ML110040148
| ML110040148 | |
| Person / Time | |
|---|---|
| Site: | 05200021 |
| Issue date: | 12/28/2010 |
| From: | Ogata Y Mitsubishi Heavy Industries, Ltd |
| To: | Ciocco J Document Control Desk, Office of New Reactors |
| References | |
| UAP-HF-10347 | |
| Download: ML110040148 (24) | |
Text
At MITSUBISHI HEAVY INDUSTRIES, LTD.
16-5, KONAN 2-CHOME, MINATO-KU TOKYO, JAPAN December 28, 2010 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Attention: Mr. Jeffrey A. Ciocco Docket No.52-021 MHI Ref: UAP-HF-10347
Subject:
MHI's Responses to US-APWR DCD RAI No.670-4773 Revision 2 (SRP 09.04.05)
References:
- 1) "Request for Additional Information No. 670-4773 Revision 2, SRP Section:
09.04.05 - Engineered Safety Feature Ventilation System Application Section: DCD section 9.4.5" dated November 30, 2010.
With this letter, Mitsubishi Heavy Industries, Ltd. ("MHI") transmits to the U.S. Nuclear Regulatory Commission ("NRC") a document entitled "Responses to Request for Additional Information No. 670-4773 Revision 2".
Enclosed are the responses to 5 RAIs that are contained within Reference 1.
This response is being submitted in two versions. One version (Enclosure 1) includes certain information, designated pursuant to the Commission guidance as sensitive unclassified non-safeguards information, referred to as security-related information ("SRI"),
that is to be withheld from public disclosure under 10 C.F.R. § 2.390. The information that is SRI is identified by brackets. The second version (Enclosure 2) omits the SRI and is suitable for public disclosure. In the public version, the SRI is replaced by the designation
"[Security-Related Information - Withheld under 10 CFR 2.390]."
Please contact Dr. C. Keith Paulson, Senior Technical Manager, Mitsubishi Nuclear Energy Systems, Inc. ifthe NRC has questions concerning any aspect of the submittals. His contact information is below.
Sincerely, Yoshiki Ogata, General Manager- APWR Promoting Department Mitsubishi Heavy Industries, LTD.
Enclosure:
- 1. Responses to Request forAdditional Information No. 670-4773 Revision 2 (SRI included version)
- 2. Responses to Request forAdditional Information No. 670-4773 Revision 2 (SRI excluded version)
CC: J. A. Ciocco C. K. Paulson Contact Information C. Keith Paulson, Senior Technical Manager Mitsubishi Nuclear Energy Systems, Inc.
300 Oxford Drive, Suite 301 Monroeville, PA 15146 E-mail: ck-paulson@mnes-us.com Telephone: (412) 373-6466
Enclosure 2 UAP-HF-10347 Docket Number 52-021 Responses to Request for Additional Information No. 670-4773 Revision 2 December, 2010 (Security excluded version)
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 12/28/2010 US-APWR Design Certification Mitsubishi Heavy Industries Docket No.52-021 RAI NO.: NO.670-4773 REVISION 2 SRP SECTION: 09.04.05 - ENGINEERED SAFETY FEATURE VENTILATION SYSTEM APPLICATION SECTION: DCD Sections 9.4.5 DATE OF RAI ISSUE: 11/30/2010 QUESTION NO. : 09.04.05-14 The staff performed an audit of MNES calculations that support the design information contained in DCD section 9.4.5.
SRP 9.4.5" "Areas of Review,"Section I, Item 2.D, states that: "Safety-related portions of the ESFVS are also reviewed with respect to the following: .... The capability of the system to circulate sufficient air to prevent accumulation of flammable or explosive gas or fuel-vapor mixtures from components such as storage batteries and stored fuel..."
This requirement formed the basis for the questions asked in RAI Number 64-735, Question Number 09.04.05-1, RAI 9.4.5-4 and its follow-up RAI Number 356-2549, Question Number 09.04.05-4.
During the staffs audit of MNES Calculation N0-EE23202 Revision 1, dated 5/10/2010" US-APWR Standard Design - Class 1E Electrical Room HVAC System (CERVS) Calculations," the staff observed that the information contained in DCD Table 8.3.2-3 for the Class 1E DC Power System read for the Battery Bank "4 - 125Vdc 60 flooded lead acid cells...". More specifically, this Table leads to the conclusion that 60 flooded lead acid cells exist for each of the four Class 1E Battery rooms displayed on Figure 9.4.5-2 of the DCD. Figure 8.3.2-1 "DC Power Distribution System (Sheet 1 of 2) Class 1E" leads to this same conclusion.
The staff noted to the applicant that 120 cells were listed Calculation NO-EE23202 to derive the ventilation flow value requirement for each battery room to limit hydrogen concentrations at or below 1% by volume.
The applicant clarified that 120 flooded lead acid cells exist in each of the four battery rooms and acknowledged that Table 8.3.2-3 and Figure 8.3.2-1 needed to be revised to provide this clarity. The applicant should also verify that other sections of the DCD which discuss the battery should be clear. For example, section 8.3.2.1.1, Class 1E DC Power System, discusses the batteries giving battery and per cell voltages. The discussion implies that a battery consists of 60 cells. Later, there is mention of a battery bank and it is not clear if this is intended to mean two batteries of 60 cells each with bank rating of 5000Ah.
The staff identified this observation to the applicant at the time of discovery and during the audit's exit briefing. The applicant concurred with this observation and agreed to revise Table 8.3.2-3 and Figure 8.3.2-1 to reflect the existence of 120 flooded lead acid cells in each of the four battery rooms.
09.04.05-1
This RAI serves as a tracking tool to ensure these changes occur.
In addition, that since Calculation NO-EE23202 serves as the bases of safety-related parameters and values found in the DCD Section 9.4.5, the staff requests that the applicant include MNES Calculation N0-EE23202" US-APWR Standard Design - Class 1E Electrical Room HVAC System (CERVS)
Calculations" as a Reference in DCD subsection 9.4.8.
References:
Sections 9.4.1 and 9.4.5 Audit Plan, dated 5/18/2010, ML101370265.
MHI's Responses to US-APWR DCD RAI No.64-735; MHI Ref: UAP-HF-08216; dated 10/6/2008; ML082830021.
MHI's Responses to US-APWR DCD RAI No. 356-2549; MHI Ref: UAP-HF-09386; dated 7/17/2009; ML092030375.
ANSWER:
Table 8.3.2-3 and Figure 8.3.2-1 will be revised to clearly state that the battery consists of two strings of 60 cells. In addition, figures for two separate battery cells will be depicted in Figure 8.3.2-1. As a result, description of Section 8.3.2.1.1 does not need to be revised.
The technical report "Safety-Related Air Conditioning, Heating, Cooling, and Ventilation Systems Calculations" (MUAP-1 0020) submitted to the NRC as described in DCD RAI No.642-4770 Question No.09.04.01-24 includes the content of Calculation NO-EE23202 and will be included as a reference in DCD subsection 9.4.8.
Impact on DCD DCD Revision 2 Table 8.3.2-3 will be revised as follows;
- a. Battery Bank 4 - 125Vdc, 2 strings of 60 flooded lead acid cells, 5000Ah*, float voltage 2.25V/cell, equalize voltage 2.33V/cell, 8 hr rating
- b. Battery Charger 4 - ac input - 480V, 3 phase, 60Hz; dc output - 125Vdc, 700A Continuous; float voltage -
135V, equalizing charge voltage 140V, 24hr recharge
- a. Switchboard 4 - 125Vdc, Main bus 3000A, 50kA short circuit
- b. Panelboards 4 - Main bus 225A continuous, 40kA short circuit 09.04.05-2
- c. Spare Battery Charger (Non-class 1E) 2 - ac input - 480V, 3 phase, 60Hz; dc output - 125Vdc, 700A Continuous; float voltage -
135V, equalizing charge voltage 140V, 24hr recharge
- Actual Ah rating is decided in accordance with manufacturer's specification.
DCD Revision 2 Figure 8.3.2-1 Sheet 1 of 2 will be revised as the attachment-i.
Impact on COLA There is no impact on the COLA.
Impact on PRA There is no impact on the PRA.
09.04.05-3
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Figure 8.3.2-1 DC Power Distribution System (Sheet 1 of 2)
M Class 1E
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 12/27/2010 US-APWR Design Certification Mitsubishi Heavy Industries Docket No.52-021 RAI NO.: NO.670-4773 REVISION 2 SRP SECTION: 09.04.05 - ENGINEERED SAFETY FEATURE VENTILATION SYSTEM APPLICATION SECTION: DCD Sections 9.4.5 DATE OF RAI ISSUE: 11/30/2010 QUESTION NO. : 09.04.05-15 The staff performed an audit of MNES calculations that support the design information contained in DCD section 9.4.5.
SRP 9.4.5, "Areas of Review,"Section I, Item 2.D, states that: "Safety-related portions of the ESFVS are also reviewed with respect to the following;...The capability of the system to circulate sufficient air to prevent accumulation of flammable or explosive gas or fuel vapor mixtures from components such as storage batteries and stored fuel;..."
This requirement formed the basis for the questions asked in RAI Number 64-735, Question Number 09.04.05-1, RAI 9.4.5-4 and its follow-up RAI Number 356-2549, Question Number 09.04.05-4.
During the staffs audit of MNES Calculation N0-EE23202 Revision 1, dated 5/10/2010" US-APWR Standard Design - Class I E Electrical Room HVAC System (CERVS) Calculations" the staff observed that the applicant used British Standard BS EN 50272- 2:2001 in its derivation of the required ventilation flow rate to keep hydrogen levels below 1% by volume within each Class 1E battery room.
The staff notes that Revision 2, Chapter 8 of the DCD does not list BS EN 50272-2:2001 as a reference.
DCD subsection 8.1.5.3.5, "Institute of Electrical and Electronics Engineers Standards" does list IEEE Std 484-2002, "IEEE Recommended Practice for Design and Installation of Large Lead Storage Batteries for Generating Stations and Substations". DCD Table 8.1-1 "Design Criteria and Guidelines for Electric Power Systems (Sheet 4 of 7)" does indicate that the US-APWR does conform with RG 1.128 "Installation Design and Installation of Vented Lead-Acid Storage Batteries for Nuclear Power Plants." RG 1.128 endorses the use of IEEE Std 484-2002 but not BS EN 50272-2:2001.
SRP 8.3.2 "DC Power Systems (Onsite)" also endorses the use of RG 1.128 and "SRP Acceptance Criteria" reads "Specific SRP acceptance criteria acceptable to meet the relevant requirements of the NRC's regulations identified above are as follows for the review described in this SRP section. The SRP is not a substitute for the NRC's regulations, and compliance with it is not required. However, an applicant is required to identify differences between the design features, analytical techniques, and procedural measures proposed for its facility and the SRP acceptance criteria and evaluate how the proposed alternatives to the SRP acceptance criteria provide acceptable methods of compliance with the NRC regulations."
09.04.05-5
Based on this, the staff requests that the applicant provide an evaluation of how the use of BS EN 50272-2:2001 provides an acceptable alternative to IEEE Std 484-2002. A comparison of the results using the two references may serve as the basis for demonstrating the BS-EN produces conservative or very similar results and is therefore an acceptable alterntative to the approved reference. In addition, if the use of BS EN 50272-2 is adequately justified, the staff requests that applicant amend the DCD to reflect its use.
The staff notes another audit observation in that DCD Revision 2, Tier 1 ITAAC Table 2.7.5.2-3 "Acceptance Criteria" 4.c still reads "The as-built Class 1E electrical room HVAC system is capable of providing battery room ventilation to maintain hydrogen concentration below 2% by battery room volume".
This needs to be changed to .below 1% by battery room volume." Staff acknowledges that MUAP-09026, Rev. 0, USAPWR DCD Revision 2 RAI Tracking Report has this correction listed as planned in DCD revision 3. This RAI will serve as a tracking tool to ensure this change occurs.
References:
Sections 9.4.1 and 9.4.5 Audit Plan, dated 5/18/2010, ML101370265.
MHI's Responses to US-APWR DCD RAI No.64-735; MHI Ref: UAP-HF-08216; dated 10/6/2008; ML082830021.
MHI's Responses to US-APWR DCD RAI No. 356-2549; MHI Ref: UAP-HF-09386; dated 7/17/2009; ML092030375.
ANSWER:
Consistent with SRP 9.4.5, "Areas of Review,"Section I, Item 2.D, Class 1E Electrical Room HVAC System provides the capability to maintain the hydrogen concentration in the Class 1E battery rooms below 1% by volume as described in DCD Section 9.4.5.2.2. In addition, consistent with SRP 8.3.2, the installation of the Class 1E batteries conforms to Regulatory Guide 1.128, InstallationDesign and Installation of Vented Lead-Acid Storage Batteriesfor Nuclear PowerPlants, Rev. 2, as described in DCD Section 8.3.2.2.2, and with IEEE Std. 484-2002, IEEE Recommended Practice for InstallationDesign and Installation of Vented Lead-Acid Batteries for StationaryApplications, as described in DCD Section 8.3.2.1.1.
The installation of the Class 1E batteries and the design of the Class 1E Electrical Room HVAC System as described in the DCD do not propose an alternative to SRP 8.3.2 or SRP 9.4.5 acceptance criteria related to the battery room exhaust ventilation. Regulatory Guide 1.128 and IEEE Std. 484, referenced in SRP 8.3.2, do not provide the methodology to be used to calculate battery room exhaust airflow rate.
The maximum hydrogen evolution rate that is provided in IEEE Std. 484, Section 5.4, is used as input to the design basis calculation of required minimum battery room exhaust ventilation airflow rate. Since further details or guidance for calculation of the minimum ventilation requirement is not described in Regulatory Guide 1.128 or IEEE Std. 484, compliance with NRC regulations is accomplished by using the IEEE Std. 484 hydrogen evolution rate as input to the calculation, and by providing reference to Regulatory Guide 1.128 and IEEE Std. 484 in the DCD (references 8.3.2-6 and 8.3.2-3, respectively).
The minimum exhaust ventilation flowrate required to maintain hydrogen levels below 1% by volume within each Class 1E battery room is calculated using the equation shown in British Standard EN 50272-2:2001, Section 8.2. The equation represents a standard industry approach to convert hydrogen evolution rate per cell per charging ampere to total hydrogen evolution per battery, and find the total dilution flowrate to maintain a specified concentration by volume. This approach is consistent with the methods recommended by battery manufacturer's literature and industry references. The British Standard EN 50272-2:2001 provides a typical boost charge current value that is used in the absence of specific battery manufacturer information, since the Class 1E batteries have not been procured at this time. The EN 50272-2 correlation includes a safety factor (multiplier) of 5.
09.04.05-6
-I
The SRP acceptance criteria related to the battery room exhaust ventilation are met by reference to RG 1.128 and IEEE Std. 484 in the DCD. British Standard EN 50272-2:2001 is referenced in the design basis calculation that was developed to support the Class 1E Electrical Room HVAC System design requirement to maintain Class 1E battery room hydrogen concentration below 1% by volume. The use of the equation from EN 50272-2 is a detail that is documented in the design basis calculation and is not necessary to be included in the DCD. Therefore, MHI concludes that the DCD does not require revision to include reference to British Standard EN 50272-2:2001. British Standard EN 50272-2:2001 is included as a Reference in the technical report "Safety-Related Air Conditioning, Heating, Cooling, and Ventilation Systems Calculations" (MUAP-10020).
As described in DCD RAI No.474-3811 Question No.09.04.05-10, DCD Rev.2 Tier I ITAAC Table 2.7.5.2-3 "Acceptance Criteria" 4.c will be revised to indicate that the acceptance criterion is that the battery room hydrogen concentration is below 1% by battery room volume.
Impact on DCD There is no impact on the DCD.
Impact on COLA There is no impact on the COLA.
Impact on PRA There is no impact on the PRA.
09.04.05-7
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 12/27/2010 US-APWR Design Certification Mitsubishi Heavy Industries Docket No.52-021 RAI NO.: NO.670-4773 REVISION 2 SRP SECTION: 09.04.05 - ENGINEERED SAFETY FEATURE VENTILATION SYSTEM APPLICATION SECTION: DCD Sections 9.4.5 DATE OF RAI ISSUE: 11/30/2010 QUESTION NO. : 09.04.05-16 The staff performed an audit of MNES calculations that support the design information contained in DCD section 9.4.5.
SRP 9.4.5, Section 111.1, requires a review for normal and emergency operations, and the ambient temperature limits for the areas serviced. DCD Section 9.4.5.2.1 indicates the annulus emergency exhaust system draws down the penetration and safeguarded component areas to a negative pressure of 0.25 in. wg with regard to adjacent areas.
This requirement formed the basis for the questions asked in RAI Number 64-735, Question Number 09.04.05-1, RAI 9.4.5-3 and its follow-up RAI Number 356-2549, Question Number 09.04.05-3.
During the audit, the staff reviewed calculation procedures and methods, including assumptions and margins, which support maintaining a negative pressure of 0.25 in. wg in the penetration and safeguarded component areas.
In particular, the staff reviewed:
- 1) MNES Calculation NO-EE23201 "US-APWR Standard Design -Annulus Emergency Exhaust System (AEES) Calculations", revision 0, dated 3/10/2010 and
- 2) MNES Calculation NO-EH80016 "US-APWR Standard Design - Safeguard Component Area and Annulus Area Volume", revision 2, dated 1/16/2010.
Calculation NO-EH80016 clearly defines, with plant annotated Figures, the Reactor Building areas that comprise the safeguard component area and the annulus area. This calculation also derives the volumes of both areas.
The staff noted to the applicant, that the DCD does not clearly define these areas nor describe these areas in sufficient detail to evaluate the efficacy of the system. The staff requested that the applicant amend DCD Section 6.5.1 to include a description of these areas and the significance of these areas in passing the surveillance requirements associated with the AEES. More specifically, the significance of these boundaries support the operability requirements for the annulus emergency exhaust system as specified in SR 3.7.11 B.1 (Rev. 2 DCD Chapter 16, page 3.7.11-4). In particular, SR 3.7.11 B.1 reads "If the penetrationor safeguardcomponent areas boundary is inoperable, the annulus emergency exhaust system trains cannot perform their intended functions." The staff also requested that the applicant revise Section 6.5.1 to include the annotated Figures from Calculation NO-EH80016.
09.04.05-8
The applicant agreed to revise the DCD section 6.5.1 to clearly define the draw down areas of the safeguard component area and the annulus area.
Since Calculations NO-EE23201 and NO-EH80016 serve as the bases of safety-related parameters and values found in the DCD Section 9.4.5, the staff requests that the applicant include:
- 1) MNES Calculation NO-EE23201 "US-APWR Standard Design -Annulus Emergency Exhaust System (AEES) Calculations" as a Reference in DCD subsection 9.4.8; and
- 2) MNES Calculation NO-EH80016 "US-APWR Standard Design - Safeguard Component Area and Annulus Area Volume" as a Reference in DCD subsection 6.5.7.
This RAI serves as a tracking tool to ensure these changes occur.
References:
Sections 9.4.1 and 9.4.5 Audit Plan, dated 5/18/2010, ML101370265.
MHI's Responses to US-APWR DCD RAI No.64-735; MHI Ref: UAP-HF-08216; dated 10/6/2008; ML082830021.
MHI's Responses to US-APWR DCD RAI No. 356-2549; MHI Ref: UAP-HF-09386; dated 7/17/2009; ML092030375.
ANSWER:
Technical report "Safety-Related Air Conditioning, Heating, Cooling, and Ventilation Systems Calculations" (MUAP-1 0020) submitted to the NRC as described in DCD RAI No.642-4770 Question No.09.04.01-24 includes the content of Calculation NO-EE23201 and will be included as a reference in DCD subsection 6.5.7 and 9.4.8.
DCD Subsection 6.5.1 will be revised to add the general arrangements that clarify the boundaries of the safeguard component area and penetration area to support the operability requirements for the annulus emergency exhaust system as specified in SR 3.7.11 B.1 Impact on DCD The second paragraph of DCD Revision 2 Subsection 6.5.1 will be revised to add as follows; "The penetration areas are located adjacent to the containment and include all piping and electrical penetration areas. The safeguard component areas are located adjacent to the containment and include ECCS components and CSS components that are installed outside of containment. The penetration areas and the safeguard component areas are shown in Figure 6.5-2 through 6.5-9."
DCD Revision 2 Subsection 6.5.1 will be revised to add the general arrangements that clarify the boundaries of the safeguard component area and penetration area as the attachment-2.
DCD Subsection 6.5.7 will be revised to add the technical report (MUAP-1 0020) as a reference.
Impact on COLA There is no impact on the COLA.
Impact on PRA There is no impact on the PRA.
09.04.05-9
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RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 12/27/2010 US-APWR Design Certification Mitsubishi Heavy Industries Docket No.52-021 RAI NO.: NO.670-4773 REVISION 2 SRP SECTION: 09.04.05 - ENGINEERED SAFETY FEATURE VENTILATION SYSTEM APPLICATION SECTION: DCD Sections 9.4.5 DATE OF RAI ISSUE: 11/30/2010 QUESTION NO. : 09.04.05-17 The staff performed an audit of MNES calculations that support the design information contained in DCD section 9.4.5. Reference Accession No.: ML101370265.
SRP 9.4.5, Section 111.1, requires a review for normal and emergency operations, and the ambient temperature limits for the areas serviced.
GDC 4 with respect to the ESFVS being appropriately protected against dynamic effects and being designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. The evaluation with respect to GDC 4 also includes evaluation of the adequacy of environmental support provided to SSCs important to safety located within areas served by the ESFVS. Per the regulatory requirements of RG 1.206, the DCD needs to contain a design of sufficient detail so the NRC staff can perform its own set of confirmatory calculations or review the applicant's calculations to support writing of the SER.
These requirements form the bases for the questions asked in RAI Number 64-735, Question Number 09.04.05-01 RAI 9.4.5-22 and its follow-up RAI Number 356-2549, Question Number 09.04.05-9.
During the staffs audit of MNES Calculation NO-EE23204, Revision 1, dated 5/18/2010, "US-APWR Standard Design - Emergency Feedwater Pump Area HVAC System," the staff noted that the applicant derived the cooling requirements for the Turbine Driven EFW pump area in two fashions in different sections of NO-EE23204. The results from each derivation differed by 2,000 Btu/hr. More specifically, in section 3.5.3 of N0-EE23204 the calculated cooling coil capacity of 62,000 Btu/Hr differed from the value derived in the "Alternate Calculation" section where the value derived was 60,000 Btu/hr. The staff acknowledges that this alternate calculation serves as a documented sanity check as to the accuracy of the more detailed base line derivation value.
The staff observed that DCD Table 9.4.5-1 for the Emergency Feedwater Pump (T/D) Area Air Handling Unit cooling coil lists the cooling coil capacity as 60,000 Btu/hr and asked the applicant why the less conservative "alternate calculation" value appears in DCD Table 9.4.5-1. The applicant acknowledged that 62,000 Btu/hr should appear in DCD Table 9.4.5-1 for the Emergency Feedwater Pump (T/D) Area Air Handling Unit and agreed to revise the DCD accordingly.
This RAI serves as a tracking tool to ensure this change occurs.
09.04.05-18
The staff notes that the following MNES calculations serve as the bases of safety related parameters and values found in the DCD Section 9.4.5.
- 1) NO-EE23203 US-APWR Standard Design - Safeguard Component Area HVAC System (SCAVS)
Calculations
- 3) N0-EE23205 US-APWR Standard Design - Safety Related Component Area HVAC System (SRCAVS)
Calculations The staff requests that the applicant include these calculations as References in DCD subsection 9.4.8.
References:
Sections 9.4.1 and 9.4.5 Audit Plan, dated 5/18/2010, ML101370265.
MHI's Responses to US-APWR DCD RAI No.64-735; MHI Ref: UAP-HF-08216; dated 10/6/2008; ML082830021.
MHI's Responses to US-APWR DCD RAI No. 356-2549; MHI Ref: UAP-HF-09386; dated 7/17/2009; ML092030375.
ANSWER:
Technical report "Safety-Related Air Conditioning, Heating, Cooling, and Ventilation Systems Calculations" (MUAP-1 0020) submitted to the NRC as described in DCD RAI No.642-4770 Question No.09.04.01-24 includes the content of Calculation NO-EE23203, NO-EE23204 and NO-EE23205 and will be included as a reference in DCD subsection 9.4.8.
According to the technical Report, the cooling coil capacity of Emergency Feedwater Pump (T/D) Area Air Handling Unit will be revised to change 60,000 Btu/hr to 62,000 Btu/hr in DCD Revision 2 Table 9.4.5-1.
Impact on DCD DCD Revision 2 Table 9.4.5-1 will be revised as follows; Emergency Feedwater Pump (T/D) Area Air Handling Unit Number of Units 2 Equipment Class 3 Seismic Category I Unit Airflow Capacity, cfm 1,300 Unit Fan Type Centrifugal Low Efficiency Filter Efficiency 25-35%
Cooling Coil Type Chilled Water Cooling Coil Capacity, btu/hr 60,0062,000 Heating Coil Type Electric Impact on COLA There is no impact on the COLA.
Impact on PRA There is no impact on the PRA.
09.04.05-19
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 12/27/2010 US-APWR Design Certification Mitsubishi Heavy Industries Docket No.52-021 RAI NO.: NO.670-4773 REVISION 2 SRP SECTION: 09.04.05 - ENGINEERED SAFETY FEATURE VENTILATION SYSTEM APPLICATION SECTION: DCD Sections 9.4.5 DATE OF RAI ISSUE: 11/30/2010 QUESTION NO. : 09.04.05-18 The staff performed an audit of MNES calculations that support the design information contained in DCD section 9.4.5. Reference Accession No.: ML101370265.
SRP 9.4.5,Section I, "Areas of Review," Item 2.D, states that: "Safety-related portions of the ESFVS are also reviewed with respect to the following .... The capability of the system to circulate sufficient air to prevent accumulation of flammable or explosive gas or fuel-vapor mixtures from components such as storage batteries and stored fuel."
This requirement formed the basis for the questions asked in RAI Number 64-735, Question Number 09.04.05-1, RAI 9.4.5-4 and its follow-up RAI Number 356-2549, Question Number 09.04.05-4.
During the staffs audit of MNES Calculation NO-EE23202 Revision 1 dated 5/18/2010" US-APWR Standard Design - Class 1E Electrical Room HVAC System (CERVS) Calculations" the staff observed that the applicant used British Standard BS EN 50272-2:2001 in its derivation of the required ventilation flow rate to keep hydrogen levels below 1% by volume within each Class 1E battery room. Section 8.1 of this British Standard reads "When the operation of the charge equipment is stopped the emission of gas from the cells can be regarded as having come to an end one hour afterhaving switched off the charging current."
During the audit, the staff observed that this information contradicts the MHI's response to RAI 64-735, RAI 9.4.5-18 b) which reads "The hydrogen concentrationwould not change following a SBO. The batteriesdo not generate hydrogen except when being chargedand would not be charging during this period."
MNES responded to this audit observation by stating that during the one hour after the start of the SBO event, the battery banks would be discharging (i.e. not sitting idle) and that during this transitional state no hydrogen gas would be generated.
There was no discussion during the audit nor commitment by MHI of amending RAI 64-735, RAI 9.4.5-18 b) response to: (a) remove this contradiction and (b) provide the basis for the conclusion that during this discharging period of one hour after the start of SBO (i.e. after suspension of charging) the battery banks would not emit additional hydrogen gas.
The staff requests that the applicant amend the response to RAI 64-735, RAI 9.4.5-18 b) to remove this contradiction and to provide the basis for the applicant's conclusion.
09.04.05-20
References:
Sections 9.4.1 and 9.4.5 Audit Plan, dated 5/18/2010, ML101370265.
MHI's Responses to US-APWR DCD RAI No.64-735; MHI Ref: UAP-HF-08216; dated 10/6/2008; ML082830021.
MHI's Responses to US-APWR DCD RAI No. 356-2549; MHI Ref: UAP-HF-09386; dated 7/17/2009; ML092030375.
ANSWER:
Batteries generate hydrogen during charging mode, and do not generate hydrogen during discharging mode. Hydrogen generation from batteries will stop due to battery discharge regardless of discharge rate.
In SBO condition, the batteries keep discharging until recharging by AAC power source. Therefore, the battery room ventilation fans do not need to operate until recharging by AAC power source after SBO occurs.
RAI No.64-735(ML082830021) RAI 9.4.5-18 b) will be amended as below:
b)The hydrogen concentratin -generation would Ret-Gha~e-§sto2 following a SBO occur. The batteries do not generate hydrogen except when being charged and would not be charging during this period.
Impact on DCD There is no impact on the DCD.
Impact on COLA There is no impact on the COLA.
Impact on PRA There is no impact on the PRA.
09.04.05-21