APTECH Nuclear Steam Generator

Nuclear Steam Generator Services

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Eddy current data evaluations

Deconvolution of RPC data

Run-time analyses

Structural and leakage analyses

Strategic analysis for long-term degradation forecasting and management planning

Development of alternate plugging criteria for axial and circumferential cracking

Run-Time Analysis for Free Span Axial Cracking of Inconel 600 Tubing

Developed an advanced version of the Monte Carlo simulation model dealing with the processes of crack initiation, crack growth, and flaw detection via NDE and tube repair or removal from service
Developed a leakage analysis model for evaluation of leak rate possibilities (this model will be incorporated into the above Monte Carlo program)
Performed independent analysis (Bayesian analysis and Monte Carlo simulation) to verify the structural and leakage results
Performed RG 1.121 analysis
Performed run-time analysis
Participated in NRC presentations

Alternate Tube Plugging Criteria Development and Applications

APTECH, in conjunction with the efforts of an equipment vendor, has developed the technical basis to support integrity evaluations for steam generator tubing with indications of circumferential cracking. APTECH's effort is focused on two areas:

Structural Analysis Tasks	Development of burst correlation Development of leak rate methodology Development of analysis methods Development of BOC model and methods for projecting EOC distributions assessment based on insitu measurement Recommend methods for structural analyses

Nondestructive Examination Tasks	NDE guidelines development Probe assessments Depth sizing Deconvolution of RPC data Recommend method for sizing NDE analysis of lab specimens Development of growth rates Indication of detection thresholds Identification of NDE uncertainties

Leakage Rate Analysis for Corrosion Degradation in Steam Generator Tubing
The objective of this project was to perform probabilistic calculations of the expected upper bound primary-to-secondary leak rates under postulated accident conditions due to corrosion degradation of steam generator tubing. The project was performed in three phases:

Phase 1	Expected upper bound leak rate under postulated accident conditions is calculated for corrosion degradation expected at end of cycle. These calculations are being used for establishing plugging criteria.

Phase 2	Updating the Phase 1 results based on a re-analysis of corrosion degradation growth rates of outage inspection results.

Phase 3	The analysis to be performed in Phase 3 consists of a multi-cycle simulation of the evolution of corrosion degradation at eggcrate support locations. The model will be benchmarked against past eddy current inspection results. The model includes incorporation of NDE sizing uncertainties and application of several statistical approaches to account for measurement uncertainties in the determination of actual degradation growth rates.

The result will provide a relatively definitive evaluation of both the risk of leakage and level of leakage during a postulated end-of-cycle steam line break accident.

Long-Term Strategic Model and Prediction of Steam Generator Tube Degradation Mechanisms
Developed LTLIFE computer program for steam generators. The capabilities of LTLIFE will permit complete and fully-probabilistic assessment on both total plant and degradation mechanism-specific bases. The specific elements of this program objective include:

Development of tube repair requirement projections for full plant life on both total plant and degradation mechanism-specific bases.
Development of both best estimate and upper 95/95 probability/confidence values for each set of projections.
Third-party review of the previous evaluation of the structural significance of axial and circumferential crack indications, including method of evaluating beginning of cycle conditions, probability of detection degradation; degradation growth rates, inspection and analysis uncertainties, and evaluation of end-of-cycle structural margins.
Calculation of probability of exceeding RG 1.121 structural limits as a function of operating time.
Calculation of the probability of the tube burst under steam line break conditions as a function of operating time.
Comparison of these probabilities to industry standards, such as those acceptable to NRC in the bobbin voltage alternate plugging criteria (APC).
Calculation of leak rate under postulated accident conditions.
Recommendation regarding prudent operating time.

Aptech Engineering Services, Inc.
601 W. California Ave., Sunnyvale, California (408) 745-7000 © 2005, APTECH Engineering Services, Inc. All rights reserved.Reproduction in whole or in part in any form without the express written permission of an officer of the company is strictly prohibited.

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