ML19199A117
| ML19199A117 | |
| Person / Time | |
|---|---|
| Site: | NuScale |
| Issue date: | 07/18/2019 |
| From: | Rad Z NuScale |
| To: | Document Control Desk, Office of New Reactors |
| Shared Package | |
| ML19199A116 | List: |
| References | |
| RAIO-0719-66323 | |
| Download: ML19199A117 (36) | |
Text
RAIO-0719-66323 July 18, 2019 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 Supplemental Response to NRC Request for Additional Information No. 484 (eRAI No. 8930) on the NuScale Design Certification Application
REFERENCES:
- 1. U.S. Nuclear Regulatory Commission, "Request for Additional Information No. 484 (eRAI No. 8930)," dated May 29, 2018
- 2. NuScale Power, LLC Response to NRC "Request for Additional Information No. 484 (eRAI No.8930)," dated September 14, 2018 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) supplemental response to the referenced NRC Request for Additional Information (RAI).
The Enclosures to this letter contain NuScale's supplemental response to the following RAI Question from NRC eRAI No. 8930:
15-27 is the proprietary version of the NuScale Supplemental Response to NRC RAI No.
484 (eRAI No. 8930). NuScale requests that the proprietary version be withheld from public disclosure in accordance with the requirements of 10 CFR § 2.390. The enclosed affidavit (Enclosure 3) supports this request. Enclosure 2 is the nonproprietary version of the NuScale response.
This letter and the enclosed responses make no new regulatory commitments and no revisions to any existing regulatory commitments.
If you have any questions on this response, please contact Matthew Presson at 541-452-7531 or at mpresson@nuscalepower.com.
Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Gregory Cranston, NRC, OWFN-8H12 Samuel Lee, NRC, OWFN-8H12 Rani Franovich, NRC, OWFN-8H12 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
RAIO-0719-66323 : NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 8930, proprietary : NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 8930, nonproprietary : Affidavit of Zackary W. Rad, AF-0719-66324 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 8930, proprietary NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
NuScale Supplemental Response to NRC Request for Additional Information eRAI No. 8930, nonproprietary NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
Response to Request for Additional Information Docket No.52-048 eRAI No.: 8930 Date of RAI Issue: 05/29/2018 NRC Question No.: 15-27 Requirements:
Title 10 of the Code of Federal Regulations, Section 50.46, Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors, requires, in part, that after any calculated successful initial operation of the ECCS, the calculated core temperature shall be maintained at an acceptably low value and decay heat shall be removed for the extended period of time required by the long-lived radioactivity remaining in the core.
10 CFR, Part 50, Appendix A, General Design Criterion (GDC) 28Reactivity limits requires that the reactivity control systems be designed with appropriate limits on the potential amount and rate of reactivity increase to ensure that the effects of postulated reactivity accidents can neither (1) result in damage to the reactor coolant pressure boundary greater than limited local yielding nor (2) sufficiently disturb the core, its support structures or other reactor pressure vessel internals to impair significantly the capability to cool the core. These postulated reactivity accidents shall include consideration of rod ejection (unless prevented by positive means), rod dropout, steam line rupture, changes in reactor coolant temperature and pressure, and cold water addition. In addition, Generic Safety Issue (GSI) 185 (Control of Re-criticality Following small break (SB) loss of coolant accidents (LOCAs) addresses scenarios of potential return to criticality following a SB LOCA resulting from insertion of unborated water into a pressurized water reactor (PWR) core.
To meet the requirements mentioned above regarding long-term cooling, the results of the accident analysis should show that for the worst case boron dilution event the capability to cool the core is maintained.
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Background:
Page 2 of the applicants report, Long-Term Cooling Methodology, TR-0916-51299-P, Revision 0, states that the criterion for the core remaining subcritical (Criterion #5) is not applicable to the Long-Term Cooling (LTC) condition since no mechanism to push a large volume of diluted water into the core inlet exists, and therefore no credible mechanism for recriticality due to boron dilution exists. However, there are postulated events that could allow the addition of cooler water with diluted boron concentrations from containment to the reactor vessel via the RRVs during the long term cooling phase following any Chapter 15 scenario. For instance, diluted or unborated water can accumulate inside containment due to steaming from the reactor vent valves (RVVs) (which may concentrate boron in the area above the core) when the reactor is being cooled by emergency core cooling system (ECCS) recirculation. The diluted or unborated water accumulating inside containment can also further mix with secondary side unborated water that was introduced into containment after a pipe carrying unborated water ruptered inside containment (see RAI 8744, Question 15.02.08-3). The diluted or unborated water can then make its way back into the reactor pressure vessel, and ultimately, into the core via the RRV ECCS recirculation path. The diluted or unborated water can affect core criticality, potentially leading to recriticality, and thus present a challenge to acceptance criteria.
This RAI is being issued, in part, as a follow-up RAI to RAI 8744, Question 15.02.08-3 after determining that RAI 8744, Question 15.02.08-3 did not provide adequate information to resolve the issue. All together, this RAI will require the applicant to detail and define the methodology used for boron transport inside the reactor pressure vessel and containment vessel after ECCS actuates as well as to present the results in the FSAR of a long-term cooling analysis that show how a bounding boron dilution event affects the criticality and coolability of the core.
The staff asked RAI 8744, Question 15.02.08-3, to require the applicant to determine if core criticality is affected by the introduction of pure, secondary side water into the core after ECCS recirculation begins following a FWLB inside containment. The applicant's response to RAI 8744, Question 15.02.08-3 argues that void fraction due to "high" decay heat limits (or precludes) the return to power evaluated in the LTC analysis. This may be true, but sufficient detail regarding void reactivity vs. dilution reactivity (core generated dilution due to boiling and unborated water pipe break generated dilution) and how these values were determined should be provided. Analysis assumptions (e.g. dilution water volume) and plots of reactivity and, if necessary, core power vs. time are necessary to address this RAI.
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Request:
The staff requests the applicant to specify and describe in sufficient detail in the FSAR a methodology used to calculate boron transport during long-term cooling following ECCS actuation after any Chapter 15 event. As part of the description of the methodology, the applicant should appropriately justify the methods, assumptions, and techniques using acceptable validation bases. Furthermore, the staff requests the applicant to provide the results of a long-term cooling analysis that show how a bounding boron dilution event affects the core criticality and coolability. These results should include the quantitative distribution of boron throughout the RCS and containment vessels as a function of time following ECCS actuation.
The analysis should consider the most limiting boron dilution volume (e.g. condensate in containment from steaming through the RVVs and from any additional un-borated water already inside containment from breaks in piping carrying un-borated water inside containment).
Similarly, the response should include the analysis assumptions and plots of various reactivity effects that determine reactor power to confirm that the core is sub-critical.
NuScale Response:
The original response to RAI 8930, question 15-27 was submitted in NuScale correspondence (RAIO-0918-61810, dated September 14, 2018). The following response replaces the original response and addresses issues that were discussed with the staff in subsequent meetings.
Six items for closure of this RAI response were identified subsequent to the original response.
A discussion of these items as well as how they are addressed in the revision to the long term cooling boron distribution methodology is given below:
- 1) Limiting NPM transient - The original response evaluated the Reactor Component Cooling Water (RCCW) line break. NuScale performed calculations for an inadvertent opening of an RPV valve (IORV) RRV and RVV in addition to an updated RCCW line break analysis, incorporating the methodology changes described below. Due to the methodology changes in items 2 and 3 the RRV event without the DHRS activated for a hot reactor condition is more limiting than the original RCCW case.
- 2) Volatility - The original methodology supporting the original RAI 8930 submittal did not account for vaporization of boric acid. This was since added to the methodology and conservatively assumed to be a boron sink term in the updated analyses. The assumed NuScale Nonproprietary
volatility fraction used is greater than the best-estimate value based on the boron volatility model by the identified uncertainty term for the duration of the evaluation period.This issue is further discussed in item number 2 of the section entitled "Boron Dilution Analysis Results with Different Assumptions," below.
- 3) CNV mixing - The original methodology had assumed uniform distribution in the CNV as a conservatism due to the treatment of the boron during the ECCS depressurization transient. Sensitivities have been added to the updated analyses to address the impact of a variety of different CNV mixing assumptions and default methodology was modified to be more conservative. The discussion of CNV mixing and associated conservatisms is included in the "Transient Results" subsection "Results of Boron Dilution Analysis with Assumptions Maximizing Volatilized Boron Loss," below.
- 4) RCS hot region inlet concentration - The original analysis had assumed the CNV concentration was applied at the inlet of the core. Sensitivities have been added to the calculations to evaluate a variety of core inlet concentration assumptions evaluating the effect on the overall volatility loss term. In the alternative boron dilution analysis described in the "Transient Results" subsection "Results of Boron Dilution Analysis with Assumptions Maximizing Volatilized Boron Loss", perfect boron mixing in the RCS cold region is assumed. As the boron concentration to be transported from the RCS cold region to the RCS hot region at both the lower plenum to core and the SG shell side to upper plenum interfaces during the ECCS recirculation phase, the RCS cold region boron concentration is used instead of using the CNV boron concentration. This assumption eventually increases the boron transport to the core because the boron concentration in the RCS cold region is higher than that in the CNV.
- 5) RCS hot region mixing - The NRC questioned the possibility of boron accumulation in the lower riser under the extreme overcooling condition where the bulk vapor generation moves into the lower riser. A significant boron concentration in the lower riser near the water level is physically not possible due to the buoyant mixing caused by the Rayleigh-Taylor instability. Furthermore, the buoyancy-induced internal circulation throughout the RCS hot region consisting of the core and lower riser would prevent such a significant non-uniform boron distribution in the lower riser. Both the buoyant mixing induced by the Rayleigh-Taylor instability and the buoyancy-induced internal circulation are supported by the Westinghouse boron mixing/transport and precipitation PIRT (Reference 7).
- 6) Lower riser precipitation mechanisms (plate-out) - The NRC raised an additional concern as to whether local solidification could occur in the lower riser. NuScale has incorporated conservative assumptions for the loss of boron from the system through possible deposition of boron in the CNV from that volatized in the RCS, which results in still significant margin to a possible criticality condition over the long term cooling evaluation NuScale Nonproprietary
period. A discussion of why boron plate-out in the lower riser region does not occur is included in the subsection entitled "Boron Plate-out Mechanisms" below.
The above issues are discussed in the balance of the response below in the presentation of the methodology, the results, and the conservatisms assumed.
Boron distribution during long term cooling time period overview As requested by RAI 8930, a systematic analysis approach has been developed for addressing possible boron transport phenomena in order to address and disposition the temporal aspects of boron distribution during the emergency core cooling system (ECCS) cooling modes. As previously addressed in RAI 8744 15.02.08-3 (Letter RAIO-0617-54560, dated June 21, 2017), this bounding transport analysis concludes that bulk boron dilution is not possible because if there is any boron initially in the reactor coolant system (RCS), it will tend to accumulate in the core region. During initial stages of ECCS operation, relatively pure water leaves the reactor pressure vessel (RPV) through the reactor vent valves (RVVs), leaving almost all of the boron in the core region. Due to the unique aspects of the NuScale module ECCS design, it is not susceptible to large pure water injections similar to a loop seal clearing in a traditional pressurized-water reactor (PWR). Regardless of the initial liquid level in the containment prior to ECCS actuation, recirculation of liquid through the reactor recirculation valves (RRVs) does not occur until pressure equalization between the containment vessel (CNV) and the RPV, at which point the recirculation rate is driven by the RCS boil off rate. Consequently, the boron mass transport balance will tend toward accumulation of boron in the core region.
Therefore, the conservative time in cycle to evaluate a loss of shutdown margin due to moderator overcooling is end of cycle, as previously concluded in response to RAI 8744 and presented in FSAR section 15.0.6.
Methodology This section provides an overview of the methodology for simplified analyses of the boron transport and distribution in the reactor coolant system (RCS) and the containment vessel (CNV) of the NuScale Power Module (NPM). The methodology is based on a control volume analysis approach using NRELAP5 calculation results to address the boron transport and distribution, including boron dilution and precipitation, for the design-basis loss-of-coolant accident (LOCA) and non-LOCA initiating events followed by the emergency core cooling system (ECCS) actuation.
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During the blowdown following ECCS actuation, some of the borated RCS liquid is transported to the CNV. Then during the recirculation, some of the borated liquid in the CNV is transported back into the RCS. For the boron transport and distribution, there are two concerns with opposite perspectives: one is boron dilution (under-concentrating boron) and the other is boron precipitation (over-concentrating boron). Therefore, the problem is how to model the boron transport without missing important transport mechanisms, and produce conservative solutions for the boron distributions from different perspectives (i.e., boron dilution and boron precipitation). The purpose and scope of the boron transport and distribution analyses can be represented conceptually as shown in Figure 1.
In Figure 1, the region bounded between the conservative boron dilution and boron precipitation models (indicated by dashed lines) can be considered as an uncertainty band for the realistic boron transport model (indicated by a solid line). It is likely that the limiting initiating events and conditions are different for the boron dilution and boron precipitation analyses. In the figure, the critical boron concentration and boron solubility limit (indicated by dotted lines) are the acceptance criteria to be compared with the conservative boron dilution and boron precipitation analysis results, respectively.
The methodology addresses the important boron transport and distribution processes and phenomena identified in the long-term cooling (LTC) phenomena identification and ranking table (PIRT) and applies to the design-basis LOCA and non-LOCA initiating events followed by the ECCS actuation. The coolant inventory and flow distributions are obtained from NRELAP5 transient calculation results, while the boron transports and distributions are calculated by solving the ((2(a),(c) transient boron transport and distribution analysis models. During the LTC period with the ECCS recirculation for either LOCA or non-LOCA initiating events, the reactor coolant would be nearly stagnant except for the inter-system water flows between the RCS and CNV through the reactor vent valves (RVVs) and reactor recirculation valves (RRVs). Considering the paths for water transport between the RCS and CNV, phase change phenomena affecting boron distribution in the RCS, and the buoyancy driven internal circulation expected in the module, as conceptually shown in Figure 2, it is concluded that ((
}}2(a),(c)
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((
}}2(a),(c)
The current NuScale boron dilution analysis methodology can be briefly summarized from the boron transport and distribution analysis methodology and the three boron dilution event analysis calculations as follows:
- ((
}}2(a),(c)
- The boron concentration transported by flow between volumes is calculated by applying a conservative boron distribution factor for each of the boron transport paths. The non-uniform boron distribution in the donor control volume is considered in determining the conservative boron distribution factor for each of the boron transport paths.
- The Bhlke et al. boron volatility model (Reference 1) is used with appropriate conservatism to evaluate the boron volatility fraction evaluation. The NuScale conditions are fully covered by the applicable ranges for the Bhlke et al. model as summarized in Table 1.
- The boron dilution analysis model is formulated in such a way that the boron concentration in the core is minimized by maximizing the boron transport out of the core and minimizing the boron transport into the core. Results from sensitivity calculations with alternate assumptions to maximize the transport of boron into the RCS hot region and the volatility fraction are also presented in this response.
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Figure 1. Conceptual Boron Transport and Distribution Analysis Results and Acceptance Criteria NuScale Nonproprietary
((
}}2(a),(c)
Figure 2. Buoyancy Driven Internal Circulations Expected during ECCS Recirculation Phase ((
}}2(a),(c)
Figure 3. Control Volumes Used in Boron Transport and Distribution Analysis Methodology NuScale Nonproprietary
Transient Results Transient calculations were developed to evaluate the boron transport and distribution for three different design-basis initiating events, i.e., IORV (RRV), IORV (RVV), and RCCW line break, followed by the ECCS actuation. Among them, the IORV (RRV) initiating event followed by the ECCS actuation without the DHRS activated for a hot reactor condition is the most limiting case. Note: The case with the DHRS activated is more realistic but less limiting, whereas the case without the DHRS activated is less realistic but more limiting. The more limiting result in terms of the margin to the critical boron concentration for the case without the DHRS activated is due to ((
}}2(a),(c)
Results of Boron Dilution Analysis with Assumptions Minimizing Boron Transport to Core The conservative (( }}2(a),(c) transient boron dilution analysis model developed by NuScale is formulated in such a way that the boron concentration in the core is minimized by maximizing the boron transport out of the core and minimizing the boron transport into the core. The results of the boron dilution analyses for the three initiating events of the IORV (RRV), IORV (RVV), and RCCW line break are plotted in Figure 4 through Figure 7, Figure 8 through Figure 11, and Figure 12 through Figure 15, respectively, providing the boron concentrations, boron masses, boron volatility fraction, and the liquid droplet entrainment vs. boron volatility comparison. The results of the boron dilution analyses using the NuScale approach show a sufficient margin to the critical boron concentration even for the most limiting case of the IORV (RRV) initiating event followed by the ECCS actuation without the DHRS activated for a hot reactor condition as shown in Figure 4. Results of Boron Dilution Analysis with Assumptions Maximizing Volatilized Boron Loss For each of the same three initiating events, an alternative boron dilution analysis is performed with different assumptions maximizing the volatilized boron loss to see any NuScale Nonproprietary
unfavorable impact on the margin to the critical boron concentration. For these alternative analyses, the following are assumed to maximize the volatilized boron loss.
- Assumption 1 ((
}}2(a),(c)
- Assumption 2 ((
}}2(a),(c)
- Assumption 3 (increased boron volatility fraction): ((
}}2(a),(c)
The results of these alternative boron dilution analyses on the boron concentrations and boron masses are presented in Figure 16/Figure 17, Figure 18/Figure 19, and Figure 20/Figure 21 for the IORV (RRV), IORV (RVV), and RCCW line break without DHRS (for all the three events), respectively. The results of the boron dilution analyses using alternate assumptions show more margin to the critical boron concentration, compared to the NuScale approach, for each of the three initiating events as shown in Figure 16, Figure 18, and Figure 20. This confirms that the NuScale approach to minimize boron transport to the hot region is conservative with respect to evaluating margin to the critical boron concentration, compared to the set of alternate assumptions. NuScale Nonproprietary
((
}}2(a),(c)
Figure 4. Boron Concentrations for IORV (RRV) without DHRS ((
}}2(a),(c)
Figure 5. Boron Masses for IORV (RRV) without DHRS NuScale Nonproprietary
((
}}2(a),(c)
Figure 6. Boron Volatility Fraction for IORV (RRV) without DHRS ((
}}2(a),(c)
Figure 7. Liquid Droplet Entrainment vs. Boron Volatility for IORV (RRV) without DHRS NuScale Nonproprietary
((
}}2(a),(c)
Figure 8. Boron Concentrations for IORV (RVV) without DHRS ((
}}2(a),(c)
Figure 9. Boron Masses for IORV (RVV) without DHRS NuScale Nonproprietary
((
}}2(a),(c)
Figure 10. Boron Volatility Fraction for IORV (RVV) without DHRS ((
}}2(a),(c)
Figure 11. Liquid Droplet Entrainment vs. Boron Volatility for IORV (RVV) without DHRS NuScale Nonproprietary
((
}}2(a),(c)
Figure 12. Boron Concentrations for RCCW Line Break without DHRS ((
}}2(a),(c)
Figure 13. Boron Masses for RCCW Line Break without DHRS NuScale Nonproprietary
((
}}2(a),(c)
Figure 14. Boron Volatility Fraction for RCCW Line Break without DHRS ((
}}2(a),(c)
Figure 15. Liquid Droplet Entrainment vs. Boron Volatility for RCCW Line Break without DHRS NuScale Nonproprietary
((
}}2(a),(c)
Figure 16. Boron Concentrations for IORV (RRV) without DHRS for Alternative Analysis Maximizing Volatilized Boron Loss ((
}}2(a),(c)
Figure 17. Boron Masses for IORV (RRV) without DHRS for Alternative Analysis Maximizing Volatilized Boron Loss NuScale Nonproprietary
((
}}2(a),(c)
Figure 18. Boron Concentrations for IORV (RVV) without DHRS for Alternative Analysis Maximizing Volatilized Boron Loss ((
}}2(a),(c)
Figure 19. Boron Masses for IORV (RVV) without DHRS for Alternative Analysis Maximizing Volatilized Boron Loss NuScale Nonproprietary
((
}}2(a),(c)
Figure 20. Boron Concentrations for RCCW Line Break without DHRS for Alternative Analysis Maximizing Volatilized Boron Loss ((
}}2(a),(c)
Figure 21. Boron Masses for RCCW Line Break without DHRS for Alternative Analysis Maximizing Volatilized Boron Loss NuScale Nonproprietary
Conservatism of NuScale Boron Dilution Analysis Model Boron Plate-Out Mechanisms ((
}}2(a),(c)
Boron plate-out is not expected in the lower riser region due to the following observations: NuScale Nonproprietary
- WCAP-17047-NP (Reference 7) outlines various solidification mechanisms which are achieved by either bulk or local super-saturation of the liquid solution. The existing precipitation analysis in the long term cooling technical report (TR-0916-51299) is sufficiently conservative to conclude any solidification of boron is not possible.
- The 2018 Morozov Journal of Physics paper (Reference 5) provides a correlation for boron vaporization fraction. The test procedure described in this paper relies on condensing of the volitized boron back into liquid solution to quantify the volatility fraction supporting the conclusion that volatized boron will not actually be a solidification mechanism as conservatively assumed in the limiting analysis.
Boron Dilution Analysis Results with Different Volatility Assumptions For the IORV (RRV) event followed by the ECCS actuation without the DHRS activated for a hot reactor condition, the boron concentration transient in each of the ((
}}2(a),(c)
For conservative, bounding Chapter 15 safety analyses for 72 hours with the WRSO assumption, the current NuScale boron dilution analysis model adopts especially the following two unrealistically conservative assumptions, among others, to minimize the boron transport to the core.
- 1. ((
}}2(a),(c)
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- 2. ((
}}2(a),(c)
Figure 24 represents the result of the current NuScale boron dilution analysis model used for the purpose of conservative bounding Chapter 15 safety analyses for 72 hours with the WRSO assumption (this figure is a repeat of Figure 4 for convenience). EPRI-NP-5558 (Reference 2) provides a plot presented by Cohen (Reference 3) compiling various data on the volatility of boric acid with no added alkali (i.e., unbuffered boric acid solution). Digitizing the data presented in the plot and providing additional data from Morozov et al. (Reference 5) and the predictions from the Glover model (Reference
- 6) and the Bhlke et al. model (Reference 1) gives Figure 26 and Figure 27 comparing the boron volatility fraction data and models from various sources in log and linear scales, respectively.
Except for the data from WAPD-MRP-49 (Reference 4) indicated by the solid pink triangle symbols in Figure 26 and Figure 27, all the boron volatility fraction data are distributed around the green dashed line predicted by the Glover model (1988). The Glover model is almost identical to the blue dotted line predicted by the best-estimate Bhlke et al. model (2008) except for higher temperature conditions due to the void fraction effect considered by Bhlke et al. The Glover model is below the red solid line predicted by the conservative (( }}2(a),(c) Bhlke et al. model used in the NuScale boron dilution analysis calculations. The data from WAPD-MRP-49 (1954) show a significantly biased slope of the boron volatility fraction trend with respect to the liquid-phase coolant temperature. Considering that the data from four different sources at low temperatures around 100oC anchor the lower end point of the extrapolated line from the consistent trend for most of the data and models, the application of the outlier data from WAPD-MRP-49 is not required to perform a conservative boron dilution analysis using the Bhlke et al. model. If using the boron volatility fraction of (( }}2(a),(c) the best value predicted by the Bhlke et al. model, based on the outlier data from WAPD-MRP-49, an excessively conservative result would be obtained as shown in Figure 25. Considering that the NuScale conditions are fully covered by the applicable ranges for the Bhlke et al. NuScale Nonproprietary
model, as summarized in Table 1, and that the boron volatility fraction of ((
}}2(a),(c) except for the outlier data from WAPD-MRP-49, as shown in Figure 26 and Figure 27, a recourse to the alternative boron volatility fraction is not required to maintain a conservative and bounding boron dilution analysis.
Table 1. Bhlke et al. Boron Volatility Model Applicability to NuScale IORV (RRV) Event NuScale Nonproprietary
((
}}2(a),(c)
Figure 22. Boron Concentrations for IORV (RRV) without DHRS (Realistic Model) ((
}}2(a),(c)
Figure 23. Boron Concentrations for IORV (RRV) without DHRS (Realistic Model + Minimized Boron Transport to Core) NuScale Nonproprietary
((
}}2(a),(c)
Figure 24. Boron Concentrations for IORV (RRV) without DHRS (Realistic Model + Minimized Boron Transport to Core + Assumed Plate-Out of Volatilized Boron) ((
}}2(a),(c)
Figure 25. Boron Concentrations for IORV (RRV) without DHRS (Realistic Model + Minimized Boron Transport to Core + Assumed Plate-Out of Volatilized Boron + Increased Boron Volatility Fraction (( }}2(a),(c) NuScale Nonproprietary
((
}}2(a),(c)
Figure 26. Comparison of Boron Volatility Fraction (in Log Scale) Data and Models from Various Sources ((
}}2(a),(c)
Figure 27. Comparison of Boron Volatility Fraction (in Linear Scale) Data and Models from Various Sources NuScale Nonproprietary
Summary and Conclusions
- 1. An overview of the boron transport and distribution analysis methodology and a summary of the conservative bounding boron dilution analysis methodology are provided.
- 2. The boron dilution analysis using the NuScale approach minimizing the boron transport to the core results in a sufficient margin to the critical boron concentration even for the most limiting case of the IORV (RRV) initiating event followed by the ECCS actuation without the DHRS activated for a hot reactor condition.
- 3. The boron dilution analysis using alternate assumptions maximizing the volatilized boron loss results in more margin to the critical boron concentration, compared to the NuScale approach, for each of the three initiating events of the IORV (RRV), IORV (RVV), and RCCW line break.
- 4. If using a more realistic boron dilution analysis model considering the buoyancy-driven boric acid mixing and the volatilized boric acid recovery on its condensation, significantly more margin to the critical boron concentration can be obtained.
References
- 1. Steffen Bhlke, Christoph Schuster, and Antonio Hurtado, About the Volatility of Boron in Aqueous Solutions of Borates with Vapour in Relevance to BWR-Reactors, International Conference on the Physics of Reactors, Nuclear Power: A Sustainable Resource, Interlaken, Switzerland, September 14-19, 2008.
- 2. Electric Power Research Institute, Boric Acid Application Guidelines for Intergranular Corrosion Inhibition, EPRI NP-5558, p. (2-18), December 1987.
- 3. Paul Cohen, Water Coolant Technology of Power Reactors, p. 225, Gordon and Breach Science Publishers, New York, 1969.
- 4. W. T. Lindsay, Pressurized Water Reactor Programe Technical Progress Report for the Period July 10, 1954, August 26, 1954, WAPD-MRP-49 (TID010028), pp. 11-54, Atomic Power Lab., 1954. (Not Available)
- 5. A. V. Morozov, A. V. Pityk, A. R. Sahipgareev, and A. S. Shlepkin, Experimental Study of Solubility of Boric Acid in Steam at Boiling, Journal of Physics: Conference Series, Vol. 1105, 2018.
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- 6. R. B. Glover, Boron Distribution between Liquid and Vapour in Geothermal Fluids, Proc. 10th New Zealand Geothermal Workshop, pp. 223-227, 1988.
- 7. Westinghouse Electric Company LLC, Phenomena Identification and Ranking Tables (PIRT) for Un-Buffered/Buffered Boric Acid Mixing/Transport and Precipitation Modes in a Reactor Vessel During Post-LOCA Conditions, WCAP-17047-NP, Rev. 0, May 2009.
Impact on DCA: There are no impacts to the DCA as a result of this response. NuScale Nonproprietary
RAIO-0719-66323 : Affidavit of Zackary W. Rad, AF-0719-66324 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com
NuScale Power, LLC AFFIDAVIT of Zackary W. Rad I, Zackary W. Rad, state as follows:
- 1. I am the Director, Regulatory Affairs of NuScale Power, LLC (NuScale), and as such, I have been specifically delegated the function of reviewing the information described in this Affidavit that NuScale seeks to have withheld from public disclosure, and am authorized to apply for its withholding on behalf of NuScale.
- 2. I am knowledgeable of the criteria and procedures used by NuScale in designating information as a trade secret, privileged, or as confidential commercial or financial information. This request to withhold information from public disclosure is driven by one or more of the following:
- a. The information requested to be withheld reveals distinguishing aspects of a process (or component, structure, tool, method, etc.) whose use by NuScale competitors, without a license from NuScale, would constitute a competitive economic disadvantage to NuScale.
- b. The information requested to be withheld consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), and the application of the data secures a competitive economic advantage, as described more fully in paragraph 3 of this Affidavit.
- c. Use by a competitor of the information requested to be withheld would reduce the competitor's expenditure of resources, or improve its competitive position, in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product.
- d. The information requested to be withheld reveals cost or price information, production capabilities, budget levels, or commercial strategies of NuScale.
- e. The information requested to be withheld consists of patentable ideas.
- 3. Public disclosure of the information sought to be withheld is likely to cause substantial harm to NuScale's competitive position and foreclose or reduce the availability of profit-making opportunities. The accompanying Request for Additional Information response reveals distinguishing aspects about the method by which NuScale develops its long term cooling analysis.
NuScale has performed significant research and evaluation to develop a basis for this method and has invested significant resources, including the expenditure of a considerable sum of money. The precise financial value of the information is difficult to quantify, but it is a key element of the design basis for a NuScale plant and, therefore, has substantial value to NuScale. If the information were disclosed to the public, NuScale's competitors would have access to the information without purchasing the right to use it or having been required to undertake a similar expenditure of resources. Such disclosure would constitute a misappropriation of NuScale's intellectual property, and would deprive NuScale of the opportunity to exercise its competitive advantage to seek an adequate return on its investment. AF-0719-66324
- 4. The information sought to be withheld is in the enclosed response to NRC Request for Additional Information No. 484, eRAI 8930. The enclosure contains the designation "Proprietary" at the top of each page containing proprietary information. The information considered by NuScale to be proprietary is identified within double braces, "(( }}" in the document.
- 5. The basis for proposing that the information be withheld is that NuScale treats the information as a trade secret, privileged, or as confidential commercial or financial information. NuScale relies upon the exemption from disclosure set forth in the Freedom of Information Act ("FOIA"), 5 USC § 552(b)(4), as well as exemptions applicable to the NRC under 10 CFR §§ 2.390(a)(4) and 9.17(a)(4).
- 6. Pursuant to the provisions set forth in 10 CFR § 2.390(b)(4), the following is provided for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld:
- a. The information sought to be withheld is owned and has been held in confidence by NuScale.
- b. The information is of a sort customarily held in confidence by NuScale and, to the best of my knowledge and belief, consistently has been held in confidence by NuScale.
The procedure for approval of external release of such information typically requires review by the staff manager, project manager, chief technology officer or other equivalent authority, or the manager of the cognizant marketing function (or his delegate), for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside NuScale are limited to regulatory bodies, customers and potential customers and their agents, suppliers, licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or contractual agreements to maintain confidentiality.
- c. The information is being transmitted to and received by the NRC in confidence.
- d. No public disclosure of the information has been made, and it is not available in public sources. All disclosures to third parties, including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or contractual agreements that provide for maintenance of the information in confidence.
- e. Public disclosure of the information is likely to cause substantial harm to the competitive position of NuScale, taking into account the value of the information to NuScale, the amount of effort and money expended by NuScale in developing the information, and the difficulty others would have in acquiring or duplicating the information. The information sought to be withheld is part of NuScale's technology that provides NuScale with a competitive advantage over other firms in the industry.
NuScale has invested significant human and financial capital in developing this technology and NuScale believes it would be difficult for others to duplicate the technology without access to the information sought to be withheld. I declare under penalty of perjury that the foregoing is true and correct. Executed on July 18, 2019. Zackary W. Rad AF-0719-66324}}