Fu Xiaogang, China Academy of Atomic Energy Sciences, Beijing 102413
Abstract: Zirconium hydride, as a solid moderated material, is widely used in both hot and fast reactors. In the process of use, the hydrogen release behavior of zirconium hydride at high temperature and the neutron irradiation performance have been two of the most concerned research issues. In this paper, the phase diagram of zirconium hydride, hydrogen release behavior at high temperature and some research results of size deformation under neutron irradiation are introduced. The application status of 6-zirconium hydride and E-zirconium hydride with different hydrogen content is introduced.
Zirconium hydride has the advantages of high hydrogen content, small neutron absorption cross section and high service temperature. It is an early moderated material used in the nuclear industry. In the late 1950s, the Heat Transfer Experimental Reactor No. 3 (HTRE-3) successfully used zirconium hydride as a moderator. Zirconium hydride (ZrH), as a moderated material, is an important component of TRIGA research reactor in the United States. In addition, zirconium hydride is used as moderator or shielding material for space reactors developed in the United States, Russia and China. The KNK-II fast reactor built in Germany uses zirconium hydride as the shielding material, and has accumulated a lot of experience. At present, zirconium hydride is also used as the moderator in the supercritical light water fast reactor designed in the United States and the large fast reactor power plant designed in Japan. In the above application process, high temperature hydrogen release of zirconium hydride and size deformation under neutron irradiation have always been the two most concerned research issues. For this reason, researchers in various countries have carried out a lot of experimental work and obtained some valuable
1 Phase diagram of zirconium hydride
Zirconium hydride is generally prepared by placing zirconium metal in high-temperature hydrogen for a period of time. The phase diagram of zirconium hydride is shown in Figure 1. When the H/Zr ratio is 1.54~1.66, zirconium hydride is the six phases of fcc structure; When H/Zr ratio is between 1.67 and 1.69, zirconium hydride is a 6 - ￡ phase with fcc and fct structures; When H/Zr ratio is 1.70 ～ 1.95, zirconium hydride is the e phase of fct structure. In the process of application and research of zirconium hydride, 6-zirconium hydride with H/Zr ratio near 1.6 and ￡ zirconium hydride with H/Zr ratio near 1.8 have accumulated the most test data. The United States and Japan tend to use 6-zirconium hydride with H/Zr ratio near 1.6, while Russia tends to use ￡ zirconium hydride with H/Zr ratio greater than 1.8.
2 Hydrogen release behavior of high ju
In terms of hydrogen release at high temperature, W. Wang et al. gave the expression o for hydrogen saturation decomposition pressure of zirconium hydride at 200 ℃~1000 ℃, as shown in the following formula.
Where C is the H/Zr ratio. In order to ensure the reliability of zirconium hydride used in space reactors, Russia has conducted hydrogen release measurement tests. The results show that the hydrogen release of zirconium hydride after 10 years of operation below 650 ℃ does not exceed 2% ∞ 1. The hydrogen content of ZrHl. 87 and ZrHl. 91 irradiated by BN-600 was measured. The results showed that × The zirconium hydride after 1026n/m2 neutron irradiation has almost no loss of hydrogen content H. The US research in the supercritical light water fast reactor shows that the hydrogen content of zirconium hydride moderated module decreases by about 2.5% after 4 years of operation, which has little impact on the reactor operation.
3 Neutron irradiation performance
In terms of irradiation performance research, the size deformation data of zirconium hydride after neutron irradiation are summarized in Table 1.
Table 1 Size Deformation of Zirconium Hydride after Neutron Irradiation
In terms of neutron irradiation, Paetz. P et al. showed that after 1.15 × After 1025n/in2 neutron irradiation, the volume expansion of ￡ zirconium hydride is 0.5%, while that of 6-zirconium hydride is basically unchanged.
Wood shall be installed and fixed under the pole, and stones shall be placed in case of emergency to ensure that the holding pole will not fall. Finally, when lifting the pole, fill and protect the pole, adjust the pole body, check whether the quality is up to standard after the completion of the whole process, and avoid uneven poles and cracks in poles.
4 Specific links of wiring installation type
The wiring installation of lOkV power line project is divided into three parts: ordinary wiring installation, horizontal pull wire installation and bow pull wire installation. First of all, during the preparation for the installation of ordinary wiring, it is necessary to select the appropriate pull rod orientation, the specific orientation of the pull pit and the retest of the pull position. When pulling the pull reel and digging the pit, pay attention to the pull reel and pull rod, the connection part of the pull pit, and also pay attention to the filling. The length of the steel strand required for the prefabrication of the stay wire shall be calculated. The length shall be measured with a ruler before making a mark. The main line and tail line shall be bound, and the clamp and the hoop of the stay wire shall be connected. During the installation of the hoop, its position shall be measured according to the situation, and a mark shall be made, and the hoop shall be installed in the appropriate place. At this time, it shall be noted that the bar and clamp shall be placed in the appropriate place to ensure the correct installation method. For the installation of UT type wire, remove the wire tightener, adjust the wire clamp, and then tighten the wire clamp, bar and steel strand. For the installation of horizontal stay wire, after all preparations are made, pull down the wire reel and dig the pit according to the same installation method of ordinary wiring. Attention shall be paid to the prefabrication of stay wire. The plumb wire and the actual horizontal line shall be measured and 0.8m shall be added to this foundation. In addition, it is also necessary to prefabricate the plumb wire and the horizontal line, drill the steel bar, and install the hoop in a proper place. When the staff installs the horizontal stay wire on the stay rod, they must pay attention to the safety protection. The staff shall pull the horizontal stay wire and install the clamp. For the installation of bow stay wire, its installation method is similar to the installation process of ordinary stay wire.
5. The conductor erection construction process of the lOkV power line project and the steps of the other process conductor erection construction processes shall first set out to make the wire tight, bind the insulator, and connect the downlead and lead wire. When paying off, set up the spool and pull the wire to the starting position of the line. Two methods can be used for paying off. One pulley is installed on the cross arm, and the wire is slowly placed in the pulley during paying off; Second, a certain length of wire is set out under the pole, and then it is lifted on the pole. After that, tie the chain block to the ground anchor or hang the tightener on the head end pole. At the end of the wire, install the wire clamp on the insulator or wire clamp, and then install the insulator. When binding the insulator, pay attention to the binding position of the linear pole wire, which needs to be bound twice. Then connect the downlead and lead wire, tension rod, corner rod and other special positions must be connected with the lead wire. In addition to the above mentioned processes, there are also some other construction processes for the lOkV power line project, such as the installation process of the step-down transformer, the installation process of the pole mounted transformer, and the construction and installation process of the pole mounted equipment grounding, which will not be described.
The lOkV power line project is related to the stability and safety of power use in cities and towns, which requires it to be more systematic, scientific and standardized. For the power sector, all parts of the construction process should be well done and supervised, especially
The part that is easy to make mistakes should be more careful to ensure that it is more standardized and standard. All kinds of construction processes shall be well used to make the lOkV power line project better serve the people.