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|Package ID||Orig. computer||Test computer|
OCA-P is a probabilistic fracture-mechanics code prepared specifically for evaluating the integrity of pressurized-water reactor vessels subjected to overcooling-accident loading conditions. Based on linear-elastic fracture mechanics, it has two- and limited three-dimensional flaw capability, and can treat cladding as a discrete region. Both deterministic and probabilistic analyses can be performed. For deterministic analysis, it is possible to conduct a search for critical values of the fluence and the nil-ductility reference temperature corresponding to incipient initiation of the initial flaw. The probabilistic portion of OCA-P is based on Monte Carlo techniques, and simulated parameters include fluence, flaw depth, fracture toughness, nil-ductility reference temperature, and concentrations of copper, nickel, and phospherous. Plotting capabilities include the construction of critical-crack-depth diagrams (deterministic analysis) and a variety of histograms (probabilistic analysis).
OAC-P accepts as input the reactor primary- system pressure and the reactor pressure-vessel downcomer coolant temperature, as functions of time in the specified transient. Then, the wall temperatures and stresses are calculated as a function of time and radial position in the wall, and the fracture-mechanics analysis is performed to obtain the stress intensity factors as a function of crack depth and time in the transient. In a deterministic analysis, values of the static crack initiation toughness and the crack arrest toughness are also calculated for all crack depths and times in the transient. A comparison of these values permits an evaluation of flaw behavior.
For a probabilistic analysis, OCA-P generates a large number of reactor pressure vessels, each with a different combination of the various values of the parameters involved in the analysis of flaw behavior. For each of these vessels, a deterministic fracture- mechanics analysis is performed to determine whether vessel "failure" takes place. The conditional probability of "failure" is simply the number of vessels that "fail" divided by the number of vessels generated.
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OCA-P, NESC No. 1125.PC, OCA-P IBM PC Version Flexible Disk Cartridge Descriptions, National Energy Software Center Note 90-88, April 18, 1990.
D.G. Ball, R.D. Cheverton, J.B. Drake, and S.K. Iskander, OCA-II, A Code for Calculating The Behavior of 2-D and 3-D Surface Flows in a Pressure Vessel Subjected to Temperature and Pressure Transients. NUREG/CR-3941 (ONRL-5934), February 1984.
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The IBM3033 version uses three mathematical routines from the proprietary Numerical Algorithems Group (NAG) library. They are G05CBF (ISEED) to set the random seed, GO5CAF(X) a uniform distribution random number generator, and GO5DDF a normal distrbution random number generator. The proprietary CA-DISSPLA graphics software (see http://www.gaeinc.com) is called to produce plots with the IBM3033 version. The IBM PC version does not produce plots.
Keywords: fracture properties, pressure vessels, pwr reactors, reactor vessels, stress analysis.