Steam generator tube failures

Burst and Leak Behaviour of SCC Degraded SG Tubes of PWRs

“…Steam generators of Pressurized Water Reactor (PWR) have suffered from many types of corrosion, such as pitting, wastage and stress corrosion cracking (SCC) in the primary and secondary sides (Kim 2003, MacDonald, 1996. Some failure events of steam generator tube have been reported in some nuclear power plants around the world (MacDonald, 1996).…”

“…Some failure events of steam generator tube have been reported in some nuclear power plants around the world (MacDonald, 1996). In order to prevent the primary coolant from leaking into the secondary side, the tubes are repaired by sleeving or plugging (Benson, 1999).…”

Estimation of the radioactive aerosols capture in accidental sequences of nuclear power plants

“…The integrity of the U-tubes of a SG may be challenged because of the high temperature and pressure conditions of the primary circuit. Consequently the U-tubes are subjected to a great variety of degradation processes (primary water stress corrosion cracking, outside diameter stress corrosion cracking, fretting, pitting, denting, high-cycle fatigue, wastage, etcetera) that can lead to tubes fissure, wall thinning, and potential leakage or finally rupture [MacDonald, 1996]. During the last years considerable efforts have been spent to understand and predict these degradation processes; however SGs steam leakage incidents have continued taken place.…”

“…As explained in detail in NUREG/CR-6365 [MacDonald, 1996], in the 90s about onehalf of the PWR NPP in the world had to plug or sleeve SG tubes in any given year. This means that about one-half of these plants were operating with tubing defects near or beyond the national limits boundaries.…”

“…The major problems that took place in the life time of SGs are listed in Table 1.4, a schematic view is displayed in Figure 1.7 and a short description of each one of them is explained in the following lines [MacDonald, 1996;Newberry, 2000]: -Denting is a mechanical deformation or a constriction of a carbon steel tube, it can takes place at a support plate intersection or within the tubular plate, and it can be CHAPTER 1 -Introduction 20 caused by the accumulation of deposits and the growth of bulky corrosion products in the annulus between the tube and its tube sheet or plate. This kind of problems has also been observed in the sludge pile region of certain plants where iron particles were embedded in the sludge pile.…”