ML23123A397
| ML23123A397 | |
| Person / Time | |
|---|---|
| Site: | 07109186 |
| Issue date: | 04/19/2023 |
| From: | Fluor Marine Propulsion Corporation |
| To: | NRC, US Dept of Energy, Naval Reactors |
| References | |
| RSS-SC-NFE-00085 | |
| Download: ML23123A397 (1) | |
Text
Fluor Marine Propulsion, LLC Post Office Box 79 West Mifflin, PA 15122-0079
RSS-SC-NFE-00085
April 19, 2023
MEETING
SUMMARY
Meeting Date April 6, 2023 Leader/Organization Naval Reactors - Reactor Refueling Division Attendees Nuclear Regulatory Commission - Office of Nuclear Material Safety and Safeguards Naval Nuclear Laboratory - Shipping Containers
Subject:
S9G PUSC; Teleconference to Discuss Nuclear Regulatory Commission Questions on the S9G in the S-6213 Power Unit Shipping Container Safety Analysis Report for Packaging Addendum; For Information (U)
PURPOSE Naval Reactors (NR) provided the S9G in the S-6213 Power Unit Shipping Container (PUSC)
Safety Analysis Report for Packaging (SARP) Addendum to the Nuclear Regulatory Commission (NRC) for concurrence through Reference (a). In the course of the review, the NRC staff identified two topics where additional clarification was desired: the development of high strength low alloy (HSLA)-100 material properties used for finite element analyses (FEA) in the SARP, and the temperatures specified in the SARP thermal and containment chapters. This meeting summary documents the discussion (conducted via Microsoft Teams) between NR, Naval Nuclear Laboratory (NNL), and NRC staff on April 6, 2023 to provide the requested clarification in support of the NRC Safety Evaluation Report.
DISCUSSION HSLA-100 Material Properties
NRC requested clarification regarding the development of material properties used to represent HSLA-100 in FEA models of the package. Specifically, clarification was requested regarding the construction of the stress-strain curves and damage initiation properties. NNL presented the development methodology and justification provided in Enclosure (1). NRC acknowledged that the Enclosure (1) information resolved their questions.
Fire Accident Temperatures
NRC requested clarification regarding the relationship between Chapters A2 (specifically, Appendix A2.10.4) and A3 of the S9G in the S-6213 PUSC SARP Addendum and Chapter 4 of the base SARP. Appendix A2.10.4 of the SARP Addendum identifies that portions of the outer surface of the packaging may become separated from the package as a result of the 10CFR71 hypothetical free drop accident condition. Loss of this material reduces the package mass
Distribution RSS-SC-NFE-00085
considered in the lumped capacitance thermal model in Chapter A3 of the addendum.
Consequently, the accident temperatures calculated for the package contents in Chapter A3 of the addendum are higher than those calculated in Chapter 3 of the base SARP. The resulting temperatures are similar in magnitude to temperatures stated in Chapter 4 of base SARP.
Given this similarity in magnitude and the fact that loss of some packaging material results in less separation between the package contents and the hypothetical fire, NRC sought clarification regarding the appropriateness of a lumped capacitance model.
NR and NNL stated that the temperatures included in Section 4.1 of the base SARP are provided only for context, are representative of the conditions under which the package contents are expected to operate in the naval reactor plant, and are not presented as thermal performance limits for the hypothetical fire accident condition. NR further stated that Section 4.3.2.3 of base SARP and Section A4.3.2.3 of the SARP Addendum identify that the melting point of the contents is the thermal limit that content temperatures are compared to and that there is significant margin to this thermal limit. NNL clarified that, apart from the reduction in mass due to packaging component separation, the configuration of the package is not significantly different than what was evaluated with a lumped capacitance model in Chapter 3 of the base SARP. Accordingly, the use of a lumped capacitance model remains appropriate given the significant margin to the thermal performance limit. NR stated that the wording and content in Sections 4.3.2.3 and A4.3.2.3 would be reviewed for clarification in the next routine revision of the SARP. NRC acknowledged that the provided clarification resolved his question.
CONCLUSION The discussion above summarizes the meeting held on April 6, 2023 between NR, NNL, and NRC staff on the S9G in the S6213 PUSC SARP Addendum. NR and NRC agree that this accurately summarizes the topics discussed with the NRC staff, which were sufficient to address the NRC staff requests for clarification.
Michael Uhl, Advisor Engineer Shipping Container Recapitalization Reactor Servicing Systems
References:
(a) G#C22-05956; S-6213 Power Unit Shipping Container-Safety Analysis Report for Packaging of S9G Power Units; Request for Nuclear Regulatory Commission Review and Concurrence (U) Dated December 28, 2022
Enclosure(s):
(1) HSLA-100 Stress Strain Curves for the S9G Power Unit in the S-6213 PUSC SARP
Enclosure (1) to RSS-SC-NFE-00085 Page i
HSLA-100 Stress Strain Curves for the S9G Power Unit in theS-6213 PUSC SARP
Prepared by:
Michael Uhl Shipping Container Recapitalization Reactor Servicing Systems
Enclosure (1) to RSS-SC-NFE-00085 Page ii
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HSLA-100 Stress Strain Curves for the S9G Power Unit in the S-6213 PUSC SARP
March 29, 2023
The Naval Nuclear Laboratory is operated for the U.S. Department of Energy by Fluor Marine Propulsion, LLC, a wholly owned subsidiary of Fluor Corporation.
Typical Construction
- Stress-strain curves for use as input in NNPP shipping container models are typically constructed as bi-linear representations: one straight-line segment in the elastic region and another straight-line segment in the plastic region.
- Further, the slope in the plastic region is intentionally depressed through the use of an end point that associates the material ultimate strength with the total elongation from a tensile specimen (rather than with uniform elongation where this strength value actually occurs)
- Material properties that include material damage/failure representations are generally constructed such that damage initiates at the uniform elongation strain of the material
- This combination of construction techniques results in conservatively low energy absorption prior to failure
2 HSLA-100
- HSLA-100 is a high strength, low alloy steel with a minimum yield strength of 100 ksiat room temperature
- Along with its relatively high strength, HSLA-100 has a relatively low room temperature uniform elongation strain of 7 percent
- However, the minimum reduction in area (which is directly related to the true strain at failure) is relatively high, at 45 percent (~0.6 true strain = ln(1/[1-RA]))
- Because of this low uniform elongation strain and high reduction in area, material inputs constructed in accordance with the typical methods used in NNPP container models would result in significant excess conservatism (i.e.,
material failures in scenarios where no material failure would be expected)
3 HSLA-100
- Consequently, an alternative material property construction approach was taken for HSLA-100:
- True Stress-True Strain behavior is represented with a tri-linear curve:
- Linear elastic representation to yield
- Linear hardening between yield and ultimate, with the ultimate strength occurring at the uniform elongation strain
- Perfectly plastic beyond uniform elongation
4 HSLA-100
HSLA-100 True Stress-True Strain Curves
140000 Typical Construction 120000 Selected Construction
100000
80000
60000
40000
20000
0 00.10.20.30.40.50.60.7 True Strain
5 HSLA-100
- Damage initiation at true strain based on minimum reduction in area with immediate element deletion (i.e., very small plastic displacement, 1x10 -5 inch, after damage initiation)
- Damage initiation strain varies with stress triaxiality ratio based on formulation from NUREG/CR-3644
NUREG/CR-3644 (LA-10007-MS), Review of Proposed Failure Criteria for Ductile Materials, F. D. Juand T. A. Butler, Los Alamos National Laboratory, 1984
6 HSLA-100
Test Data
Damage initiation curve (immediate element deletion upon further straining)
7 HSLA-100
- To validate the selected construction, NNL performed simulated tensile tests with both a typical stress strain curve construction and the curve selected for HSLA-100
- These simulations also evaluated the effect of different damage initiation criteria:
- Uniform elongation
- Total elongation
- Failure strain (based on reduction in area)
8 HSLA-100
Test Data
Selected Construction, D.I. @ Failure Strain
Typical Construction, D.I. @ Total Elongation Typical Construction, D.I. @ Uniform Elongation
9 HSLA-100
- Selected stress-strain curve allows for strain localization (necking), which does not occur in typical construction
Typical Construction Selected Construction
10 HSLA-100
- Selected property construction provides a conservative representation of the material behavior while avoiding the excess conservatism of the typical construction
11 References
- Chae, 2004 Damage Accumulation and Failure of HSLA-100 Steel,
D. Chae, and D.A. Koss, Materials Science and Engineering A366, 2004, pp. 299-309
- Majzoobi, 2016 Ductile to Brittle Failure Transition of HSLA-100 Steel at High Strain Rates and Subzero Temperatures, G.H.
Majzoobi, A.H. Mahmoudi, and S. Moradi, Engineering Fracture Mechanics 158, 2016, pp. 179-193
- Xue, 2003 Constitutive Response of Welded HSLA-100 Steel, Q. Xue, et. al.,
Materials Science and Engineering A354, 2003, pp. 166-179
- DTRC-88/38 DRTC-SME-88/38, Mechanical Property Characterization of HSLA-100 Steel Plate (U), R.E. Link, and E.J.
Czyryca, David Taylor Research Center, Dated December 1988
- GD-TFT/500413 95:TFT/50041/3.8/D470, Mechanical Properties Test, T.F. Trimble, General Dynamics -Electric Boat Division, 1995
[Internal NNPP Documentation]
12