Opinion ID: 150668
Heading Depth: 3
Heading Rank: 1

Heading: Davis-Besse Nuclear Power Station

Text: Davis-Besse is a two-loop, pressurized water reactor that is composed of a large cylindrical chamber filled with coolant water (the Reactor Pressure Vessel or RPV). Uranium rods at the core of the vessel fuel the nuclear reaction that heats the coolant water. The nuclear reaction is controlled by introducing boric acid and/or control rods into the reactor vessel. The control rods are inserted through sixty-nine penetration nozzles (tubes that are approximately four inches in diameter) that penetrate through the head of the reactor (approximately ten feet in diameter) into the reactor chamber. There is a gap between the RPV head and reflective metal insulation that encloses closure flanges and studs. The gap is narrowest at the top of the head, where it is only two inches wide. Control rod drive mechanisms (CRDMs) allow the operators to lower the control rods into the reactor to control the rate of the nuclear reaction, and, thus, the energy output. The nozzles are welded onto the vessel head using a J-groove on the underside of the steel head, which is 6.5 inches thick. The internal walls of the RPV and the underside of the RPV head are covered in non-corrodible stainless steel, but the RPV and the external components are made of carbon steel, which is corrodible by the boric acid in the coolant water if it escapes the RPV. This can happen when the coolant water leaks through the flanges that connect the CRDMs to the nozzles above the RPV head. Davis-Besse had a history of flange leakage and developed the Boric Acid Corrosion Control Procedure (BACCP), which it implements during inspections, to address this problem. Davis-Besse operates in two-year fuel cycles and, therefore, shuts down the reactor only during the biennial refueling outages (RFOs). Davis-Besse was scheduled to conduct RFO13 (the thirteenth RFO conducted at Davis-Besse) in April 2002. In addition to permitting refueling, the RFOs are the primary opportunity for inspections and maintenance that cannot occur while the reactor is in operation. The RFOs at issue in this case are RFO 10 (1996), RFO 11 (1998), and RFO 12 (2000). During an RFO, in order to visually inspect the nozzles and the RPV head, operators must insert a camera through a series of eighteen weep holes that are five by seven inches in size and that line the bottom of the RPV head above the head flange connecting the RPV head to the RPV. Because of the limited accessibility of the camera, it is impossible to visually inspect the very top of the RPV head and the nozzles located there. Siemaszko was in charge of inspecting and cleaning the RPV head during RFO12 in 2000, but was not present during the RFOs in 1996 and 1998. Prasoon Goyal, another engineer at Davis-Besse, oversaw this task during RFO10 in 1996 and reviewed the inspection reports following RFO11 and RFO 12. Another engineer, Peter Mainhardt, supervised inspection and cleaning during RFO11 in 1998. As of 2001, Goyal continued to work at Davis-Besse as an engineer, and Mainhardt worked for FENOC as an independent contractor preparing for RFO 13. The 1996 RPV head inspection lasted only one hour due to limitations on the technicians' exposure to radiation. During that inspection, Goyal directed two technicians who were moving a camera on a pole across the vessel head. He watched on a monitor and narrated the camera location based on the stud hole numbers (the numbers on the studs between the weep holes). The nozzles are not numbered, so this is the only way to determine and document the condition of each nozzle based on the camera visual. Ed Chimahusky, a systems engineer in charge of coolant systems from 1991 to 1997, testified at Siemaszko's trial that by using a camera through the weep holes, [i]f you did the best you could, you could probably look at ... 70 percent of [the RPV head]. Goyal, in testimony and in a Potential Condition Adverse to Quality report (PCAQ) submitted to superiors after RFO 10, estimated that he was able to inspect fifty or sixty percent of the head area in 1996 and noted that it was difficult to estimate the amount of boron deposits on the head because of the limited visual inspection. In his PCAQ, Goyal attributed the boron deposits to flange leaks. The PCAQ also noted several deposits ranging in color from white to brown to rust. In both the PCAQ and in testimony, Goyal noted that the boron deposits and limited visual access prevented full implementation of the BACCP. Consequently, in the PCAQ, Goyal suggested modifications to the RPV head that would permit better access, such as installing access doors. The modifications were never made. Mainhardt conducted a similar inspection with the help of technicians during RFO 11 in 1998. He testified that he found [l]ots of flakes [of boric acid], ... also some fist-sized clumps ... which would be particles all stuck together, one area that kind of was pasty looking, ... maybe like a paste that hardened there, and some streaks on the control ride drive tubes [and around cracks in the insulation at the top of the head] that looked like milk. Goyal reviewed Mainhardt's PCAQ report and again faulted flange leaks with causing the boron deposits. The RFO11 PCAQ, signed by Goyal, stated that most of the head area was covered with an uneven layer of boric acid along with some large lumps of boric acid. That PCAQ referred back to the RFO 10 PCAQ and the need for corrective action. The 1998 PCAQ also stated that [t]he reactor vessel head was cleaned as best as we can and noted that the cleaning was video recorded. Siemaszko conducted RFO 12's RPV head cleaning after attending a training session on BACCP. Mainhardt, who inspected the outside of the RPV head personally, stated that there were heavy streams of red/brown boric acid ... stream[ing] out of the [weep] holes and submitted photographs (the red photographs) and a PCAQ to his supervisors and, he alleges, to the NRC's resident inspector (who did not recall receiving it). The deposits prevented insertion of the camera into five of the weep holes and visually impaired inspection through other weep holes. The deposits also required more elaborate cleaning maneuvers than previous inspections, which had used a vacuum cleaner to remove boron deposits. In 2000, Siemaszko directed the technicians to spray hot, distilled water onto the RPV head to loosen the deposits and to use bars to knock off chunks of deposits and to flush them out through the weep holes. One of the members of the cleaning crew testified that they [g]ot what [they] could get removed but that deposits remained on the RPV head. Greg Gibbs, a consultant brought to Davis-Besse to prepare for RFO13, reviewed the cleaning tapes of RFO12 and testified that, although the areas on the curvature of the hemispherical head were essentially cleaned, ... as you got up near the top, there were large significant accumulations of boric acid near the top center of the head. Gibbs noted that, in parts, there were crystals that were almost solid and almost touching the mirror insulation, so you had ... areas there at the top of the head that were just entirely covered with boric acid. Despite the incomplete cleaning during RFO12, an industry magazine congratulated Siemaszko on removing the deposits. However, Siemaszko later admitted to Goyal that the cleaning had been incomplete at the top of the head. The RFO 12 PCAQ again attributed the increased boron accumulation to flange leakage. In a 2000 PCAQ, Siemaszko noted that the RPV head should be free of boron deposits to adequately inspect the nozzles in accordance with an NRC letter requiring plants to inspect the CRDMs adequately. Siemaszko put the RPV head on a restraint that required action before the plant was put back into operation. His supervisor, David Geisen, removed the restraint, however, stating that the RPV head would be cleaned of all boron deposits before it was put online. It was not.