ML120730659

Request for Additional Information #2 for Nuclear Energy Institute TR 09-10, Rev 1, Gas Management

ML120730659
Person / Time
Site:	Nuclear Energy Institute
Issue date:	03/19/2012
From:	Stuchell S Licensing Processes Branch (DPR)
To:	Jeffrey Riley Nuclear Energy Institute
Stuchell S, NRR/DPR,301-415-1847
References
TAC ME5291
Download: ML120730659 (11)

Text

March 19, 2012 Mr. James H. Riley, Principal Engineer Nuclear Generation Division Nuclear Energy Institute 1776 I Street, NW, Suite 400 Washington, DC 20006-3708

SUBJECT:

REQUEST FOR RESPONSE TO SECOND SET OF ADDITIONAL INFORMATION QUESTIONS RE: TOPICAL REPORT 09-10, REVISION 1, GUIDELINES FOR EFFECTIVE PREVENTION AND MANAGEMENT OF SYSTEM GAS ACCUMULATION (TAC NO. ME5291)

Dear Mr. Riley:

By letter dated December 21, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML110240124), the Nuclear Energy Institute (NEI) submitted for U.S.

Nuclear Regulatory Commission (NRC) staff review Topical Report (TR) NEI 09-10, Revision 1, Guidelines For Effective Prevention And Management Of System Gas Accumulation (ADAMS Accession No. ML110030918). TR NEI 09-10, Revision 1, provides recommendations and guidance to nuclear generating stations for the effective implementation of programs and processes to prevent and manage gas intrusion and accumulation in plant systems.

By letter dated August 4, 2011 (ADAMS Accession No. ML112140617), the NRC submitted to NEI, the first set of questions concerning NEI 09-10, Rev 1. On October 28, 2011, NEI responded to the NRC (ADAMS Accession No. ML113220311).

Upon further review of TR NEI 09-10, Revision 1, the NRC staff has determined additional information is needed to complete the review. The NRC requests your response to the enclosed Request for Additional Information (RAI) within 90 days of issuance of this letter.

If you have any questions regarding this matter, please contact me at (301) 415-1847.

Sincerely,

/RA/

Sheldon D. Stuchell, Sr. Project Manager Licensing Processes Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Project No. 689

Enclosure:

RAI questions

ML112140617), the NRC submitted to NEI, the first set of questions concerning NEI 09-10, Rev 1. On October 28, 2011, NEI responded to the NRC (ADAMS Accession No. ML113220311).

Upon further review of TR NEI 09-10, Revision 1, the NRC staff has determined additional information is needed to complete the review. The NRC requests your response to the enclosed Request for Additional Information (RAI) within 90 days of issuance of this letter.

If you have any questions regarding this matter, please contact me at (301) 415-1847.

Sincerely,

/RA/

Sheldon D. Stuchell, Sr. Project Manager Licensing Processes Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Project No. 689

Enclosure:

RAI questions DISTRIBUTION:

PUBLIC PLPB R/F RidsNrrDpr SStuchell RidsNrrLADBaxley RidsNrrDssSnpb AUlses JJolicoeur WLyon RidsOgcMailCenter RidsAcrsAcnwMailCenter JGall RidsNrrDprPlpb ADAMS Accession No.: ML120730659 NRR-106 OFFICE PLPB/PM PLPB/LA SRXB/BC PLPB/BC PLPB/PM NAME SStuchell DBaxley AUlses JJolicoeur SStuchell DATE 03/15/2012 03/16/2012 03/14/2012 03/19/2012 03/19/2012 SECOND SET OF REQUEST FOR ADDITIONAL INFORMATION QUESTIONS REGARDING TOPICAL REPORT 09-10, REVISION 1, GUIDELINES FOR EFFECTIVE PREVENTION AND MANAGEMENT OF SYSTEM GAS ACCUMULATION NUCLEAR ENERGY INSTITUTE PROJECT NO. 689 As a result of the continued review of Topical Report (TR) NEI 09-10, Revision 1, the U.S.

Nuclear Regulatory Commission (NRC) requests a response to the following requests for additional information (RAI) questions. Each RAI question is in bold type. Clarification that underlies the RAI question is provided in un-bolded type. The intent of the RAI questions is a result where there are no unresolved issues in the final NEI 09-10, Rev 1-A.

RAI 2-1 Is it the Nuclear Energy Institutes (NEIs) intent that the NEI 09-10 Rev 1 Topical Report explicitly indicate that operating experience be incorporated into the gas management program or that incorporation be only encouraged as stated in TR Section 6?

The importance of understanding gas intrusion and accumulation mechanisms and the possibility that a mechanism may apply to other systems is identified, as is the need for the gas intrusion program owner to review all plant and industry operating experience. However, the TR does not explicitly indicate operating experience must be incorporated into the gas management program in the same fashion as the quality assurance program. The NRC staff requires that operating experience must be an integral part of a gas management program as opposed to the TR approach that encourages licensee documentation of operating experience.

RAI 2-2 Does NEI plan to expand the discussion of gas transport methodologies in TR Section 7 to identify the need for using a staff-approved or a well-supported gas transport analysis method?

The TR states that if an evaluation supports a determination that gas intrusion into a system would not adversely affect the ability of the system to perform its function then the system can be considered to not be an in-scope system and no further evaluation is required. The NRC has found that such evaluations are often incorrect or inadequately supported by experimental data or theoretical understanding. Consequently, due to the complexity and variability of gas evaluation methods, the evaluation method should either have been approved by the staff or be well understood and applied by experts who are well versed in such applications. The TR should emphasize the need for an acceptable evaluation before concluding that a system is an out-of-scope system.

In regard to prediction methods and to the statement that scope may be narrowed to portions of a system where gas accumulation can affect functionality, the NRC staff notes that gas volumes that are predicted to not affect functionality and that are excluded from further consideration must be documented. Trivial volumes, such as occasional bubbles in a horizontal pipe that cannot be reasonably removed, do not require documentation. Treatment of design ENCLOSURE

limits and operating limits is discussed in NEI 09-10 Sections 9 and 12, respectively. The evaluation methods discussed in the above paragraph apply.

RAI 2-3 Vortexing is identified in TR Section 4 as a gas intrusion mechanism. Does NEI plan to expand the discussion of vortexing in that section or in TR Section 7?

Vortexing prediction methods are not addressed in the TR. The TR must identify that vortexing is within the scope of Generic Letter 2008-01 gas issues and this must be addressed on a plant-specific basis until the NRC issues or endorses an acceptable approach. This must be identified in the revised TR. Further, due to the complexity and variability of vortex calculation methods, the need for using a staff-approved or a well-supported gas transport analysis method is to be emphasized in the TR.

RAI 2-4 TR Section 8 discusses monitoring and accessibility but accessibility is not defined.

What are the criteria that determine whether a surveillance location is accessible?

The report states that Monitoring may not be practical for locations that are inaccessible due to radiological, environmental conditions, the plant configuration or personnel safety, but it does not address accessibility. The NRC staff considers all locations accessible unless actual environmental conditions constitute a hazard to personnel or are such that conducting the surveillance in the specific locations will result in an unacceptable dose. Considerations of such aspects as high environmental temperatures or local high temperatures that constitute a burn hazard also apply to determination of non-accessibility. Regardless of accessibility considerations, surveillance is required for all locations of concern unless it is acceptably determined that the surveillance is not necessary to reasonably ensure operability.

An example that illustrates the need for increased guidance is classification of accessibility based on a posted high radiation area. Assume there are six locations within a posted high radiation area where surveillances are needed, five surveillances can be performed with negligible dose, and none of the surveillance locations entails personnel hazards such as high local temperatures. The NRC considers the five locations to be accessible whereas NRC inspectors have observed licensee facilities where the six locations were considered inaccessible.

RAI 2-5 Should the lists of precursors in Sections 4 and 12.1 include a condition where the system configuration may result in a temperature that is greater than saturation temperature?

Some system configurations may result in a temperature that is greater than the saturation temperature at the interface with system components that are expected to be at a lower temperature. For example, the NRC staff is aware of a condition where a high-pressure system operating at an elevated temperature caused steam to form on the low-pressure side of a closed valve where there should not have been a void. Attempts to eliminate the void were complicated by boiling due to the high temperature interface as steam was vented.

RAI 2-6 Technical specifications (TSs) are mentioned in TR Section 13.4 and in Attachment 4 to the TR but there is no mention that many TSs are incomplete. Does NEI plan to revise the TR to address how licensees should address this condition?

Regardless of whether located in TSs, the Final Safety Analysis Report, procedures, or the corrective action plan, the primary requirement is that monitoring must be sufficiently frequent to reasonably ensure continued operability of the subject systems. Licensees that use extended frequencies, such as 24 months as specified in TSs, without acceptable justification, do not meet this requirement. Many licensees have a 31-day TS surveillance requirement but conditions may exist where this is inadequate to reasonably ensure operability. Conversely, aspects of some systems may be consistent with less frequent surveillances but it is necessary to comply with the TS.

RAI 2-7 TR Section 13 states that "Operability Determination or Functionality assessment processes are not required if the . as found gas volume is below the design limit."

Please clarify this statement with respect to a determination that the as-found gas volume may be below the design limit but the monitoring process must reasonably ensure that the design limit is not exceeded before the next scheduled monitoring.

TR Section 12.2 states, The monitoring plan must be developed to ensure the system meets the design limit and must reasonably ensure the system is capable of performing its design function throughout the next monitoring interval. The TR Section 13 quote is not consistent with the latter part of the Section 12.2 quote and is not acceptable as written. This must be corrected. The TR also states that, "the discovery of all gas accumulation that exceeds the design limit should be entered into the stations corrective action program. An immediate Operability Determination or functionality assessment is required if discovered gas volume is greater than the monitoring procedure design limit." In light of the previous staff observation, it is not clear if the monitoring procedure design limit takes into account the predicted behavior until the next monitoring, although trending is identified in Section 12.8 that can provide information to support predicted behavior. The need to remain below the design limit throughout the next monitoring period should be clarified.

RAI 2-8 TR Section 9 addresses acceptance criteria and Attachment 4 covers situations where the acceptance criteria have been exceeded. This is not clear with the result that the discussion in the two sections appears to be inconsistent. What TR clarifications does NEI plan to make to eliminate the potential misunderstanding?

RAI 2-9 The requirement that the instantaneous void fraction must be less than 1.7 times the TR Tables 1 and 2 allowable pump suction void fractions was concluded by mutual judgment of industry and NRC staff representatives following the June 2010, meeting at NEIs Washington, DC location (References 5, 6, and 7). The TR discussion identifies a factor of 1.7 but does not apply it to the Table 1 and 2 criteria. Rather, the TR provides a discussion of typical transient behavior that fits within the 1.7 factor and attempts to conclude that there will be no slug flow.

An alternate to using the 1.7 factor is to acceptably demonstrate that dispersed bubbly flow exists at the pump inlet throughout the transient and that the average void fraction meets the Table 1 and 2 criteria. Provide an in-depth justification for not requiring the 1.7 factor or discuss the alternate bubbly flow criterion as a means of meeting the no slug flow requirement. If the dispersed bubbly flow criterion is selected, provide a reference that defines bubbly flow and discuss how this approach reasonably ensures that no slug flow will occur at the pump.

RAI 2-10 The discussion of "Net Positive Suction Head Required (NPSHr) for Pumps" includes the following statements:

The timeframe for a pump to experience a gas intrusion event is expected to be at the beginning of an event, when the pump is automatically started by the plants ECCS

[emergency core cooling system] actuation systems. This is the time of maximum NPSH available as well, since suction sources are at their highest elevations, and the fluids are at their coldest temperatures. It is also expected that any gas voids present would be transported through the pump at a time when margin in NPSH available is quite large.

Switching from the refueling water storage tank (RWST) to the containment sump can occur when pressure is low and temperature is close to saturation where meeting NPSHr can be a challenge. Clarify the discussion with respect to this observation.

RAI 2-11 The NRC staff reviewed the newest versions of the TR references. Some of the TR references are to older versions of the documents that were not reviewed. The TR references should be updated to reflect the newest document versions.

The references are as follows:

• Investigation of Simplified Equation for Gas Transport, Westinghouse Electric Company, for the PWR Owners Group, WCAP-17276-P, Rev. 0, September 2010.

Not received. Reviewed Revision 1, ML110480381, January 2011.

• FAI/09-130, "Technical Basis for Gas Transport to the Pump Suction," Fauske

&Associates, LLC for the PWROG, December, 2009.WCAP-17271-NP, Rev. 0, Air Water Transport in Large Diameter Piping Systems: Analysis and Evaluation of Large Diameter Testing Performed at Purdue University - Volumes 1-3, Westinghouse Electric Company, for the PWR Owners Group, No ML, September 2010. Replaced by FAI/09-130-P, "Technical Basis for Gas Transport to the Pump Suction," Fauske &Associates, ML110480456, December, 2010.

• BWROG-TP-08-017, 0000-0086-7825-R0, Potential Effects of Gas Accumulation on ECCS Analysis as Part of GL 2008-01 Resolution, GE Hitachi Nuclear, for the BWR Owners Group, August 2008. Reviewed version is Potential Effects of Gas Accumulation on ECCS Analysis as Part of GL 2008-01 Resolution, Proprietary ML091250362, non-proprietary ML091250361, April 30, 2009.

• BWROG-TP-08-020, 0000-0088-8669-R0, Effects of Voiding on ECCS Drywell Injection Piping (TA 354), GE Hitachi Nuclear, for the BWR Owners Group, September 2008. Reviewed version is Effects of Voiding on ECCS Drywell Injection Piping, ML091250178, April 30, 2009. Please provide a pdf version of this document. Note that ML091250178 is only a one page cover letter.

• LTR-LIS-08-543, PWROG Position Paper on Non-condensable Gas Voids in ECCS Piping; Qualitative Engineering Judgment of Potential Effects on Reactor Coolant System Transients Including Chapter 15 Events, Task 3 of PA-SEE-450, Westinghouse Electric Company, for the PWR Owners Group, No ML, August 19, 2008. Reviewed version is same title, ML090980303, dated April 2, 2009.

RAI 2-12 Sections 3.1.3 and 3.1.4 of Reference 1 summarize the status of available data. In general, data for large diameter ( > ~ 3 inches) elbows is insufficient to support modeling of horizontal elbows, data obtained from the Purdue tests provides support for transient modeling of elbows in a horizontal to vertically downward orientation and limited support of vertically downward to horizontal configurations. Some vortexing and tee information is stated to exist but is not addressed in the reference, the available models are not yet adequate in all situations, and there is a significant knowledge gap in these areas.

For example, some of the phenomena of potential concern were observed during the Arizona Public Service test program that is summarized in the references Section 3.2 and is the subject of RAI question 2-13, below.

The references Section 4 summarizes the conclusions of an expert panel that addressed the state of knowledge.1 Areas identified where an improved understanding of phenomena is necessary to perform a best estimate evaluation where a bounding approximation may be inadequate include:

"a. Kinematic shock at vertical plane elbows.

b. Vortexing at offtakes.

c. Phase separation at tees.

d. Flow stratification in horizontal pipes.

e. Pump entrance phenomena / piping entrance configuration."

Phenomena that need to be well understood to assure that re-accumulation of gas and subsequent formation of slug flow does not occur are:

a. Flow stratification in horizontal pipes.

b. Pump entrance phenomena (piping entrance configuration).

1 The work is addressed in Swartz, M., Phenomena Identification and Ranking Table (PIRT) to Evaluate Void Fraction / Flow Regime at ECCS, RHR and CS Pump Suctions, Westinghouse Electric company LLC, WCAP-17167-NP, Rev. 0, December, 2009. The report was not provided to the NRC although members of the NRC staff have read the report and judged it to provide excellent coverage of the state of knowledge. The WCAP Section 4 summary is sufficient for the review being conducted here.

Reference 1 concluded the discussion with phenomena related to the pump and piping configuration directly upstream of the pump should be considered as part of ongoing pump gas intrusion tolerance investigations and any future pump testing efforts. Flow stratification in horizontal pipes can lead to an accumulation of gas, for instance in an offtake or tee geometry. Once gas is accumulated, a subsequent instability can lead to a large surge in gas downstream. Currently, no modeling approaches exist that can account for this type of behavior. And flow stratification in horizontal pipes, leading to downstream surges in gas is the most significant knowledge gap identified by the PIRT (Phenomena Identification and Ranking Table) panel.

Typical high-pressure injection (HPI) pump suction configurations include downward flow in a vertical pipe with an elbow to a horizontal pipe that has a small length to diameter ratio with a reducer immediately upstream of the pump entrance. This configuration may be inconsistent with pump vendor recommendations and is not replicated in the Purdue testing. Further, typical pump suction headers include offtakes /

tees that are also not replicated in the testing. Consequently, modeling of such configurations must be done with care and a safety factor will likely be necessary to compensate for the lack of knowledge and supporting data. Further, in some circumstances, simply assuming all of the gas passes in one direction as a worst case may be inadequate to address the gas surge concerns, a potential condition that should be addressed as part of the overall modeling.

What are plans to address these areas?

Another configuration that may be of concern is a vertical residual heat removal pump where flow from a horizontal pipe passes through an elbow and short vertical pipe before entering the pump. Conversely, some HPI pumps take suction direct from a vertical pipe where the factor of four criterion identified in Section 6.0 (Page 41) of FAI/09-130-P (Reference 3) is applicable.

Where information is insufficient to support application of a generic approach such as the simplified equation discussed in Reference 2, it may be necessary for individual licensees to address the issues on a plant-specific basis.

RAI 2-13 Reference 3 states that the measured void fraction is never one and that this demonstrates the most important observation from the tests that, as a result of the kinematic shock, the two-phase flow regime is bubbly flow, not slug flow. (First paragraph of Section 5.1) This appears to be inconsistent with some of the Purdue test results where slug flow was observed at void fractions of less than one. Please explain.

This is discussed in Section 5.1 of Reference 3 where the rationale is that the vertically located differential pressure instrument used to determine void fraction never indicated zero and therefore a gas slug could not have existed. Test results are stated to provide maximum void fractions as high as 0.48, apparently due to the influence of buoyancy as downward velocity in the downcomer approaches bubble rise velocity. The length of pipe covered by the instrument is not identified nor is its transient response addressed. For example, the sketch in Figure B-2 indicates that the length is about 2/3 of the vertical pipe length whereas the sketch in Figure B-1 shows about 1/4 of the length - not surprising since sketches are not necessarily to scale.

Further, the test configuration with a lower 4-inch horizontal pipe and a 3-inch vertical pipe would influence behavior in the region of concern. One may postulate that a 4 inch vertical pipe

or a larger diameter pipe would have exhibited behavior similar to the Purdue test results or that a pipe larger than 4 inches would have reacted differently since countercurrent or co-current slug flow may occur in larger diameter pipes where it would not in smaller diameters. Finally, lower Froude numbers will not result in transit of a large upper void as a slug into lower piping.

In any event, these observations appear to raise questions regarding the validity of the Reference 3 conclusions.

RAI 2-14 Reference 2s Figure B-3 provides void fraction at the bottom of the downcomer as a function of time for Test PVA22. This starts at 0, maximizes at about 0.21, and the transient is over in about 30 seconds. Yet the void fraction remains at about 0.02 for the remainder of the plot that ends at 120 sec. Figure 9 provides the same information for Test PVA21 where the behavior is similar although the maximum void fraction is about 0.13, and void fraction is zero after about 30 seconds. Table B-1 does not identify any difference between the tests. The NRC staff does not understand the Figure B-3 non-zero behavior since the void source is finite unless for some reason the void is circulating in the bottom of the downcomer. Figure B-4 is stated to provide a comparison of gas transport to the pump compared to the initial gas inventory and may provide some insight, but the figure in the NRC staffs copies of the report is a solid black rectangle and provides no information.

(a) Explain the differences, and (b) provide a legible Figure B-4.

RAI 2-15 Reference 2 reported that the kinematic shock was about 1 ft below the bottom of the piping high point for Froude number, NFR , = 0.6 and the void fraction at that location was about 0.23. With a slip ratio of 0.72, the void fraction of the flow being transported to the pump would be approximately 0.29. It continues with Figure B-5 shows that this represents the upper limit of values observed for Froude numbers of 0.6 (velocity of 0.61 m/s) (2 ft/sec). As the Froude number decreases, the buoyancy influence increases and some large values of local void fraction can occur. Nonetheless, this method of assessing the void fraction at the bottom of the downcomer is demonstrated to be consistent with experiments and if anything conservatively biases to the maximum value. Figure 10 is identical to Figure B-5 except the line labeled Calculated Peak Void Fraction @ 0.25 is at elevation 0.32 in Figure 10 and is at elevation 0.25 in Figure B-5.

This appears to be an error in one or both figures. The NRC staff requests clarification.

RAI 2-16 As discussed in References 2 and 3, a factor of four criteria has been established for determining that downcomer length is sufficient to reasonably ensure that fluid exiting a downcomer is characterized as bubbly flow. Reference 2 describes the Palo Verde and Purdue test facilities where the NRC staff determined that the factor of four criteria for downcomer length is met. However, at NFR = 2.5, in the 6 and 8 inch Purdue tests, co-current slugs moved down the vertical pipe and the Purdue report stated that Trailing slugs were observed near the end of the transient and were characterized by complete flushing of the gas held up in the top horizontal header, elbow and kinematic shock region. Discuss this observation with respect to the validity of the factor of four criteria.

RAI 2-17 A simplified equation has been developed for analysis of transient gas movement in pressurized water reactor (PWR) suction piping. A key aspect of configurations where the simplified equation can be applied is establishment of the kinematic shock and bubbly flow toward the bottom of a vertical downcomer, an aspect that is discussed in References 2 and 8 and is investigated in the referenced test programs. However, horizontal slug flow was observed in the lower horizontal pipe in both the 8- and 12-inch Purdue tests. In the 8 inch tests, it occurred at NFR = 1.65 and an initial void fraction of 20 percent. In the 12 inch tests, it occurred at NFR = 1.0 and an initial void fraction of 5 percent. Counter-current slug flow was observed after a large portion of the void had passed through the system for NFR < 1.0. Aspects of these observations are addressed in Section 3.4.2.3 of Reference 8, which stated:

The gas transport testing conducted at Purdue University forms the validation basis for the Simplified Equation. This program addressed the transport of gas through piping systems. As such, the flow dynamics at the inlet to pumps was not within the scope of this program. Therefore, any additional limitations that are needed to deal with specific pump inlet concerns will have to be identified as part of a future PWROG project.

The TR needs to be updated to clearly reflect that it is the users responsibility to acceptably address phenomena issues associated with the lower horizontal pipe leading to the pump suction when using the simplified equation.

RAI 2-18 Identify Reference 17 that is not included in the references listed in Reference 3 but is referenced in the report.

RAI 2-19 In Reference 4, Q, the pump flow rate at the fully run-up condition, is not provided.

Provide this value.

RAI 2-20 In Reference 4, the pump shutoff pressure is given on Page 28 as 27 psig and on Page 79 as 18 psig. What is the correct value?

REFERENCES

1. Air Water Transport in Large Diameter Piping Systems: Analysis and Evaluation of Large Diameter Testing Performed at Purdue University, Volumes 1, 2, and 3, WCAP-17271, ML110490356, October, 2010, August, 2010, and August 2010, respectively.

2. Investigation of Simplified Equation for Gas Transport, Westinghouse Electric Company, for the PWR Owners Group, WCAP-17276-P, Rev. 0, September 2010. Not received. Reviewed Revision 1, ML110480381, January 2011.

3. FAI/09-130, "Technical Basis for Gas Transport to the Pump Suction," Fauske

&Associates, LLC for the PWROG, December, 2009.WCAP-17271-NP, Rev. 0, Air Water Transport in Large Diameter Piping Systems: Analysis and Evaluation of Large Diameter Testing Performed at Purdue University - Volumes 1-3, Westinghouse Electric Company, for the PWR Owners Group, No ML, September 2010. Replaced by FAI/09-130-P, "Technical Basis for Gas Transport to the Pump Suction," Fauske

&Associates, ML110480456, December, 2010.

4. FAI/08-70, Rev.1, Gas-Voids Pressure Pulsations Program, Fauske & Associates, LLC, for the PWR Owners Group, ML090990426, September 2008.

5. Gall, Jennifer, Meeting With The Nuclear Energy Institute (NEI) And Industry Representatives To Discuss NRC Generic Letter 2008-01, Managing Gas Accumulation In Emergency Core Cooling, Decay Heat Removal, And Containment Spray Systems, NRC Memorandum, ML101650201, June 24, 2010.

6. Guidance To NRC/NRR/DSS/SRXB Reviewers For Writing TI Suggestions For The Region Inspections, ML102080675, June 4, 2010. The latest version of this guidance is Revision 11, ML111660749, May 23, 2011.

7. Guidance To NRC/NRR/DSS/SRXB Reviewers For Writing TI Suggestions For The Region Inspections, ML101590268, June 7, 2010.2

8. Swantner, Stephen R., "Investigation of Simplified Equation for Gas Transport,"

Westinghouse Electric Company LLC, WCAP-17276-P Revision 1, January 2011.

2 ML102090074 provides emails covering exchange of information between NRC and NEI.

ML110340116 provides the minor comments referenced in ML102090074. These comments were included in the NRCs criteria provided in the ML101590280 ADAMS package.