Radiochemical Processing Laboratory High-Level Vault Characterization Report

Abstract

SummaryThe High Level Vaults (HLV) consists of three underground concrete vaults containing seven tanks. The tanks were used to support a variety of radiochemical processes conducted in the High Level Radiochemistry Facility (HLRF) hot cells. The HLRF is located adjacent to the east wall of the 325 Building, which also is known as the Radiochemical Processing Facility (RPL).Initial radiological and chemical conditions and video documentation of the interior of the HLV were obtained by disassembling the HLV high efficiency particulate air (HEPA) filter housings and inserting remote monitoring equipment through the openings. The radiological dose rates obtained near the filter housing inlets ranged from less than the minimum detectable amount (MDA) to 150 mRem/hr. The results indicated that the HLV access cover block could be safely removed.The weather barrier covering the HLV cover blocks was removed and discarded. To extend the working surface, a two-foot strip of concrete was installed around the perimeter of the HLV. Reinforced plastic sheeting was secured over the cover blocks to prevent rainwater incursion into the HLV.A work structure (containment) was erected over the HLV so the vault could be accessed while maintaining a radiologically controlled environment over the work area. The containment was installed so that both the key cover block and the inlet HEPA filter were enclosed. Positioning the containment in this manner was instrumental in maintaining proper air flow when removing and replacing the vault cover blocks. The vaults were exhausted via the RPL Radioactive Exhaust Ventilation System, and the existing system design and configuration was adequate to exhaust the containment and the vault being accessed.A portable gantry hoist erected inside the containment was used to remove the HLV key access cover block. A remotely operated vehicle (ROV), hand-held reach tools, and associated sampling equipment were inserted into each HLV via an open access cover block. The ROV was equipped with a robotic arm that was used to transport and maneuver radiological survey and characterization sampling equipment through the interior of the HLV. Hand-held extension tools manipulated through the HLV access openings were also used to obtain radiological dose rates and characterization samples.Characterization samples consisted of several removable contamination smears from the surfaces of the HLV walls and tanks, liquid obtained from the HLV sump trenches, and samples of debris (soil) from the HLV floor. Samples were submitted to the analytical laboratory and analyzed for total alpha (TA), total beta (TB), alpha energy analysis (AEA), gamma energy analysis (GEA), and beryllium by inductively coupled plasma (ICP) spectrophotometry. The analytical results indicated that the radiological characteristics were consistent within each HLV, and no beryllium was detected in the characterization samples.The dose data obtained during characterization activities indicate the maximum dose rates on the tanks are approximately 160 m...