High performance prestressed steel strand produced by our company
15.7mm - 1770Mpa / 1860Mpa
21.6mm - 1860Mpa
With the advantages of high bearing capacity, low relaxation, good flexibility and easy threading, it is the most ideal reinforcement for nuclear power containment structure.
It has the following characteristics:
1. Tensile strength
Above 1860MPa
The design life of nuclear power plant is generally 40 years. During the whole service period, it is necessary to ensure that the containment has sufficient precompression stress. The design prestress value meets the design requirements of NB / T20303-2014[Design requirements for prestressed concrete containments for pressure water reactor nuclear power plants], ACI 359-07[ASME Boiler and Pressure Vessel Committee.Boiler and Pressure Vessel Code: ACI 359-07] and RCC-CW [AFCEN.Rules For Design and Construction of PWR Nuclear Civil Works,France: RCC-CW] , so as to resist the cracking of containment caused by excessive internal pressure in loca and lead to nuclear radiation. In general, the stress value of nuclear island is more than 1000 tons grade.
2. Yield strength
The yield force to maximum force ratio is more than 92%.
The tension control stress of the prestressed system of nuclear power plant is 0.8fpy, which is higher than that of the prestressed system of civil engineering and bridge engineering, which is at the level of 0.7fpy,
3. Relaxation property
the stress loss of steel strand in 50 years is less than 20% under the condition of 40 ℃ and at 0.8FPY
The steel strand for nuclear containment is required to have very low relaxation rate, Sufficient prestress should be provided in the design life, and the service life of the nuclear power plant may be extended after the evaluation. The prestressed system is required to have a high level of prestress after 40-50 years. The relaxation rate of steel strand should not be higher than 4.5% under the initial force of 80% for 1000 hours.According to the calculation formula of relaxation value after 1000 hours given in DEB-FIP 《MODEL CODE》,the relaxation value of 50 years is about 3 times of that of 1000 hours, about 13% - 14%. The average ambient temperature of containment of nuclear power plant is about 40 ℃ in summer,
therefore, the stress loss of steel strand in 50 years is less than 20% under the condition of 40 ℃ and at 0.8FPY.
Prestressed steel strand is one of the most important materials in nuclear power plant construction. The requirements for the quality of steel strand are more from the perspective of safety. The containment is under static load for a long time. However, once the loca occurs and the internal pressure is too large, the prestressed system must be able to resist the internal pressure to ensure that the containment will not crack and produce nuclear radiation. Therefore, the quality of steel strand, especially the long-term relaxation property, is very important
4.The actual elongation of steel strand is more than 5%.
5. Deflection tensile properties
the deflection tensile coefficient is below 15%
The smaller the stress loss, the better. According to the requirements of international standards, the deflection tensile coefficient is below 28%, and the actual control level is below 15%.
