The Paton Welding Journal, 2013, №01



2013 №01 (01)

2013 №01 (03)

---

The Paton Welding Journal, 2013, #1, 5-10 pages  

INVESTIGATION OF STRESS-STRAIN STATE OF WELDED STRUCTURES FROM AUSTENITIC STEEL AT RADIOACTIVE IRRADIATION

O.V. MAKHNENKO and I.V. MIRZOV

E.O. Paton Electric Welding Institute, NASU, Kiev, Ukraine
 
 
Abstract
Nuclear reactor reflection shield is exposed to high doses of radiation, leading to its noticeable deformation and closing of the clearance between the reflection shield and cavity wall. This leads to a change of heat exchange in the reactor core that may have hazardous consequences in terms of violation of temperature mode of reactor operation. To evaluate the radiative swelling of the reflection shield, a 2D finite element model was constructed, using calculation algorithms well-tested at the E.O. Paton Electric Welding Institute, in which isotropic volumetric deformations were assigned as radiative swelling. The model non-linearly takes into account the dependence of radiative swelling of the reflection shield material on irradiation temperature, stressed state and plastic deformations. The model also describes the change of yield limit of welded cavity wall, as a function of irradiation temperature and accumulated radiation dose. After 25 years of reactor operation the maximum value of swelling deformations in reflection shield material is equal to 1.3%, reaching 1.8 after 40 years, and 3.7 after 60 years. Maximum radial displacements of the reflection shield outer surface during reactor operation are equal to 11.2 mm after 25 years, 12.9 mm after 40 years, and 16.1 mm after 60 years. In a more conservative model, not allowing for the history of volumetric deformation accumulation, reflection shield swells by 26 % over 60 years of operation that corresponds to even greater radial displacements of reflection shield outer surface in the outward direction. Results on swelling and radial deformations of the reflection shield derived allowing for the stressed state are indicative of a possible contact of reflection shield with the cavity welded wall during reactor operation. Such a contact can greatly affect the stress-strain state of the cavity welded structure, therefore, it requires a more detailed study. 9 Ref., 2 Tables, 14 Figures.
 
 
Keywords: welded metal structures, austenitic steel, stress-strain state, reflection shield, reactor service life, radiative swelling, numerical model, cavity wall
 
 
Received:                10.09.12
Published:               28.01.12
 
 
References
1. (2011) Additional operations on assessment of technical state of reactor elements of power unit No.1 of OP Yuzhno-Ukrainskaya. Assessment of radiative swelling of reflection shield: Report. NRI Rez.
2. Kursevich, I.P., Margolin, B.Z., Prokoshev, O.Yu. et al. (2006) Mechanical properties of austenitic steels in neutron irradiation: Influence of different factors. Voprosy Materialovedeniya, 48(4), 55-69.
3. Borodin, O.V., Bryk, V.V., Voevodin, V.N. et al. (2006) Microstructural mechanisms of low-temperature radiative swelling and embrittlement of materials of WWER-1000 reactor devices. In: Problems of resource and safe service of structures, constructions and machines. Kyiv: PWI.
4. (2008) Determination of current values of mechanical properties of vessel internals elements: Report. NRI Rez.
5. Shary, N.V., Semishkin, V.P., Piminov, V.A. et al. (2004) Strength of main equipment and pipelines of WWER reactor facilities. Moscow: IzdAT.
6. Makhnenko, V.I. (1976) Computational methods of investigation of welding stress and strain kinetics. Kiev: Naukova Dumka.
7. Margolin, B.Z., Kursevich, I.P., Sorokin, A.A. et al. (2009) On problem of radiative swelling and embrittlement of austenitic steels. Pt 2. Physical and mechanical principles of embrittlement. Voprosy Materialovedeniya, 51(2), 99-111.
8. Vasina, N.K., Margolin, B.Z., Gulenko, A.G. et al. (2006) Radiative swelling of austenitic steels: Influence of various factors. Processing of experimental data and formulation of determinant equations. Ibid., 48(4), 69-89.
9. Votinov, S.N., Prokhorov, V.I., Ostrovsky, Z.E. (1987) Irradiated stainless steels. Moscow: Nauka.

---

Suggested Citation

O.V. MAKHNENKO and I.V. MIRZOV (2013) INVESTIGATION OF STRESS-STRAIN STATE OF WELDED STRUCTURES FROM AUSTENITIC STEEL AT RADIOACTIVE IRRADIATION. The Paton Welding J., 01, 5-10.

---