Role of in-service stress and strain fields on the hydrogen embrittlement of the pressure vessel constituent materials in a pressurized water reactor. (December 2017)

• Record Type: Journal Article
• Authors: Toribio, J.; Vergara, D.; Lorenzo, M.
• Is Part Of: Engineering failure analysis. Volume 82(2017)
• Page Start: 458
• Page End: 465
• Publication Date: 2017-12
• Subjects: BWR boiling water reactor -- EAC environmentally assisted cracking -- HE hydrogen embrittlement -- LWR light water reactor -- NPP nuclear power plant -- NRPV nuclear reactor pressure vessel -- PWR pressurized water reactor -- RPV reactor pressure vessel -- VVER Vodo-Vodyanoi Energetichesky Reaktor -- WWER water–water energetic reactor -- 1D one-dimensional -- A zone of wall corresponding to the cladding layer -- B+ zone of the base material layer with tensile residual stress -- B− zone of the base material layer with compressive residual stress -- C hydrogen concentration -- C0 hydrogen concentration in a material free of stress and strain -- D hydrogen diffusion coefficient in the metal -- DA hydrogen diffusion coefficient in the metal of stainless steel (layer A) -- DB hydrogen diffusion coefficient in the metal of low carbon steel (layer B) -- J hydrogen flux -- KS hydrogen solubility -- KSε hydrogen solubility component depending on plastic strain -- r0 inner radius -- r radial coordinate -- R molar gas constant -- ttemp tempering time -- Ttemp tempering temperature -- tserv in-service time -- T absolute temperature -- VH partial molar volume of hydrogen -- w width of nuclear reactor pressure vessel wall -- wA width of the 1st layer (cladding) made of stainless steel -- wB width of the 2nd layer (base material) made of low carbon steel -- z axial coordinate -- εP cumulative plastic strain -- εPij components of the cumulative plastic strain tensor -- εPA cumulative plastic strain at the cladding layer -- εPB + cumulative plastic strain at the tensile residual stress zone of the base material layer -- εPθ circumferential cumulative plastic strain -- εPθ, Α circumferential cumulative plastic strain at the cladding layer -- εPθ, Β circumferential cumulative plastic strain at the base material layer -- εPz axial cumulative plastic strain -- εPz, A axial cumulative plastic strain at the cladding layer -- εPz, B axial cumulative plastic strain at the base material layer -- σ hydrostatic stress -- σA residual stress at the cladding layer -- σB + tensile residual stress at the base material layer -- σB − compressive residual stress at the base material layer -- σθ circumferential stress -- σθ, Α circumferential stress at the cladding layer -- σθ, Β circumferential stress at the base material layer -- σr radial stress -- σz axial stress -- σz, A axial stress at the cladding layer -- σz, B axial stress at the base material layer; Nuclear reactor pressure vessel -- Pressurized water reactor -- Hydrogen embrittlement -- Residual stress and strain; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2017.08.004
• Languages: English
• ISSNs: 1350-6307

Abstract

Abstract: The in-service brittle fracture of a structural component of a nuclear power plant (NPP) is a problem of major concern in engineering. During nuclear energy generation, the wall of the nuclear reactor pressure vessel (RPV) is exposed to a hydrogenating environment leading to a fracture phenomenon known as hydrogen embrittlement (HE). This in-service failure is ruled by hydrogen diffusion from the hydrogenating source (the inner side of the RPV) towards certain places inside the vessel where hydrogen is accumulated and microstructural damage is located. The diffusion process is highly influenced by the stress and plastic strain distributions. For achieving a realistic estimation of the hydrogen accumulation by diffusion, both the in-service thermal stress and the manufacturing induced residual stress and strain (due to tempering heat treatment) must be taken into account. In this paper, a numerical analysis of the hydrogen diffusion assisted by stress and strain is carried out to find out the hydrogen accumulation within the wall of a real pressurized water reactor (PWR) for diverse heat treatment conditions. Results reveal the key role of the in-service thermal stress which enhances the hydrogen diffusion through the constituents' materials of a PWR pressure vessel. Highlights: Residual stress-strain affects the hydrogen embrittlement (HE) of the base material. The resistance to hydrogen embrittlement is improved by adding a cladding layer. HE problems arise in the interface between the base material and the cladding layer. A rise of tempering temperature improves the HE resistance of the vessel material. An increase of tempering time improves the HE resistance of the vessel material. Enlarging the tempering time is better than increasing the tempering temperature.