ML16274A001

PWR MSIP Analysis and Measurements

ML16274A001
Person / Time
Site:	Calvert Cliffs
Issue date:	09/30/2016
From:	Michael Benson, Patrick Raynaud, David Rudland NRC/RES/DE
To:
David Rudland
References
Download: ML16274A001 (10)

Text

PWR MSIP Analysis and Measurements David L. Rudland, Mike Benson and Patrick Raynaud Office of Nuclear Regulatory Research Division of Engineering U.S.NRC Meeting On Mechanical Stress Improvement Processes And The Calvert Cliffs Experience Wednesday, September 28, 2016 2160578193

PWR MSIP

• In 2007-8, RES responded to an NRR request to

- Develop criteria for evaluating the effectiveness of proposed Stress Improvement (MSIP) processes in producing compressive residual stresses and assistance in confirming appropriate changes in inspection frequency that may accompany application of effective Stress Improvement processes.

• RES developed plan, conducted numerical analyses, and conducted experiments to meet the need

• RES confirmed the efficacy of the MSIP approach 2

PWR MSIP Numerical Studies

• Results summarized in

- Battelle report, Evaluation of the mechanical stress improvement process (MSIP) as a mitigation strategy for primary water stress corrosion cracking in pressurized water reactors, ML092990638

• Investigated three geometries

- Hot Leg

- Pressurizer Surge

- Pressurizer Safety Nozzle 3

PWR MSIP Numerical Studies 4

All axi-symmetric analyses on pipe Modelled both welds and MSIP Conducted a variety of sensitivity analyses Conducted numerical flaw analyses

PWR MSIP Sample Results 5

Safety Nozzle Geometry Hoop Stress Axial Stress

PWR MSIP Strain Measurements

• Results summarized in

- PNNL report, Surge Nozzle NDE Specimen Mechanical Stress Improvement Analysis, ML111960318

• Pressurizer Surge Nozzle

• Some difficulty was encountered in calculating stresses from strain due to plasticity - Predictions were reasonable 6

PWR MSIP Strain Measurements 7

Strain gage location Numerical analyses Comparison

PWR MSIP UT Measurements

• Results Summarized in

- PNNL report, Surge Nozzle NDE Specimen Mechanical Stress Improvement Analysis, ML113010152

• Ignalina (shop and field SS welds) and Pressurizer surge (from strain gage study)

• Service induced IGSCC and implanted flaws 8

PWR MSIP UT Measurement 9

The INPP data displayed a significant reduction in flaw length and amplitude after MSIP application and one flaw had become transparent to ultrasound The surge line specimen showed almost no change in length or depth after MSIP - attributed to initial stress state and implanted flaw misalignment 1.5 MHz, Line Scan Data after MSIP

PWR MSIP Summary Reports

• Assessment of MSIP:

- A PNNL Report, Assessment of the Mechanical Stress Improvement Process for Mitigating Primary Water Stress Corrosion Cracking in Nickel Alloy Butt Welds in Piping Systems Approved for Leak-Before-Break, ML13330A972

- Uses previous work to draw conclusions on efficacy of MSIP and assesses inspection intervals per CC N770

• PWSCC Mitigation

- NUREG/CR-7187 - Managing PWSCC in Butt Welds by Mitigation and Inspection 10