ML18121A416
| ML18121A416 | |
| Person / Time | |
|---|---|
| Site: | 05200046 |
| Issue date: | 05/01/2018 |
| From: | Korea Hydro & Nuclear Power Co, Ltd |
| To: | Office of New Reactors |
| Shared Package | |
| ML18121A414 | List: |
| References | |
| MKD/NW-18-0064L | |
| Download: ML18121A416 (4) | |
Text
19-83_Rev.2 - 1 / 3 KEPCO/KHNP REVISED RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION APR1400 Design Certification Korea Electric Power Corporation / Korea Hydro & Nuclear Power Co., LTD Docket No.52-046 RAI No.: 433-8363 SRP Section: SRP 19 Application Section: 19.1 Date of RAI Issue: 03/08/2016 Question No. 19-83 All design certification applications under 10 CFR 52.47 shall satisfy the requirements of 10 CFR 52.47(a)(27) that a description and results of a design-specific PRA be provided as part of the application for design certification. The estimate of containment fragility as a function of pressure and associated temperature loads needs to be developed for use in the design-specific PRA.
APR1400 DCD Tier 2, Figure 19.1-47: Total Containment Fragility Curve shows the results of the containment fragility analysis, which includes the sum of the probability density functions for each failure mode considered. Section 19.1.4.1.2.2 and Table 19.1-28 provide the failure locations and failure modes considered for the containment ultimate pressure capacity and also for the containment fragility calculation.
- a. In Section 19.1.4, the applicant lacks a description of a specific analytical process used to determine the containment pressure fragility and associated failure modes. The staff reviewed the Ultimate Pressure Capacity Report (APR1400-K-P-NR-013605-P) and requests the applicant provide the following information in the DCD:
i An explanation of whether severe accident temperature effects on material properties were considered.
ii A clarification of the basis for the assumed temperature (400 F) and the relationship between that temperature and the temperature reduction factors in Section 5.6 of the report.
iii A description of the consideration of uncertainties iv A description of how the uncertainty for the different parameters considered in the analysis is estimated and aggregated.
19-83_Rev.2 - 2 / 3 KEPCO/KHNP
- b. In Section 19.1.4.2.1.2.2, the applicant lists the personnel emergency exit airlock as a failure location contributing to the containment pressure fragility. There are no corresponding failure modes included in Table 19.1-28 or Figure 19.1-47. Describe the basis for the selection of failure locations and failure modes considered and confirm whether the failure of the personnel emergency exit airlock was included in the analysis.
Response - (Rev. 2)
- a. Containment Ultimate Pressure Capacity Analysis (UPC) in DCD Section 19.1.4.2.1.2.2 is revised as shown in Attachment 1.
i The bounding harsh environmental conditions are determined by simulating a broad spectrum of accident sequences including LBLOCA, MBLOCA, SBLOCA, TLOFW, and SBO, and dominant PRA sequences using the MAAP code. Long term atmospheric temperature after temperature spikes is enveloped by a temperature of 460 K (368 °F) (Reference 19.2.3.3.7.2.1). Based on long term temperature, 400°F is conservatively assumed for the strength properties of reinforcing and prestressing steels.
ii The relationship between the long term temperature 400°F and the temperature reduction factor is clarified based on The Structural Engineer, The effect of elevated temperatures on the strength properties of reinforcing and prestressing steels, M. Holmes, R.D. Anchor, G.M.E.Cook & R.N.Cook, Vol. 60B, No. 1, March 1982. This report shows that the typical strength properties of reinforcing and prestressing steels tested at room temperature after heating to an elevated temperature and gradually reduced under the conditions of concrete cracking and reinforcement yielding.
iii For controlling failure modes, the uncertainties associated with the median capacities are evaluated. The uncertainties, M and S, represent variability due to a lack of knowledge related to difference between the analytical model and the real structure. The modeling uncertainty (M) such as internal force distribution, failure criteria, the use of empirical formulae in tendon and reinforcing steel placement, and variability in force-deformation relations is considered. The strength uncertainties (S) are associated with variability related to the material resistance.
The variability in concrete strength, tendon and reinforcing steel strength, steel liner strength, and the influence of elevated temperature on the material strengths are considered.
iv The random variable (uncertainty in the median pressure capacity) is assumed to be lognormally distributed with unity median and lognormal standard deviation (U). This assumption is considered to be appropriate, since parameters that influence containment capacity, such as material strengths, are best represented by lognormal distributions. The uncertainty (U) can be developed from combinations such as SRSS of the strength uncertainties (S) and modeling uncertainty (M).
19-83_Rev.2 - 3 / 3 KEPCO/KHNP
- b. The selection of emergency exit airlock failure location was based on the review of research results such as Containment Integrity Research at Sandia National Laboratories, NUREG/CR-6906 and design UPC outputs (structural drawings, containment penetration detail). These results show that the unhomogeneous part of containment is relatively vulnerable than other parts and the failure modes are listed based on such results.
The personnel emergency exit airlock was included in the analysis and Table 19.1-28 of DCD Section 19.1 is replaced as shown in Attachment 2.
The personnel airlock and personnel emergency exit airlock have the same dimension and material properties, therefore both airlocks have the identical pressure capacity.
Impact on DCD The changes that were proposed in the original response to this RAI have been incorporated into Revision 2 of the DCD; therefore, only the pages containing proposed changes as a result of Revision 2 of this response are included in the Attachment.
Table 19.1-28A is revised in accordance with DCD Tier Rev. 2 Chapter 3.8.1.4.11 as shown in Attachment.
Impact on PRA There is no impact on the PRA.
Impact on Technical Specifications There is no impact on the Technical Specifications.
Impact on Technical/Topical/Environmental Reports There is no impact on any Technical, Topical, or Environment Report.
RAI 433-8363 - Question 19-83_Rev.2 Attachment (1/1)
APR1400 DCD TIER 2 RAI 433-8363 - Question 19-83_Rev.2 Table 19.1-28a Comparison of Containment Pressure Between 19.1, 19.2 and 19.3 11.1 19.1 19.2 19.3 (Probabilistic Risk (Severe Accident (Beyond Design Basis Assessment) Evaluation) External Event)
Containment 162.7 psig 123.7 psia 12.9 kg/cm2 g
Pressure (median pressure) (184 psia)
Requirement - RG 1.216 Position 2 RG 1.216 Position 1 Definition Containment pressure Containment pressure Ultimate pressure 158 evaluated by containment resulting from severe capacity of containment fragility analysis (Probabilistic accident (Deterministic Containment Pressure) Containment Pressure)
Detailed The total probability of Factored Load Deterministic evaluation Information containment failure can be Category (FLC) of the design of the g obtained by integration process structure. 184 psia was given the rupture mode and the calculated to be the leak mode. pressure at which the 158 maximum strain of the PTOTAL_FAIL = 1 - (1-PRUPTURE) liner plate and horizontal
- (1-PLEAK) tendon is 0.8 percent.
The containment failure 0.4 probability becomes 0.5 (i.e.,
50 percent) when the containment pressure is 162.7 psig.
Reference 19.1.4.2.1.2.2 19.2.4 3.8.1.4.11 19.1-491 Rev. 2