Task 3: Irradiation Embrittlement of RPV Steels

The purpose of this task is to examine two important issues affecting the application of thermal-annealing procedures to RPVs. The first addresses the effects of temper embrittlement on the coarse-grained heat-affected-zone in RPV steels. The second examines the effects of reirradiation on K_Jc and K_Ia in order to evaluate the relative changes in the recovery and reembrittlement between CVN and fracture-toughness properties and a detailed examination of reembrittlement rates. These questions will be addressed using the irradiation-anneal-reirradiation (IAR) facility designed, fabricated, and installed as part of the previous HSSI (L1098) program and with a matrix of irradiated and annealed JRQ specimens supplied by the Swiss Paul Scherrer Institut (PSI).

To better understand the necessity of performing a three-dimensional TORT calculation of the HSSI-IAR/UCSB facility to determine the fluence for the specimens within the facility, Figure 1 shows the complete TORT model. The pool of water in which the reactor core and capsules are sitting in is not shown. The “large box” in the center is the FNR core. In the periodic green-red structure, the green areas show the fuel element side plates (made of aluminum) while the red areas are the homogenized zones of fuel plates and coolant. On the east side the reactor, the core guard plate as well as the thermal shield of the irradiation facility are shown as the thin blue plates. The green box to the east of the core is the water surrounding the capsules, which are shown in red. Only the top of the capsules can be seen with the IAR north and south capsules sandwiched between the taller UCSB capsules. The two blue bodies on the bottom represent the support structure. The blue body to the north of the core is the D₂O tank, and to the north of it another body of water is shown.