Brief introduction of special cables for the hotte

2022-09-19
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Brief introduction of special cables for nuclear power stations

according to the national energy consumption statistics in 2002, the national commodity energy consumption is 1.48 billion tons of standard coal, ranking second in the world. Among them, coal accounts for 66.1%, oil 23.4%, natural gas 2.7%, hydropower 7.1%, and nuclear power 0.7%. In addition, the consumption of straw and fuelwood in rural areas reached 280 million tons of standard coal. In short, the application of nuclear power energy in China is very uncoordinated with the speed of economic development. Then from the analysis of the shortage of power supply, the state recently announced the situation of the power industry, the national power generation in the first quarter of 2004 was 479.4 billion kwh, and the power consumption capacity of the whole society was 480.5 billion kwh. In the first quarter of 2004, 24 provinces and cities shut down power. Main reasons for insufficient power generation: ⑴ except for the Three Gorges, the water volume of 24 key hydropower stations in China is more than 10% less than that in the same period of each year. ⑵ the supply of coal for power generation was insufficient. In the first quarter, the national coal social inventory fell by 16.6% year-on-year, and the coal inventory of enterprises fell by 6.84% year-on-year. (3) railway transportation is restricted, and the satisfaction rate of the whole railway loading is only 35%. In 2004, the electricity consumption of the whole society was about 2172.5 billion kwh, with a net increase of 284.4 billion kwh, an increase of about 15% year-on-year. The newly installed power generation capacity nationwide is 41.74 million KW, including 8.17 million kw of hydropower, 31.85 million kw of thermal power and 1.65 million kw of nuclear power. At the end of 2004, the total installed capacity reached 432million kW, achieving the adjusted growth target of the tenth five year plan two years ahead of schedule, with a year-on-year increase of 10.7%. It is estimated that by 2008, the power supply and demand will tend to be balanced or slightly affluent. It is reported that the total project scale of the power plant to be approved has reached 250million kW, which is 2/3 of the current national installed capacity. Based on this calculation, the approximate annual growth rate is 10.5%, which shows the scale of power construction and development. In terms of technology, China will research and develop thermal power, gas, hydraulic, nuclear power and wind power generation equipment at the same time

· the approval right for the construction of nuclear power plants is highly centralized in China. In the coastal areas with developed economy and concentrated power load, nuclear power plants will become an important pillar of the power structure. Recently, the State Council made a decision on the further construction of China's nuclear power plants and approved the expansion projects of Sanmen in Zhejiang and Lingao in Guangdong; In addition, Guangdong Yangjiang nuclear power project and Zhejiang Qinshan Phase II expansion project are in the process of submission for approval. As of July, 2004, a total of 9 nuclear power units have been put into operation in China. There are several nuclear power plant sites in other provinces along the eastern coast, and preliminary work is currently under way. It is estimated that 27 million KW nuclear power units will be built by 2020. In other words, in the next 16 years, the installed capacity of new nuclear power generation will reach 30million kW, and the construction of two to three nuclear power units will start every year. By 2020, the proportion of nuclear power in the total power generation capacity will rise from the current 1.8% to 4%. Since the operation of the current nuclear power plant requires a large amount of water, the main layout of the planned nuclear power plant is to consider the southeast coastal provinces. As for the investment in nuclear power construction, foreign economic experts believe that to complete such a large-scale nuclear power project, according to conservative estimates, the investment is also more than $40billion. China National Nuclear Corporation hopes that the average localization rate of new nuclear power plants can reach 60%, so it is estimated that $24billion (about 200billion yuan) of goods may be localized. From the analysis of China's wire and cable industry, at the current level of cable manufacturing technology, the localization rate of wire and cable can reach more than 95% by further improving equipment and product development

· cables for conventional power plants, whether power, control, instrumentation, digital and thermocouple cables, have mature domestic manufacturing technology and rich production capacity. However, there are still some problems to be solved for cables used in unconventional power generation areas of nuclear power plants. Further improve the quality and variety development of existing 1E class K3 cables, and the construction of 1E class K1 cables and their test bases are also tasks that should be considered at present. Since the development of nuclear power plants is a top priority, the standard of cables for nuclear power plants will inevitably be put on the agenda. The design of nuclear power plants in China is affected by France, the United States and Russia. Therefore, the technical requirements of nuclear power design departments for cables are not completely unified, so the enterprise standards of various cable plants are also different. From the point of view of safety, reliability and enforceability, whether the 1E cable standard can be jointly drafted by many parties and formulated as a national standard is a complex issue, which requires coordination from many parties. Domestic class 1E cable is defined as follows: it refers to the completion of reactor emergency shutdown; Containment isolation, core emergency cooling, reactor waste heat export, reactor containment heat export; Safety level of electrical system equipment that can prevent radioactive substances from discharging into the surrounding environment. K3 cable refers to the cable that can perform its specified functions outside the containment under normal conditions and seismic loads. According to this definition, it is not too much to be a mandatory national standard, and the preparation and specific operation of standard formulation should be fast rather than lazy. In terms of application, the cable varieties for nuclear power are basically the same as those for general thermal power plants, but their material composition and test items are quite different. The main varieties are 1 kV and below power cables, control cables, instrument cables, thermocouple compensation cables and 6/10kv power cables

· at present, the insulation in China is mainly cross-linked polyolefin, and the sheath is mainly thermoplastic polyolefin. In the future, it may be necessary to increase the application proportion of ethylene propylene rubber insulation and cross-linked polyolefin sheath varieties. 1E class K1 cable needs to undergo radiation test. The general conditions are as follows: (1) heat aging test, 138 ℃ for 300 hours in the United States, equivalent to 40 years of use. (2) Irradiation test and aging test are carried out with cobalt source γ In the X-ray irradiation test, the absorbed dose of cables in moderate environment in the United States is 7 × 105 Gy, 15 for harsh environments × 105 Gy 。 (3) To simulate the loca-helb test, the cable is placed in the container for cyclic test at the specified temperature, steam pressure and time, and the chemical solution is sprayed at the same time. Usually, the solution containing 1.5% boric acid is used, and its pH value is adjusted to 10.5 with sodium hydroxide at room temperature as the solution. The jet flow to the horizontal projection plane is 34.2 i/min m2. (4) Immersion voltage withstand test, at γ After the irradiation test, for cables in moderate environment, it is qualified to wind them on a metal cylinder with 20 times the outer diameter of the cable, and for cables in severe environment, it is 40 times the diameter, and then immerse them in room temperature water, apply voltage with a gradient of 3.15 mv/m, and do not break down for 5 minutes. The above is only a general description of the cable test for nuclear power plants, and there are many specific rules for the actual test

· roughly in the mid-1980s, China began to study and develop wires and cables for nuclear power stations on the basis of digesting and combining the specifications of American thermal power stations. The former first Ministry of machinery industry assigned a task: the cables were trial produced by Shanghai cable factory and Shenyang cable factory, and the cables were comprehensively evaluated by Shanghai Cable Research Institute. Although the work at this stage is of a bottom-up nature, it is very helpful for future development. In the late 1980s, a large number of imported cable sheaths of Daya Bay nuclear power station cracked. Shanghai Cable Research Institute was entrusted to conduct tests and analyze the root causes of the cracking. Finally, foreign investors agreed to economic claims. Since it is impossible for foreign countries to provide cables again in time, the cables that must be replaced are supplied by Shanghai cable factory in time and operate normally. In the middle and late 1990s, China accelerated the construction of nuclear power plants, and the wire and cable manufacturers for nuclear power plants have entered the stage of market competition. So far, the wire and cable testing center and technology development center of Shanghai Cable Research Institute have carried out more than ten tests and evaluations of wires and cables for nuclear power stations. The results show that it is not easy technically to produce comprehensive and high-quality wires and cables for nuclear power stations. In the last two years, quality problems are still found in the cables that have been delivered for use. In the future, more wires and cables for nuclear power stations should be listed, and more attention should be paid to the quality of cables

I Classification of cables in nuclear power plants

cables in nuclear power plants are mainly used in nuclear reactor buildings, nuclear auxiliary buildings, and steam turbine buildings. Cables are generally laid in pipelines or trunking, requiring reliable service life, thermal stability, moisture resistance, chemical stability, and radiation resistance. In order to ensure the high reliability of system design and avoid serious economic consequences caused by equipment damage, repeated multi-channel independent line systems and devices are usually used. Usually, two sets of independent line systems are used for power cables and three sets of independent line systems are used for control cables

class 1E cables for nuclear power plants are divided into three categories according to the safety category of electrical system equipment of nuclear power plants: K1, K2 and K3. Safety categories K1, K2 and K3 have the following definitions:

K1 electric actuator. Installed in the containment of nuclear reactor, it can still perform its specified functions under normal environmental conditions and below SL2 (safe shutdown earthquake) load and during or after the accident

k2 electric actuator. Installed in the containment of nuclear reactor, it can still perform its specified functions under normal environmental conditions and SL2 (safe shutdown earthquake) load

k3 electric actuator. Installed outside the nuclear reactor containment, it can still perform its specified functions under normal environmental conditions and SL2 (safe shutdown earthquake) load

the operating environment of the three types of cables varies greatly, among which the operating environment of K1 type is the worst, and the performance requirements of the cable are the most stringent. It can be put into operation only after the simulated coolant loss accident (LOCA) test. According to the actual operating environment of the cable, when a loca occurs in the nuclear power plant, the cables inside and outside the containment vessel will be severely tested. Some people believe that the cables installed in the nuclear reactor building should be subject to simulated loca tests; Secondly, only by being able to produce class 1E K1 cables, it can be proved that the cable manufacturer has the ability to produce nuclear grade cables. The structural design and performance indicators of the cables are best determined according to the specific conditions of the two operating environments of the reactor building and the nuclear auxiliary building

common varieties of cables in nuclear power plants are: 6/10 kV and 0 6/1 kV power cable, 0 There are 5 kinds of 6/1 kV control cables, 300/500 V instrument cables and 300/500 V compensation conductors

the following table is the specification table of a domestic company:

Table 1 type name of cable for class 1E nuclear power station

type

name

yjy K3

copper core XLPE absolutely has peak retention, damage automatic shutdown, overcurrent Overload automatic protection function margin halogen-free low smoke polyolefin sheathed 1E class K3 power cable for nuclear power station

yjy23 k3

copper core XLPE insulated steel tape armored halogen-free low smoke polyolefin sheathed 1E class K3 power cable for nuclear power station

yjyj k1

copper core XLPE insulated halogen-free low smoke flame retardant thermosetting sheathed 1E class K1 power cable for nuclear power station

yjyj23 k1

copper core XLPE insulated steel tape armored Halogen free low smoke flame retardant thermosetting sheathed 1E class K1 power cable for nuclear power station

kyjy k3

copper core XLPE insulated halogen-free low smoke polyolefin sheathed 1E class K3 control signal cable for nuclear power station

kyjy23 k3

copper core XLPE insulated steel tape armored halogen-free low smoke polyolefin sheathed 1E class K3 control signal cable for nuclear power station

kyjyj k1

copper core XLPE insulated halogen-free low smoke flame retardant thermal cable

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