1. NAME AND TITLE

OCTAVIA: Code System to Calculate Pressure Vessel Failure Probabilities.
 

2. CONTRIBUTORS

U.S. Nuclear Regulatory Commission, Washington, DC, through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.
 

3. CODING LANGUAGE AND COMPUTER

Fortran IV; IBM370 (P00460I037000).
 

4. NATURE OF PROBLEM SOLVED

OCTAVIA (Operationally Caused Transients And Vessel Integrity Analysis) calculates the probability of pressure vessel failure from operationally-caused pressure transients which can occur in a pressurized water reactor (PWR). For specified vessel and operating environment characteristics the program computes the failure pressure at which the vessel will fail for different-sized flaws existing in the beltline and the probability of vessel failure per reactor year due to the flaw. The probabilities are summed over the various flaw sizes to obtain the total vessel failure probability. Sensitivity studies can be performed to investigate different vessel or operating characteristics in the same computer run.
 

5. METHOD OF SOLUTION

The analysis approach involves calculation of vessel failure pressures using fracture mechanics methods and estimation of pressure-transient characteristics using historical nuclear data. The pressure vessel is described by input data, such as vessel wall thickness, inside radius, copper and phosphorus content, residual stress, flaw sizes, fluence, and temperature. The failure pressure for a given flaw is calculated using linear-elastic and elastic-plastic methods. After obtaining the failure pressure for a given flaw size, the probability evaluation is performed. The probabilities for the different flow sizes are then summed to obtain the total probability of pressure vessel failure from the various flaws which might exist in the vessel.
 

6. RESTRICTIONS OR LIMITATIONS

Maxima of 100 temperatures, 12 fluences and 8 flaw sizes with the program's current dimensioning. Only axially oriented flaws in the vessel beltline are considered.
 

7. TYPICAL RUNNING TIME

The sample problem requires < 2 seconds on an IBM 9672.
 

8. COMPUTER HARDWARE REQUIREMENTS

OCTAVIA requires approximately 170K bytes of storage for execution of the sample problem on an IBM370/195 or 3033.
 

9. COMPUTER SOFTWARE REQUIREMENTS

The code is written in Fortran IV for OS/370. It was executed at RSICC on an IBM 9672, but plotting was not implemented. No changes were made to the source when it was transferred to RSICC and released in March 2001.
 
 
 

10. REFERENCES

a) Included in documentation:

W. E. Vesely, E. K. Lynn, and F. F. Goldberg, "The Octavia Computer Code: PSR Reactor Vessel Failure Probabilities Due to Operationally Caused Pressure Transients," NUREG-0258 (March 1978).
 

b) Background information:

J. G. Merkle, G. D. Whitman, and R. H. Bryan, "An Evaluation of the HSST Program Intermediate Pressure Vessel Tests in Terms of Light-Water-Reactor Pressure Vessel Safety," ORNL-TM-5090 (November 1975).
 

11. CONTENTS OF CODE PACKAGE

Included in the package are the referenced document in (10.a) and one 3.5" DOS formatted diskette which includes source code and sample problem input. No executables are included with the package.
 

12. DATE OF ABSTRACT

March 2001.
 

KEYWORDS: PWR; REACTOR SAFETY