ML101680258
| ML101680258 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/2011 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| Bayssie Mekonen/RES 251-7489 | |
| Shared Package | |
| ML101680222 | List: |
| References | |
| DG-1224 RG-1.044, Rev. 1 | |
| Download: ML101680258 (5) | |
Text
Staff Responses to Public Comments on Draft Regulatory Guide DG-1224, Control of the Processing and Use of Stainless Steel dated June 2009 (Proposed Revision 1 of Regulatory Guide 1.44 dated May 1973)
- 1. James H. Riley, NEI (NEI) 2. J.A. Gresham, Westinghouse (W) 3. V. Hull, Dominion (DOM)
(ML092220038) (ML092370506) (ML092400354)
(via S. Findlan, EPRI)
Public Comments NRC Response The notices requested comments on all of these draft regulatory Extension to October 1, 2009 granted per guides by August 31, 2009. NEI and EPRI are collecting and NRC 7590-01-P dated August 11, 2009 consolidating industry comments on these draft guides, but it has (ML092230530).
become apparent that it will not be possible to complete a comprehensive review of all of these documents in the time available, NEI-1 The information contained in these draft guides is important to the industry's work on primary system materials and it is important to carefully evaluate the changes proposed. NEI is therefore requesting a 30-day extension of the public comment period on these draft guides until October 1, 2009, to allow adequate time to complete and document our review.
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Public Comments NRC Response The second paragraph under Discussion mentions detrimental The second paragraph of Section B, materials and stress-corrosion cracking. It is recommended this Discussion, of the RG is changed as follows:
paragraph be clarified since no guidance on the limits is provided.
Process controls should be exercised in W-1 accordance with good manufacturing
/welding practices and knowledge gained from operating experience during all stages of component manufacturing Paragraph 3 continues the discussion about detrimental materials and The first two sentences of the third paragraph elevated temperature but provides no guidance on the limits or of Section B, Discussion, of the RG are "reasonable care" that should be taken. It is recommended these changed as follows:
statements be clarified. The statement regarding the pickling of sensitized stainless begs the question why a sensitized stainless steel All cleaning solutions, processing would be used. Please explain or justify. compounds, degreasing agents, and other foreign materials should be completely removed at any stage of processing before any elevated temperature treatment and before hydrotests in accordance with W-2 guidelines of approved manufacturing/elevated temperature treatment procedures. Reasonable care should be taken to keep (1) fabrication and construction areas clean, (2) components protected and dry during storage and shipment, and (3) all crevices and small openings protected against contamination as identified in approved manufacturing quality assurance procedures Page 2 of 5
Public Comments NRC Response Paragraph 7 provides guidance for intergranular corrosion testing for The staff disagrees with the commenter.
non-L and L grades. Westinghouse disagrees that intergranular There is evidence throughout the industry that W-3 corrosion testing for non-L and L grades should be performed because sensitization has occurred even on L grade there is not enough carbon for sensitization to occur. material.
Paragraph 9 and 10 discusses qualification but should be clarified as The second bullet associated with Paragraph to what the "adequate documentation" should be. 10 of Section B, Discussion of the RG W-4 provides clarification for what constitutes adequate documentation and service experience.
Page 2, second sentence in part B under Discussion. There should be The first two sentences in the first paragraph some distinction between intergranular stress-corrosion cracking of Section B, Discussion, of the RG are (SCC) and transgranular SCC. Sensitization plays no role in changed as follows:
transgranular SCC.
Control of the application and processing of stainless steel to avoid severe sensitization is DOM-1 needed to diminish the numerous occurrences of intergranular stress corrosion cracking in sensitized stainless steel components of nuclear reactors. Test data demonstrate that sensitized stainless steel is significantly more susceptible to intergranular stress corrosion cracking than is nonsensitized Page 3, 3rd Full Paragraph: Chloride, Fluoride, and Oxygen levels are Reference to the plant UFSAR is plant-specific DOM-2 consistent with UFSAR. and is therefore not appropriate for generic regulatory guidance.
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Public Comments NRC Response The last paragraph in Section C6, can be more specific regarding the The RG does not only apply when welding on need to control welding practices to avoid excessive sensitization of materials with > 0.03 carbon. Regulatory the HAZ. Does this only apply when welding on materials with > .03 Position 6 applies to all unstabilized, austenitic carbon? Also, what exactly are the welding practices (heat input and stainless steels of the AISI Type 3XX series interpass temperature) that need to be controlled? The last paragraph used for components that are part of (1) the of the discussion section specifically mentions heat input and interpass reactor coolant pressure boundary, (2) temperature. The discussion section and regulatory position section systems required for reactor shutdown, (3) should be consistent. systems required for emergency core cooling, and (4) reactor vessel internals that are relied on to permit adequate core cooling for any mode of normal operation or under credible postulated accident conditions.
Position 6 of Section C, Regulatory Position, of the RG is revised as follows:
PG&E-1
- 6. Welding practices and, if necessary, material composition should be controlled to avoid excessive sensitization of base metal heat-affected zones of weldments. Controls to prevent sensitization of the material during welding include maintaining low heat input and limiting the interpass temperature.
- 7. An intergranular corrosion test, such as specified in Regulatory Position 3 above, should be performed for each welding procedure to be used for welding material having a carbon content of greater than 0.03 percent.
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Public Comments NRC Response In the second to last paragraph of the discussion section, it mentions Base material thickness affects the cooling performing the qualification tests on material with the minimum and rate, thereby affecting the time in the maximum thicknesses anticipated. Wouldn't the worst case be the sensitization temperature range. However, material with the minimum thickness (due to slow cooling rate)? The the slowest cooling rate is not necessarily maximum thickness would provide the fastest cooling rate and best obtained with the thinnest base material PG&E-2 chance of preventing sensitization. Based on this, testing should only anticipated. For example, the final pass on a be required using the minimum thickness material anticipated. multipass, 10 cm (4 inch) thick weldment may have a slower cooling rate than the final pass on a 0.5 cm (0.2 inch) thick weldment.
Therefore, testing of both thicknesses is necessary.
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