Patent Number: 
Section: claims

1. A computational system for performing a safety analysis of a postulated Loss of Coolant Accident in a nuclear reactor for a full spectrum of break sizes including large break, intermediate break and small break, comprising:a single input model which includes noding for the full spectrum of break sizes of the postulated Loss of Coolant Accident, said input model includes an input deck which identifies parameters of the nuclear reactor selected from the group consisting of reactor geometry, initial conditions and boundary conditions, and parameters of the postulated Loss of Coolant Accident, said parameters comprising constant parameters and variable parameters;an uncertainty database including a random sampling of uncertainty values for specific parameters identifying phenomena expected to occur during the postulated Loss of Coolant Accident, a range of said specific parameters including the full spectrum of break sizes of the postulated Loss of Coolant Accident, such that a random sampling of uncertainty values is identified for the full spectrum of Loss of Coolant Accident break sizes including the large break, intermediate break and small break;an input processor to assign uncertainty values for the break size of the postulated Loss of Coolant Accident, to extract the uncertainty values from the uncertainty data base, to generate the input deck including the uncertainty values for the break size, and to execute a Loss of Coolant Accident simulation for the uncertainty values, said Loss of Coolant Accident simulation including a plurality of transient simulations executed in parallel on a cluster of processors, wherein the uncertainty values are ranged and combined following the random sampling and wherein a transfer function C(t) between a random set of values for uncertainty parameter X and a figure of merits according to peak clad temperature (PCT) and maximum local oxidation (MLO) is analyzed using the following formulation:                    {                                            PCT                                                          MLO                                      }                              i          =          1                ,        …        ,        N              =                  C        ⁡                  (          t          )                    ⁢                        {                                                                      X                  1                                                                                                      X                  2                                                                                    ⋮                                                                                      X                  h                                                              }                                      i            =            1                    ,          …          ,          N                      ,where N represents a sample size; anda code to compute a response of the nuclear reactor to the Loss of Coolant Accident simulation for the uncertainty values. 2. The computational system of claim 1, wherein the uncertainty data base is generated by obtaining a sampling of uncertainty values. 3. The computational system of claim 2, wherein the sampling of uncertainty values is obtained by a random sampling approach. 4. The computational system of claim 1, wherein the nuclear reactor is a light water reactor. 5. The computational system of claim 1, wherein the uncertainty database is electronically stored. 6. The computational system of claim 1, wherein the specific parameters further comprises break type. 7. The computational system of claim 6, wherein the break type is selected from the group consisting of double-ended guillotine and a split break. 8. A computational method for safety analysis of a postulated Loss of Coolant Accident in a nuclear reactor for a spectrum of break sizes including large break, intermediate break and small break, comprising:developing a single evaluation model;creating a single input template comprising plant-specific data of the nuclear reactor including constant values and variables, one of the variables being break size of the postulated Loss of Coolant Accident, the break size selected from the spectrum of break sizes including large break, intermediate break and small break;entering the input template into the evaluation model;employing a random sampling procedure to generate a database for the variables and to assign numerical values to the variables, one of the variables being break size for the postulated Loss of Coolant Accident, the break size selected from the spectrum of break sizes including large break, intermediate break and small break;transforming the input template into N input models, wherein N represents a number of variations;executing the N input models in parallel on a cluster of processors, the executing includes assigning uncertainty values for the break size, wherein the uncertainty values are ranged and combined following the random sampling procedure and wherein a transfer function C(t) between a random set of values for uncertainty parameter X and a figure of merits according to peak clad temperature (PCT) and maximum local oxidation (MLO) is analyzed using the following formulation:                    {                                            PCT                                                          MLO                                      }                              i          =          1                ,        …        ,        N              =                  C        ⁡                  (          t          )                    ⁢                        {                                                                      X                  1                                                                                                      X                  2                                                                                    ⋮                                                                                      X                  h                                                              }                                      i            =            1                    ,          …          ,          N                      ,where N represents a sample size;obtaining results for each of the N input models;post-processing the results; andobtaining statistical merits to demonstrate compliance with design acceptance criteria. 9. A computational method for safety analysis of a postulated Loss of Coolant Accident in a nuclear reactor for a spectrum of break sizes including large break, intermediate break and small break and break types, comprising:developing a single evaluation model for the spectrum of break sizes including large break, intermediate break and small break;creating a single input template to load into the evaluation model, the input template comprising plant-specific data of the nuclear reactor including constant values and uncertainty values, two of the uncertainty values being break size and break type of the postulated Loss of Coolant Accident, the break size selected from the spectrum of break sizes including large break, intermediate break and small break, and the break type selected from double-ended guillotine and split break;employing a random sampling approach to generate model parameters, to assign numerical values to the uncertainty values and to generate a database of uncertainty values, the uncertainty values encompassing the spectrum of break sizes and break type for the postulated Loss of Coolant Accident;generating variations of the input template to represent different values for the uncertainty values;executing a plurality of transient simulations to encompass the spectrum of break sizes and break type for the postulated Loss of Coolant Accident, the executing includes assigning uncertainty values for the break size, wherein the uncertainty values are ranged and combined following the random sampling approach and wherein a transfer function C(t) between a random set of values for uncertainty parameter X and a figure of merits according to peak clad temperature (PCT) and maximum local oxidation (MLO) is analyzed using the following formulation:                    {                                            PCT                                                          MLO                                      }                              i          =          1                ,        …        ,        N              =                  C        ⁡                  (          t          )                    ⁢                        {                                                                      X                  1                                                                                                      X                  2                                                                                    ⋮                                                                                      X                  h                                                              }                                      i            =            1                    ,          …          ,          N                      ,where N represents a sample size;computing a response of the nuclear reactor for the spectrum of break sizes and break type for the postulated Loss of Coolant Accident for the postulated Loss of Coolant Accident; and post-processing the results to obtain statistical figure of merits to demonstrate compliance with design acceptance criteria.