10 CFR 50.71(e) - Maritime Administration - U.S. Department of ...

Updated Final Safety Analysis Report - (STS-004-002)Table 13-10 Volume of water remaining in the Primary Coolant systemComponentVolume (gallons)Reactor vessel bottom head 734.3Cold leg (port and starboard) piping 142.6Port Steam Generator 138.8Hot leg (stbd) piping 65.9Hot Leg (port) piping 0Total 1435.8Assuming the activity in the water is uniform throughout the plant and represented by theactivity in the steam generator and using a conservative water volume of 1500 gallons(5.68E6 ml), the total estimated activity is:Cs-137Co-6013.1.9 Reactor Pressure Vessel (RPV)(1.04E-3 μCi/ml)(5.68E6 ml) = 5910 μCi or 5.91 mCi(1.45E-6 μCi/ml)(5.68E6 ml) = 8.24 μCiThe 2004 analysis determined that the actual dose rate, 7 mR/hour, at the RPV external wall near thecore mid-height location, is about an order of magnitude lower than expected. The estimated doserate, 85 mR/hour, was made using a point source approximation along the centerline of the vessel atmid-core height.The higher estimated versus measured dose suggested an over prediction of the total RPV curiecontent in the original analysis. The difference between measured and calculated is likelyattributable to one or more of the following factors:Over prediction of thermal neutron flux in the core internals;Use of high natural cobalt (Co-59) content (0.141%) for analysis (maximum ASTMvalues); and/or,Under prediction of Co-60 gamma shielding/absorption by the heterogeneous arrangementof core internals and structural components that tend to depress neutron flux during normaloperation.In response to the much lower than expected dose rates in the vicinity of the RPV, physical samplingof the RPV outer wall, selected internals, and the primary (neutron) shield tank was conducted todevelop an actual radiological profile of the constituent materials.In 2005, the Curie content and radio isotopic composition of the reactor pressure vessel, internals andprimary (neutron) shield tank is determined by extraction of metal samples at selected locations.Using a precision gun-drilling or boring operation, an access hole was extended through the externallead shield, the inner and outer annuli of the primary (neutron) shield tank, the insulation layer, RPVwall and inner weld deposit cladding, and finally through the outer and middle thermal shieldssurrounding the core volume. Material extraction was achieved by sleeving the drill bits andprogressively decreasing the access hole diameter at each component interface. Refined calculationswere performed based on the integrated actual reactor power history, actual radiochemical data fromreactor components and realistic neutron flux approximations.Rev. VI 144