ML11249A010

Staff Responses to Public Comments on DG-1197

ML11249A010
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Issue date:	11/08/2012
From:	Office of Nuclear Regulatory Research
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DG-1197 RG-1.090, Rev 2
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Response to Public Comments on Draft Regulatory Guide (DG)-1197 Inservice Inspection of Prestressed Concrete Containment Structures with Grouted Tendons Proposed Revision 2 of Regulatory Guide (RG) 1.90 A notice that Draft Regulatory Guide, DG-1197 (Proposed Revision 2 of RG 1.90) was available for public comment was published in the Federal Register on April 28, 2011 on page 76 FR 23845. The Public Comment period ended June 26, 2011. Comments were received from the organizations and individuals listed below. The U.S. Nuclear Regulatory Commission (NRC) has combined the comments and NRC staff disposition in the following table.

Comments were received from the following:

James H. Riley Etienne GALLITRE Gayle Elliott Nuclear Energy Institute Chef de Groupe Génie Civil Gayle.elliott@areva.com 1776 I Street NW, Suite 400 Electricity de France ADAMS Accession No. ML11188A068 EDF - DIN Washington, DC 20006-3708 SEPTEN/GS Phone: 202-7398137 12-14 avenue Dutrievoz Fax: 202.533 0193 69628 Vileurbanne cedex jhr@nei.org etienne.gallitre@edf.fr ADAMS Accession No. Tél. : 04 72 82 71 60 ML11173A065 ADAMS Accession No. ML12178A428 Item Comments By NRC Response The NRC staff does not agree with the comment requesting the removal of the discussion of corrosion on page 4. Wide-spread corrosion will cause distress to a containment structure. In Regulatory Position C.2 Discussion of corrosion should be removed visual examination is listed as one element of a recommended ISI 1 from this document or clearly linked solely to NEI-1 program. However, the availability of visual examination is limited for visual examination as it is misleading in the grouted tendons. Also, with the advancement of the technology, current context. detection of corrosion is now possible through non-destructive examination (NDE). The intent of the Regulatory Guide (RG) is to use both visual and instrumented monitoring as part of a containment ISI program as opposed to solely relying on visual examinations.

RESPONSE TO PUBLIC COMMENTS ON DRAFT REGULATORY GUIDE DG-1197:

INSERVICE INSPECTION OF PRESTRESSED CONCRETE CONTAINMENT STRUCTURES WITH GROUTED TENDONS Item Comments By NRC Response Page 4, item c: The effect of differential thermal expansion or contraction on the The staff agrees that the change is very minor within operational 2 internal stress state of the containment would NEI-2 temperature limits. However, the existing language is correct because be very minor within operational temperature licensees need to consider that the factors discussed may be cumulative.

limits.

The term elastic shortening is used The staff agrees that the usage of the term elastic shortening without throughout. Does this refer to curing 3 NEI-3 further explanation may be misleading and, therefore, has added a shrinkage? If so, it is misleading. Please use a definition for elastic shortening in the glossary section of the RG.

more descriptive term.

Page 5, item c: The use of fiber optic Bragg grating strain sensors can be very simply The staff disagrees with this comment. The staff believes that the item is temperature compensated and have been used acceptable as written and the agency cannot recommend one particular 4 NEI-4 in geological applications in recent years. I brand name because there are other brands that are acceptable for would strongly advocate their usage for this purposes of the RG.

application.

Page 5, last paragraph states Any significant decrease in the stiffness of the structure because of loss of prestress would result in The staff does not agree with the comment stiffness is a function of cracking of the structure under pressure.

Youngs modulus of the steel and would be constant. Stiffness is also a Stiffness is a function of Youngs modulus of function of the effective cross sectional area of steel and concrete; not the steel and would be constant. This should 5 NEI-5 only the steel. Under a pressure load, prestress steel is designed and probably be worded differently. In addition, used to control the extent and width of the cracks. Therefore, a local cracking suggests a local tensile field had significant loss of prestress generally results in cracking of the concrete been reached. It is not necessarily indicative of structure. The staff guidance is retained as written.

general internal stress state of the structure.

The staff does not agree with the comment. The paragraph is discussing deformation monitoring for Alternative B. The intent is to monitor Page 6, second paragraph mentions deformations at locations where these deformations are measurable deformation in millimeters. Giving a strain value (hence the minimum value specified). The staff does not believe that 6 would be much more useful because it is NEI-6 specifying strains is appropriate because deformations would not normalized by gauge length.

necessarily be measured using strain gauges. This is also consistent with American Society of Mechanical Engineers (ASME) CC-6410(c) for initial structural integrity testing (ISIT).

Page 6, last paragraph: Concrete having a The staff agrees with the comment, and modified the paragraph to more 7 pulse velocity < 4000m/s being indicative of NEI-7 clearly state that concrete pulse velocity below 4,000 meters per second poor quality is a somewhat dubious statement could indicate concrete of questionable quality, and that visual 2

RESPONSE TO PUBLIC COMMENTS ON DRAFT REGULATORY GUIDE DG-1197:

INSERVICE INSPECTION OF PRESTRESSED CONCRETE CONTAINMENT STRUCTURES WITH GROUTED TENDONS Item Comments By NRC Response and should be mechanically tested. Pulse examination may need to be supplemented by other methods, (e.g.

velocity alone is not sufficient to characterize impact hammer or pullout test) to characterize the mechanical properties mechanical properties. of the concrete.

Page 7, Figure 1: Linearity of the bound lines assumes Youngs modulus of the concrete is constant with time, hence the estimate may be The staff agrees with the comment. Compliance with the regulatory somewhat conservative. The NRC may guide is not required. Also, in paragraph 2 of page 5 the NRC 8 NEI-8 consider allowing utilities exceptions if they can recommends that an applicant establish a band of acceptable prestress demonstrate that a change in Youngs modulus levels similar to that illustrated in Figure 1.

in the plant concrete over time merits a recomputation of bound lines.

The staff agrees with the comment because recommendation for placement of surveillance tendon is important. See Figure 3 for changes.

Page 8, last item a. 1-3: Suggest adding some Figure 3 Containment diagram showing typical locations of test tendons language as to placement of surveillance 9 NEI-9 and instrumentation shows the placement of surveillance tendons, e.g.,

tendons, e.g., at 120 deg spacing for vertical at 120 deg spacing for vertical tendons and dome tendons. No change tendons.

has been made for the 120 deg (in other words 60 deg) family. The staff has added a diagram for dome tendons at 90 deg.

Page 10, 3.1.1.b: Recommend changing the language of these three items to denote The staff agrees with the comment and has used the suggested wording 10 NEI-10 Parallel to tendons. Using along suggests in C.2.2.1.1.b. (2), (3) and (4) to improve the clarity of the RG.

the tendons themselves are instrumented.

The staff does not agree with the comment. The identified paragraph is discussing prestress level monitoring for Alternative A. The intent is for Page 10, 3.1.2.a.(3) and page 12, 3.1.2.c:

the instruments to withstand cyclic compression loading during the life of Strain values would be more useful here.

the nuclear power plant. The staff does not believe specifying strains is 11 Calculation would be based on lower bound of NEI-11 appropriate because cyclic compression loading is more naturally Youngs modulus and Poissons ratio for specified in terms of stress. Stresses can be converted to strains as concrete within spec.

needed (depends on site-specific Youngs modulus and Poissons ratio).

The staff agrees in part with this comment because the proposed change Page 14, 5.1.a: Consider removing tendon will add clarification. Staff replaced the word tendon with post-12 NEI-12 and replacing with post tensioning direction. tensioning direction. The sentence in 5.1.a has been revised to read in the direction of the tendon (post-tensioning direction).

Page 2, Section B, Discussion, Background, The staff agrees with the comment. According to Section 3.8.1.6.3, of the 3rd. paragraph, line 2: Change the ultimate U.S. Evolutionary Power Reactor (U.S. EPR) Final Safety Analysis 13 AREVA-1 strength value for the grouted tendon from Review Tier 2, Revision 2, there are 55 seven-wire strands in each 1,625 tons to 1,725 tons. The EPR tendon tendon. The ultimate strength is 270 ksi and the tendon cross section is 3

RESPONSE TO PUBLIC COMMENTS ON DRAFT REGULATORY GUIDE DG-1197:

INSERVICE INSPECTION OF PRESTRESSED CONCRETE CONTAINMENT STRUCTURES WITH GROUTED TENDONS Item Comments By NRC Response ultimate design strength is nominally 1,725 12.76 in2. This results in an ultimate strength of 3445.2 kips or 1722.6 tons. There are no known impacts to the ISI tons, close to the nominal value provided. The statement has been objectives in the guide by making this change. revised to say 1725 tons.

The staff agrees with the comment in part. The staff recognizes the cost-effectiveness aspect of the comment. However, monitoring the prestress level and pressure testing is part of Examination of Concrete Page 5, Section B, Discussion, Monitoring Containments which is mandated by 10 CFR 50.55a(b)(2)(viii), which Alternatives for Grouted Tendons, Monitoring incorporates ASME Section XI, IWL. The ASME ISI at 5 year intervals the Prestress Level and Pressure Testing was established by industry data and research and judged to be a (Alternative A), last paragraph, line 5: The sufficient time period to detect trending in degradation. Therefore, the pressure testing interval in the first 10 years inspection interval of 5 years in the RG is required by the ASME code.

should be consistent with the Integrated 14 Leakrate Testing frequency in 10 CFR 50, AREVA-2 ILRT is mandated by 10 CFR 50.54(o) which is subject to the Appendix J, Type A testing. Both the ILRT and requirements set forth in Appendix J to 10 CFR Part 50 Pressure Testing requires the unit to be shutdown and the containment pressurized.

Industry may be able to develop operational experience data to support a This is a significant impact on the plant change to either of these rules. However, since these rules are currently availability. The test frequency must be in effect, the staffs recommendation for pressure testing must remain as consistent.

stated. Licensees may schedule integrated leak rate testing (ILRT) and pressure testing at the same time if appropriate to optimize plant shutdown.

Page 8, Section C. Regulatory Position, paragraph 1.d: Same comment as item 2. Test 15 AREVA-3 See staffs response to AREVA-2.

interval should be consistent with the ILRT for both Alternative A and Alternative B.

The staff agrees and has revised the RG as follows because the Page 8, Section C. Regulatory Position, comment is to add the tendon type that is used for new design of US paragraph 2.a, item (3): Add gamma tendons, EPR:

the representative manner for testing a gamma

1. The staff added the following statement to the background tendon is two gamma tendons for the design discussion in Section B at the end of paragraph 6: The gamma using two 90 degree families of tendons. The tendon is anchored at the base of the containment in the tendon 16 US EPR design utilizes a gamma tendon for AREVA-4 gallery and extends vertically up and over the dome and is dome prestressing. The gamma tendon is anchored at the dome ring girder.

anchored at the base of the containment in the

2. The staff also added the following item (4) to Regulatory tendon gallery and extends vertically up and Position C.2.a: two gamma tendons for the design using two 90-over the dome and is anchored at the dome degree families of tendons.

ring girder.

17 For completeness, the requirements for the AREVA-5 The staff agrees that referencing the requirements for the inspection of 4

RESPONSE TO PUBLIC COMMENTS ON DRAFT REGULATORY GUIDE DG-1197:

INSERVICE INSPECTION OF PRESTRESSED CONCRETE CONTAINMENT STRUCTURES WITH GROUTED TENDONS Item Comments By NRC Response inspection of greased tendons in RG 1.35 greased tendons in RG 1.35 would contribute to the completeness of the should be included in DG-1197. RG 1.35 is RG and therefore has added a sentence to Regulatory position C.2.1.c to applicable to nongrouted containments. The refer to Regulatory Guide 1.35.

requirements for inspection of the greased tendons in ungrouted test tendons in the grouted containment should be added to DG-1197.

Page 9, Figure 2: Same comment as item 2.

The staff disagrees with this comment and will retain the test frequency Test interval should be consistent with the for Alternative B at 5-year intervals. The test frequency is based on 18 ILRT. Also the test interval shown after 10 AREVA-6 ASME code, section XI, IWL-2400 which is required by 10 CFR 50.55a.

years should reflect once every 10 years for See also the staff response to AREVA-2.

Alternative B.

The staff agrees and has added instrument locations parallel to gamma Page 10, paragraph 3.1.1.b.(3): same comment 19 AREVA-7 tendons to Regulatory Position -C.2.2.1.1.b.(4). See also the staff as item 4. Add gamma tendons.

response to AREVA-4.

Page 11, Figure 3: Add figure for dome The staff agrees with this comment because it will add more clarity. The tendons that are at 90 degrees. Indicate two staff has revised Figure 3 to show dome tendons. Figure 3 also indicates 20 typical locations for test tendons and AREVA-8 typical locations for test tendons and instrumentation across the center of instrumentation across the center of the dome the dome at 90 degrees.

at 90 degrees.

Page 12, paragraph 3.1.4.a: Same comment as The staff disagrees with this comment. Alternative A allows for a item 2. Test interval should be consistent with relaxation in the pressure testing frequency because additional the ILRT. Note that the relaxed test frequency 21 AREVA-9 monitoring of the containment structure is performed by instrumentation.

is recognized in this paragraph for Alternative See also the staff response to AVERA-2.

B, whereas, it is only recognized for Alternative A in Regulatory Position 1.d.

Page 14, paragraph 4.2.a.(1), Inspection of Anchorage Assemblies: Add gamma tendons.

A minimum of 4 gamma tendons, two of which The staff agrees with this comment and has added a fourth item to are located in each 90 degree group (two Regulatory Position C.2.3.3.a.(4). According to Section 3.8.1.1.2 of U.S.

families of tendons), randomly distributed to EPR FSAR Tier 2, Revision 2, a total of 104 gamma tendons divided into 22 AREVA-10 provide random sampling. two groups are placed 90 degrees apart in the reactor containment building dome. See also the staff response to AREVA-4.

The staff reviewed the comment and determined that the final version of

Background:

Just before Force Monitoring of RG 1.90 is clear abourt frequency. Refer section B.2, C.2.2, and Figure 5

RESPONSE TO PUBLIC COMMENTS ON DRAFT REGULATORY GUIDE DG-1197:

INSERVICE INSPECTION OF PRESTRESSED CONCRETE CONTAINMENT STRUCTURES WITH GROUTED TENDONS Item Comments By NRC Response Ungrouted Tendons we could add Periodic 2, 23 pressure tests are more frequent for alternative EDF-1 B than for Alternative A (which is the case in the figure of the RG). We think this point as a background element is also important.

The staff agrees with this comment because the minimum requirement is In France we instrument current zones of dome for pressure testing. For monitoring by instrumentation, high redundancy and cylinder wall; with a high redundancy level level is recommended which is also covered in the RG. The staff has

- these gauges can effectively be interpreted.

deleted the last sentence in Regulatory Position C.2.2.1.1.b which stated We have some doubt about our capacity to 24 EDF-2 Figure 3 delineates the typical planes and tendons. The staff added the interpret gauge distributed in the concrete following sentence to Regulatory PositionC.2.2.1.1.c. Figure 3 near tendons--it is possible but as the stress delineates the minimum requirements of the typical planes and tendons diffuse in the structure, the connection between for pressure testing. Redundancy level of instruments is stated in section measurement and cable is not obvious.

B and C2.2.1.1.c.

The NEA report about August 1997 in Civaux says that stress cells in the concrete were The staff agrees with the comment on the deficiency of stress cells.

deficient (Belgium article). It is possible to However, the RG recommends the use of several types of 25 measure directly stress in concrete, but it is EDF-3 instrumentation in addition to the use of stress meters and provides a difficult task we perform only in special statement that the complete understanding of instrumentation readings is occasions, not for containment periodic required. Therefore, the RG is sufficient as written.

measurements.

Alternative A is very well described in Section

a. Section b could explain which zones have to be monitored (presenting this one as a minimum which has to be measured during the The staff agrees that these minimum locations need a very large all life time--that is to say which need redundancy in order to establish measurement error, to detect any redundancy and replaced if needed). Our structural abnormal behavior, and to manage gauges over their lifetime.

minimum locations are for EdF is: Dome Also, the staff agrees that the local instruments at these minimum (center/two directions); Cylinder wall (two locations are complemented by other devices such as invar wire located 26 locations/two directions); Gouset (two EDF-4 near the minimum areas for validation. Therefore, the staff has added location/two directions). This minimum text to Regulatory Position C.2.2.1.c to this effect.

locations need a very large redundancy to See also the staff response to comment EDF-2.

confirm measurement error, to detect any structural abnormal behavior if suspected and to manage gauges lifetime. These local instruments are completed by other devices such as invar wire located near the minimum areas for validation.

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RESPONSE TO PUBLIC COMMENTS ON DRAFT REGULATORY GUIDE DG-1197:

INSERVICE INSPECTION OF PRESTRESSED CONCRETE CONTAINMENT STRUCTURES WITH GROUTED TENDONS Item Comments By NRC Response The staff disagrees with this comment. The commenter suggests that the Section C could be modified, only by writing staff specify the total number of gauges to be used (at the beginning).

shallto measured strain, temperature in The guide, as written, provides a reference to current industry practice for concrete. This minimum device can be the total number of gauges at existing plants. However, the total number 27 completed by other instruments to measure EDF-5 of instruments may vary from plant to plant. Also specifying the number stress and other parameters in concrete, bars of instruments at the beginning only may be misinterpreted to mean that and tendons. Effectively the total number of licensees do not need to maintain the instruments throughout the life of gauges may be 250 to 300 (at the beginning). the structure. The NRC expects an appropriate number of instruments to be retained operable for the whole service life of the structure.

Section 3.1.3.a: There is a little ambiguity about The staff agrees that the use of the word interpret alone is ambiguous the word interpretation. Does it mean that the and has added the phrase (review recorded data to determine prestress licensee has to produce a report every 2 28 EDF-6 level) after the word interpret in the second sentence of C.2.2.1, months? Or has to produce a report where data subsection Monitoring Instrumentation Functionality, bullet a. to improve corresponding to a 2-month period are clarity.

interpreted?

General comment on Alternative B:

Several containments in France without any The staff acknowledges the commenters statement. The staff is loss of rigidity during pressure test have shown investigating the general comment that several containments in a loss of pre-stress in concrete due to concrete France without any loss of rigidity during pressure test have shown a 29 EDF-7 creep, it is the reason why we explain to loss of pre-stress in concrete due to concrete creep. NRC guidance US/EPR staff that it would be better not to have may be revised if this research indicates that the current "zero" permanent instrument (minimum with recommendation is not sufficient. This is noted as a future action.

very few redundancy).

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