conditions and engineering investigation means, resulting in the accuracy of the data and documents not conforming to the actual situation of on-site construction or failing to meet the requirements of on-site construction, or even making major mistakes. 2) Timeliness of design documents. Due to the delay of design progress, drawings and documents urgently needed for construction cannot be provided in time. 3) Coordination of design disciplines. Nuclear power project is a comprehensive project, which needs the coordination of nuclear power, electric power, thermal control, welding, civil engineering, installation and debugging. Problems in any link may affect the accurate release of relevant documents.
(2) The influence of construction factors. 1) technical capacity of the construction unit. The construction unit should have the corresponding project management ability and experience, engineering and technical conditions, construction strength and equipment. To ensure that the project has the basic conditions for technical realization. For example, the construction unit lacks relevant operating experience in new technologies, which leads to a large number of problems in the construction process. 2) Engineering changes. Due to the large-scale nuclear power project, long construction period, many disciplines involved, mutual influence and restriction, and great influence by policies and regulations, engineering changes will inevitably occur during the construction process. For example, because the foundation design data is inaccurate, the site construction situation is different from the design drawings, or the quantity of works included in the contract is temporarily increased or decreased, the engineering change must be started.
2. Risk factors of construction activities
(1) construction organization planning factors. 1) Continuity of the construction process. Because the upstream construction has lagged behind, the subsequent construction can't start on time. Improper planning on the construction site leads to the interaction between processes. For example, tower cranes occupy the construction site, but they cannot be dismantled on schedule. Improper construction organization plan, cross construction of different types of work causes mutual influence. 2) The timeliness of construction-related work. Construction related documents were not reported in time, and the change of construction scheme was not notified to the general contractor in time during the construction process, which led to the failure of normal construction.
(2) Problems related to the construction unit in construction activities. 1) Change and determine the construction unit. The construction unit cannot be determined for a long time or needs to be changed during the construction process, which leads to the construction work not being carried out normally. 2) The construction unit violates regulations. Violation of the construction sequence, construction not according to the drawings, over-top construction, etc. , which may not only affect the quality and safety of the project, but also affect the progress of the project due to rework or shutdown. 3) The process construction documents of the construction unit. Relevant documents do not meet the design requirements, and the report is not timely and accurate, resulting in the related projects not having the conditions for commencement.
3. Risk factors of construction management
(1) Building safety factor. Improper safety measures during construction, incomplete construction safety and labor protection articles, etc., will turn into safety accidents once conditions are met. Safety accidents will inevitably bring losses to people or property and increase the project cost. Especially in nuclear power projects, what should the public establish for nuclear power in the event of an accident? Safety and environmental protection? Image will cause great damage, which is not conducive to the development of nuclear power.
(2) The influence of construction quality factors. 1) The construction quality is unqualified. Due to the lack of technical ability of the construction unit, the lack of quality awareness of the construction personnel or other external reasons, the construction quality may be unqualified, leading to problems such as rework or shutdown, and delaying the project progress. 2) Construction quality management. Do not report construction quality accidents, delay or inaction in construction quality treatment, etc. , not only can't cover up the problem, but make the problem that should have been solved long ago backlog, or even worsen. 3) Construction quality supervision. Poor quality self-inspection by the construction unit or insufficient supervision by the owner and supervisor may lead to the construction personnel taking the construction quality problems lightly and laying a hidden danger for the quality.
(3) Construction organization and coordination factors. 1) Coordination among responsible entities. Including the coordination between the project owner and the general contractor, the coordination between the owner or the general contractor and the design, manufacturer, construction and supervision, and the coordination between subcontractors. These responsible subjects may come from different countries and have different cultural and technical backgrounds. In the process of coordination and communication, differences should be properly handled in time so as not to affect the progress of the project. [1]2) Internal coordination of the project. The nuclear power project involves many disciplines, systems, disciplines and processes, and the normal progress of the project depends on the good coordination and cooperation of each operation in time and space.
4. Risk factors of construction resources
(1) Construction personnel factor. 1) personnel quality/qualification. Due to the weak safety or quality awareness of construction personnel, the construction safety or engineering quality is affected; There is a shortage of qualified personnel. 2) Brain drain. Due to poor construction conditions and insufficient fund allocation, a large number of construction workers may be lost, resulting in insufficient manpower. 3) Personnel deployment. Due to the temporary deployment of personnel, such as rushing to work, the manpower allocation of the project may be temporarily unbalanced.
(2) the influence of construction machinery and materials. 1) Material and equipment supply. Some materials are difficult to supply and purchase, and the procurement cycle is too long, which leads to the lag of supply. For some domestic equipment, due to the limited production capacity and domestic technical level of manufacturers, the manufacturing cycle is too long or unqualified products and rework occur, so that the goods can not be delivered on time. 2) Matching of materials and equipment. On-site equipment and materials are not urgently needed on site, but urgently needed on site cannot arrive in time, which not only affects the construction progress, but also wastes the on-site storage space and increases the storage pressure. Field equipment does not meet the design specifications or technical specifications, which increases the time and workload of verification and confirmation of related work. If the equipment cannot be used for installation, it will also affect the construction progress. 3) Configuration of machinery and materials. For limited machinery or materials, temporary deployment may be required due to rush. If the configuration is not reasonable enough, it will affect the overall construction progress. Background processing is also affected by machinery and material allocation, and prefabrication may not keep up with the field demand. 4) Acceptance and storage of materials and equipment. The acceptance of materials and equipment on site is not in place, which may make the problem not exposed in time, and it is not until the construction recipients that the materials and equipment do not meet the requirements. Poor storage management may affect the quality of materials and equipment and fail to meet the requirements in construction.