RAIO-0218-58624, LLC - Response to NRC Request for Additional Information No.295 (Erai No. 9216) on the NuScale Design Certification Application
| ML18043B167 | |
| Person / Time | |
|---|---|
| Site: | NuScale |
| Issue date: | 02/12/2018 |
| From: | Rad Z NuScale |
| To: | Document Control Desk, Office of New Reactors |
| References | |
| RAIO-0218-58624 | |
| Download: ML18043B167 (21) | |
Text
RAIO-0218-58624 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com February 12, 2018 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738
SUBJECT:
NuScale Power, LLC Response to NRC Request for Additional Information No.
295 (eRAI No. 9216) on the NuScale Design Certification Application
REFERENCE:
U.S. Nuclear Regulatory Commission, "Request for Additional Information No.
295 (eRAI No. 9216)," dated December 12, 2017 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) response to the referenced NRC Request for Additional Information (RAI).
The Enclosure to this letter contains NuScale's response to the following RAI Questions from NRC eRAI No. 9216:
06.02.06-14 06.02.06-15 06.02.06-16 06.02.06-17 06.02.06-18 06.02.06-19 06.02.06-20 06.02.06-21 This letter and the enclosed response make no new regulatory commitments and no revisions to
any existing regulatory commitments.
If you have any questions on this response, please contact Marty Bryan at 541-452-7172 or at
mbryan@nuscalepower.com.
Sincerely,
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'LUHFWRU, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8G9A Omid Tabatabai, NRC, OWFN-8G9A Samuel Lee, NRC, OWFN-8G9A : NuScale Response to NRC Request for Additional Information eRAI No. 9216 y,
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RAIO-0218-58624 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com :
NuScale Response to NRC Request for Additional Information eRAI No. 9216
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-14 Regulatory basis is 10 CFR 50, Appendix J and 10 CFR 50.12(a)(1)
As stated in NuScale Exemption Request #7, the potential vessel leakage pathways are testable containment penetrations, total CNV leakage can be quantified via 10 CFR 50, Appendix J, Type B and C tests, thus assuring that CNV leakage does not exceed allowable leakage rate values.
The above statement makes the assumption that there can be no leakage through the containment other than through the penetrations. The CNV is constructed of stainless steel in the lower section, while the upper section is carbon steel, lined with stainless steel. The vessel would sit in a pool of borated water. What is stainless steels susceptibility to pitting in borate water? If the stainless steel cladding becomes pitted, what would happen to the underlying carbon steel vessel? Would this be susceptible to leakage over time?
NuScale Response:
The CNV exterior surface cladding material and weld overlay process is discussed by FSAR Section 6.1.1.1. The stainless steel cladding is not susceptible to pitting due to borated water.
Therefore, it is not necessary to consider through wall leakage due to pitting. The CNV cladding material is currently being used in tanks and vessels to hold water with boric acid at operating sites with no significant indications of degradation due to boric acid exposure. Additionally, NuScale is performing ISI inspections of the containment vessel surfaces to verify that there is no degradation of the stainless steel surfaces that can cause a breach of the cladding and degrade the vessel.
Impact on DCA:
There are no impacts to the DCA as a result of this response.
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-15 Regulatory basis is 10 CFR 50, App. J and 10 CFR 50.12(a)(1)
NuScales technical report, TR-1116-51962, Sect. 4.1, Manufacturing Facility Testing and Inspection, states the CNV is hydrostatically tested in the factory in accordance with ASME Subsection NB-6000. ASME Subsection NB-6111, Scope of Pressure Testing, states All pressure-retaining components, appurtenances, and completed systems shall be pressure tested. The preferred method shall be a hydrostatic test using water as the test medium. Bolts, studs, nuts, washers, and gaskets are exempted from the pressure test. Explain how this structural integrity test confirms the leak tightness of the bolted flanges. Explain how this test could identify vessel leakage or weld leaks if bolted flanges are allowed to leak.
NuScale Response:
A hydrostatic test is performed at a minimum pressure of 125% of the design pressure on every containment vessel (CNV) prior to its going into service. Joints (including gasketed joints),
connections, and regions of high stress are tested and examined for no leakage indications at the hydrostatic test examination pressure per ASME BPVC paragraph NB-6224. The hydrostatic test is performed with all gaskets, bolts, washers and nuts installed and tensioned to the proper torque.Therefore, the hydrostatic test demonstrates that the CNV closure flange, cover flange seals and welds allow no leakage at a minimum pressure of 125% of the design pressure.
Impact on DCA:
There are no impacts to the DCA as a result of this response.
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-16 Regulatory basis is 10 CFR 50, Appendix J and 10 CFR 50.12(a)(1)
NuScales technical report TR-1116-51962, Table 5-2, Summary of Test and Inspection Elements, states that CNTS leakage test will be conducted in accordance with ASME Class 1,Section XI, IWB Exam Category B-P.
ASME Section XI requirements, IWB-2500-1 (B-P) Exam Category, requires a system leakage test of all pressure retaining components at the end of a refueling outage. This test is comparable to a GDC 52 and Appendix J Type A test. This is done with the reactor coolant boundary in a normal alignment for operation, and is conducted at normal operating pressure and temperature. This ensures the reactor coolant system integrity is ready for the next cycle.
Will a comparable test be conducted for the containment vessel since it will be subject to ASME Class 1 in service inspection (ISI) requirements? If a comparable test is conducted for the CNV, identify what pressure will it be conducted, and explain why this supports the request for not testng at the design pressure and testing time for the Type A test.
NuScale Response:
While the requirements of ASME BPVC Section XI Table IWB-2500-1 (B-P) and 10 CFR 50 Appendix J Type A tests are similar, they are testing different readiness conditions of the containment vessel (CNV). The 10 CFR 50 Appendix J Type A test is to demonstrate that known containment leakage paths are satisfactorily sealed, and that no new leakage paths have developed. The ASME BPVC Section XI test confirms the readiness of a pressure vessel to be placed into operation.
The requirements of ASME BPVC Section XI Table IWB-2500-1 (B-P) govern a pressure test that is performed at the vessel's operating pressure at 100% power conditions and at a temperature above the most limiting material brittle fracture temperature, prior to the vessel going into service per IWB-5200. The NuScale power module (NPM) CNV is under a vacuum
NuScale Nonproprietary and at a temperature equal to the reactor pool temperature during normal operation at 100%
power. So no full CNV pressure test is required to occur at the end of an outage period to meet the requirement of Table IWB-2500-1 (B-P). After a refueling or maintenance outage period and reassembly of the NPM is complete, all dual O-ring seals except the CNV manway are 10 CFR 50 Appendix J Type B tested through the test ports to a pressure of at least the peak accident pressure (Pa), while the NPM is still in the refueling bay. The Type B testing of the CNV manway is tested once the CNV is placed in the operating bay. Type B testing is used to verify that both O-rings are sealed to the peak accident pressure, confirming the integrity of the bolted flange connection and thereby meeting the intent of Table IWB-2500-1 (B-P).
Prior to the reactor producing power all water is evacuated from the CNV and a vacuum pulled within the CNV. If either air or water leakage occurs, the leakage will be detected by the containment evacuation system (CES). The leakage criteria will be based on the ability to draw a vacuum and margin to CES capacity.
A hydrostatic test at a minimum pressure of 125% of the design pressure is performed on every containment vessel (CNV) prior to going into service. No leakage indications at the hydrostatic test examination pressure are permitted. Therefore, the hydrostatic test demonstrates that the CNV flange connection seal design allows no leakage at a minimum pressure of 125% of the design pressure and that the CNV shell is leak tight. This also confirms the seal design is leak tight under loaded conditions that exceed peak accident pressure.
After refueling, the Type B leak test is performed which pressurizes the space between all of the flanged joint seals. The Type B pneumatic testing pressure is at least Pa, and permits no significant drop in pressure once the Type B pressure is reached and leakage measurement is being performed. A Type A test pressurizes the inside of the vessel and only confirms the inner O-ring or a combination of the inner and outer O-ring is sealed. The Type B leak test confirms that both the inner and outer O-ring seal is established and that the leakage is within acceptable range. This assures that the fit-up has been acceptably performed and that leakage is within expected allowances.
Impact on DCA:
There are no impacts to the DCA as a result of this response.
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-17 Regulatory basis is 10 CFR 50, Appendix J and 10 CFR 50.12(a)(1)
NuScale FSAR section 6.2.6 states, in part, based on the high pressure and safety functions of the CNV, the Inservice Inspection Program requires the CNV to meet ASME class 1 requirements, similar to the RPV. The CNV design allows for visual inspection of the entire inner and outer surfaces.
NuScale FSAR section 6.2.1.6 states, in part, enhanced inspection requirements are provided for the CNV in excess of the Class MC requirements of ASME BPVC,Section XI, Subsection IWE. The CNV augmented inspections are based on Class 1 requirements of ASME BPVC,Section XI. The CNV inspection elements are provided in Table 6.2-3. An inspection element is a combination of a component and the inspection requirements.
Table 6.2-3, Containment Vessel Inspection Elements, does not address the containment shell inspection. Staff requests NuScale add the Examination Category and the Examination Method for the CNV shell to the table. If the CNV upper section, which is clad inside and outside, has different Categories or Examination Methods, address the distinction. Staff requests that FSAR Table 6.2-3, be revised to reflect the response and to include the CNV shell inspection. Indicate whether the inspection is inside or outside the CNV.
Staff requests that NuScale confirm that the CNV shell inspection will occur during each refueling outage. Include this frequency in the Notes column of FSAR Table 6.2-3.
Staff also requests that NuScale TR-1116-51962, Table 5-2, Summary of Test and Inspection Elements, be revised to include the CNV shell Examination Categories and Examination Methods.
NuScale Operating Procedure, OP-0000-10842, rev 0, NuScale Module Refueling Operations should also be updated to include the CNV shell inspection.
NuScale Nonproprietary NuScale Response:
FSAR Table 6.2.3 is updated to provide visual examination categories and methods for internal and external surfaces of the containment vessel (CNV). The CNV is designed and inspected as if it were a reactor pressure vessel, therefore, it is necessary to inspect the interior surfaces consistent with Table IWB-2500-1 (B-N-1, B-N-2, B-N-3). There are no inspections that ASME BPVC requires for a reactor pressure vessel exterior surfaces, however a metallic containment requires a VT-3 inspection of any wetted surfaces, therefore the wetted exterior surfaces of the CNV will be inspected consistent with Table IWE-2500-1 (E-A) for wetted containment vessel surfaces. This requirement is relaxed to a general visual inspection for the top of the CNV head since this surface is not typically wetted.
FSAR Table 6.2-3 and TR-1116-51962 have been modified to add the inspection requirements for the CNV.
Impact on DCA:
Table 6.2-3 and related Technical Report TR-1116-51692, NuScale Containment Leakage Integrity Assurance, have been revised as described in the response above and as shown in the markup provided with this response.
NuScale Containment Leakage Integrity Assurance Technical Report TR-1116-51962-NP Draft Rev. 01
© Copyright 2016 2018 by NuScale Power, LLC 33 Table 5-2 Summary of test and inspection elements Description Exam Category Examination Method CNV shell and head welds B-A Volumetric CNV support welds B-A, B-K, F-A Surface, volumetric CNV nozzle-to-shell welds B-D Volumetric or not required per B-D, Note 1 Nozzle-to-safe end dissimilar metal welds Note: Safe end is a short length of Class 1 pipe that is welded between the forged CNV pipe penetration and the CIV body.
B-F Surface and volumetric, surface ECCS pilot valve body to safe end welds B-J Exempted by IWB-1220 due to small size PSCIV (GDC 55) body to safe end welds B-J Surface and volumetric Exemption per IWB-1220 due to small size not applied PSCIV (GDC 56) body to safe end welds C-F-1 Surface Exemption per IWB-1220 due to small size not applied SSCIV body to safe end welds C-F-1 Surface and volumetric Decay heat removal inner and outer safe end-to-piping welds C-F-1 Surface and volumetric CNV ports, manways, EPAs and ECCS pilot valve body-to-bonnet seals Appendix J Type B
Pneumatic leakage CNTS leakage test B-P VT-2 Required for all pressure retaining components CNV exterior surface N/A VT-3 for wetted surfaces General visual for surfaces that are normally dry. Based on the requirements from IWE-2500-1 (E-A).
CNV interior surfaces B-N-1 VT-3 5.2 Inservice Testing of the Containment System The NuScale standard IST Plan, as defined in FSAR Section 3.9.6, identifies all valves with specific leakage criteria. Valves with specific leakage criteria as a containment boundary are identified as LTJ, a valve with an Appendix J Type C leakage test requirement. The IST Plan also specifies test frequencies that are pursuant to the requirements of 10 CFR 50, Appendix J, Option A, (III)(D)(3). The NuScale IST program identifies all valves in the NuScale design that have a Type C test requirement. The NuScale IST plan specifies IST requirements for the NuScale Power Plant design.
NuScale Final Safety Analysis Report Containment Systems Tier 2 6.2-60 Draft Revision 1 RAI 05.02.04-3, RAI 06.02.01-3, RAI 06.02.02-2, RAI 06.02.06-17, RAI 06.02.06-18, RAI 06.06-3 Table 6.2-3: Containment Vessel Inspection Elements Component Description Examination Category Examination Method Notes CNV Shell and Head Welds Bottom head to core region shell B-A Volumetric Core region shell to lower transition shell B-A Volumetric Lower transition shell to lower flange B-A Volumetric Upper flange to RPV support lug shell B-A Volumetric RPV support lug shell to steam plenum access shell B-A Volumetric Steam plenum access shell to upper shell B-A Volumetric Upper shell to top head B-A Volumetric Support Welds Support skirt ring to support skirt F-A Visual Support skirt to bottom head B-K Surface or volumetric CNV shipping/storage support lug B-K Surface CNV support lug B-A Volumetric Alignment pin to threaded insert B-K Surface Instrument enclosure base to CNV None None Exempted by IWF-1230 CNV Nozzle to Shell Weldsand Head Welds Feedwater lines B-D Volumetric Examination requirement IWB-2500-7(b)
Main steam lines B-D Volumetric Examination requirement IWB-2500-7(b)
CRDS return line B-D Volumetric Examination requirement IWB-2500-7(b)
CVCS makeup line B-D Volumetric Examination requirement IWB-2500-7(b)
CVCS pressurizer spray line B-D Volumetric Examination requirement IWB-2500-7(b)
I&C Divisions B-D Not required See Table IWB-2500-1 (B-D) Note 1 Containment evacuation system line B-D Volumetric Examination requirement IWB-2500-7(b)
Containment flood and drain system line B-D Volumetric Examination requirement IWB-2500-7(b)
CRDS supply line B-D Volumetric Examination requirement IWB-2500-7(b)
CVCS letdown line B-D Volumetric Examination requirement IWB-2500-7(b)
RPV high point degasification line B-D Volumetric Examination requirement IWB-2500-7(b)
Pressurizer heater power (Elect-1 and 2)
B-D Not required See Table IWB-2500-1 (B-D) Note 1 I&C channels A-D B-D Not required See Table IWB-2500-1 (B-D) Note 1 Decay heat removal system lines B-D Volumetric Single sided, shell side. Examination requirement IWB-2500-7(b)
NuScale Final Safety Analysis Report Containment Systems Tier 2 6.2-62 Draft Revision 1 CRDM access opening None VT-1 No inspection requirement. Augmented to VT-1 when bolts are removed.
CRDM power None VT-1 No inspection requirement. Augmented to VT-1 when bolts are removed.
RPI groups None VT-1 No inspection requirement. Augmented to VT-1 when bolts are removed.
CNV manway None VT-1 No inspection requirement. Augmented to VT-1 when bolts are removed.
SG inspection ports None VT-1 No inspection requirement. Augmented to VT-1 when bolts are removed.
PZR heater access ports None VT-1 No inspection requirement. Augmented to VT-1 when bolts are removed.
Bolting CNV main flange bolts B-G-1 See Notes Per Note 7 of B-G-1, surface examination is permitted when bolts are removed.
CNV bolting two inches or less in diameter B-G-2 VT-1 Examine if removed.
CNV Shell CNV shell exterior surfaces below CNV head weld N/A VT-3 Augmented examination of wetted surface area based on IWE-2500-1 (E-A).
To be inspected once per inspection period.
CNV shell exterior surfaces above CNV head weld N/A General Visual Augmented based on IWE-2500-1 (E-A).
To be inspected once per inspection period.
CNV shell interior surfaces B-N-1 VT-3 To be inspected once per inspection period.
Table 6.2-3: Containment Vessel Inspection Elements (Continued)
Component Description Examination Category Examination Method Notes
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-18 Regulatory basis is 10 CFR 50, Appendix J and 10 CFR 50.12(a)(1)
NuScale TR-1116-51962-NP, Rev 0, NuScale Containment Leakage Integrity Assurance Technical Report, states in section 5, that CNV bolted flanges have their bolts inspected per ASME XI, Category B-G-1 or B-G-2, each time the bolting is removed. The TR, Appendix A, Table A.1, Type B Containment Penetrations lists the bolted containment penetrations. In addition to the CNV main flange, identify which of these flanges are opened at each refueling. If the flanges are not opened at each refueling, indicate the minimum frequency at which the flanges will be opened, and therefore the bolts inspected.
Staff also requests that NuScale TR-1116-51962, Table 5-2, Summary of Test and Inspection Elements, be revised to address the CNV main flange Examination Category and Examination Method.
NuScale Response:
ASME BPVC Section XI Table IWB-2500-1 (B-G-1) requires the containment closure flange bolts, nuts and washers to be inspected each interval (10 year period). The access cover studs are less than 2 inch diameter and per ASME BPVC Section XI Table IWB-25500-1 (B-G-2) are only required to be inspected when the connection is disassembled or bolting is removed (see Table IWB-2500-1 (B-G-2) Note 1). The CRDMs and pressurizer heaters are designed for a 60 year life. Therefore, the CRDM cover (CNV25), CRDM power cover (CNV37), PZR power covers (CNV15-16), RPI group 1 and 2 cover (CNV38-39) and two PZR heater access covers (CNV31-32) are not expected to be removed for the life of the plant. However, if maintenance is required for the CRDMs or pressurizer heaters, the covers would be removed and the bolts inspected at that time. The upper CNV head manway cover (CNV24) and upper CNV manway cover (CNV26) are expected to be removed every outage and these bolts would therefore be inspected each interval. The four SG access covers (CNV27-30, I&C channel A-D (CNV17-20) and I&C Division 1 and 2 (CNV8-9) covers may be removed every outage and will be inspected
NuScale Nonproprietary once an interval when removed.
TR-1116-51962, Table 5-2 has been modified to add inspection elements for the flange bolting (B-G-1) and cover bolting (B-G-2).
Impact on DCA:
Technical Report TR-1116-51962, NuScale Containment Leakage Integrity Assurance, has been revised as described in the response above and as shown in the markup provided in this response.
NuScale Containment Leakage Integrity Assurance Technical Report TR-1116-51962-NP Draft Rev. 01
© Copyright 2016 2018 by NuScale Power, LLC 33 Table 5-2 Summary of test and inspection elements Description Exam Category Examination Method CNV shell and head welds B-A Volumetric CNV support welds B-A, B-K, F-A Surface, volumetric CNV nozzle-to-shell welds B-D Volumetric or not required per B-D, Note 1 Nozzle-to-safe end dissimilar metal welds Note: Safe end is a short length of Class 1 pipe that is welded between the forged CNV pipe penetration and the CIV body.
B-F Surface and volumetric, surface ECCS pilot valve body to safe end welds B-J Exempted by IWB-1220 due to small size PSCIV (GDC 55) body to safe end welds B-J Surface and volumetric Exemption per IWB-1220 due to small size not applied PSCIV (GDC 56) body to safe end welds C-F-1 Surface Exemption per IWB-1220 due to small size not applied SSCIV body to safe end welds C-F-1 Surface and volumetric Decay heat removal inner and outer safe end-to-piping welds C-F-1 Surface and volumetric CNV ports, manways, EPAs and ECCS pilot valve body-to-bonnet seals Appendix J Type B
Pneumatic leakage CNTS leakage test B-P VT-2 Required for all pressure retaining components CNV exterior surface N/A VT-3 for wetted surfaces General visual for surfaces that are normally dry. Based on the requirements from IWE-2500-1 (E-A).
CNV interior surfaces B-N-1 VT-3 5.2 Inservice Testing of the Containment System The NuScale standard IST Plan, as defined in FSAR Section 3.9.6, identifies all valves with specific leakage criteria. Valves with specific leakage criteria as a containment boundary are identified as LTJ, a valve with an Appendix J Type C leakage test requirement. The IST Plan also specifies test frequencies that are pursuant to the requirements of 10 CFR 50, Appendix J, Option A, (III)(D)(3). The NuScale IST program identifies all valves in the NuScale design that have a Type C test requirement. The NuScale IST plan specifies IST requirements for the NuScale Power Plant design.
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-19 Regulatory basis is 10 CFR 50, Appendix J and 10 CFR 50.12(a)(1)
NuScale calculation EC-A011-3036, rev 1, 28 Dec 2016, CNV Ultimate Pressure Integrity Analysis assumed a maximum allowable gap of 0.030 between the bolted flanges at the center of the outer O-ring. This is intended to represent the maximum gap before unacceptable NuScale FSAR section 6.2.6.2 states that all CNV bolted flanges have dual O-ring seals. flange leakage would occur. (This value is currently identified as ODI-15-0140).
Explain how this maximum flange gap will be verified, including but not limited to, the following items: Where will the CNV be during verification? Will this verification be automated? Will it require special tools? Will it be measured at each bolted flange? Will it be measured during each refueling? When will this maximum allowable gap value be finalized?
NuScale Response:
When a seal fabricator is selected a seal design will be established and tested to identify at what amount of separation the O-ring seal is lost. When the design and testing of the O-ring design is finalized the maximum allowable gap at the O-ring will be established. If leakage is found to occur at less than 0.030" the design will be re-evaluated in accordance with the design process.
The 0.030" gap identified in EC-A011-3036 does not occur until the CNV internal pressure exceeds the design pressure. As indicated by TR-0917-56119, Revision 0, Section 4.2, a flange gap of 0.030" forms at a CNV internal pressure of 1240 psi, which exceeds both the CNV analyzed peak pressure of 951 psia and design pressure of 1000 psia. The gap that occurs is from prying occuring on the joint as a result of high internal pressure. There is no tooling or means of measuring the gaps on the CNV flanges as internal pressure is increased to high pressure. At the end of an outage period when the flange connections are re-assembled and all fasteners torqued to their required tension there will be no gap at the flanged connection.
NuScale Nonproprietary The 10 CFR 50 Appendix J Type B testing of required NPM bolted connections will be performed at the end of every refueling / maintenance outage in the refueling bay before the NPM is moved to its operating bay. The type B testing will be performed for a majority of the vessel flanges while the module upper section is in the dry dock. The final type B test of the containment closure flange will be completed when the CNV has been reassembled while in the containment flange tool. The final access flange tests will be performed with the module on the containment flange tool or in the operating bay. Testing will be performed manually, with a predesigned test rig for type B testing, which will need no special tooling. The type B test pressurizes the space between the O-rings with air and is evaluated to confirm pressure is not lost across either seal.
The equipment used to support Type B leakage testing is not automated. Attachment of test lines and the process of testing does not require any specialized tooling.
Impact on DCA:
There are no impacts to the DCA as a result of this response.
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-20 Regulatory basis is 10 CFR 50, Appendix J and 10 CFR 50.12(a)(1)
NuScale calculation EC-A011-3036, rev 1, 28 Dec 2016, CNV Ultimate Pressure Integrity Analysis section 3.1 lists several criteria, any of which would fail the CNV. One criterion is exceeding a flange gap of 0.030 in. at the outer O-ring of any bolted CNV opening. Calculation Table 5-2, Flange Gap vs. Pressure from 1000 psi to 1800 psi, shows that CNV31 flange gap for the pressurizer heater access port, is exceeded at less than the hydrotest pressure of 1250 psia.
Explain how this is an acceptable hydrotest pressure.
Another CNV failure criterion is the loss of bolt preload occurring at any bolted CNV opening. As is shown in calculation Table 5-1, Stud Preload and Pressure to Lose Preload, all pressures exceed the 1240 psia ultimate pressure. These results illustrate the importance of correctly calculating and applying the bolt preloads. These current preload values are assumed, and require verification {ODI-14-0141}.
When will these stud preload and pressure to lose preload values be finalized?
NuScale Response:
The final bolt preload will be established when the NB-3200 design by analysis is performed for each access opening. The design by analysis is needed to establish the stress induced on the fasteners during transient events. The preload will be established to generate the largest preload while keeping fastener stresses below NB-3200 limits. Completion of the NB-3200 evaluations support completion of the CNV design report which is tracked with ITAAC 02.01.01.
The response to eRAI 8858 Question 03.08.02-8 transmitted by NuScale letter RAIO-1017-56886, dated October 27, 2017 addresses the difference between pressure for the hydrostatic test and the CNV ultimate pressure integrity and why the hydrostatic pressure test is acceptable.
NuScale Nonproprietary Impact on DCA:
There are no impacts to the DCA as a result of this response.
NuScale Nonproprietary Response to Request for Additional Information Docket No.52-048 eRAI No.: 9216 Date of RAI Issue: 12/12/2017 NRC Question No.: 06.02.06-21 In Exemption Request 10 CFR 50 App A, GDC 52, Containment Leak Rate Testing, NuScale states Type B and C testing, inspections, and administrative controls (e.g., configuration management and procedural requirements for system restoration) to assure leakage integrity associated with activity-based failure mechanisms (i.e., assures that CNV penetrations and CIVs remain within allowable leakage rate values after system and component modifications or maintenance)
Staff notes that there is recent operating experience related to the opening and closing of reactor pressure vessels during refueling, which have involved leaking bolted flanges, overtorqued flange bolts, malfunction of specialized bolting equipment, deformed O-ring seals, and stud tensioner malfunctions. These failures have been self-evaluated as resulting from refueling equipment malfunction, inadequate operator training, human error, software, inadequate procedures, and misinterpretation of measurement data.
Because this exemption request relies upon heavily on administrative controls, staff requests NuScale address how they will ensure leakage integrity for a design which has no operating experience with these controls. Explain how NuScale procedures differ (i.e., are superior) from current plants such that these errors are reasonabily concluded to be eliminated; or provide an alterative means that will demonstrate that the adminstrive controls provide the necessary assurance.
NuScale Response:
Local Leak Rate Testing Requirements NuScale performs Type B and C testing in accordance with the requirements of 10CFR 50, Appendix J. Specifically, all Type B seals are tested during reactor shutdown for refueling or maintenance. If any of these penetrations are opened during the refueling outage, the penetration is subject to an as-left Type B test, prior to returning the reactor to an operating mode requiring containment integrity. Type C tests are performed during each reactor shutdown for refueling. If any maintenance is performed on a CIV that could affect its leakage integrity, an as-left Type C test is performed, prior to returning the reactor to an
NuScale Nonproprietary operating mode requiring containment integrity.
Each Type B and Type C boundary is tested as-found every outage to verify containment leakage integrity. This not only ensures the 10 CFR 50, Appendix J criteria of 0.60(La) is satisfied, but as-found test results confirm that the previous outage containment performance was satisfactory. Administrative controls are in place to ensure maintenance is performed correctly and the NPM is left in an operational condition when it leaves the refueling bay prior to startup. The as-left Type B test ensures that the reassembly of the NPM was performed satisfactory and that the penetration will meet overall containment leakage requirements for the next fuel cycle. Compliance with the post outage testing (both Type B and Type C test) is the demonstration that the NPM is ready for service.
Recent Operational Experience The question discusses recent operating experience (OE) related to the opening and closing of reactor pressure vessels. The staff identified the following INPO references concerning this OE:
Plant ref #
Brunswick Unit 2 251881 Indian Point 3 319574 Surry Unit 1 246324 Palo Verde Unit 3 308940 Point Beach Unit 2 320146 Catawba Unit 2 315843 Catawba Unit 2 308349 Cook Unit 1 242224 Salem Unit 2 416600 Callaway Unit 1 251791 Most of the OE ( 7 of the 10 cited instances) identified addresses tool failures that impacted outage durations and did not result in flange leakage when the plant returned to an operating mode. NuScale can not evaluate the applicability of this OE since NuScale tooling has not yet been selected.
Of the other three cited OE, two of the cited instances (Cook Unit 1 and Salem Unit 2) involved bolting degradation caused by material susceptible to PWSCC. NuScale follows the guidance of NUREG-1339 by use of SA-564, Grade 630 S17400 (17-4 PH) condition H1100 bolting material in un-submerged locations and SB-637, N07718 (Alloy 718) austenitic stainless steel bolting material, that is resistant to PWSCC, in submerged locations.
In the Brunswick Unit 2 case, the plant had to shutdown because of excessive reactor head flange leakage, due to inadequate reactor vessel stud tension (about 10 per cent of the required amount), as discussed by INPO OE # 251881 and LER 2-2011-002, dated January 16, 2012.
NuScale Nonproprietary The cause was attributed to inadequate tensioner hydraulic pressure, which resulted from human error, combined with inadequate procedural guidance to ensure critical data (hydraulic pressure and stud elongation) was correctly interpreted. The OE also indicates that no post maintenance hydrostatic testing was performed after reactor head flange reassembly (testing flange sealing). NuScale can not address applicability of the inadequate procedural guidance, since tooling has not been selected, and associated procedural guidance has not been developed. However, following reassembly of a NuScale CNV flange, a Type B leakage test will be performed that could detect inadequate stud tension. In the case of Brunswick 2, subsequent testing of the RV flange joint was not performed after reassembly.
Conclusion The NuScale design and procedures will follow the ASME BPVC and 10 CFR 50 Appendix J Type B and Type C requirements, as discussed above. Compliance with these requirements confirms the as left-condition of the NPM flanges and valves meet the stringent Type B and Type C Acceptance Criteria given by 10 CFR 50, Appendix J. NuScale will perform visual inspection of the CNV interior and exterior surfaces to detect flaws that are not detected by Type B and Type C testing. Therefore, Type B and Type C testing, inspections and administrative controls meets the underlying purpose of General Design Criterion 52.
Impact on DCA:
There are no impacts to the DCA as a result of this response.