Abstract
Nowadays the total electricity generated in nuclear power plants in Russian Federation is approximately 18% of all power generation. There are 36 reactors in operation in Russia, 19 of which are reactor plants WWER-1000. A planned operation lifetime of these plants is 30 years and most of them have served for this period. To extend reactor working lifetime it is necessary to carry out the calculation for possibility justification of continued operation of reactor equipment and pipelines. The paper presents the static strength calculation of DN 350 branch pipe cutting-in in the main circulation pipeline of reactor plant WWER-1000. According to calculation results a following conclusion is made: if the static strength of DN 350 branch pipe cutting-in meets the requirements of technical standard, the continued operation of this pipeline section will be possible.
Highlights
The main circulation pipeline is an element of reactor plant primary circuit designed for a coolant circulation from nuclear reactor to steam generator and backwards
A "cold" leg consisting of two pipeline sections connecting steam generator outlet branch pipe with main circulation pump outlet branch pipe and main circulation pump outlet branch pipe with reactor outlet branch pipe
The analysis of calculation results revealed that the reduced stresses in the main circulation pipeline and branch pipe did not exceed the allowed values for the following loading combinations: normal operation breakdown + design basis earthquake, normal operation breakdown + maximum calculation earthquake
Summary
The main circulation pipeline (figure 1) is an element of reactor plant primary circuit designed for a coolant circulation from nuclear reactor to steam generator and backwards. The main circulation pipeline forms 4 circulation loops, either of which includes: A "hot" leg – a pipeline section connecting reactor outlet branch pipe with steam generator outlet branch pipe. A "cold" leg consisting of two pipeline sections connecting steam generator outlet branch pipe with main circulation pump outlet branch pipe and main circulation pump outlet branch pipe with reactor outlet branch pipe. The outer diameter size (850 mm) is chosen according to the conditions of ensuring the acceptable friction loss of main circulation circuit. The connecting pipeline inner diameter is chosen according to the limiting conditions of pressure difference acceptable value (0.39 MPa) between the pressurizer and the main circulation pipeline in non-stationary modes without the integrity loss of primary or secondary.
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