Cyclic strength of the equipment of nuclear power plants made of 22K steel
- PDF / 463,582 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 35 Downloads / 194 Views
CYCLIC STRENGTH OF THE EQUIPMENT OF NUCLEAR POWER PLANTS MADE OF 22K STEEL B. T. Timofeev 1 and Zh. L. Bazaras 2
UDC 620.194:620.197.3
We generalize experimental data on the low-cycle durability of 22K steel and its welds, i.e., materials of which the steam separators of nuclear power plants with RBMK-1000 reactors are made. These experimental data are compared with the reference curve for carbon steels according to the Standards PNAÉ G-7-002-86 currently in force. We show that the values of safety factor are provided in the assessment of the cyclic strength of separators made of 22K steel. Hence, the service life of the equipment of nuclear power plants of the first generation with RBMK-1000 reactors made of 22K steel can be extended for 15 years.
The most voluminous statistical material has been accumulated on the fatigue damages of the drums of steam generators of nuclear power plants (NPP) made of 22K steel [1 – 6]. All these damages represent comparatively shallow cracks in the zones of stress concentration and, hence, do not affect substantially the lifetime of boiler drums [6]. Furthermore, these damages were not numerous. However, in connection with the extension of the service life of NPP equipment, including steam-and-water separating drums (SWSD), this problem remains urgent as well. The strength of equipment made of 22K carbon steel and its welded joints was earlier studied at some length [2, 7 – 12]. In the present paper, we consider the cyclic strength of SWSD in connection with the extension of the service life of equipment for NPP of the first generation with RBMK-1000 reactors for 15 to 20 year over the specified lifetime. The experimental data on the low-cycle fatigue resistance of welds of 22K steel, presented in this paper, describe not only the thermal state of materials corresponding to the conditions of manufacture of SWSD but also other variants of their state, which can take place in the manufacture of different equipment of this steel. In particular, we give some data for the metal of welds made by manual electric arc and automatic welding under a flux layer both after tempering and without heat treatment after welding. In the manufacture of separators, the following methods are applied: electroslag welding with Sv-10G2 wire for the longitudinal welds of shells, automatic welding with Sv-08A wire under a flux layer for their circular welds, and manual electric arc welding with UONI-13/55 electrodes for the attachment of branch pipes to the shell. During the specified service life of NPP with RBMK reactors, more than 1000 loading cycles of the loop of multiple forced circulation are possible, which leads to the necessity of studying the cyclic strength of materials of which separators are made. We carried out tests for low-cycle fatigue of five melts of the base metal produced by different melting processes and of the metal of welded samples made by different welding methods. We tested the melts of steel of each melting process and each kind of semifinished item. To study the weld metal,
Data Loading...
