ML18017A123

Draft Safety Evaluation Report for Westinghouse WCAP-17938 Topical Report, Revision 2, AP1000 In-Containment Cables and Non-Metallic Insulation Debris Integrated Assessment, Project 0811 (Public)

ML18017A123
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Site:	PROJ0811
Issue date:	01/30/2018
From:	Habib D C NRC/NRO/DNRL/LB4
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References
WCAP-17938-P, Rev 2
Download: ML18017A123 (57)

Text

Draft Safety Evaluation "AP1000 In-Containment Cables and Non

-Metallic Insulation Debris Integrated Assessment" WCAP-17938-P, Revision 2 Project No. 0811

1.0 INTRODUCTION

In September 2004, NUREG

-1793, "Final Safety Evaluation Report Related to Certification of the AP1000 Standard Design" (FSER) (Reference

1) was issued by the staff of the U.S. Nuclear Regulatory Commission (NRC). The staff issued Supplement 1 to the FSER in December 2005 (Reference 2) to address details related to rulemaking, and it issued Supplement 2 to the FSER in September 2011 (Reference 3) to address changes proposed in the design certification amendment. The amendment included changes through Revision 19 to APP-GW-GL-700, "AP1000 Design Control Document" (DCD), dated June 2011 (Reference 4). NUREG-1793, Supplement 2, contains the staff's evaluation of how the amended AP1000 design addresses Generic Safety Issue 191, "Assessment of Debris Accumulation on Pressurized

-Water Sump Performance

," (GSI-191) (Reference 5), and Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design

-Basis Accidents at Pressurized

-Water Reactors" (GL 2004-02), dated September 13, 2004 (Reference 6). Westinghouse Electric Company (Westinghouse) issued WCAP-17938, "AP1000 In-Containment Cables and Non

-Metallic Insulation Debris Integrated Assessment," Revision 2 , in June 2017 (Reference 7, hereinafter, "the WCAP")

.1 It reevaluates the GSI

-191 and GL 2004-02 debris assessment for the AP1000 as described in the DCD. Specifically, the WCAP assesses the potential for the generation of debris from nonmetallic insulation (NMI) (e.g., microporous insulation in the neutron shield blocks) in the reactor cavity and electrical cables in the containment. As discussed in the WCAP, the GSI-191 and GL 2004

-02 debris assessment for the AP1000 showed that no fibrous debris is generated in a loss

-of-coolant accident (LOCA). DCD Section 6.3.2.2.7.1, "General Screen Design Criteria," documents this, stating that, "a LOCA in the AP1000 does not generate fibrous debris due to damage to insulation or other materials included in the AP1000 design." This conclusion is based on the use of metal reflective insulation (MRI) or a suitable equivalent 2 and the lack of fibrous insulation and other sources of fiber located in the LOCA jet impingement zones. As discussed in the WCAP, the AP1000 plant design includes NMI in the reactor cavity that is designed to perform as a suitable equivalent to MRI. Additionally, the plant design includes in

-containment electrical 1 Previous v ersions of t h e WCAP r eview ed by the staff as par t of t his ev aluation were submitted to NRC on March 12 , 20 15 (Reference 8), and November 20, 2015 (Reference 9).

2 As des cribed in th e WCAP and t he AP1000 DCD, a suitable equ ivalent i nsulation is o ne that i s en capsulated in stainless steel that is seam welded, so that LOCA jet impingement does not damage the insulation and generate debris. Insulation that could be damaged by LOCA jet impingement is also a suitable equivalent if the resulting insulation debris is not transported to the containment recirculation screens, to the in-containment refueling water storage tank screens, or into a direct vessel injection (DVI) or a cold

-leg LOCA break that becomes submerged during recirculation. In order to qualify as a suitable equivalent insulation, testing must be performed that subjects the insulation to conditions that bound the AP1000 plant conditions and demonstrates that debris would not be generated. If debris is generated, testing or analysis (or both) must be performed to demonstrate that the debris is not transported to an AP1000 plant screen or into the core through a flooded break.

It would also have to be shown that the material used would not generate chemical debris.

cabling that may contain fibrous and other materials (jackets, wrappings, and filler materials) that may be directly impinged upon by a jet of water from a LOCA. Neither the applicant's DCD evaluation addressing GSI

-191 and GL 2004-02 nor the staff's FSER considered encapsulated NMI or cabling. To address these items, Westinghouse developed a program to evaluate any potential impacts to the current licensing basis from the exposure of cables to direct jet impingement by water from a LOCA and to qualify encapsulated NMI as a suitable equivalent to MRI. The purpose of the program was to define a zone of influence (ZOI) applicable to cables and to confirm that the encapsulated NMI met the requirements of suitable equivalency and may be used in place of MRI at discrete locations in the reactor cavity. The program included jet impingement testing of neutron shield blocks (e.g., encapsulated NMI) and cabling, and submergence testing of neutron shield blocks.

This safety evaluation (SE) describes t he staff's review of the WCAP and responses to requests for additional information (RAI) issued by the staff. The general approach followed in this SE, beginning with the introduction in Section 3.1.2, is to describe the applicant's evaluations and conclusions in a section of the WCAP, followed by the staff's evaluation of that section, as appropriate. Beginning with Section 3.2, the numbering system used in the technical evaluation section (Section 3) parallels the section numbering in the WCAP (e.g., Section 3.2 of the SE corresponds to Section 2 of the WCAP, Section 3.3 of the SE corresponds to Sectio n 3 of the WCAP, and so on).

2.0 REGULATORY EVALUATION

The following Commission regulations pertain to the evaluation of the AP1000 and water sources for long-term recirculation cooling after a LOCA: General Design Criterion 35, "Emergency core cooling," of Appendix A, "General DesignCriteria for Nuclear Power Plants," to Title 10 of the Code of Federal Regulations(10 CFR) Part 50, "Domestic Licensing of Production and Utilization Facilities," as itrelates to providing abundant emergency core cooling to transfer heat from the reactorcore following a LOCAGeneral Design Criterion 38 , "Containment heat removal," as it relates to the ability ofthe containment heat removal system to rapidly reduce the containment pressure andtemperature following a LOCA and to maintain these indicators at acceptably low levels 10 CFR 50.46(b)(5), as it relates to requirements for long

-term cooling in the presence ofLOCA-generated and latent debrisAppendix D to Part 52

-Design Certification Rule for the AP1000 DesignA specific area of the staff's review under these regulations is to confirm that adequate long

-term cooling is available when considering debris resulting from a LOCA. The staff evaluated the AP1000 design against these regulations with regard to this issue. Because the applicant is reassessing debris resulting from a LOCA for the design, these regulations remain applicable for the staff's review of the WCAP.

3.0 TECHNICAL EVALUATION

3.1 GENERAL 3.1.1 AP1000 Description The DCD Tier 2, Section 6.3.2.2.7, "IRWST and Containment Recirculation Screens," describes the evaluation of the water sources for long

-term recirculation cooling following a LOCA, including the in

-containment refueling water storage tank (IRWST). It consider s debris resulting from a LOCA together with debris that exists before a LOCA (i.e., latent debris). Item 3 in DCD Tier 2, Section 6.3.2.2.7.1 states that MRI or a suitable equivalent is used on the reactor vessel, each reactor coolant pump (RCP), the steam generators, the pressurizer, and all lines designated Class 1 under the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). In addition, MRI is used inside containment where insulation would be subject to jet impingement. As a result, an AP1000 LOCA would not generate fibrous debris.

Item 10 of DCD Tier 2, Section 6.3.2.2.7.1, states that other potential sources of fibrous material, such as ventilation filters or fiber-producing fire barrier s , are not located in jet impingement damage zones or below the maximum post

-LOCA floodup water level. Supplement 2 to the FSER, Section 6.2.1.8, "Adequacy of In

-Containment Refueling Water Storage Tank and Containment Recirculation Screen Performance," evaluates DCD Tier 2, Section 6.3.2.2.7, and replaces the analysis documented in NUREG

-1793. Supplement 2 to the FSER, Section 6.2.1.8.2.1, "Break Selection," states the following:

In the AP1000 design, there are only three sources of debris that transport with the recirculating water: latent or resident containment debris, debris from post

-accident chemical effects, and debris from coatings located in the zone of influence (ZOI) of a LOCA jet.

Supplement 2 to the FSER , Section 6.2.1.8.2.2, "Zone of Influence/Debris Generation and Characterization (Excluding Coatings),"

states the following:

In the AP1000, metal reflective insulation (MRI) or a suitable equivalent is specifically required on the reactor vessel, RCPs, steam generators, pressurizer, and all ASME Code Class 1 lines. MRI is also required at any location within the insulation ZOI. . . . If insulation in the AP1000 ZOI is not MRI, it must meet the DCD definition of suitable equivalence, which requires that the insulation be tested at conditions that bound the AP1000 operation. . . . It also requires that the NRC approve the test applicability and any subsequent analysis. This is appropriate because there are no clearly defined protocols for jet impingement testing, and all previous submittals on this type of testing were subject to staff evaluation.

DCD Tier 2, Section 6.3.2.2.7.1, Item 10 prohibits other potential sources of fibrous material, such as ventilation filters or fiber producing fire barrier s, in the insulation ZOI. The staff agrees that this design commitment, in combination with the previously discussed insulation commitments, excludes all potential sources of fibrous debris except latent debris from the ZOI.

3.1.2 Introduction

The WCAP summarize s the AP1000 licensing basis assessment of potential debris sources during design

-basis accidents. DCD Tier 2, Section 6.3.2.2.7.1 documents this assessment and states that, "a LOCA in the AP1000 does not generate fibrous debris due to damage to insulation or other materials included in the AP1000 design." In Section 1, the WCAP states, "This is based on the use of MRI or a suitable equivalent and the elimination of fibrous insulation and other sources of fiber." As stated in the WCAP, the AP1000 plant design includes encapsulated NMI in the reactor cavity that is designed to be a suitable equivalent to MRI. Additionally, the AP1000 plant design includes in-containment electrical cabling that may contain fibrous and other materials (jackets, wrappings, and filler materials) that may be directly impinged upon by a LOCA jet. The WCAP assesses whether the encapsulated NMI contained in neutron shield blocks meet s the definition of a suitable equivalent insulation through a test program that include s jet impingement and submergence testing. Th is test program identifie s the material

-specific performance (i.e., ZOI) of the AP1000 encapsulated NMI when exposed to representative LOCA conditions and assesses the chemical effects because of submergence. The WCAP assesses the potential for cables to become a debris source through a test program that conducted jet impingement testing. The cable test program identifie s the material-specific performance (i.e., ZOI) of the AP1000 plant cables when the cables are exposed to representative LOCA conditions. As noted in the WCAP, the potential for chemical effects due to cables had been addressed previously and is not impacted by the WCAP.

In conjunction with the test program , the WCAP also applies an evaluation methodology described in a guidance report prepared by the Nuclear Energy Institute (NEI).

The guidance report, NEI 04-07 , "PWR Sump Performance Evaluation Methodology," Revision 0, issued December 2004 (Reference

10) was approved by the staff's SE (Reference 11) with conditions and limitations. The WCAP applied an evaluation methodology described in Section 6, "Alternate Evaluation," of NEI 04-07. Specifically, the WCAP defines a debris generation break size for the AP1000 plant. In addition, the WCAP applies more realistic analysis methods when assessing main coolant pipe breaks between the debris generation break size and a double-ended guillotine break (DEGB) of the largest pipe in the reactor coolant system (RCS). As stated in its introduction, the purpose of the WCAP is to obtain NRC approval for the following items:

A ZOI o f four pi pe diameters (4D) applicabl e to A P1000 plant i n-co ntainment c ablingbounded by t esting and analysis pr esented i n this t opical report. The N MI i n t he vessel i nsulati on system (RVIS) lowerneut ronshielding (LNS) and t he water i nlet door s, an d the NMI i n the neutron s hieldblocks of t herefueli ng cavity f loor mod ul e (CA 31) is a suitabl e equivalent t o M RI for thel ocationsbounded by t esting and analysis present ed in this topical r eport.

The use of N EI-0 4-0 7]. . . alternative methodology fordefining debris generation break size for postulated accidents in the AP1000 plant

.NRC Staff Evaluation Th e staff review ed the WCAP in terms o f t he request t o approve a 4 D ZOI for AP1000 in-containment cabling. The staff's review of an industry guidance report (NEI 0 4-07), the associat ed SE , and NUREG/CR-6808, "Knowledge Bas e for t he Effect o f Debris on Pressurized Water Reactor Emergency Core Cooling Sump Performance," (Reference 12) did not reveal any exist in g data on ZOI s associated with cabling.

Section 3.3.3.3 of th i s SE discusses t he staff's acceptance o f an AP1000 in-c ontainment cable ZOI of 4D. Th e staff als o review ed the WCAP i n terms o f t he request t o approve tha t the NMI i n t he RVIS LN S, t he R VIS w ater i nlet doo rs, and the CA31 neutron shield blocks is a suitable equivalent to MRI for the locations boun ded by testing and analysis. The staff's review of NEI 04-07 , t he associat ed SE , and NUREG/CR-6808 did not reveal any existing dat a from testing these types o f components (e.g., neutron shiel d blocks). Sections 3.3.3.4 , and 3.5 of this SE discuss t he staff's acceptance of these items a s suitable equivalent s t o MRI. Finally, t he sta ff reviewed the WC AP i n terms o f t he request t o use t he alternate evaluation methodology as discussed in NEI 04-07 and the associat ed SE. The staff's investigation did not reveal any operating reactor licensee that has ad opt ed the NEI 04-0 7 alternate evaluation methodology.

Section 3.4 of this S E discusses t he staff's acceptance of the use of the alternate evaluati on methodology to determine debris generation break sizes for potential debris sources. 3.2 POTENTIAL SOURCES OF ADDITIONAL DEBRIS (WCAP-17938, SECTION 2) Section 2 of the WCAP is divided into two subsections that describe cables and reactor vessel cavity NMI materials.

3.2.1 Cables In Section 2.1, the WCAP states that the AP1000 plant design includes cabling that a LOCA jet may impinge upon directly. These cables may contain fibrous and other materials (jackets, wrappings, and filler materials) that were not considered in the initial GSI

-191 debris source term evaluation.

To address the cabling issue, jet impingement testing and component characterizations were performed on AP1000 plant cables that may be directly impinged upon by a LOCA jet. The WCAP states that submergence testing of cables was not necessary because submerged cables have been a part of the AP1000 plant design since its inception and have been dispositioned as having negligible chemical effects. The WCAP states that Westinghouse obtained several types of AP1000 plant cable for the jet impingement test program, including l ow-voltage, jacketed, insulated, single-conductor cables; low-voltage, jacketed, multiconductor cables; and medium

-voltage, jacketed power cables. The cables used in the plant jet impingement test program were procured from among the cables produced for in

-containment equipment qualification testing. These cables met all cable material design criteria and specifications for cables used in the AP1000 plant containment.

3.2.2 Reactor Vessel Cavity Non metallic Insulation I n Secti on 2.2, t h e WCAP states that the AP1000 evaluation addressing GSI-191 and GL 2004-02 accounts for zero fibrous LOCA-generated debris from insulation , based on the use of MRI or a suitable equivalent.

The WCAP states that NMI is use d in the AP1000 RVIS and t he CA31 reactor cavity floor structural module neutron shields. Radiation shielding is located in three areas i n t he reactor cavity with two areas c ontaining N MI: the R VIS LNS and the C A 31 module. T he neutron s hield blocks c ontaining N MI ar e. In addition, N MI i s us ed in t hat c ompris e the R VIS w ater inlet door s. The WCAP s tates that a ll NMI in the reactor ca vity is located below t he LOCA f loodup leve l and has the pot ential t o be fully su bmerged. T he neutron shielding located i n t he CA 31 module is in close pr oximity t o t he reactor co olant l oop and piping for t he DVI line. The WCAP identifies t hat the p otential debris f rom t he reactor cavity NMI was not co nsidered i n the licensing basi s si nce only insulation that i s a suitable equivalent t o MRI i s al lowed in the containment.

The WCAP further descr ibes t he l ocation, materials o f co nstruction, and arrangement o f t he nonmetallic m aterials i n t he reactor ca vity (e.g., the RVIS w ater i nlet door s, th e RVI S LNS, and t he CA3 1 neutron s hielding). With r egar d t o potential debris s ources, t he RVIS w ater i nlet doo rs ar e made of . Th e RVI S LNS con sists o f . Th e CA31 ne utron s hield blo cks, i nc luding supplemental s hield blocks, a re . Th ese blocks r educe t he a mount o f radiation streaming upwards i nto c ontainment.

Each CA31 neutron shield block has . NRC Staff Evaluation Th e staff reviewed the descriptiv e informati on about AP1000 plant in-c ontainment cables. The WCAP i ndicates that t he design includes ca bling that may be impacted by a LOCA and that these cables may contain fibrous and other m aterials that m ay impact G SI-1 91 debris so urce term ev aluations.

The WCAP states that ca ble s were not considered i n the i nitial G SI-1 91 debris source t erm. It discusses pe rformi ng jet impingement t esting t o address t he cabling debris so urce term and s tates t hat submergence testing is no t needed. As par t o f the cable review, i t w as not cl ear t o t he staff that t he ca bles selected for testing adequately r epresent all ca bles found within the AP1000 plant.

In a l etter dated May 11, 2016 (Reference 13), the staff issued RAI-ICC&NMI-008, asking the applicant to clarify in the WCAP whether the cables selected for testing bound the plant in

-containment cables. In a response dated July 1 4, 2016 (Reference 14

), the applicant proposed revisions to the WCAP reflecting the fact that the cables tested bound the specifications for cables that will be used in the containment. The staff finds the response acceptable as the applicant clarified that the tested cable s adequately represent AP1000 in-containment cables. Because the tested cables bound the design criteria and specifications for cables used in the containment, the staff finds that the tested cables are an acceptable test article for use in establishing a cable's ZOI. The staff consider s RAI-ICC&NMI-008 to be a closed item , based on a revision to the WCAP. Section 3.3.3.3 of this SE discusses t he staff's review of cable testing. WCAP Section 2.1 states that chemical effects associated with the cable debris are small compared to other sources of chemical effects. The applicant based this on conclusions from a December 2010 letter to the NRC Chairman from the Advisory Committee on Reactor Safeguards (Reference 15), a February 2009 phenomena identification and ranking table (PIRT) evaluation sponsored by the staff (Reference 16), and December 2006 chemical effects testing sponsored by the staff (Reference 17

). In a more recent (March 2011) PIRT report (Reference 18), the staff addressed the potential for chemical effects as a result of the radiolysis of electrical cable insulation. The report concluded that the strong acids generated by radiolysis would be neutralized by the pH 3 buffer in containment. The AP1000 design basis, as modified by the WCAP, uses an approach to chemical effects based on WCAP

-16530-NP-A, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI

-191," issued March 2008 (Reference 19), which the staff found acceptable. Based on the conservative assumptions in this approach, the staff found it unnecessary to consider cable insulation and jacket materials. In addition, the calculation of the required amount of pH buffer in containment includes the acid expected to be generated by the radiolysis of these materials. Therefore, the staff finds that the potential chemical effects from cable insulation and jacket materials have been adequately addressed, and no additional evaluation is necessary in the WCAP. The staff reviewed the descriptive information provided on NMI in the reactor cavity. Because the WCAP indicates that all reactor cavity nonmetallic materials are located below the LOCA floodup level and some are in close proximity to reactor coolant loop and DVI piping, the staff considers that submergence testing and jet impingement testing are the appropriate tests to address debris sources. As part of the WCAP description, the staff expected to see a discussion of NMI testing, comparable to the testing discussion provided for cables.

In a letter dated May 11, 2016, the staff issued RAI-ICC&NMI-009, asking the applicant to include a discussion about NMI testing. In a response dated July 5, 2016 (Reference 20

), the applicant provided a markup of WCAP Section 2.2, in which the applicant stated that suitable equivalency for NMI is achieved through jet impingement testing and submergence testing. The staff find s the response acceptable because the applicant described the NMI tests in the WCAP. The staff consider s RAI-ICC&NMI-009 to be a closed item, based on a revision to the WCAP. Sections 3.3.3 and 3.3.4 of this SE discuss t he staff's review of NMI (e.g., neutron shield blocks) jet impingement and submergence testing, respectively. 3 pH is a scale that tells how acidic or alkaline a substance is.

More acidic solutions have lower pH. More alkaline solutions have higher pH.

3.3 GSI-191 TEST PROGRAM

SUMMARY

(WCAP-17938 , SECTION 3) Section 3 of the WCAP summarizes the tests that were performed to understand the effects of jet impingement and submergence on the reactor cavity NMI and the in

-containment cabling.

These tests include the following: cable jet impingement testing reactor vessel insulation jet impingement testing reactor vessel insulation submergence testingIn addition, Section 3 of the WCAP discusses the confined jet behavior in the AP1000 reactor vessel cavity and the applicability of the results of the free jet impingement testing performed at the National Technical Systems (NTS) facility.

3.3.1 Jet Impingement Test Background Section 3.1 of the WCAP discusses a test program designed to establish the reactor cavity NMI as a suitable equivalent to MRI from a debris production standpoint and to establish a defensible cable ZOI.

For NMI , the WCAP states that testing that bounds the AP1000 plant conditions must be performed in order to show that an insulation type qualifies as a suitable equivalent to MRI. The WCAP elaborates that the only form of testing that could subject the reactor cavity NMI to conditions that bound the AP1000 plant is jet impingement testing performed at bounding conditions. Jet impingement testing focused on the RVIS type blocks, as this was the most limiting at the time of testing. The WCAP indicates that the results of jet impingement testing on test specimens are used to draw conclusions about the behavior of the LNS and the CA31 neutron shield blocks, and water inlet doors.

For cabling in containment, the WCAP discusses that testing is needed to establish a material

-specific ZOI (the zone around a pipe break in which debris is generated for a given material) because no cable ZOI data was discovered in current GSI

-191 documentation. The WCAP discusses the initial development of ZOIs used to resolve GSI

-191 and reflected in NEI 04-07 and the companion staff SE. The WCAP states that to address some of the uncertainties in formulating ZOIs for specific materials (as defined in NEI 04

-07), a group of licensees within the Pressurized

-Water Reactor Owners Group (PWROG) chose to pursue jet impingement testing using subcooled water at pressurized-water reactor (PWR) nominal temperature and pressure conditions.

The WCAP states that the results of the PWROG jet impingement testing, as documented in FAI/11-0497, "PWROG Model for the Two Dimensional Free Expansion of a Flashing, Two

-Phase Critical Flow Jet," Revision 1, issued February 2012 (Reference 21), showed that the test facility was capable of producing a subcooled jet that was representative of the range o f temperatures and pressures associated with a PWR large

-break LOC A. The WCAP states that the approach to qualifying NMI as a suitable equivalent considers acceptance criteria in the AP1000 certified design that allows for some damage to the target materia l. Specifically

-

A suitable equivalent insulation is one that is encapsulated in stainless steel that isseam welded, so that LOCA jet impingement does not damage the insulation andgenerate debris; or, if debris is generated, the resulting debris is not transported tothe containment recirculation screens, to the IRWST screens, or into a DVI or a coldleg LOCA break that becomes submerged during recirculation. It would also have tobe shown that the material used would not generate chemical debris.Similarly, the WCAP

's approach to ZOI development for cables considers acceptance criteria that allows for and accounts for some damage to the cable material. Specifically

- determining incipient damage (the amount of damage that resulted in the generationof a negligible amount of debris) using an approach to measure the amount of debris generated or clearly define a nodamage ZOIThe WCAP describes that, for bo t h the neutron shield block and ca bl e jet impingement test programs , a process w as dev eloped to demons trate that the acceptance criteri a were met.

The p rocess det ermi ned the amount o f m aterial l ost d uring eac h test by . 3.3.2 Jet Impingement Test Facility Section 3.2 o f t he WCAP includes a schematic o f the test facility. T he WCAP states that t he facility use d for jet impingement testing i s capable of simulating the conditions o f a hi gh-energy line break, representative of a cold leg break, within the AP1000 containment.

The thermal

-hydraulic conditions (e.g., pressure, temperature, and flow) wer e selected so that conditions associated with a postulated break i n the primary piping were accurately simulated, and the dat a from the experiment will be directly applicable to and bounding o f the AP1000 plant.

The WCAP states that a co l d leg break provides t he highest potential for damage base d on the thermal hydraulic conditions exhibited by the break, and that the parameters associated with the cold leg break in th e test facility present a limiting break with respect t o t he NMI and cables.

3.3.2.1 Comparison of PWROG Facility wit h AP 1000 Plant Facility Section 3.2.1 of the WCAP contains figures that compare t he PWROG test facility with th e AP1000 plant test facility. T he WCAP states that t he major components o f t he t w o facilities ar e identical from a practical standpoint , and a review of t he components ensure s that t he choke point o f t he facility is a t the n ozzle e xit. The m ajor di fference bet ween the facilities i s t he approach t o . This difference

, an d the associated difference in instrumentation location, ha s the effect of slightly reducing recorded pressure at t he reducer, where the diameter of t he piping changes. 3.3.2.2 Comparison of PWROG Facility D at a with AP1000 Facility Data Section 3.2.2 of the WCAP contains figures (e.g., showing pressure, temperature, and flow versus time) that compare the AP1000 test facility dat a t o t he PWROG test facility dat a. The WCAP co ncludes that these comparisons ensure that the AP1000 test facility reproduce s the sam e conditions and out put as t he PWROG test facility , and that bo t h tests ar e conservative wit h respect t o a full-scale LOCA i n t he AP1000. 3.3.2.3 Comparison of AP1000 Plant Licensing Basis wit h AP 1000 Plant Facility Data Section 3.2.3 of the WCAP compares t he high-pressure subcooled jet generated at the experimental facility t o a LOCA response i n the AP1000 plant.

The WCAP concludes that testing conducted at the facility is conservative wit h respect t o the AP1000 pl ant licensing basi s large-break LOCA. NRC Sta ff Evaluation Th e staff reviewed t he goals of the jet impingement test program as stated in the WCAP-namely, to establish t he NMI in the reactor cavity as suitabl e equivalent insulation and to establish a defensible ZOI for cables. Section 3.1 of t he WCAP states that "the only form of testing that co ul d subject t he reactor cavity non-metallic materials t o conditions t hat bound t he AP1000 plant i s jet impingement testing performed at bounding conditions."

In general, th e staff agrees t hat a demonstration of testing perform ed at bounding conditions with no damage that could lead to debris generation would be necessary to establish NMI as a suitable equivalent. Section 3.3.3.4 of this S E gives t he staff's evaluation of t he jet impingement testing, while Section 3.3.3.5 evaluates the bounding nature o f t he testing. The acceptance criteri a for qualifying NMI as a suitable equivalent, as stated in t he WCAP, i s encapsulated in stainless steel that i s seam welded and allows f o r damage as long a s debris i s no t generated.

T he staff finds this acceptable, a s long as fibrous debris generation is precluded entirely, as t he impact o f fiber in t he AP1000 post-accident environment i s more important than i n traditional GSI-191 analyses because of the assumptions m ade about the low fiber total in the AP 1000 plant. Similarly, the acceptance criteria relat ed to defining the ZO I for cables i n containment use s t he approach defined in NEI 04-07, which requires the applicant to define the ZOI for incipient damage (resulting i n a negligible amount o f debris) and either measure the amount o f debris generated or clearly define a no-damage ZOI.

T he staff finds tha t this approach is appropriate for this particular applicati on as t he applicant has chosen to define a no-damage ZOI. Th e staff reviewed the comparison o f t he test facility as i t w as use d for the jet impingement tests to t he PWROG blowdown test facility.

The t wo series of t ests o ccurred in t he sam e facility , and t he AP1000 tests m odifie d the facility slightly t o . The NRC Office o f Nuclear R egulatory Research r eviewed the PWROG test facility and found it to be designed appropriately and capable of producing conditions representative of a PWR cold-leg brea k.4 Th e staff visited t he facility use d for t he A P 1000 jet impingement testing as part of pre-applicati on interactions with t he applicant (Reference 22). Th e staff found that t he differences between the PWROG facility and the AP1000 blowdown facility would have no impact on t he test results, and that t he AP1000 blowdown facility w as appropriate for producing a jet simulating PWR LOCA conditions. Th e staff reviewed the comparison in the WCAP of the PWROG facility data with the dat a from the AP1000 blowdown facility.

Because the AP10 00 facility targets were not instrumented, the validity of this comparison is important in determining whether t he A P 1000 facility pr oduc ed a jet with representative pressure and mass flow. The staff found that t he two facilities produced 4 "Technical Review of a Two

-Dimensional Free Expansion of a Flashing, Two

-Phase, Critical Flow Jet," April 30, 2012 (ADAMS A c c ession N os. ML121010457 and ML121010493).

practically i dentical pr essure distributions a t the n ozzle exit.

The ups tream pressure r eadings differed s lightly because of the change i n measurement l ocation from

,although t he t wo data s ets a re consistent with one another when taking this c hange intoaccount. The data sets show .Th e staff , therefore , concludes that t he two facilities pr oduce results that are consistent. T heAP1000 blowdown facility target pressures ca n be expect ed to align with those measured forth e PWROG facility , given that the upstream pressure and temperatures are consistent.Th e applicant assert ed in the WCAP that t he test facility i s conservative compared with a large

-break LOCA under actual AP1000 plant conditions. T he staff reviewed the data presented in Section 3.2.3 of t h e WCAP , comparing da t a from t he two test facilities t o the mass flux expected t o result from a LOCA i n the AP1000 based on the licensing ba sis ac cident anal ysis. With the exception of the , t he c onditions pr oduced by t he t est facility bound the conditions resulting from a full-s cale LOCA for t he dur ation of t he bl owdown. In an ef fort t o understand t he i mpact o f L/D , 5 in a letter dated May 11, 2016 (R eference 13), th e staff issu ed RAI-I CC&NMI-0 02 and -0 03. I n a respons e dated J uly 14, 2016 (R eference 14), the appl icant c larified t hat 3.3.3 Jet Impingement Tests 3.3.3.1 Jet Impingement Test Objectives Section 3.

3.1 of the WCAP discusses the jet impingement test objectives for AP1000 cables and the neutron shield blocks. The WCAP states that data and observations collected from the tests and test specimens were used to determine a ZOI for cables and suitable equivalency for encapsulated NMI. 3.3.3.2 Jet Impingement Test Specimens Section 3.3.2 of the WCAP is divided into two subsections that describe the cable specimens and neutron shield block specimens. 5 Test distances are expressed as X = L/D to maintain consistency between the scaled test values and the prototypic plant v alues.

I n Secti on 3.3.2.1, "Cable Specimens,"

the WCAP states that the applicant tested five types of electrical cables. Each cable type was tested with and without aging to bound cable conditions over 60 years of operation. The cable arrangement used in the tests placed the cables in the known jet field for defining the cable material destruction pressure and ZOI.

In Section 3.3.2.2, "Neutron Shield Block Specimens," the WCAP states that three neutron shield block test specimen configurations (i.e., Type s I, II, and III) were subjected to testing.

The WCAP includes figures that show a typical neutron shield block construction and the variations among the three test specimen configurations. 3.3.3.3 Cable Jet Impingement Test Summary Section 3.

3.3 and associated subsections o f t he WCAP summarize the cable jet impingement testing. The WCAP states that t he goal of t he cable jet impingement test i ng wa s to define a ZOI outside of which cables exposed to a LOCA jet d o not contribute t o t he AP1000 plant debris source term.

The cable tests were separated into two groups, large and small, and tested at varying distances from the jet nozzle. Following a successful facility t est (i.e., th e AP1000 test facility pr oduced a j et that bounds t he l icensing basis for the AP1000 plant), c ables were evaluated for any dam age. The damage evaluation was us ed to determin e the c able ZOI. . WCAP Section 3.3.3.5, Table 3-5, "Cable Jet Impingement Test Results," presents t he cabl e test results. T he WCAP states that t he results o f t he cable jet impingement test program show that no damage and no l oss of material w as se en at 4 = L/D. Based on t he results o f the cabl e jet impingement test program, a ZO I of 4 D is applied to t he AP1000 plant i n-containment cables that m ay be directly impinged upon by a LOCA jet. The WCAP also not es that there ar e cables that ca nnot be relocated outside of a 4 D ZOI and that t hese cables are protected by a number of differen t protection schemes. NRC Staff Evaluation Th e staff accepts that the test methodology applied to determine t he destruction pressure o f t he cables represents a viable approach for evaluating cable performance following a postulated accident. The staff evaluated whether the document ed testing in the WCAP met the stated goal to determine an appropriate, technically defensible, realistic ZOI for cables. T he staff's SE for NEI 04-07 notes that "the correlation between any prediction of jet pressure and an experimental observation of damage pressure de pends on how t he measurements w er e taken, how the debris w as characterized, and w hat t he thermodynamic conditions o f t he test actually were." As noted i n Section 3.3.2.3 of this S E , th e staff accepts that the facility use d for t he AP1000 testing is capable of producing relatively representative test conditions, so the primary concer n in quantifyi ng a ZOI for the cables lies in t he experimental observation and debris characterization.

Cables w ere tested at v arying di stances L/D r angi ng from . With one exception, no damage was observed at di stances o f 4 = L/D or greater. Th e damag e from the one t est occurred because of that w ere not r epresentative of pl ant conditions and wer e rectified i n subsequent tests. T he staff witness ed testing as pa rt o f pr e-application activities (R efere nce 22), including t he . Th e staff agreed with t he WCAP's assessment that t he w as l ikely not representative of as-b uilt c able installation, bu t that t he i ssue would need to be c orrected i n future t esting and appropriately di spositioned.

Asi de from the issue , th e staff als o noted that

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temperature conditions for the cables were not necessarily at representative conditions w hen compar ed t o the plant cables. The WCAP notes t hat the primary difference is t he temperature of the cables, and that the cables reach temperatures similar t o those i n the plant within 2-3 seconds o f test initiation.

T he staff recognizes that t he minimal difference in temperature for such a short period is unlikely to impact t he results of the jet impingement testing. During t he course of the review, t he staff was unable to determine i n t he context o f t he WCAP whether restraining the cables in the test w as representative of (or a t least conservative when compared with) t he i n-plant cables. As such, in a letter dated May 11, 2016 (Reference 13), t he staff issued RAI-ICC&NMI-005, asking the applicant t o justify in the WCAP that the testing configuration o f t he c ables i s c onservative.

I n a respons e dated July 14, 2016 (R eference 14), the applicant not ed t hat cables ar e un restrai ned . The s taff a grees that t he facility r estraints w ere needed t o ensur e t he tested cables were exposed t o jet pressure. The applicant revised the WCAP to clarify this, and t he staff finds the updated text acceptable. Therefore, th e staff consider s RAI-ICC&NMI-005 to be a closed item. While the staff found the test facility acceptable for producing a conservative jet with respect t o the AP 1000 (see Section 3.3.3.5 of this SE), test repeatability and verifiability are important i n providing assurance that t he testing w as acceptable, given the lack o f measurement a t the target. Th e staff reviewed data from upstream o f t he jet nozzle, and testi ng for the cables shows t hat the pressur e and temperature v alues ar e i n good a greement, both with each other and with the previous i nstrumented testing c arried out by t he PWROG. In addition, . The staff considers that t he as serti on that "no cables w ere damag ed by t he jet" w hen damage oc curred because of does not ade quately c ommunicat e the issue (WCA P Table 3-5), and, w hil e auditing the test report (R eferenc e 23), f ound that the test ac ceptance criteri a wer e inconsistent w ith the descripti on in t he WCAP. As s uch, in a letter da ted M ay 1 1, 2016 (R eference 13), t he staff i ssued RAI-IC C&NMI-0 04, asking the appl icant t o clarify t he per ceived discrepancy, which appl ies to bot h the cables and the neutron s hiel d blocks. I n a response dated July 14, 2016 (R eference 14), t he appl icant s tat ed that . Ultimately, as t estin g was repeated at 4 = L/D w it h no damage t o t he c ables, the staff views RAI-I CC&NMI-0 04 a s closed. Testing showed . As such, th e staff agree s t hat no deb ris is pr oduced at 4 = L/D. Because of the uncertainties inherent in evaluating the pr ecise pressure at t he target, t he staff agrees with the WCAP's choice of 4 = L/D. At this distance, no damage occurred in successful tests. This i s consistent with the more straightforward option identified by t he staff i n its SE of NEI 0 4-0 7 , to defi ne t he ZOI at a distance wher e no jacketing i s br eached in any w ay. Th e staff does not entirely agree with the s tatement i n the WCAP t hat . The W CAP compares the productio n of debris fines from cables t o that of k-w ool and -1 3 - calcium s ilicate described in the SE for N EI 0 4-0 7 and states that s imilar fractions o f fines production occurr ed for the cables.

Because most c ables , i n comb ination w ith the des ign-b asis requirement o f no additional debr is production i n t he AP1000, th e staff a grees that the use of 4 = L/D i s most app ropriate and finds that th e WCAP r equest of a ZOI of 4 D for c ables i s acceptable. As par t of the review, it w as not clear to the staff that , in the context of t he WCAP, the cables tested bounded all cables located within the AP1000 plant. A s discussed in Section 3.2.2 of this SE, the staff issued RAI-ICC&NMI-008, asking the applicant to clarify i n t h e WCAP the representativ e characteristics of the cables.

In t h e response, t he applicant proposed revisions t o t he WCAP reflecting t he fact that the cables test ed bound t he specifications for those int ended for use i n the AP1000.

Additionally, t he staff notes that t he performance of cables within the ZOI i s outsi de the scope o f t he WCAP's request for staff review and approval (see Section 3.1.2 of this SE). The WCAP indicates that cables within the ZOI would produce debris in the absence of a suitable protective enclosure. Given the importance o f the justification of the unprotected cable ZOI , t he staff considers the suitability of t he protection scheme use d for cables inside the ZO I equally important. Therefore, a licensee that references this WCAP should assess whether the cable protection schemes incorporated into the design prevent t he generation of debris from cables located within the 4 D ZOI , and determine that t he protection schemes, i n and o f themselves, do not introduce potential debris sources. The discussion of limitations and conditions in Section 4.0 o f this S E addresses t hi s topic. 3.3.3.4 Neutron Shield Block Jet Impingement Test Summary Section 3.3.4 and associated subsections of the WCAP summarize the neutron shield block jet impingement testing. The WCAP states that the goal of the jet impingement testing is to assess whether the neutron shield block satisfies the definition of suitable equivalent insulation for the AP1000 plant encapsulated NMI. Following a successful facility test (i.e., AP1000 test facility produced a jet that bounds the licensing basis for the AP1000 plant), neutron shield blocks were evaluated for any damage. Overall, seven tests were conducted on three neutron shield block configurations, with the following results: The Ty p e I neu tron s hield block des ign . The Type II neut r on shiel d block des igned . The Type III neu tron s hield block s howed . In addition, t he Type III n eutron s hield block

. NRC Sta ff Evaluation Th e staff reviewed the jet impingement testing summarized in t he WCAP t o qualify the neutron shield blocks encapsulated NMI as a suitable equivalent t o MRI. The bl ocks w ere tested using three di fferent c onfigurations at v arying di stances. . In order t o qualify t he blocks as a suitable equivalent, t he test pr essure should bound the pressur e the blocks will experience in the plant. Because of the nature o f t he confined jet and t he uncertainty associated with the pressure t he blocks w ill be exposed to (see S ection 3.3.3.5 of t his SE), th e staff felt that t esting performed at w as l ikely t o bou nd the pl ant configuration but that this te st ing was not nec essarily by itself justification of suitable equivalency.

The applicant c onducted addi tional testing at . Th e staff witnessed t he t esting of the blocks

, t he staff conclude s that the te st configuration was a reasonable representation of t he blocks being subject ed to a s ignificantly g reater forc e than would occur i n the pl ant des ign. In the test wit h . Th e staff views this t est as m erely highlighting the r obust n ature o f t he bl ocks. , as discussed i n Section 3.3.

3.5 of t his SE. -1 5 -

As w as the case with cable testing, test repeatability and verifiability are important in providing assurance t hat t he testing was ac ceptable to th e s taff. For t he blocks, no testing on t he Ty pe III blocks w as r epeated, bu t t esting took pl ace at f or all t hree types of bl ocks. Each test showed similar damage profiles t o the bulk metal of the blocks, with the primary difference in the tests being the extent o f the weld damage.

Pressure and temperature data for t hese runs also show r easonable agreement w ith the PWROG d ata and bet ween the t ests t hemselves; thus , the staff agrees w ith t he WCAP's as sertion o f r epeatability when applied to the tests a t . Temperature and pressure dat a for t he te sts at were also consistent

, but i nteractions with th e te s t fixture preclude direct comparison between t he two tests. The WCAP describes t hose tests as measure s of additional assurance that were performed und er substantially more conservative conditions t han the bl ocks i nstalled in the pl ant w ould experience. Based on the discussi on in Secti on 3.3.3.5 o f this SE , staff c onsiders t he testing performed at represents a reasonable approximation of the pressures that would be experienced by the blocks in the actual p lant co nfiguration.

, i t is r easonabl e to assume that t he bl ocks w ill not fail under l oads ex perience d for the limiting break in the cavity region. F urther margin is p resent i n t he testing becaus e the t ested blocks outer e ncapsulation t hickness, w hile blocks i n the plant will use t hicker construction.

F or an add itional m easure o f conservatism, t esting w as per formed at , t he testing de monstrat ed that the bl ocks were robust and could w ithstand su bstantially greater p ressures t han they would be expected to experience. Therefore, the staff finds t hat th e NMI blocks perform as a suitable equivalent for MRI fro m the perspective of debris g eneration when subjected to pressures associat ed with jet i mpingement forces f ro m break distances o f at l east i n the plant co nfiguration.

This finding is based on the co mbination of testing expect ed to be bou nding given the analysis (see Section

3.3.3.5 of this SE) and the performance of t he bl ocks dur ing testing conducted at that is m ore conservative than would be experienced in the as-b uilt desi g n. Finally, t he staff's evaluation of NMI was limited to their qualificati on as performing a s a suitable equivalen t f or MRI only from the perspective of debris generation.

Th e staff did not evaluate other impacts on t he AP1000 plant as a result of the changes i n t he reactor cavity associated with t h e installation of NMI (e.g., neutron shield blocks).

For example, t he staff's evaluation did not assess the shielding or insulation performance of t he neutron shield blocks.

Licensees should ensure that the impacts t o the AP1000 design of structures, systems, and components as a result o f the NMI changes hav e been fully evaluated. Licensees should also assess t he need fo r a license amendment request i n accordance wit h t he requirements o f Section VIII.B.5.b of Appendix D, "Design Certification Rule for the AP 1000 Design," t o 10 CFR Part 52, "Licenses, Certifications, and Approvals f or N uclear Power Plants." The discussion of limitations and conditions in Section 4.0 o f this S E addresses this topic. 3.3.3.5 Considerations Resulting from Confined Jet Behavior The WCAP indicates that t he reactor v esse l cavity i s a more confined space as compar ed to other regions o f containment.

T he jet impingement testing performed at t he NTS facility , as discussed in Section 3.3

.3 of thi s S E , recreated a freely expanding jet. The freely expanding jet was al lowed to expand into an approximately infinite volum e, and there were no discharge volume constraints on the jet behavior. I n WCA P Section 3.3.5 and associat ed subsections, t he applicant discusse d the implications of a jet discharging in a confi ned space and compared the -1 6 -

confi ned jet behavior and characteristics t o that o f t he jet impingement testing at t he NTS facility. Specifically, t he applicant surveyed the open literature (References 3-15, 3-17, 3-18, and 3-19 o f t he WCAP) for confined jet empirical data, related t he da t a t o the AP1000 plant configuration, related the derived confi ned jet considerations to develop a prediction of t he NMI jet i mpingement p ressure in the pl ant, and r elated that prediction to t he NTS t esti ng performed at . Figure 3-66 and Table 3-9 of t he WCAP sh ow key dimensions o f the NMI pertaining to the cold-leg break location and the reactor vessel for assessing confined jet behavior in the AP1000 reactor vessel cavity. Dimension variable D is the co ld-leg pipe diameter.

Dimension variable X' is t he distanc e from t he outer boundary of t he reactor vessel t o t he weld at t he reactor vessel nozzle inlet.

Dimension variable R is the vertical distance from the cold-leg weld at t he reactor vessel inlet nozzle to t he top of t he NMI. The applicant us ed t hese dimensions t o relate the test results contai ned i n the cited open literature to the AP1000 plant geometry. Reference 3-15 of the WCAP is a National Aeronautics and Space Administration technical not e that is based, in part, on a survey o f t he literature on the effect on th e flow fiel d caused by impingement on a flat plate. Reference 3-15 used certain physical parameters to define the characteristics of the jet flow , including dividing the jet flow into distinct regions. Figure 3-64 of the WCAP, taken from its Reference 3

-15 , show s four j et flow regions resulting from a jet impinging on a flat plate. Region I of the j e t flo w field is t he region defi ned as t he jet core and extends from t he nozzl e exit to the apex o f t he potential core. It represents t he region of flow establishment.

Region II is t he region o f establish ed flow in the direction of t he jet bey ond the apex of t he potential jet core. Region III is t he region in which the jet i s deflect ed from the axial direction associated with impingement on t he plate or surface. Region IV is t he wall j et region, where the direct ed flow increases in thickness as t he boundar y layer builds up along the solid surface. This i s a region characterized by boundary layer growth radially from t he stagnation point (wher e t he jet center line impinged on t he surface). In addition, WC AP Reference 3-15 indicates that i t w as confirmed empirically t hat no change i n jet surface characteristics occurred, such that t he jet spreading rate, velocity profile, and pressure distribution wer e not impacted when the plate was sp ac ed greater t han or equal t o two pipe diameters from the jet source. Refer ence 3-17 o f t he WCAP describes an experimental and numerical study to investigate the flow field of a confi ned jet issuing from a nozzle from the lower surface (referred t o as the confinement plate) and impinging normally on the upper surface (referred to as t he impingement plate). Figure 3-67 of th e WCAP i ncludes a si de-by-side comparison o f t h e WCAP Reference 3-17 confined jet facility apparatus t o the AP1000 plant geometry. The comparison shows that the Reference 3-17 test apparatus i s similar t o t he AP1000 plant configuration.

The confinement plate simulates t he reactor cavity wall; t he impingement plat e represents the reactor vessel. The traversing system o f t he testing apparatus allow ed for motion in bot h the axial and radial directions. In this manner, t he jet pressure on the impingement pl at e could be determined based on a range o f confinements (defined as the impingement plate distance t o nozzl e diameter, X'/D) r anging from 0.2 to 6. From T abl e 3-9 of the WCAP, t he A P1000 plant reactor v essel spacing t o cold-l eg diameter i s X'/D o f , s o t he tested r anges enc ompassed t he geometric confinement o f the AP1000 pl ant configuration.

The WCAP states that one observati on from t he Reference 3

-17 testing is that the presence o f t he impingement plate causes t he flow to deflect abou t one jet diameter above the impingement plate. Figure 3-68 of t he WCAP shows the variability in pressure distribution associated with confined jet behavior tak en from the results o f the Reference 3-17 study. Specifically, i t shows t hat the pressure distributi on for t he confinement at X'/D of 1 is very similar t o that o f the confinement at X'/D o f 6 , -1 7 -

which corresponds t o that o f a fr ee jet and indicates t hat a t a value of X'/D o f 1, the jet pressure field is near ly c onverged to that of the f ree jet pressure field.

Therefore, t h e applicant concluded that for the AP1000 pl ant c onfinement r atio of , whic h was encompassed by t he test ranges of Reference 3-1 7 t esting, t he jet pr essure field is anal ogous t o that o f t he free jet. Similar t o WC AP Reference 3-17 discussed abov e, Reference 3-18 o f t he WCAP also investigated t he behavior of a confined jet.

Figure 3-6 9 of t he WCAP shows t he schematic test facility. T he confining plate was mounted on a traversing mechanism that w as used to change the distance between the nozzle exit on the t op confining plate and t he bottom impingement plate. Measurements were performed for jets with nozzle

-to-plate distances of X'/D of 0.25 to 6 diameters.

T he effect o f t he confinement on the flow field was examined usi ng measurements of the static and fluctuating wall pressures i n these jets.

Figure 3-70 of the WCAP shows t he distributions of the static pr essure from t he stagnati on point t o an R/D o f 4 for t he top and t he bottom plates (where R i s the vertical distance from t he centerline to the target). This figure was reproduced from the test results i n WCAP Reference 3-18 for a n unconfined free jet and confi ned jets with various confinement o f X'/D o f l ess t han or equal to 1. The figure shows t hat static pr essure decrease d from t he stagnation point and approaches a tmospheric pressure at R/D o f 1 for t he unconfined jet.

It al so shows t hat confinement ratios o f less t han 1 could potentially result i n a change in the jet behavior s uch t hat free jet analogies m ay no t be applicable.

This l evel o f confinement may result in boundary layer detachment in Region IV (as depicted in Figure 3-64 of the WCAP), which is di fferent t han that o f t he free jet. The A P1000 plant value for an R/D o f for N MI i s denot ed by a vertical r ed line in Figure 3

-70 that is locat ed in a region where the wall pressures for the top and bottom plates ar e analogous t o the unconfined free jet. Furthermore, t he WCAP also state s that for a confinement o f X'/D greater than 1, the effects o f confinement ar e negligible and the wall pressure distributions ar e nearly identical , as substantiated by the Reference 3-17 testing.

Reference 3-19 of the WCAP is a confined jet study that focused on t he static wall pressure distributi on to hel p underst and t he impact o f co nfinement ratio on pressure di stribution. Figure 3-7 2 of t he WCAP shows the experimental setup. It is similar t o t he other t est apparatuses i n that an impingement plate and a confinement plate are attached to a traversing system to allow f o r testing at different X'/D values. A pressur e tap is use d to determi ne the variability of R/D on pressure distribution.

Figure 3-7 3 of t he WCAP shows t he results o f confi ned jet i mpingement t esting (with confinement rati o rangi ng from 0.25 to 4) as c ompared t o the results of f ree jet testing. The A P1000 plant v alue of R/D o f for N MI i s denot ed by t he r ed vertical l ine shown in Figure 3-73. Figure 3-73 shows that at R/D o f 2, t he w all s tatic pressure has converged t o that of the f ree jet r egardless of t he confinement r atio. Th e applicant stated t ha t i t has surveyed the above-referenced open literature to reach t he conclusi on that t he NMI free-je t testing is representative of t he jet behavior even in the confined configuration that exists in the reactor cavity. WC AP Reference 3-15 indicates t hat no change in jet surface cha racteristics occu rred when the plate was spaced greater t han or equal t o 2D (i.e., two pipe diam eters) from t he jet source. WC AP Reference 3-1 7 declared a confinement X'/D greater t han 6 to be analogous t o the free jet, but Reference 3-18 actually performed experiments with and without the confinement plat e to unequivocally asce rtain the difference. Bot h tests s howed that c onfinement r atios greater t han about 1 yiel ded free jet behav ior. Furthermore, for the AP1000 plant v alues o f a confinement r atio of and an R/D value o f , t he c onfined j et be havior i s anal ogous t o t h e fr ee jet; thus, t he results o f t he A P1000 plant free j et testing pe rformed a t t he NT S facility are applicable for as sessing the confi ned jet behavior i n t he reactor vessel ca vity of t he AP1000 plant configuration.

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I n WCAP Section 3.3.5.5, the applicant referenced NUREG/CR-2913 , "Two-Phase Jet Loads," issued January 1983 (Reference 3-16 of t h e WCAP), for assessing the jet impingement pressure at t he A P 1000 NMI. NUREG/CR-2913 was developed to predict t he direct jet impingement on a target resulting from a jet source. Figure 3-79 of the WCAP reproduces Figure A.103 fro m NUREG/CR-2913. Th e applicant used the information i n Figure 3-79 , with the AP1000 plant v al ue of R/D denot ed by t he red dot, along with the NMI dat a included in Table 3-10 of t he WCAP to develop a prediction of the NMI target jet impingement pressure in the AP1000 plant.

Th e applicant stat ed that this target pressure is conservatively assu m ed to be a constant p ressure d istribution along the t op s urface o f t he N MI w ith no radial de gradation.

Moreover, t he applicant used the N TS jet t esting rake dat a for to determine the facility-i nduced pressure distribution on the NMI top s urface and concluded that t he NTS j et impingement t est a t bounded t he pr edicted NMI j et i mpingement pressure i n the AP1000 plant.

In addition, the applicant indicated t h at i n t he case of postulated break, the N MI could possibly experience . Therefore, t he applicant concluded that placing the NMI at th e free jet centerline stagnation point of t he NTS t est facility resulted in a conservative test condition as compar ed to what t he jet would actually experience in the plant configuration.

NRC Staff Evaluation

Th e staff reviewed th e applicant's approach t o assessing the confined jet behavior i n t he reactor vessel cavity of the AP1000 plant.

As described above , t he applicant survey ed the open literature (WCA P References 3-15, 3-17, 3-18, a nd 3-19) for confined jet empirical dat a and relate d that data t o the AP1000 plant configuration.

T he applicant described the respective study or testing performed in each of th e open literature references. T he applicant also include d multiple figures in t he WCAP t o describe the test facility and show t hat t he test apparatus i s similar t o t he AP1000 plant configuration.

T he applicant then described t h e findings related to the effects on confi ned jet behavior for the various confinement tests described in these references. Moreover, t he applicant discussed h ow these results could be used to address t he confined jet behavior for t he AP1000 reactor vessel cavity because the tested ranges encompassed the geometric configuration of the AP 1000 plant wit h respect to jet confinement. Furthermore, t he applicant relat ed these confined jet considerations t o develop a prediction of the NMI j et i mpingement pressure i n the plant and s howed that the pr edicted NMI j et impingement pr essure w ould be bounded by t he NTS facility j et t esting pe rformed at . Based on its review of the information provided i n WCAP Section 3.3.5 and associated subsection s as described above, t he staff determined that i t needed additional information and clarifications for t he issues described below. Th e staff foun d t he applicant's statement on pa ge 3-60 of revision 1 of the WCAP about t he pressure c oefficient t o b e unclear. Text at the t op of t his page states that t he pressure is approximately uni ty f or an AP1000 plant X'/D o f , w hile text at the bottom o f the page s tates that t he pr essure c oefficient i s approximately z er o for an AP10000 plant

. In a letter d ated May 11, 2016 (R eference 13), t he staff issued RAI-I CC&NMI-01 4 , ask ing the appl icant to c larify t he perceiv ed discrepancy.

In a response da t ed July 14 , 2016 (R eference 14), t he applicant indicated that the discrepancy was the r esult o f a typo graphical e rror and s hould be -1 9 -

corrected.

The applicant revised Item 4 on page 3-61 o f the WCAP to state that t he pressure coefficients ar e approximately unity at an H/D of z er o (where H/D is referred to as r/D in Figure 3-68 of the WCAP).

T he staff found t he applicant's WCAP revision acceptable beca use it clarifies the perceived discrepancy.

Th e staff consider s RAI-ICC&NMI-014 to be a closed item. T he applicant stated, on pag e 3-61 of the WCAP , that the testing results in Reference 3-17 of the WCAP indicate that t he flow deflects about a jet diameter above the impingement plat e for an X'/D of less t han 2. The staff found that statement unclear. In a letter dated May 11, 2016 (Reference 13), the staff issued RAI ICC&NMI-01 6 , asking the applicant t o clarify that statement.

In a response dated July 14, 2016 (Reference 14), t he applicant indicated that it would revise t he WCAP to state that the presence o f t he impingement plate causes t he flow t o deflect abou t a jet diameter above the impingement plate. T he staff found t he applicant's revised WCAP statement acceptable because the revised statement clarifies the observation about the results in Reference 3

-17 with regard to flow deflection as a result o f the presence of the impingement plate. Th e staff consider s RAI-ICC&NMI-016 to be a clos ed item. T h e applicant's discussion about the jet flow region that the NMI would experience i n the case of pos tulated br eak was not c lear. As des cribed above, t he applicant s tated that the NMI w ould probably experience . However, i n order t o technically j ustify t he v alidity o f th at c omparison , the applica nt needed t o provi de additional information about the jet regi on for which the NMI would experience jet impingement in the case of a postulated pipe break. In a letter dated May 11, 2016 (Reference 13), t he staff issue d RA I-ICC&NMI-020 , asking the applicant to clarify t he flow regi on for which the NMI would experience jet impingement in the cas e of a postulated pipe break.

In a response dated August 23, 2016 (Reference 25), the applicant stated that an evaluati on was performed to substantiate t he region of the jet impacting the NMI.

Using Equation C-6 i n American National Standards Institute (ANSI)/American N uclear Society (ANS) 58.2-1988, "Design Basis for Protection of Light Water N uclear Power Plants Against t he Effects o f Postulated Pipe Rupture

" (Reference 4-4 of t h e WCAP), t he applicant determine d that the region of t he jet impacting the NM I is outsi de Region I (as depicted i n Figure 3-64 of the WCAP); that is, it is outside the jet core. T he applicant further stated that ANSI/ANS 58.2-1988 may conservatively over predict the asymptotic pl ane and t he jet ar ea , and the jet could experience a Region IV jet instead. The applicant , therefore, concluded that t he use of Figure 3-78 in the WCAP t o predict t he jet velocity and the associated compariso n result is valid. Th e staff found th e applicant's response acceptable because the applicant provided sufficient information to substantiate t he jet flow region t o which the NMI would be subjected in the case o f a postulated break.

Furthermore, the response demonstrated that placing t he NMI at t he jet centerline stagnation point of t he test facility resulted in a conservative test condition as compared t o the conditions th e NMI would actually experience in the plant configuration.

T he applicant revised th e WCAP to include a discussion to this effect a t the beginning o f Section 3.3.5. Th e staff consider s RAI-ICC&NMI-020 to be a close d item. I n summary, t he staff determined that th e applicant provided adequate information to substantiate its c onclusion that , for the AP1000 pl ant v alues o f a confinement r ati o of and an R/D value o f , t he c onfined jet be havior i n the r eactor v essel c avity i s anal ogous to t he free jet. Th us, t he results o f t he AP 1000 plant f ree jet t esting perform ed at t he NTS f acility are applica bl e for assessing the confined jet behavior in the reactor vessel cavity of t he AP1000 -2 0 -

plant configuration.

Specifically, t he WCAP addresses which data were used and where the data cam e from , and it demonstrates t he applicability of the results contained in the tests referenced from t he ope n literature t o the A P1000 plant geometric c onfiguration.

In addition, as descri bed above, t he applicant has s how n that the NTS j et i mpingement test a t bounded the predicted NMI j et impingement pressure i n the AP1000 plant. T he applicant also demonstrated t hat placing the NMI at t he jet centerline stagnation point o f t he NTS test facility resulted in a conservative test condition as compar ed to t he potential je t from t he AP1000 plant configuration.

Therefore, as discussed abov e, the staff finds th e applicant's appr oach t o a ssess the confined jet behavior in the A P 1000 reactor cavity acceptable. 3.3.4 Neutron Shield Block Submergence Test Summary and Objectives Section 3.4 and associated subsections of the WCAP discuss submergence tests to evaluate the potential chemical effects of the materials and design features of the neutron shield blocks.

The tests were designed to determine whether elements were released and chemical precipitates formed from NMI and materials with different levels of encapsulation.

3.3.4.1 Neutron Shield Blocks Submergence Test Summary The WCAP proposes the use of NMI in the RVIS water inlet doors , neutron shield blocks (LNS), and in the CA31 module, each at a different elevation. Since all of these elevations would be submerged following a LOCA, Section 3.4.1 of the WCAP explains that all of the materials in the doors and blocks were tested to understand their individual potential to produce chemical precipitates and potentially contribute to the AP1000 chemical effects analysis. The materials were tested in simulated PWR water with prototypical post

-LOCA temperature, pressure, and pH buffering.

3.3.4.2 Submergence Test Specimens Secti on 3.4.2 of t h e WCAP describes the seven specimens used i n t he submergence testing program and how t hey relate to t he different locations in the RVIS and t he CA31 module. Five of the samples w ere a s ingl e material; four o f these samples had no enc apsulation and one w as encapsulated in stainless s teel w ith an edg e exposed. T he four fully ex posed samples w ere . The s ixth and seventh specimens were simulated shield blocks t hat i ncl uded neutron abs orber material, , en closed in a . These two specimens differed i n that t heyi ncorporated materials from t wo different manufacturers.

On e sample had no foil enc apsulating the internal c omponents (). No specimens represented the proposed design w ith a stainless s teel c ase. Testing a sample would yiel d no information about chemical effects f rom t he internal components.

3.3.4.2.1 Acceptance Criteria The ac ceptance criteri on for each submergence t est w as confirmation that t he t est w as performed ac cording to t he test p rocedure and c onditions.

In this context, m eeting t he acceptance criteri on di d not i nvolve the interpretation of t he meaning or ac ceptability of t h e test results. The applicant c oncluded that t he test c onditions w ere maintai ned as s pecified and, therefore, met t he acceptance criteri on. On that basis, the applicant fou nd the test results valid for evaluation. 3.3.4.2.2 Test Conditions Each sample w as exposed in a separate pressure vessel in a solution representing the AP1000 post-L OCA s um p fluid, i ncluding bo ric ac id, a pH b uffer of trisodium phos phate, and a s pecified temperature and pr essure profile.

Each v essel w as e quipped with . The submergence t est cond ition s w ere specified to bound the design basis accident conditions with additional margin added t o bot h temperature and pressure. In addition to temperature, pressure, and water chemistry, t he mass o f each vessel was monitored to determi ne when flui d woul d be added to maintain its level. 3.3.4.2.3 Sampling P rocedure . T he samples w ere used for c hemicalanalysis and t he detection of c hemical precipitates.

.3.3.4.2.4 Submergence Test R esults . During it s audit (R eference 23), the applicant ex plained the information i n the table.

Th e WCAP notes t hat . . -2 2 -

. 3.3.4.2.5 Impact on C hemical E ffects . Therefore, t he WCAP concludes, chemical effect s do not have t o be considered for t he NMI blocks to meet t he AP 1000 licensing basis that a suitable equivalent t o MRI generates no chemical effects. NRC Staff Evaluation The chemical effects design-basis methodology for the AP1000 is t he staff-approved WCAP-16530-NP-A base model, which calculates t he release o f elements that could contribute to chemical precipitates in containment.

The proposed neutr on shield blocks ar e not a standard material cl ass i n t he WCAP-16530-NP-A methodology, and they contain materials not ev aluated for WCAP-16530-NP-A. Therefore, considering the materials and configurations, the effect o f the neutron shield blocks without intact encapsulation on the AP1000 design-basis chemical debris quantity ca nnot be determined directly by the submergence tests. The applicant use d the submergence test results to obtain soluti on chemistry values that could be entered i nt o the calculation given in WCAP-1 6530-N P-A. The pr ogram al so included a t est des igned t o detect chemical pr ecipitates t hat may . For i ntact s tainless steel enc apsulation, the blocks w ould contribute no c hemical e ffects , given the negligible corrosion of stainless s teel in reactor coolant and bu ffered post-L OCA f luid. Th e staff evaluated the submergence testing wit h respect t o how t he testing was used to prevent t he neut r on shield blocks and water inlet doors from generating chemical effects. Acceptance is base d on one of t he requirements in AP1000 DCD, Section 6.3.2.2.7.1 , for a suitable equivalent t o MRI. This requirement states that "it would also have to be shown that t he material used would not generate chemical debris." Although the submergence testing w as used to quantify the effect o f incomplet e encapsulation in a chemical effects calculation (WCAP Section 5.1.

4), t he testing was used mainly t o show t hat complete encapsulati on was necessary to prevent t he release o f elements that could generate chemical effects. Th e staff did not evaluate the submergence testing methodology as a way to conservatively or realistically determi ne the presence, composition, or quantity o f chemical precipitates.

T he staff considered this unnecessary because the applicant's approach to chemical effects w as t o isolate the neutron shielding and insulati on materials through design. Th e staff determi ned that t he s ubmergence t est specimens w ere representative of the m aterials to be us ed in t he pl ant d esign. The test s pecimens i ncluded -2 3 -

). However, i n a letter da t ed May 11, 2016 (Reference 13), t he staff issued RAI-ICC&NMI-029 , asking the applicant to clarify the type of NMI used i n the neutron absorber blocks, water inlet door s, submergence testing, and the WCAP-16530-NP-A chemical effects analysis. I n a response dated July 14, 2016 (R eference 14), t he appl icant s tat ed that w as us ed in the submergence t esting and was the material specified f or t he neutron absorber bl ocks and w ater i nlet doo rs. T he staff finds t his ac ceptable because the r esponse c larifies t hat the insulation material us ed i n the submergence t esting is t he s ame material us ed in the plant des ign. Th e response also s tated t hat Temp-M at i nsulation was us ed in a WCAP-1 6530-N P-A anal ysis instead of M icrotherm, as discuss ed further i n the ev aluation of WCAP Section 5.1.4 (S ection 3.5.1.4 of t his SE). Based on t he di scussion abov e, t he s taff considers R AI I CC&NMI-0 29 to be a closed item. In a l etter da ted May 11, 2016 (R eference 13), the staff issued RAI-I CC&NMI-0 30 , a sking the applicant t o expla in how t he test c onditions w ere "limiting" w ith respect to post-L OCA c onditions.

In its r esponse dated July 5, 2016 (R eference 20), the applicant ex plained that t he t esting temperature, pr essure, a nd water chemistry r anges w ere selected t o pr omote hi gher rates o f corrosi on and dissolution t han c ompared t o pl ant conditions following a design-b asis-a ccident LOCA. Th e t est temperature and pressure w ere equivalent t o t he equipment qualification

requirements, which ar e higher t han t he c ontainment pressure and t emperature responses

given in AP 1000 DCD Section 6.2 , "Containment S ystems." The w ater c hemistry (boron and pH) w as m eant t o represent pl ant c onditions.

The response al so proposed corresponding

changes t o WCAP Section 3.

4.2.2 t o r eflect t he e xplanation.

T he staff finds t his ex planation acceptable because it c larifies that t he t esting w as des ig ned to produce higher c hemical r elease rates t han pr ototypical c onditions.

T he staff di d not v erify t he t emperature and pH dependence of t he releas e rates f or all of t he tested materials as the t ests r esults s howed that el ements w ere released into s olution if t he encap su lations are n ot s ealed. T he staff notes t hat i n the t ests us ed to develop the methodology i n WCAP-1 6530-N P-A , higher t emperature c aused higher release rates for microporous i nsulation and aluminum a t constant pH. The appl icant revised t he WCAP as s hown in the r esponse; therefore, the staff considers R AI-I CC&NMI-0 30 to be a closed item. Th e staff did not ev aluate the c apability of t he chemical anal yses and filtering tests t o characterize the chemistry o f the solutio ns or t he ability to detect chemical pr ecipitates.

Some of t he results des cribed in the WCAP were unexpected.

For ex ample, ac cording to WCAP Table 3-1 2, . Th e methodology i n WCAP-1 6530-N P-A, w hich is t he des ign basis for t he AP1000, would likely pr edict more pr ecipitates from this s ampl e t han fro m any ot her because it con servatively as sumes that aluminum i s c ompletely i nsoluble and therefore, will f orm a precipitate t hat c auses h ead loss. . Th e staff considered a more detailed level of r eview of t he test results and interpretations to be unnecessary because the applic ant des igned t he neutron s hield blocks an d inlet door s to isolate t he internal m aterials f rom t he external environment.

From t hat pe rspective, t he staff found t hat the information about s ubmergence t esting i n S ection 3.4 of t he WCAP is acceptable because it describes t he testing and r esults i n sufficient de tail t o determi ne that w ithout i ntact -2 4 - encapsulation, t he materials in the neutron shiel d blocks m ay introduce elements into solution that contribute t o chemical effects. Th e staff determi ned that i t needed additional i nformation to clarify or c orrect the interpretation of r esults. Specifically, t he staff had difficulty und erstanding . In a l etter dated May 11, 2016 (Reference 13), t he staff issued RAI-I CC&NMI-0 31 , asking t h e applicant t o clarify how . I n a response dat ed August 23, 2016 (R eference 25), the applicant indicated that . The s taff finds t h e response acceptabl e because i t clarifies t he appl icant's interpretation of the results i n t he WCAP. The applicant revised the WCAP as shown in the response; t herefore, t he staff c onsiders R AI-I CC&NMI-0 31 to be a closed i tem. The r espo nse to RA I-I CC&NMI-0 31 considers . In a letter dated May 11, 2016 (Reference 13), the staff issued RAI-ICC&NMI-032 , asking for clarification about a reference (WCA P Reference 3

-29) that i s included in the reference list i n WCAP Section 3.

6 but i s not discussed in t he text. I n a response dated July 5, 2016 (Reference 20), t he applicant stat ed that t he reference was not use d in the WCAP and would be deleted. The applicant deleted the unuse d document reference in Rev. 2 of t h e WCAP; therefore, t he staff considers RAI-ICC&NMI-032 to be a closed item. 3.3.5 Characterization of CA31 Neutron Shielding Material Secti on 3.5 of the WCAP and associat ed subsections describe the C A 31 neutron s hielding material, w hich is ." Section 3.5 ex plains t hat . 3.3.5.1 Impact o f C A31 Neutron Shielding M aterial on C hemical E ffects Section 3.5.

1 states that no chemical e ffects ar e e xpect ed from i n the RVIS and CA31 components.

This i s bas ed on the construction of the shield blocks ( ) preventing contact o f the w ith the p ost-L OCA fluid, and on the b eing considered non

-reactive in the expected environment. 3.3.5.2 Impact on C ontainment R ecirculation Screens Section 3.5.2 describes the reasoning that no transport of the is expected for this design. This section begins with a s ummary of the screen design for the PXS, which includes screens, r ecirculation screens, trash racks, and d ebris c urbs. The t ransport analysis c onsiders the location o f . This section also addr esses t he po tential for transport o f par ticles (assum ed to be r eleased from t he encapsulation) by describing Westinghous e settlement t esti ng of performed for t he WCAP, and pr evious N RC-sp onsored t esting of d ebris transport al ong a floor. The pr evious testing i s doc umented in NURE G/CR-68 08. The WCAP des cribes t he flow velocities i dentified in NURE G/CR-68 08 for moving the debris al ong t he floor and for lifting the debris ov er obstructions.

T he Westinghouse s ettling tests c oncluded that

. NRC Staff Evaluation The WCAP p roposes using in t he CA 31 module neutron s hield blocks bec ause of i ts thermal s tability and neutron shielding capability.

The m aterial i s bei ng specified ac cording to an ASTM s tandar d that d efines phy sical and chemical r equirements for i n various nuclear appl ications. It h as been used in applications s uch as . The hi gh t hermal s tability m akes i t s uitabl e for us e as a is w e ll within it s range of stability.

The av erage par ticle diameter o f . During audi t interactions (Ref erenc e 26), t he applicant pr oposed changing the av erage pa rticle diameter from a s ingle number t o t he rang e detailed in the procurement s pecification.

The staff finds the proposed changes (Referenc e 27) ac ceptable because they a re consistent w ith procurement specifications and t he s taff considers the propos ed changes t o be a confirmatory i tem , pe nding an updat e t o t he WCAP. A g oal o f t he des ign is to pr event deb ris generation and transport, p rimarily w ith . The staff determi ned from a r egulatory audi t (Re ference 26) that was subject ed t o jet i mpingement testing, as di scussed in Secti on 3.3.3.4 of t his SE. Therefore, t he characterization of the C A31 modul e neutron s hielding m aterial des cribed in Section 3.5 of the WCAP appl ies m ainly t o an unexpect ed failure of the shield blocks t o contain the shielding

material i n a LOCA, as w ell as t o c hemical reactivity i n t he normal oper ating environment.

-2 6 -

The s taff considered pot ential c hemical e ffects from t he unde r no rmal oper ating conditions and in the anticipated po st-L OCA env ironment. Research conducted on under c onditions lik e the operating c onditions for t he shield blocks (hot and humid air) indicates . Therefore, the staff finds i t ac ceptable to neglect any effect o f n ormal ope ration on the chemical e ffects anal ysis. If the g ets out o f t he box i n a LOCA, no chemical e ffects ar e ex pect ed because of

. Wit h respect to settling a nd transport o f , t he WCAP co ncludes that , t he s taff finds i t reasonable to postulate t hat most o f the w ould settle i n the reactor c avity. However, s inc e material releas ed from the blocks c ould settle i n the r eactor c avity, noz zle gallery, or a s team generator compartment, the staff evaluated the potential t ransport.

The s taff c ompare d material size, dens ity, and flow velocity t o the NRC reports on coating debris t ransport. NUREG/CR-6 916 doc uments transport t esting o f c oating chips w ith density i n the rang e 1.15 g/cm 3 (0.042 lb/in

3) t o 2.5 g/cm 3 (0.09 lb/in 3), and t hree size ranges bet ween 0.4 m m (0.016 inches) and 50.8 m m (2.00 inches). The dens ity o f 2.5 g/cm 3 (0.09 lb/in 3), corresponding to an epoxy/inorganic z inc coating system, i s appr oximately t he same as T he WCAP s tates that for t he A P1000, -2 7 - . The s taff's c onsiderati on of the CA31 neutron s hielding m aterial des cribed i n WCAP S ection 3.5 indi cate th at if p articles get out o f the shield blocks , they w ill s ettle and not transport t o t he screen or generate c hemical e ffects. The staff finds t hat this p rovides addi tional c onservatism i n meeting the des ign of a suitable equivalent i nsulation. 3.4 DEBRIS GENERATION BREAK SIZE DETERMINATION (WCAP-17938, SECTION 4) Section 4 of the WCAP discusses documents (WCAP References 4-1 and 4-2) that provide guidance for resolving GSI

-191. In particular, these documents provide an alternate evaluation methodology that may be used to demonstrate acceptable containment sump performance. The WCAP indicates that the alternate evaluation methodology allows for an alternate design

-basis break size in conjunction with the baseline methodology for the RCS and attached piping. It also allows for the use of realistic analysis assumptions and credit for nonsafety systems and operator actions when evaluating up to a full DEGB of the RCS main loop piping.

The WCAP states that the alternate evaluation methodology consists of three main components: debris generation break size, Region I analysis, and Region II analysis. The WCAP discusses each of these components and their application to the AP1000 plant as described below. 3.4.1 Debris Generation Break Size Section 4.1 of the WCAP defines the debris generation break size s as follows: For all ASME Code Class 1 auxiliary piping (attached to the AP1000 plant RCS main loop piping) up to and including a DEGB of any of these lines, the GSI

-191 design

-basisrules apply

.For breaks in the AP1000 plant RCS main loop piping (hot leg and cold leg piping) up toa size of equivalent break diameter to that of a 14

-inch (35.56 cm) Schedule 160 pipe(approximately 11.188 inches (28.418 cm)), the GSI-191 design

-basis rules apply(applicable to Region I).For breaks in the AP1000 plant RCS main loop piping (hot leg and cold leg piping) withequivalent diameter greater than that of a 14

-inch (35.56 cm) Schedule 160 pipe(approximately 11.188 inches (28.418 cm)) and up to the DEGB, mitigative capabilitymust be demonstrated, but GSI

-191 design-basis rules may not necessarily apply(applicable to Region II).The WCAP states that the AP1000 plant RCS piping is fabricated of forged seamless stainless steel without longitudinal or electroslag welds or cast fittings. In addition, the piping complies

-2 9 - with the requirements of the ASME Code,Section II (Parts A and C),Section III, and Section IX, and adheres to the requirements of Regulatory Guide 1.44, "Control of the Processing and Use of Stainless Steel," issued March 2011 (Reference 31), for the use of Series 300 stainless steel materials. The WCAP claims that these fabrication techniques minimize the risk of primary water stress

-corrosion cracking failure throughout the RCS piping system. The WCAP states that the staff found the pipe break spectrum listed above for evaluating debris generation to be acceptable (Reference 11) and that licensees could use the debris generation break size for distinguishing between Region I and Region II analyses when using the alternate evaluation methodology. The WCAP states that these conclusions are applicable to the AP1000 plant RCS loop piping and the associated RCS main loop branch piping.

NRC Staff Evaluation

The staff reviewed the debris generation break size discussion as described in the WCAP.

Because the approach (pipe break spectrum listed above) discussed in the WCAP is consistent with an approach previously reviewed and approved by the staff (Reference 11), the staff finds the WCAP approach to debris generation break size acceptable.

In addition, although the WCAP mentions that the alternate evaluation methodology allows for the use of nonsafety structures, systems, or components or operator actions when evaluating up to a full DEGB of the RCS main loop piping, the WCAP does not propose to credit the use of nonsafety systems or operator actions when evaluating up to a full DEGB of the RCS main loop piping. As such, the staff's review d oes not include credit for nonsafety systems or operator actions when evaluating up to a full DEGB of the primary system piping. If a licensee or applicant seeks to credit operator actions or nonsafety systems to demonstrate mitigative capability for postulated pipe breaks consistent with the alternate evaluation methodology, then the staff would need additional information in order to reach a conclusion on the acceptability of the applicant's approach. Therefore, Section 4.0 of this SE includes a limitation and condition to clarify that th e staff's review of the acceptability of the alternate evaluation methodology for the AP1000 design excludes the use of nonsafety systems and operator actions.

Furthermore, in a letter dated May 1 1, 2016 (Reference 13), the staff issued RAI-ICC&NMI-033, asking the applicant to confirm the description of the RCS piping and how these features were used in determining the debris generation break size. In a letter dated July 5, 2016 (Reference 20), the applicant clarified that the WCAP describe s the piping features to indicate a low failure susceptibility of the RCS piping, and that the alternate evaluation methodology did not consider these features for determining the debris generation break size. The response also proposed a corresponding revision to the WCAP stating that the break size determination did not credit the RCS piping features. The proposed WCAP revision also correct s a statement that the piping has no dissimilar welds, replacing it with a statement that there are no cast fittings or Alloy 600 weld metals. The staff finds this acceptable because the revised description of the RCS piping is consistent with that in the AP1000 DCD, Revision 19, and the applicant did not credit these RCS piping features in determining the debris generation break size. Therefore, the staff considers RAI

-ICC&NMI-033 to be a closed item , based on the WCAP revision. 3.4.2 Region I Analysis Section 4.2 of the WCAP describes the Region I analysis as an evaluation of the RCS main loop piping and every branch line connected to the RCS main loop piping. For the Region I analysis,

-3 0 - all lines are evaluated for debris generation and transport using the baseline methods defined in NEI 04-07 and as modified by the SE on NEI 04

-07. The Region I analysis includes an evaluation of all break sizes up to and including the debris generation break size (i.e., 14-inch pipe (35.56 cm)) of the main loop piping. A DEGB of the main loop branch piping is assumed, as described in WCAP Section 4.1.

The WCAP states that while the SE for NEI 04-07 allows for the use of a volume

-equivalent ZOI radius for the calculation of the ZOI volume, this method is not employed for the AP1000 analyses. The ZOI radius proposed in WCAP Section 3 (i.e., cables and neutron shielding) is based on jet impingement testing with the target material placed on the jet centerline. The ZOI radius for the material as determined from testing is equal to the centerline distance from the break location to the target at which the material did not fail.

WCAP Table 4

-1 compares the volume

-equivalent spherical ZOI approach to the WCAP

's approach to ZOI. The results in WCAP Table 4-1 illustrate that the volume

-equivalent spherical ZOI radii are bounded by spherical radii that use the centerline target distance determined from jet impingement testing. The WCAP concludes that the approach taken for calculating the ZOI dimensions for the AP1000 plant is conservative since the proposed WCAP ZOI is based on centerline target distance rather than the volume

-equivalent model.

NRC Staff Evaluation

The staff reviewed the Region I analysis as described in WCAP Section 4.2. The staff finds the WCAP approach to Region I analysis is acceptable because the approach is consistent with the Region I approach in NEI 04-07 as previously reviewed and approved by the staff's SE (Reference 11), with the exception of the calculation of ZOI for NMI and cables. For the calculation of ZOI for NMI and cables, WCAP Section 4.2 discusses two models. The first model is the approved spherical model defined by NEI 04-07 (i.e., volume-equivalent). The second model is a spherical model with a defined radius equal to the centerline distance from the break location to the target material at which the material did not fail. The WCAP employs the second m odel for assessing NMI and cables. The WCAP also states that the spherical model from NEI 04

-07 is not employed for the AP1000 plant analysis. The statement that "this method [the NEI 04-07 spherical model] is not employed for the AP1000 plant analyses" pertains only to NMI and cable materials. The ZOI radii for the materials discussed in the WCAP (i.e., cable and NMI) are based on the centerline distance from the break location to the target at which the material did not fail (see Section 3.3.3 and associated subsections of this SE). As shown in WCAP Table 4-1, the WCAP ZOI approach increases the resultant ZOI as compared to the NEI 04

-07 approved approach. The staff finds the WCAP approach to ZOI is acceptable due to the increase in ZOI (greater volume about the break in which the fluid escaping from the break has sufficient energy to generate debris) when compared to the ZOI model approved by the staff in the review of NEI 04-07. 3.4.3 Region II Analysis Section 4.3 of the WCAP describes the Region II analysis. The Region II analysis includes evaluations of break sizes in the RCS main loop piping (hot and cold) greater than the debris generation break size defined in the Region I analysis and up to the DEGB of the largest pipe in

-3 1 - the RCS. The WCAP states that the Region II analysis only considers the RCS main loop piping because all primary

-side attached auxiliary piping is fully addressed as part of the Region I analysis.

The WCAP states that the Region II analysis is performed in the same manner and with the same methods used in the baseline analyses with respect to ZOI models and assumptions. However, the Region II analysis allows for more realistic analytical methods and assumptions such as limited pipe displacement. Crediting limited pipe displacement requires the application of results from pipe break analyses that may be used to limit the maximum break size to be evaluated. The WCAP proposes that if analyses show that limited (main coolant) pip e displacement (i.e., a limited separation break) will occur, then an equivalent break diameter for the limited separation break may be used to determine the ZOI for the Region II analyses.

NRC Staff Evaluation

The staff reviewed the WCAP's approach to the Region II analysis. The WCAP approach is to credit limited pipe displacement in the Region II analysis. Credit for limited pipe displacement is consistent with the provisions of the Region II analysis in NEI 04-07 previously reviewed and approved by the staff (Reference 11) and is therefore acceptable. Sections 3.4.3.1 and 3.4.3.2 of this SE provide t he staff's review and evaluation of the WCAP

's approach to and definition s for limited pipe displacement. The WCAP description of the Region II analysis allows for crediting operator actions. In a letter dated May 11, 2016 (Reference 13), the staff issued RAI ICC&NMI

-0 22, asking the applicant to explain assumptions which may be employed in the analysis. In a response to RAI-ICC&NMI-022 dated August 23, 2016 (Reference 25), the applicant included a markup to the WCAP clarifying that no credit was taken for better estimate assumptions or operator actions as part of the Region II analysis. The staff finds this revision to the WCAP acceptable because it clarifie s the applicant's position on the credit taken for operator actions in the Region II analysis. Therefore, the staff considers RAI-ICC&NMI-022 to be a closed item. 3.4.3.1 Full Separation Break Section 4.3.1 of the WCAP describes the methodology for determining the ZOI for a full separation break used in the Region II analysis. It states that if a pipe displacement or structural analysis is not performed, or if the analysis results in a break with lateral pipe displacement greater than 1 diameter and axial displacement greater than 0.5 diameter, then a full separation DEGB of the RCS main loop piping must be assumed. The radius of the spherical ZOI used in a Region II analysis is defined using the inner diameter of the RCS main loop piping multiplied by a scaling factor determined for the specific material to be evaluated.

The spherical ZOI is modeled with the defined radius applied to the axial centerline of the pipe.

NRC Staff Evaluation

The staff reviewed the applicant's methodology for determining the ZOI for a full separation break used in the Region II analysis. The staff finds the applicant's methodology acceptable because it is consistent with the provisions of the Region II analysis for assessing full separation break in NEI 04-07 previously reviewed and approved by the staff (Reference 11).

-3 2 - 3.4.3.2 Limited Separation Breaks Section 4.3.2 and the associated subsections of the WCAP describe the methodology for determining the ZOI for limited separation break used in the Region II analysis. The WCAP states that if a structural or pipe displacement analysis results in a lateral displacement of less than one diameter and an axial displacement of less than or equal to 0.5 diameter, then the Region II analysis may use a limited separation break in determining the alternate break size. The WCAP states that one of the key parameters of the circumferential break with limited separation is the value of the axial displacement. Similar to the inner diameter of the pipe for a full separation break, the axial displacement acts as the characteristic length for the simplified expanding jet model included in Appendix C to ANSI/ANS 58.2

-1988 (Reference 4

-4 of the WCAP). WCAP Sections 4.3.2.1 and 4.3.2.2 describe the equations for determining the equivalent diameter for a limited separation break with lateral displacement of less than or equal to the pipe wall thickness, as well as a limited separation break with lateral displacement greater than the pipe wall thickness and less than 1 diameter. For a limited separation break with lateral displacement of less than or equal to the pipe wall thickness, the equivalent diameter is defined by the axial displacement. For a limited separation break with lateral displacement greater than the pipe wall thickness and less than 1 diameter, both the axial and lateral displacements are considered in the equivalent break diameter. The applicant stated that for those cases in which the method in WCAP Section 4.3.2.2 results in an equivalent diameter larger than the pipe diameter, the pipe diameter is to be used to calculate the radius of the spherical ZOI. Moreover, the equivalent diameter multiplied by a scaling factor determined for the specific material to be evaluated is used in determining the spherical ZOI used in the Region II analysis for the AP1000 plant. NRC Staff Evaluation The staff reviewed the applicant's methodology for determining the ZOI for limited separation break used in the Region II analysis. The staff found that the method used by the applicant to define the break size is conservative compared to the method presented in ANSI/ANS 58.2-1988 for limited separation breaks, as discussed in Section 4.3.2 of the WCAP.

Whereas the ANSI/ANS 58.2

-1988 methodology defines a limited separation break as having an axial displacement of less than or equal to 0.5 diameter and a lateral displacement of less than or equal to the pipe wall thickness, the applicant's approach extends the ANSI/ANS 58.2-1988 methodology to include an axial displacement of less than or equal to 0.5 diameter and a lateral displacement greater than the pipe wall thickness and up to 1 pipe inner diameter. Using this extended method, the equivalent diameter of such a limited separation break is more conservative because both the axial and lateral displacements are considered in the equivalent break diameter, which yield s a larger ZOI volume for the limited separation break in the Region II analysis. Therefore, the staff found the applicant's methodology as described in WCAP Section 4.3.2 acceptable because the methodology conservatively determines the ZOI for limited separation break in the Region II analysis, as described above.

-3 3 - 3.4.4 Reactor Coolant System Main Loop Piping Displacement Analysis 3.4.4.1 Analysis Overview Section 4.4 and associated subsections of the WCAP provide information related to the RCS main loop piping displacement analysis performed by the applicant in support of the Region II analyses. The applicant stated that a structural evaluation of the AP1000 RCS main loop piping was performed using ANSYS LS

-DYNA to evaluate pipe whip and displacement in the RCS main loop piping. This analysis, documented in APP

-PL01-P0C-003 (Reference 4

-7 of the WCAP), used finite element models run on ANSYS LS-DYNA to demonstrate that the hot legs and cold legs do not fully separate as a result of a LOCA. The LOCA pipe reaction forces assumed for each DEGB scenario were calculated in APP

-PL01-P0C-002 (Reference 4

-6 of the WCAP). The applicant stated that five break scenarios shown in Figure 4

-3 of the WCAP were analyzed. The applicant also discussed how the five postulated break scenarios and locations were strategically chosen to bound breaks at all locations along the hot

-leg and cold

-leg piping. In addition, Figures 4-4, 4-5, 4-6, and 4-7 of the WCAP show the respective thrust force vectors and the associated moment arms for each of the postulated break scenarios. Table 4-3 of the WCAP gives the results of these pipe displacement analyses.

NRC Staff Evaluation

The staff reviewed the applicant's RCS main loop piping displacement analyses described above. To support the review of the applicant's piping displacement analyses, the staff conducted an audit (Reference 23) of the applicant's RCS main loop piping displacement analyses. Two key documents included in this audit, which took place March 16-17, 2016, were two non

-docketed Westinghouse calculation notes (References 4

-6 and 4-7 of the WCAP).

WCAP Reference 4

-6 document s Westinghouse's methodology for calculating the pipe reaction forces for the AP1000 loop piping resulting from a DEGB of the hot

-leg and cold

-leg loop piping.

The calculation s of the pipe reaction forces were then provided as inputs to a nonlinear structural analysis described in Reference 4

-7 of the WCAP to mechanistically determine the magnitude of the pipe displacement that would occur as a result of a DEGB of AP1000 RCS loop piping. Reference 4

-7 of the WCAP presents the methodologies and results for determining the pipe movement for five postulated RCS DEGBs as identified in Section 4.3 of the WCAP. Based on its review of the information provided in Section 4.4.1 and References 4

-6 and 4-7 of the WCAP, the staff found that the applicant's RCS main loop piping displacement analyses are acceptable because the applicant's analysis strategies and methodologies are consistent with the pertinent engineering practices for determin ing the potential pipe displacement and are technically justified. Specifically, the applicant properly determined the force vector and the associated length of moment arm for the respective postulated break locations. The applicant then calculated the resultant moment by taking the product of the force vector and the moment arm and generated the associated potential pipe displacement for the respective postulated break locations. In addition, the applicant has provided sufficient information to substantiate its conclusion that the five postulated break scenarios and locations chosen are representative and bound breaks at all locations along the hot

-leg and cold

-leg piping.

-3 4 - 3.4.4.2 Pipe Displacement Results Table 4-3 in Section 4.4.2 of the WCAP gives the results of the hot

-leg and cold

-leg pipe displacement analyses for the five break locations of the AP1000 RCS main loop piping described in Reference 4

-7 of the WCAP.

NRC Staff Evaluation

The staff reviewed the results of the hot

-leg and cold

-leg pipe displacement analyses presented in Table 4-3 of the WCAP. The staff finds these results acceptable because the y are consistent with those shown in Reference 4

-7 of the WCAP, which the staff assessed during the March 16-17, 2016 audit (Reference 23) and found it acceptable as discussed in Section 3.4.4.1 of this SE. 3.4.4.3 Application of Results to Region II Analyses Section 4.4.3 and the associated subsections of the WCAP describe how the results of the piping displacement presented in Table 4-3 of the WCAP were used to support the AP1000 plant Region II analyses. The applicant stated that, following the methodology described in WCAP Section 4.3, the equivalent break diameter was determined for each of the five DEGB scenarios and was compared to the 14-inch (35.56 cm) Schedule 160 break size already used as the basis for the Region I analysis. To ensure the validity and conservatism of the use of a spherical ZOI model based on a 14

-inch (35.56 cm) Schedule 160 break diameter, the representative geometry of each limited separation break was also determined. The geometries of the limited separation breaks were determined using anticipated operating and boundary conditions during the AP1000 plant LOCA transient and compared to the geometry of a fully separated DEGB. The applicant stated that this comparison relied on the staff's SE to NEI 04-07 (Reference 4-2 of the WCAP) in conjunction with the expanding jet models provided in Appendix C to ANSI/ANS 58.2

-1988. Moreover, the applicant indicated that a simplified volumetric comparison was proposed as a qualitative method of comparing the circumferential break jet expansion geometries with limited separation to the full separation DEGB jet expansion geometry. Appendix C to ANSI/ANS 58.2

-1988 describes two regions of a jet that will occur following a LOCA. Using the methodology described in the WCAP, the Region 1 and 2 volume s (as shown in Figure (A) of Figure 4-8) of the expanding jet for each of the five limited separation break scenario s were compared to the volume s of Region 1 and 2 (as shown in Figure (B) of Figure 4-8) of the expanding jet for both ends of a DEGB with full separation for a 14

-inch (35.56 cm)

Schedule 160 pipe. This method was chosen as a simplified alternative to the calculation and comparison of jet isobars using the circumferential limited separation jet model and the full separation jet model. WCAP Sections 4.4.3.1 and 4.4.3.2 discuss the results of the equivalent break diameter calculations and expanding jet geometry comparisons.

NRC Staff Evaluation

The staff reviewed the applicant's approach for applying the results of piping displacement presented in Table 4-3 of the WCAP to support the AP1000 plant Region II analyses as described above. The staff found that the applicant's approach followed the staff SE on NEI 04-07 and the expanding jet models in Appendix C to ANSI/ANS 58.2

-1988 in its comparison of the spherical ZOI model based on a 14

-inch (35.56 cm) Schedule 160 break size to the representative geometry of each limited separation break. Therefore, the applicant's approach is acceptable.

3.4.4.3.1 Hot-Leg Break Evaluations 3.4.4.3.1.1 Hot-Leg Double-Ended Guillotine Break at t he Reactor Vessel Nozzle Section 4.4.3.1.1 of the WCAP discusse s the evaluation of a hot-leg DEGB a t t he reactor vessel nozzle. Table 4-3 of the WCAP shows t hat the hot-l eg br eak at th e r eactor vessel noz zle resulted in an axial displacement o f . T he applicant then concluded that a spherical ZO I based on the w ould also conservatively bound this l imited separation break o f t he hot-l eg b reak a t the reactor v essel nozzle. Giv en that the ZO I for a fully s eparated br eak o f a , t he applicant concluded that the Region I anal ysis bounds the R egion II analysis m odeling a hot-l eg DE GB at the reactor v essel noz zle. NRC Sta ff Evaluation Th e staff reviewed the applicant's evaluation of h ot-leg DEGB at t he reactor vessel nozzle as described above.

T he staff finds th e applicant's evaluation and the conclusion acceptable because the evaluati on followed the methodology described in Section 4.4.3 of the WCAP , which t he staff found acceptable as described i n Section 3.4.4.3 o f this SE. Consequently, t he applicant has ade quately s ubstantiated i t s conclusi on that t he Region I an alysis bounds t he Regi on II anal ysis m odeling . 3.4.4.3.1.

2 Hot-Leg Double-Ended Guillotine Break at the Steam Generator Section 4.4.3.1.2 of the WCAP discusse s the evaluation of a hot-leg DEGB a t the steam generator.

Table 4-3 of the WCAP shows t hat the hot-l eg break at t he steam g enerator r esulted in an axial displacement

-3 5 -

. Th e applicant then c oncl uded that a s pherical Z OI based on w ould also conservatively bound this limited separation break of the hot-l eg br eak a t t he s team generator.

Giv en that the ZO I for a , t he applicant concluded that the Region I anal ysis bounds the R egion II anal ysis m odeling . NRC Staff Evaluation Th e staff reviewed the applicant's evaluation of a hot-leg DEGB a t t he steam generator as described above.

T he staff found that some statements in t he WCAP contain discrepancies in defining t he core l engt h and the distance from the break pl ane t o the asymptotic pl ane for t he limit ed separation model.

In a letter dated May 1 1 , 2016 (Reference 13), the staff issued RAI ICC&NMI-026, asking t h e applicant t o clarify the perceiv ed discrepancies.

In a response dated August 23, 2016 (Reference 25), t he applicant indicated that t hose statements were unclear because of a typographical error and inadequate explanation.

The applicant proposed revision s t o Sections 4.4.3.1.2, 4.4.3.2.2, and 4.4.3.2.3 o f the WCAP to clearly define t he core length and t he distance from the break plane to the asymptotic pl ane for th os e limited separation models. Th e staff found t he applicant's revisions acceptabl e because the revised WCAP clarified the perceived discrepancies. Therefore, the staff consider s RAI ICC&NMI-026 to be a close d item. I n summary, t he staff finds th e applicant's evaluation and conclusion acceptable because t he evaluation followed t he methodology described in Secti on 4.4.3 o f t he WCAP , which was f ound acceptabl e by t he staff as described in Section 3.4.4.3 o f this SE. Consequently, t he applicant has ade quately s ubstantiated it s conclusion that the Region I anal ysis bounds t he Region I I analysis m odeling . 3.4.4.3.1.3 Hot-Leg Break Region II Results Section 4.4.3.1.3 of the WCAP summarizes the results of t he AP1000 hot-leg break Region II analysis. Th e applicant stated that for the Region I hot-leg break analysis, a debris generation break size was defined as that o f a 14-inch (35.56 cm)

Schedule 160 pipe. T he applicant stated that , as shown by t he results o f the analyses presented in Sections 4.3.1.1 and 4.3.1.2 of the WCAP, the worst possible mechanical break displacement results i n a ZOI that i s smaller t han that assumed i n the Region I analysis. This ZOI i s considered at al l points along the RCS hot leg to determi ne the location that will produce the maximum debris. T he resultant debris generation, with no other bes t estimate assumptions considered, cannot b e greater t han t he debris generation from t h e Region I analysis. NRC Staff Evaluation

Th e staff reviewed the applicant's summary o f the results of t he AP1000 hot-leg break Region II analysis presented in Section 4.4.3.1.3 of the WCAP. Th e staff finds the summary acceptable because it is consistent with the results o f the analyses presented in Sections 4.3.1.1 and -3 6 -

4.3.1.2 of the WCAP, which was found acceptable by the staff as described in Sections 3.4.4.3.1.1 and 3.4.4.3.1.2 of this SE. 3.4.4.3.2 Cold-Leg Break Evaluations 3.4.4.3.2.1 Cold-Leg Double-Ended Guillotine Break at the Reactor V essel N ozzle Section 4.4.3.2.1 of the WCAP discusse s the evaluation of a cold-le g DEGB at the reactor vessel noz zle. Table 4-3 of t h e WCAP show s that the c old-l eg b reak a t the r eactor v essel nozzle resulted in an ax ial displacement

. As des cribed i n WCA P Section 4.3.2.2, the e quivalent di ameter cannot exceed t he pipe diameter. For those case s in which t he WCA P Section 4.3.2.2 method results in an equivalent diameter larger t han the pipe diameter, the pipe diameter will be used to calculate the r adius o f the spherical Z OI and t he break w ill be consider ed a DEGB w it h full separation.

Therefore, t he applicant concluded t hat a . NRC Staff Evaluation Th e staff reviewed the applicant's evaluation of a cold-leg DEGB at t he reactor vessel noz zle as described above.

T he staff finds th e applicant's evaluation and conclusion acceptable beca use the evaluati on followed the methodology described in Section 4.3.2 o f the WCAP , which t he staff found acceptable as des cribed i n Section 3.4.3.2 o f t his S E. Consequently, t he applicant has ade quately s ubstantiated it s conclusi on that a s pherical Z OI bas ed on . 3.4.4.3.2.2 Cold-Leg Double-Ended Guillotine Break at the Reactor Coolant Pump Section 4.4.3.2.2 of the WCAP discusse s the evaluation of a cold-leg DEGB a t the RCP. Table 4-3 of the WCAP show s that the cold-l eg break at t he RCP resulted in an axial displacement o f w ould also conservatively bound this l imited separation br eak o f the cold-l eg break at t he RCP. -3 7 -

Furthermore, t he applicant stated that the ZO I for a fully separated break o f a 14-inch (35.56 cm) Schedule 160 pipe would bound t he parameters o f the limited separation; however, the calculated equivalent break diameter w as found to be greater t han the i nner diameter o f the 14-i nc h (35.56 cm)

Schedule 160 pipe (11.188 inches (28.418 cm)). As a result, a Region II analysis i s to be assesse d for .NRC Staff Evaluation Th e staff reviewed the applicant's evaluation of a cold-leg DEGB at t he RCP as described above. T he staff finds the applicant's evaluation and conclusion acceptable because the evaluation followed t he methodology described in Section 4.4.3 o f the WCAP , which t he staff found acceptable as des cribed in Section 3

.4.4.3 o f th is SE. Consequently, t he applicant has adequately s ubstantiated i t s conclusion that a R egion II anal ysis i s t o be assess ed . 3.4.4.3.2.3 Cold-Leg Double-Ended Guillotine Break at the CA01 Module Penetration Section 4.4.3.2.3 of t he WCAP discusse s the evaluation of a cold-leg DEGB a t the CA01 module penetration.

Table 4-3 of the WCAP show s that the cold-l eg break at t he r eactor v essel nozzle resulted in an ax ial displacement

. Furthermore, t he applicant stated that based on the break results for t he cold leg a t the reactor vessel nozzle and the RCP presented i n WCA P Sections 4.4.3.2.1 and 4.4.3.2.2, respectively, a Region II anal ysis i s t o be perform ed for t he c old-l eg break with a spherical ZO I bas ed on a diameter o f from t he r eactor v essel noz zle t o the CA01 m odul e penetration , and a spherical ZO I bas ed on an e quivalent di ameter o f ( from the CA01 m odule penetration t o t he RCP. NRC Staff Evaluation Th e staff reviewed the applicant's evaluation of a cold-leg DEGB at t he CA01 module penetration as described above. Th e staff finds t he applicant's evaluation and conclusion acceptable becaus e t he evaluation followed t he methodology described in Section 4.4.3 of the WCAP , which t he staff found acceptable as described in Section 3.4.4.3 o f this SE. Consequently, t he applicant has adequately substantiated it s conclusion that a Region II -3 8 -

analysis i s t o be perform ed for the cold l eg with a spherical ZO I ba sed on a diameter o f from t he reactor v essel noz zle to the C A01 module penetration, and a spherical ZO I ba sed on an equivalent di ameter o f from t he CA01 module penetration t o the RCP. 3.4.4.3.2.4 Cold-Leg Break Region I I Results Section 4.4.3.2.4 of the WCAP summarizes the results of the AP1000 cold-leg break Region II analysis. Th e applicant stated that for the Region I cold-leg break analysis, a debris generation break size was defined a s that o f a 14-inch (35.56 cm)

Schedule 160 pipe. T he applicant stated that t he AP1000 plant RCS cold leg is divided into two primary segments: (1) t he cold-leg segment located inside the steam generator compartment, extending from t he RCP throug h the CA01 module penetration, and (2) the cold-leg segment located inside the nozzle gallery, extending from t he CA01 modul e penetrati on t o the reactor vessel noz zle. Th e applicant further stated that , as shown by t he results o f t he analyses presented in Secti ons 4.3.2.2 and 4.3.2.3 o f t he WCAP, the worst possible mechanical break displacement for al l possible break locations inside the steam generator compartment and through t he C A 01 module penetration results i n a ZOI that i s smaller t han t hat assumed in the Region I analysis. This ZOI i s co nsider ed at al l points along the RCS cold leg to determine t he location that will pr oduce t he maximum debris. T he resultant debris generation, with no other be st estimate assumptions considered, ca nnot be greater t han t he debris generation from t he Regio n I analysis. Moreover, t he applicant stated that , as shown by t he results o f t he analyses presented in Sections 4.3.2.1 and 4.3.2.3 of t he WCAP, the worst possi bl e mechanical break displacement for al l possible break locations inside the reactor nozzle gallery from t he reactor nozzle to the CA01 module wall was determined to occu r a t the co ld-leg reactor nozzle, and this displacement is greater than the debris generation break size used i n t he Region I analysis. Therefore, the applicant appl i ed this maximum br eak size t o the location s along the RCS cold leg from the reactor nozzl e to t he CA0 1 module wall.

In addition, t he applicant stated that the limiting break siz e for each segment i s t o be applied to any location on the corresponding cold-leg segment that results in the maximum debris generation. NRC Staff Evaluation Th e staff reviewed th e applicant's summary o f the results o f A P 1000 cold-leg break Region II analysis presented in Section 4.4.3.2.4 of the WCAP. Th e staff finds it acceptable because t he summary as presented is consistent wit h t he results o f the analyses described in Sections 4.4.3.2.1 , 4.4.3.2.2, and 4.4.3.2.3 of the WCAP , which t he staff found acceptable as described in Sections 3.4.4.3.2.1, 3.4.4.3.2.2, and 3.4.4.3.2.3 of this SE. 3.5 NONMETALLIC INSULATION SUITABLE EQUIVALENCY (WCAP-179 38 , SECTION 5) Section 5 of t he WCAP s tates t hat t he encapsulated NMI c ontained i n t he RVIS L NS b locks, the CA31 neutron shield blocks, and the RVIS w ater inlet door s, , is a suitable equivalent t o MRI for the locations bou nded by testing and analysis.

NRC S ta ff Evaluation Based on t he WCAP NMI testing information and associated staff evaluations (i.e., Sections 3.3.3 and 3.3.4 of this SE) and t he analysis in the remainder o f Section 3.5 of this -3 9 -

SE , the staff find s that t he RVIS LN S bl ocks, th e CA31 neutron s hield blocks, and the RVIS water i nlet door s, , ar e a suitable equivalent t o M RI for t he ir locations bounded by testing and analysis and evaluated in th e WCAP. 3.5.1.1 Debris Generation Section 5.1.1 of the WCAP st at es that there is no debris production from t he NMI contained within the neutron shiel d blocks (i.e., LNS and CA31) or t he RVI S water inlet doors. NRC Staff Evaluation Base d on the WCAP NMI testing information and associat ed staff evaluation s (i.e., Sections 3.3.3 and 3.3.4 of this S E) and th e analyses in the Subsection s of 3.5.1.1 of this SE, the staff find s that there is no debris pr oducti on from t he neut r on shield blocks o r water inlet doors. 3.5.1.1.1 Jet Impingement Debris Section 5.1.1.1 o f t he WCAP states that jet impingement testing w as used t o determi ne the ZO I for t he RVIS LNS, the CA31 neutron shielding, and the water inlet doors. With the materia l ZOI defined through testing

, i t w as possible to verify t hat debris would not be generated in the plant from a break of the hot-leg, cold-leg, o r DVI piping. NRC Staff Evaluation Based on the information i n the WCAP and th e associat ed staff evaluation in Section 3.3.3.4 of this SE , the staff find s that the jet impingement testing used t o determine the ZOI i s acceptable. 3.5.1.1.1.1 Establishing the Zone of Influence Section 5.1.1.1.1 of the WCAP defines ZOI as the spherical volume about a break in which the fluid escapi ng from the break has sufficient ener gy t o generate debris from insulation, coatings, or o ther m aterials w ithin the zone.

T he WCAP states t hat j et impingement t esting was conducted on a neutron s hield block test s pecimen , and the bl ock maintained its enc apsulation i ntegrity and did not generate debris at a ZO I. T he WCAP pr ovides a calculation descri bi ng how t he ZO I w as det ermined by t esting. The WCAP states that the jet impingement test results ca n be appli ed t o the CA31 neutron shielding, w ater i nlet doo rs, and the RVIS U pper N eutr on Shield (UNS) and LNS. The WCAP i ndicates t hat the CA31 m odule uses . T h e UNS and LNS bl ocks use . The construction of the installed blocks is m ore robust t ha n that o f the tested shield block.

The WCAP indicates that the RVIS water inlet doors are located much farther from a potential pipe break than the tested ZOI, and, because of the intervening structures and components, a LOCA jet has no direct path to the water inlet doors.

-4 0 -

NRC Staff Evaluation

Th e staff finds that jet impingement test results can be applied t o assess the CA31 neutron shielding, R VIS LN S, and the w ater i nlet doo rs b ecause testing de monstrat ed that t he shield block maintained i ts i ntegrity and did not generate debris a t a Z OI. For t he CA 31 shield block s , this finding i s supported by its enhanced construction a s compared t o that of the test article. Similarly , for the LNS, the staff finding is supported b y the LNS's enhanced construction as compared t o that of the test article and because the RVIS LN S is located far from a potential pipe break (near the bottom o f t he reactor vessel), with many intervening structures and components between the break and RVIS LN S. For the water inlet door s, this finding is supported because th e RVI S water inlet doors are located far fro m a potential pipe break (below the bottom o f the reactor vessel), with many intervening structures and components between the break and t he RVIS water inlet door s. The staff evaluation for suitable equivalency did not include the UNS because the UNS i s not subject t o the approval items identified i n WCAP Secti on 1.1, "Purpose." 3.5.1.1.1.2 NEI 0 4-07 Approach to Determining th e Zone of Influence Secti on 5.1.1.1.2 of t he WCAP compares th e staff-approved methods (Reference 11) use d to determine ZOI v ersus th e WCAP's determin ation of ZOI. The WCAP pr ovides information to demonstrate the conservatism i n selecting a Z OI bas ed on jet i mpingement t esting. NRC Staff Evaluation Th e staff reviewed the ZOI discussion in WCAP Secti on 5.1.1.1.2. T he staff agrees that the WCAP appr oach t o determining a ZOI f or NMI , based upon jet impingement testing, demonstrates conservatism i n comparison with the staff-approved ZOI approach (Reference 11) and is therefor e acceptable.

3.5.1.1.1.3 Debris Generation Assessment Secti on 5.1.1.1.3 of t he WCAP states that a debris generation assessment w as perform ed for each potential pipe break in the reactor vessel cavity for t he RVIS and t he CA31 neutron shielding.

T he WCAP states that t he RVIS LN S and water inlet doors ar e far enough aw ay from the potential pipe breaks that they are not within the ZOI and do not generate debris from a LOCA jet. The WCAP provides figures t h at show the plan view and elevation views of t he nozzle gallery ar ea. NRC Staff Evaluation Th e staff reviewed the debris generati on assessment for the RVIS LN S and water inlet doors (located in t he bottom region of t he reactor vessel cavity). Based on WCAP Section 2.2 location informati on and Figures 5-3 through 5-1 5, t he staff agree s that the RVI S L NS and water i nlet doors are locat ed far from the potential pi pe breaks and are not w ithin t he ZO I. Because of t he constructi on of t he RVIS LN S and w ater i nlet doors and their d istanc e from any pot ential break locati on (much greater than the 3D ZOI established by testing similarly constructed items), th e staff find s it reasonable to co ncl ude tha t t he RV I S LNS and water inlet doors do not generate debris from a LOCA jet. -4 1 -

3.5.1.1.1.3.1 Direct V essel Injecti on Pipe Break Section 5.1.1.1.3.1 o f the WCAP p rovides t he debris generation assessment for the DV I p iping. The ZO I w as c alculated using t he full i nner diameter o f t he D VI pi pe of . The result i s that the C A 31 neutron shielding is outside the ZOI. NRC Staff Evaluation Th e staff reviewed the debris generation assessment for the DVI line break in the reactor vessel cavity r egion , including WCAP Fi gures 5-7 and 5-8 (elevation and plan views, r espectively).

Bas ed on the fi gures, the appl ication of a ZO I reveals t hat t he CA31 neutron s hielding is outside the ZOI sphere. Because the WCAP applied the appropriate ZOI to assess the debris generati on potential o f the DVI line break i n the reactor cavity region, the staff considers the results acceptable. Therefore, t he staff finds that t he CA 31 neutron shielding would not generate debris from a DEGB o f the DVI line in th e reactor cavity. 3.5.1.1.1.4 Hot-Leg Pipe Break Section 5.1.1.1.4 of the WCAP anal y ze s a hot-leg pipe break for t he AP1000 plant using the Regi on I and Region I I analysis (i.e., alternate evaluation methodology) discussed in Section 3.4 of t his SE. Section 5.1.1.1.4.1 of the WCAP provides the Region I analysis of t he hot-leg piping.

The resulting spherical ZO I i s small enough that the CA31 neutron shielding is outside the ZOI. Therefore, t he Region I analysis determi ned that a break in the ho t-leg piping in the react or cavity would generate no debris from encapsulated NMI. Section 5.1.1.1.4.2 o f the WCAP provides the Region II analysis o f the hot-leg piping.

A pi pe break analysis w as performed for a break a t the hot-leg nozzle to determine the pipe movement and resulting break area. The analysis showed that t he resulting pipe break ar ea w as l ess t han the break area used i n the Region I analysis. Because the break size used in the Region I analysis i s greater t han the break size used i n the Region II analysis, the Regi on I analysis i s more conservative.

NRC Staff Evaluation

Th e staff reviewed the debris generation assessment for the hot-leg pipe break in the reactor vessel cavity region discussed above and depicted in WCAP Figures 5-9 and 5-10 (elevation and plan views, respectively), in conjunction wit h t he pipe break analysis assessed in Section 3.4.4 of this SE. Based on t he figures and the realistic pipe break analysis , t he application of a 3D ZOI on the hot-l eg reveals that t he CA31 neutr on shielding i s outside the ZOI sphere. Because t he WCAP appropriately applied the alternate evaluation methodology and ZOI t o assess the debris generation potential o f the hot-leg break i n t he reactor cavity region, t he staff considers t he results acceptable. Therefore, t he staff finds that t h e CA 31 neutron -4 2 - shielding would not generate debris from encapsulated NMI due to a hot-leg break in the reactor cavity. 3.5.1.1.1.5 Cold-Leg Pipe Break Section 5.1.1.1.5 of the WCAP provides an analysis o f a cold-le g pi pe break for t he AP1000 plant using the Region I and Region II analysis (i.e., alternat e evaluati on methodology) discussed in Section 3.4 of this SE. Section 5.1.1.1.

5.1 o f the WCAP provides the Region I analysis o f t he cold-leg piping. The resulting spherical ZO I i s small enough that the CA31 neutron shielding are outsi de the ZOI. Therefore, t he Region I analysis determi ned that no debris would be generat ed from a break i n t he cold-leg piping i n t he reactor cavity. Section 5.1.1.1.

5.2 o f the WCAP provides the Region II analysis o f the cold-leg piping.

A pi pe break analysis w as per formed for a break a t the cold-leg nozzl e to determine the pi pe movement and resulting break area. The analysis showed that t he resulting pipe break ar ea was greater than t he br eak ar ea us e d i n the Region I anal ysis. The am ount o f movement indicated that

. The WCAP states that the Region II analysis allows realistic assumptions to be used in the debris generation assessment, such as taking credit for intervening robust structures.

The WCAP indicates t hat staff approved industry guidance (Reference 11) permit s truncating a ZOI if there ar e robust barriers. At t he cold-leg nozzle break location , t he CA31 neutron shield blocks ar e located within t he CA31 structural floor module. The module separates t he refueling cavity and the nozzle gallery.

The WCAP states that the CA 31 module is a robust structure that would prevent impingement o f the CA31 neutr on shielding by a LOCA jet. For t he Region II analysis, the ZOI w as truncated by the CA 31 module. NRC Staff Evaluation

Th e staff reviewed the debris generation assessment for the cold-l eg pipe break in the reactor vessel cavity region discussed abov e and depicte d in WCAP Figures 5-11 through 5-15 (elevation, top, and plan views), in conjunction with th e pipe break analysis assessed i n Section 3.4.4 of this SE. Ba s ed on pipe break ana lysis, t he application of a Z OI to t he c old leg reveals t hat the CA31 neutron s hield blocks a re outside the ZOI s phere or behi nd robust b arriers. Because t he WCAP appr opriately appl ied the alternate ev aluation methodology and ZO I to assess the debris generation potential o f NMI f or a cold-leg break i n t he reactor cavity region, the staff considers the results acceptable.

Therefore, the staff finds t hat the CA 31 neutron shielding would not generate debris from a cold-leg break in the reactor cavity. 3.5.1.1.2 Submergence Debris The principal desi g n featur e to prevent chemical effects from t he shield blocks and water inlet doors i s t he s eam welding of t he s tainless s teel e ncapsulation.

Since each shield block al so has

. WCAP S ection 5.1.1.2 closes w ith t wo s imilar statements th at the s tainless s teel des ign does not pr oduce debris an d, therefore, no addi tional chemical e ffects have to be considered with respect t o t he RVIS. Chemical effects f rom t h e neutron absorber material in the CA 31 modul e and U NS i s addr essed i n WCAP S ection 3.5.1.

NRC Staff Evaluation

Based on it s review of the jet i mpingement t esting and submergenc e test results, t he staf f determined that the , there is a potential for c hemical e ffects from c ontact b etween the shield block internal materials (insulation and shielding) and the post-LOCA f luid. However, b y limiting applicati on of t he WCAP to plants w ith the amount o f aluminum evaluated i n WCAP Section 5.1.4, there i s significant margin between the ca lculated chemical e ffects and the amount t ested for s trainer and i n-v essel head loss i n the A P1000 design. . According to t he chemical effects m ethodology in WCAP-1 6530-N P-A, . If these materials c ontain aluminum, i t would be possibl e for ad ditional pr ecipitates i f th e solution reaches t he encapsulated material and aluminum i s r eleas ed and t hen diffuses outside the bl ock. As s uggested i n WCAP Section 3.6.2.4 , . Th e staff finds i t acceptable to stat e that no additional ch emical effects have to be considered from th e RVIS. This i s b ased mainly o n the isolation from t he post-L OCA recirculating fluid provided by t he seam-we lded design as required by t he AP1000 DCD. -4 4 -

the LNS, only if i nternal wrappers ar e not i ntact. . Th e WCAP-16530-NP-A m ethodology i s conservative , and t he act ual amount of aluminum being used inside AP1000 containments pr ovides s ubstantial m argin. The aluminum quantity i s discussed i n the staff's e valuation of WCAP S ection 5.1.4.

Chemical effects f rom t he neutron abso rber material in the CA31 module shield blocks are addressed in Secti on 3.3.5 of this SE. 3.5.1.2 Aging Effects The neutron shield blocks and RVIS w ater i nlet d oors a r e fabricat ed from a combination of . As des cribed i n WCAP Section 2.2, no t al l o f these materials are included in the blocks i n all locations. Section 5.1.2 o f t he WCAP describes t he pot ential aging effects for thes e materials and how t he design addresses t he a ging effects that ar e expected t o be significant.

The WCAP considers . Th e WCAP identifies

. Of these a ging e ffects , the WCAP i ndicates . As par t o f audi t interactions, the applicant submitt ed a letter (Reference 27) proposing a new WCAP S ection 5.1.2.1.

WCAP S ection 5.1.2.1 is an assessment of pot ential ag ing effects for the neut ron absorber material us ed i n the CA31 shield blocks, including oxidation, gas generation, and swelling.

This section also i ncluded an assessment o f t hermal ex pansion. (Thermal ex pansion of th e LNS is a ddressed in WCAP S ection 5.1.3.

Potential chemical effects f rom t he ar e addressed i n SE Section 3.5.1). The s taff c onsiders t he revisions pr oposed i n the l etter to be a confirmatory i tem pending an update to

t he WCAP. -4 5 - . NRC Staff Evaluation For , t he staff finds t he WCAP's discussion of aging effects acceptabl e with respect t o qualification of t he radiation shield blocks and insulation doors. The blocks ar e normally dry, so corrosion and stress

-corrosion cracking of austenitic stainless steel ar e not concerns during normal operations. Following a LOCA, corrosion and stress-corrosi on cracking of austenitic stainless st eel are also not concerns beca use the pH of the post-LOCA fluid is buffer ed to neutral and alkaline pH values. Branch Technical Position 6-1 states t hat t he pH of post-LOCA fluid in PWRs should be maintained above 7

.0 in order t o prevent stress-corrosion cracking of austenitic stainless steel. Th e resistance to degradation of au stenitic s tainless steel unde r no rmal oper ating and pos t-L OCA c onditions i s a reas on that th e AP 1000 DCD specifies it fo r t he encapsulation of NMI. .  :  : ... . Comparing these aging effects to those described in the WCAP, the staff determined that the WCAP accurately identifies the aging mechanisms and effects. The staff concluded that the WCAP correctly i dentifie s as t he o nly ag ing effect t hat the design needs t o address f rom t he standpoint o f debris g eneration. The other main effects

--a r e not s ource s of deb ris generation because the material i s contai ned in the foil and seal ed box. . I n a l etter dat ed Ma y 11, 2016 (Reference 13), t he staff issued RAI-I CC&NMI-0 34 and asked the appl icant t o i ndicate . I n a r esponse da ted July 14 , 2016 (R eference 14), t he applicant and c onsiders R AI-I CC&NMI-0 34 close d. I n a letter dated August 22, 2016 (Reference 34), the staff issu ed RAI-ICC&NMI-036 asking the applicant t o assess th e types and amounts o f gases released, t he temperature and pressure corresponding to t he quantities of gas , and the potential impact o f the gases on structures, systems, and components in any par t o f the containment o r containment system. I n its response dated November 16 , 2016 (Reference 35), t he applicant assessed the normal operational impact of t he gases on structures, systems, and components by assumi ng th a t all the released gas was hydrogen, adjusted for containment conditions, and all t he released gas was retained with in the containment during one full f uel cycle (i.e., 24 months). Assuming that the containment w as no t purged during the fuel cycle, t he applicant's analysis indicat ed that t he global containment hydrogen concentration would be 0.092 volume percent a t the end o f a 24-month fuel cycle; well bel ow the AP1000 containment hydrogen alarm setpoint (3 percent)and hydrogen lower flammability limit (4 percent). Additionally, the applicant discussed that t heareas w her e the shield blocks are located ar e serviced by ventilation air from the containmentventilati on system that provides cooling ai r and functions to mix the containment buildingatmosphere , preventing higher local concentrations. T he staff find s th e applicant's responseacceptabl e with respect to the impacts on structures, systems, and components during normaloperations because the applicant conservatively assessed the types of gases (i.e., assume d allgas w as hydrogen) and t he released quantities (i.e., buildup over a 24-mont h fuel cycle, with nopurging) and showed that there w as significant margin to hydrogen flammability limits. Inaddition, t he applicant's ventilati on air discussi on provided reasonable assurance that localizedconcentrations o f hydrogen were unlikely t o form in the reactor cavity and nozzle gallery.

-4 7 -

Furthermore, the applicant's containment ai r filtration system i s desi g ned to purge the containment at regular intervals during t he fuel cy cle, which would decrease hydrogen concentration and further contribute to mixing. The applicant also indicated that passive autocatalytic recombiners, installed in containment, w oul d prevent hydrogen concentration from reaching flammability limits. With respect t o beyond-design-basis events , the applicant assesse d the amount o f gas produced by t he neutron shield blocks i n a typical f uel cycle. The staff finds t hat the assessment i n the RAI response is acceptable because the applicant reviewed the impact o f combustible gas on the safety analysis and confirmed the amount o f gas produced by the neutron shield blocks is negligible in compariso n to the overall am ount o f hydrogen gas generated v i a cl ad oxidation. In the response t he applicant also provides a proposed markup to DCD Tier 2, Section 9.5.1.2.1.1, under t he "Control o f Combustible Materials" subheading (t he final changes t o t he FSAR will be made by t he licensee). Th e staff finds t h e proposed markup acceptable beca use t he markup describes t he off-gassing from the neutron shield blocks in t he containment during normal operation. Base d on the discussion above and a revision to t he WCAP that incorporates t he pr opos ed markup , th e staff consider s RAI-ICC&NMI-036 to be a close d item. The onl y ot her aging mechanism that would be a concern in this application is t he hi g her solubility o f Boraflex ov er time, w hich is described in EPRI TR-103300. WC AP Section 5.1.2 identifies t his phenom enon , but the WCAP does not c onsider i t appl icable because the des ign . However, W CAP Section 5.1.4 addresses th e increased solubility f or t he hypothetical c ase of f ail ed encapsulation . With respect t o aging of , the s taff reviewed Section 5.1.2

.1 submitted in the appl icant's September 25 , 2017 , supplem ent to the WCAP (Reference 27). Section 5.1.2

.1 addresses oxidation, g as generation, and s welling as pot ential ag ing effects. The staff evaluated the significance o f as pa rt o f chemical e ffects i n S ection 3.3.5 of this SE. As described i n that section, t he s taff concluded t hat the . WCAP Section 5.1.2.1 on aging includes a discussion of thermal expansion resultin g from t he differen ce between plant operating and shutdown conditions.

As par t o f the regulatory audit, t he staff c onfirm ed that t he applicant ev aluated thermal ex pansi on using t he full t emperatur e range and conservative thermal ex pansion coefficient (relative to s upplier d ata sheets).

Based on its ev aluati on of p ropos ed WCAP S ection 5.1.2.1, t he staff agrees with the applicant's conclusion that po tential aging e ffects o f t he will not adv ersely i mpact its des ig n functions i n this appl ication. The s taff c onsiders i nclusion of p roposed Section 5.1.2.1 in the W CAP is a confirmatory item pending an update t o t he WCAP. T h e staff finds t he information i n WC AP Section 5.1.2 acceptable because it accurately identifies t he agi ng mechanisms as t hey relat e t o the design o f the NMI and doors and the resulting prevention of chemical effects. -4 8 -

3.5.1.3 Thermal Expansion of Lower Neutron Shield Neutr on Shielding Material Section 5.1.3 of the WCAP describes thermal analysis and testing associated with the LN S blocks. Testing conducted at t he LNS neut ron s hielding material t emperature limit s f ound . NRC Staff Evaluation . . Ba sed on the provided analysis i n conjunction with t he substantial margin between the maximum expected temperature and the maximum acceptable temperatur e for t he material, sta ff agrees with the assessment stated in the WCAP that t he LNS blocks w ill not generate debris a s a result of thermal conditions during all design basis acci d ent scenarios. 3.5.1.4 Additional Conservatisms Section 5.1.4 of the WCAP describes circumstances that the applicant considers as contributors t o the overall conservatism o f the suitable equivalency analysi s (e.g., chemical effects assessment, jet impingement testing and submergence testing). NRC Staff Evaluation Chemical Effects Assessment Section 5.1.

4 of WCAP-1 7938 provides insights into how certai n factors are sources o f conserva tism. One such f actor is t he inventory d uring construction of al uminum pa rts in p la nt components. Th e staff found from its regulatory audi t (R eference 23) that -4 9 -

. Maintaining t he amount o f margin in the c alculati on depends on the aluminum inventory remaining bel ow the allowable amount, and on the assumptions use d for incorporating the submergence test results. Th e staff considers the submergence testing useful for providing insights i nt o the potential chemical effects from t he proposed RVIS changes. T he staff also recognizes that the testing was not designed to directly support calculations of the amount o f chemical debris the blocks would produce under prototypical pl ant conditions. Neither t he design of the test specimens nor t he ratio of material surface area or volume to liquid volum e w as prototypical.

Studying t he sensitivity to limited communication between t he block internals and post-LOCA fluid requires assumptions about how much of the material i n the blocks would be exposed to t he soluti on and contribut e to chemical effects. Th e staff determi ned how the applicant performed these analyses through a regulatory audi t i n March and April 2016 (Reference 23). The audit i ncluded t he aluminum inventory and the chemical effects calculations.

The audit enabl ed the staff to understand ho w the applicant calculated the appr oximat e mass and surface area of al uminum from t he i nventory. The chemical e ffects c alculation explained how

. The staff also followed the calculations from t he s tarting point throug h t he chemical effects spreadsheet in WCAP-16530-NP-A to confirm its understanding o f the applicant's analysis. The calculations demonstrate the difficulty of, and judgment require d in, specifying the quantity o f material t o i nclude i n the chemical effects sensitivity calculation, but the staff found the approach reasonable for t hat purpose. However, without any change t o t he amount o f submerged aluminum allowed i n containment, there i s no margi n for the small amount o f chemical effects from unexpected conditions.

Although t he chemical e ffects methodology i n WCAP-1 6530-N P-A does no t p redict addi tional chemical pr ecipitati on from , i t does pr edict addi tional p recipitati on from silicon in the pr esence of aluminum-c ontaining materials, s uch as the . Therefore, in a letter da ted May 11, 2016 (Reference 13), t he staff issued RAI-ICC&NMI-035 , asking the applicant t o specify a condition on the use of t he WCAP that sets a quantitative limit on the amount o f aluminum permitted in containment su ch that adequat e margin will be maintained to accommodate the use of the neutron shield blocks.

I n a response dated July 14, 2016 -5 0 -

(Reference 14), t he applicant stated that a quantitative limit on aluminum d oes not need to be a conditi on for use o f t he WCAP because the neutron shield blocks will not contribute any chemical debris, and because AP1000 licensees ar e reducing the aluminum limit through a licensing basi s departure. Th e staff does not agree with this assertion. The staff find s t he WCAP acceptable to use onl y when the allowable amount o f aluminum i s limited as described because neither t he aluminum inventory nor t he licensing basis departures a r e controlled by t he WCAP approval. The current licensing basi s allows 60 pounds (27 kg) of aluminum, and conditions leading to a small amount of additional c hemical e ffect s c annot be rul ed out. For the applicant's al uminum assumption of 40 pounds (1 8 kg) and 13.3 ft 2 (1.24 m 2), and , t he amount o f chemical pr ecipitat e calculated using WCAP-1 6530-N P-A i s app roximately 14 pounds (6.4 kg). A s di scussed in WCAP Section 5.1.4, . These res ults r epresent significant margin below t he licensing basis o f 57 pounds (26 kg), and the staff considers t his margin adequat e to ac commodat e t he use of t he neutron s hield blocks.

Therefore, t he staff's approval of t h e WCAP is l imit ed to plants that hav e no more t han 13.3 ft 2 (1.24 m 2) of al uminum submerged i n containment following a LOCA. The discussion of l imitations and conditions i n Section 4.0 o f t his S E ad dresses t his topic. Therefore, t he staff c onsiders RAI-I CC&NMI-0 35 to be a closed i tem, bas ed on the al uminum l imitatio n and condition di scussed in Section 4.0 o f this SE. Jet I mpingement Testing The WCAP discusses t hat j et impingement t esti ng on the neutron shield blocks w as per formed at on fully exposed blocks and blocks w ith a replicate reactor c avity c over pl ate. . The s taff finds that t he pr oximity o f t he test a rticl e t o the jet, t est configuration, and t he ov erall pl ant geometry provide useful i nformati on that s upports the suitable equivalency of the NMI blocks. Submergence Testing Th e WCAP describes submergence test procedures that are interpreted as conservative compared t o pl ant conditions. These relat e to pressurization of the test specimens o r actual shield blocks and t he corresponding potential for exchange betw een the internal materials and external f luid. . -5 1 -

-5 2 - 3.6 REGULATORY IMPACTS 3.6.1 Licensing Basis Changes Section 6.1 of the WCAP proposes the following changes to AP1000 DCD/UFSAR Tier 2: In DCD/UFSAR Subsection 6.3.2.2.7.1, item 3, this WCAP is added as a reference thatdemonstrates suitable equivalency for AP1000 reactor vessel neutron shield blocks.The shielding locations that were considered in this report are detailed in Section 2.2 of the WCAP. In DCD/UFSAR Subsection 6.3.2.2.7.1, item 12, it is noted that D [diameter] can bedetermined using DEGB of primary system piping or an alternate debris generation sizefrom the alternate evaluation approach of NEI 04

-07 ([WCAP] Reference 6

-3). Theusage of the alternate evaluation approach used is detailed in Section 4 of this WCAP. In DCD/UFSAR Subsection 6.3.2.2.7.1, item 12, this WCAP is added as a reference thatsupports a 4D ZOI radius for AP1000 plant in

-containment cables. In DCD/UFSAR subsection 6.3.9, this WCAP and NEI 04

-07 are included in theSection 6.3 references subsection

.In DCD/UFSAR subsection 9.5.1.2.1.1, a statement is added related to off

-gassing fromneutron shield blocks.

NRC Staff Evaluation

The proposed changes to Tier 2 are consistent with the staff's evaluation of the WCAP and, therefore, are acceptable.

3.7 CONCLUSION

S Section 7.0 of the WCAP summarizes the tests and analysis that determine (1) a ZOI for AP1000 plant in

-containment cabling, (2) suitable equivalency to MRI for AP1000 plant reactor vessel cavity NMI, and (3) use of the alternate evaluation methodology to determine the ZOI radius for Region I and II analyses for an integrated debris assessment. NRC Staff Evaluation The staff finds acceptable, subject to the limitations and conditions described in Section 4.0 below, the application of a 4D ZOI radius for AP1000 plant in

-containment cables based upon the testing and analysis described in the WCAP. Section 3.3.3.3 of this SE discusses the basis for this conclusion.

The staff finds acceptable, subject to the limitations and conditions described in Section 4.0 below, the determination that NMI located in the reactor vessel cavity of the AP1000 plant is a suitable equivalent under the AP1000 licensing basis for the locations that were bounded by testing and analysis. Section 3.5 and associated subsections of this SE discuss the basis for this conclusion.

-5 3 - The staff finds acceptable, subject to the limitations and conditions described in Section 4.0 below, the application of the alternate evaluation methodology to determine the ZOI radius for Region I and II analyses for an integrated debris assessment. Section 3.4 and associated subsections of this SE discuss the basis for this conclusion.

3.8 APPENDIX A - AP1000 DCD REVISION 19 MARKUPS Appendix A to the WCAP provides markups to the AP1000 DCD that address the licensing basis changes discussed in Section 3.6.1 of this SE. NRC Staff Evaluation The proposed changes to AP1000 DCD Tier 2, Revision 19, Section 6.3.2.2.7.1 and Section 6.3.9, are consistent with the staff's evaluation of the WCAP and, therefore, are acceptable.

4.0 LIMITATIONS AND CONDITIONS The staff makes the following limitations and conditions with regard to the WCAP:

The performance of cables within the ZOI is outside the scope of the WCAP's requestfor staff review and approval (see Section 3.1.2 of this SE). Therefore, an AP1000licensee or applicant that references this WCAP must asse ss that the cable protection schemes incorporated into the design function to prevent the generation of debris fromcables located within the 4D ZOI and that the protection schemes, in and of themselves,do not introduce potential debris sources (see Section 3.3.3.3 of this SE).The sta ff's review of the acceptability of the alternate evaluation methodology(i.e., NEI 04-07) for the AP1000 design excludes the use of nonsafety systems andoperator actions (see Sections 3.4.1 and 3.4.3 of this SE).The staff's evaluation of NMI was limited to NMI functioning as a suitable equivalent forMRI in the reactor cavity region only from the perspective of debris generation. The staffdid not evaluate other impacts on the AP1000 plant due to changes in the reactor cavityassociated with the installation of neutron shield blocks. For example, the staff'sevaluation did not assess the shielding or insulation performance of the neutron shieldblocks. Licensees or applicants are responsible to ensure that the impacts to theAP1000 design of structures, systems, and components resulting from these changeshave been fully evaluated. Licensees are responsible to also assess the need for alicense amendment request in accordance with the requirements of 10 CFR Part 52, Appendix D, Section VIII.B.5.b (see Section 3.3.3.4 of this SE).The staff's approval of the WCAP is limited to plants that have no more than 13.3 ft 2(1.24 m 2) of submerged aluminum submerged in containment following a LOCA (seeSection 3.5.1.4 of this SE).

5.0 CONCLUSION

The staff reviewed the WCAP, which determined that encapsulated NMI in the reactor cavity is a suitable equivalent to MRI. The encapsulated NMI is contained within the RVIS lower neutron

-5 4 - shield blocks, water inlet doors, and the refueling cavity floor module (CA31) neutron shield blocks. Additionally, the WCAP establishes an AP1000 plant in

-containment electrical cable ZOI based upon the potential for electrical cables to be directly impinged upon by a LOCA jet and become a debris source. Furthermore, the WCAP applies the alternate evaluation methodology (Reference s 10 and 11) to the AP1000 plant to determine debris generation break sizes for potential debris sources. Based on this review, the staff finds that the approach described in the WCAP, qualified by the limitations and conditions stated in Section 4.0 of this SE and by confirmatory items , provides an acceptable AP1000 plant

-specific evaluation that demonstrat es the following

Encapsulated NMI contained within the reactor vessel cavity region is a suitableequivalent to MRI

. The AP1000 plant in

-containment electrical cables will not generate debris outside a ZOIdefined by a radius of 4D. The alternate evaluation methodology for determining debris generation break size isapplied appropriately in the WCAP, consistent with NEI 04-07 and the associated SE

.

6.0 REFERENCES

1.U.S. Nuclear Regulatory Commission, NUREG-1793, "Final Safety Evaluation ReportRelated to Certification of the AP1000 Standard Design," September 2004 (ADAMSAccession No. ML043570339).

2.U.S. Nuclear Regulatory Commission, NUREG-1793, Supplement 1, "Final SafetyEvaluation Report Related to Certification of the AP1000 Standard Design,"

December 2005 (ADAMS Accession No.

ML060330557).

3.U.S. Nuclear Regulatory Commission, NUREG-1793, Supplement 2, "Final SafetyEvaluation Report Related to Certification of the AP1000 Standard Design,"September 2004 (ADAMS Accession No. ML112061231).

4.Westinghouse Electric Company LLC, APP-GW-GL-700, "AP1000 Design ControlDocument ," June 2011 (ADAMS Accession No. ML11171A500).5.U.S. Nuclear Regulatory Commission, Generic Safety Issue 191, "Assessment of DebrisAccumulation on Pressurized

-Water Sump Performance," (GSI 191) Footnotes 1691 and1692 to NUREG

-0933, 1998 , (ADAMS Accession No.

ML11353A382

).6.GL 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation duringDesign-Basis Accidents at Pressurized

-Water Reactors" (GL 2004 02), September 13, 2004 (ADAMS Accession No.

ML042360586).7.Russ, P. A., Westinghouse Electric Company LLC, WCAP

-17938-P, Revision 2(Proprietary), and WCAP

-17938-NP, Revision 2 (Nonproprietary), "AP1000 In-Containment Cables and Non Metallic Insulation Debris Integrated Assessment,"June 7, 2017 (ADAMS Accession No. ML17163A296).

8.Russ, P. A., Westinghouse Electric Company LLC, WCAP

-17938-P, Revision 0 (Proprietary), and WCAP

-17938-NP, Revision 0 (Nonproprietary), "AP1000

-5 5 - In-Containment Cables and Non Metallic Insulation Debris Integrated Assessment,"

March 12, 2015 (ADAMS Accession No. ML15076A069). 9.Russ, P. A., Westinghouse Electric Company LLC, WCAP

-17938-P, Revision 1 (Proprietary), and WCAP

-17938-NP, Revision 1 (Nonproprietary), "AP1000 In-Containment Cables and Non Metallic Insulation Debris Integrated Assessment,"November 20, 2015 (ADAMS Accession No. ML15329A152).

10.NEI 04-07, Revision 0, "PWR Sump Performance Evaluation Methodology," NuclearEnergy Institute, December 2004 (ADAMS Accession No. ML050550138).

11.U.S. Nuclear Regulatory Commission, Washington, DC, "Safety Evaluation by the Officeof Nuclear Reactor Regulation Related to NRC Generic Letter 2004 02, Nuclear EnergyInstitute Guidance Report (Proposed Document Number 04

-07), 'Pressurized WaterReactor Sump Performance Evaluation Methodology,'" December 6, 2004 (ADAMSAccession No. ML050550156).

12.NUREG/CR-6808, "Knowledge Base for the Effect of Debris on Pressurized WaterReactor Emergency Core Cooling Sump Performance," prepared for the U.S. NuclearRegulatory Commission by Los Alamos National Laboratory, Los Alamos, NM,February 2003 (ADAMS Accession Nos. ML030780733 and ML031060173).

13.Bavol, B., U.S. Nuclear Regulatory Commission, Letter to Mr. Zachary Harper, Manager,Westinghouse Electric Company, "Request for Additional Information Letter No. 01 forReview of Westinghouse Electric Company's Submittal of WCAP

-17938, Revision 1,'AP1000 In-Containment Cables and Non

-Metallic Insulation Debris IntegratedAssessment,'" May 11, 2016 (ADAMS Accession No.

ML16133A199).

14.Russ, P.A., Westinghouse Electric Company, Letter to Document Control Desk, U.S.Nuclear Regulatory Commission, "Submittal of Responses to NRC Request forAdditional Information (RAI) Letter No. 01 for WCAP

-17938-Subset 2," July 14, 2016(ADAMS Package Accession No. ML16202A185).15.Abdel-Khalik, A., Advisory Committee on Reactor Safeguards, Letter to the HonorableGregory B. Jaczko, Chairman, U.S. Nuclear Regulatory Commission, "Long

-Term CoreCooling for the Westinghouse AP1000 Pressurized Water Reactor," December 20, 2010 (ADAMS Accession No. ML103410348).

16.NUREG-1918, "Phenomena Identification and Ranking Table Evaluation of ChemicalEffects Associated with Generic Safety Issue 191," U.S.

Nuclear RegulatoryCommission, Washington, DC, February 2009 (ADAMS Accession No.

ML90780090).

17.NUREG/CR-6914, Volume 1, "Integrated Chemical Effects Test Project:

ConsolidatedData Report," prepared for the U.S. Nuclear Regulatory Commission by Los AlamosNational Laboratory, Los Alamos, NM, December 2006 (ADAMS Accession Nos.ML071800338 and ML071800343).

18.U.S. Nuclear Regulatory Commission, "Evaluation of Chemical Effects Phenomena Identification and Ranking Table Results," March 2011 (ADAMS Accession No.ML102280594).

-5 6 - 19.U.S. Nuclear Regulatory Commission, "Final Safety Evaluation by the Office of NuclearReactor Regulation, Topical Report WCAP

-16530-NP-A, 'Evaluation of Post-AccidentChemical Effects in Containment Sump Fluids to Support GSI

-191,' Pressurized WaterReactor Owners Group Project No. 694," (ADAMS Accession No. ML073520891).

20.Russ, P.A., Westinghouse Electric Company, Letter to Document Control Desk, U.S.Nuclear Regulatory Commission, "Submittal of Responses to NRC Request for Additional Information (RAI) Letter No. 0 1 for WCAP-17938-Subset 1," July 5, 2016(ADAMS Package Accession No.

ML16189A237).21.U.S. Nuclear Regulatory Commission, FAI/11-0497, "PWROG Model for the TwoDimensional Free Expansion of a Flashing, Two

-Phase Critical Flow Jet," Revision 1,February 2012 (ADAMS Accession No. ML12124A157).22.Burkhart, L., U.S.

Nuclear Regulatory Commission, Letter to Mr. Zachary Harper,Manager, Westinghouse Electric Company, "Interim Audit Summary for Submergence Testing of Non

-Metallic Insulation and Jet Impingement Testing of Non

-MetallicInsulation and In

-Containment Cables in Support of AP1000 Topical Reports

-Presubmittal Phase," dated November 18, 2014 (ADAMS Package Accession No.ML14289A243

).23.Dixon-Herrity, J., U.S.

Nuclear Regulatory Commission, Letter to Mr. Zachary Harper,Manager, Westinghouse Electric Company, "Audit Summary for Review of WCAP

-17938, Revision 1, "AP1000 In

-Containment Cables and Non

-Metallic Insulation DebrisIntegrated Assessment," February 23, 2017 (ADAMS Package Accession No.ML16292A861).

24.Burkhart, L., U.S.

Nuclear Regulatory Commission, Letter to Mr. Zachary Harper,Manager, Westinghouse Electric Company, "Test Observation Summary for JetImpingement Testing of Non

-Metallic Insulation in Support of the Presubmittal Phase forAP1000 Topical Report WCAP

-17938," Washington, DC, September 8, 2015 (ADAMSPackage Accession Nos. ML15238B542).25.Russ, P.A., Westinghouse Electric Company, Letter to Document Control Desk, U.S.

Nuclear Regulatory Commission, "Submittal of APP

-GW-GLY-115 Revision 0 and APP

-GW-GLY-116 Revision 0 "Responses to NRC Request for Additional Information (RAI)Letter No. 01 for WCAP

-17938-Subset 3," August 23, 2016 (ADAMS PackageAccession No. ML16238A50 4).26.Dixon-Herrity, J., U.S.

Nuclear Regulatory Commission, Letter to Mr. Paul Russ,Director, Westinghouse Electric Company, "Audit Summary for Review of WCAP

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