A1.01/07 A2 Steam Generator In-service Inspection - Medzamor NPP

A comprehensive ISI programme of the Steam Generators will assure their safe and reliable operation in the Armenian NPP with a resultant benefit to the overall Nuclear Safety of the NPP Steam Generator Tube Rupture (SGTR) has been shown by several Probabilistic Safety Assessments as one of the important contributors to the overall core damage frequency.? Rigorous control of SG tubing will therefore be highly beneficial to the plant safety. It will also benefit plant availability.

Complementary to other EC as well as international activities on safety improvements of the Armenian NPP, the objectives of this proposed project are to address the safety issues on the safe and reliable operation of the Unit 2 Steam Generators as follows:

• Review of the results of the last performed Steam Generator ISI and plant Operating Experience Program.
• Agree suitable eddy current probe types and a plugging criterion.
• Tube inspection of all six Steam Generators (100% of tubes).
• Inspection of hot and cold collector welds and threaded holes in primary collector.
• Analysis of the results. The result of each sample inspection shall be classified into one of the categories defined in the Technical Requirements in 4.1.1.2 and 4.1.1.3.
• Plugging of the tubes which do not meet the acceptance criteria, including the supply of suitable plugs.
• Preparation of the Final Report with the complete results of the Steam Generator inspection.

As the last SG inspection was performed in 1994-1995, 100% inspection of all tubes of all six SGs will be performed.

Therefore the purpose of this contract is to provide timely identification of degradation of tubing and other components in the steam generator which might lead to tube rupture or other failures and which could pose a risk to the safety of the plant and the environment.

The EC Consultant has been awarded through an open tendering a service contract to perform a comprehensive In-service inspection of all six steam generators at Unit 2 of Armenia NPP (ANPP). A service contract was placed in August 2008 and the entire scope of In-service inspection activities at all six steam generators was performed during the extended annual outage from 25 September until 27 October 2008.

It has been observed that the required scope of work is in accordance with requirements in Terms of References includes the following:

• Eddy current inspection of 5536 tubes in each of six steam generators over the full length from hot or cold collector (or on both half-lengths from hot or cold collector to the U-bend). Total number of tubes to be inspected: 33216.
• Ultrasonic 100% inspection from the inside of two circumferential collectors welds ID 886mm and ID 800mm in both hot and cold collectors of six steam generators. Total number of welds to be inspected: 24.
• Ultrasonic 100% inspection from the outside of collector to pipe circumferential weld Dn500mm in both hot and cold collectors of six steam generators. Total number of welds to be inspected: 12.
• Eddy current inspection of 20 threaded openings on both hot and cold collector flanges of six steam generators. Total number of threaded openings to be inspected: 240.
• All NDT examinations have been performed by qualified personnel, in accordance with approved procedures and equipment that have been used during the inspection activities.

The Final report consist of 6 Parts; each part documents a specific inspection activity in detail. The part six contains the quality assurance programme used during the inspection.
The Final report Part 1 contains a list of all examination procedures with title pages approved by the ANPP Chief Engineer; as well as respective certificates for NDT equipment, and NDT personnel involved in the inspection activities.

The Final report Part 2 to 4 contains summary of test results, supporting scans, analysis logs, and flow assessment sheets; Part 5 contains a detailed description of Steam Generator tube plugging activities.
The following inspection results were reported:

• Results of Steam Generator tube eddy current inspection showed that total of 472 tubes were plugged (943 plugs) according to a plugging criterion proposed in Organisation & Methodology and approved by Armenia NPP and Armenia Nuclear regulatory Authority (ANRA).
• Results of inspection of Steam Generator main flange threaded holes showed that there was no reportable indication found.
• Results of Steam Generator collector welds ultrasonic examination showed that some indications are still within the limit but further monitoring is recommended for all reported indications during the next scheduled outages in order to determine possible flaw growth.

Steam Generator In-service inspection activities performed in the frame of this service contract are very well documented. The scope of Steam Generator In-service inspection complies with what has been requested in the Terms of reference.

The In-service inspection activities were performed by qualified personnel, using the qualified NDT equipment along with an approved (by the plant) quality plan and inspection procedures.

The plugging criterion (≥ 40% tube wall loss) applied for Steam Generator tubes is conservative, it has been approved by the plant and regulatory body, and provides for acceptable safety margin.

The Consultant has performed all the inspection activities on time along with an agreed schedule for the plant 2008 outage.