ML24271A045
| ML24271A045 | |
| Person / Time | |
|---|---|
| Site: | 99902071 |
| Issue date: | 10/23/2024 |
| From: | NRC/NRR/DANU/UAL2 |
| To: | X-Energy |
| Ondra Dukes, NRR/DANU | |
| Shared Package | |
| ML24271A042 | List: |
| References | |
| Xe-100 | |
| Download: ML24271A045 (1) | |
Text
Enclosure Readiness Assessment Observations: X Energy LLCs., Xe-100 Graphite Structural Analysis and Qualification Methodologies Draft Topical Report On September 5, 2024, the U.S. Nuclear Regulatory Commission (NRC) staff completed a readiness assessment of the draft topical report, Graphite Structural Analysis and Qualification Methodologies Topical Report. The NRC staff met with X Energy, LLC., (X-energy) to discuss the following observations for X-energys consideration for revising the topical report before its submittal to the NRC staff for review:
1.
X-energy should provide clarification regarding the scope of the topical report and/or additional detail in the following areas:
a.
It appears that the draft topical report does not include information regarding some of the bounding conditions (e.g., specific numerical values) of temperature, fluence, and stress that would be experienced by the respective graphite grades during operation as shown in the table below. It is not clear if it is X-energys expectation that the NRC staff review and evaluate the topical report without such information and, if that is the case, what conclusions it would be able to reach. The bounding conditions are necessary to establish the operating envelope within which models can be determined to appropriately represent the physical behavior of the graphite.
Location Temperature Fluence Stress Time Dimensional change In the Graphite Core Assembly (GCA)
Lowest temperature Highest fluence Highest compressive stress Adjacent to the control rod channels Highest temperature Turnaround fluence and percent relative to the turnaround fluence Highest tensile stress N/A Temperature associated with the earliest point for turnaround Crossover fluence and percent relative to the turnaround fluence N/A Time measured in years at the points of interest.
The earliest turnaround and crossover fluences in the GCA and adjacent to the control rod channels are of particular interest.
Dimensional change at the points of interest In addition, separate figures representing the existing data, and planned testing and areas of extrapolation for the design envelope may be important to be clearly presented in the topical report depending on X-energys desired review scope.
b.
The NRC staff understands the scope of this topical report review to include the NRC staffs review and approval of sections 4 and 6. There are several reference documents that contain aspects important to the qualification of the graphite.
X-energy should clarify if the referenced documents in sections 4 and 6 are within the requested scope of the NRC staffs review and approval. For example, IGNIS appears to be an essential aspect of the analysis described in the topical report. It is not clear to the NRC staff what conclusions X-energy requests that the NRC staff reach regarding the IGNIS model in this topical report, nor what information X-energy believes that the NRC staff should review to reach such conclusions, given that a large amount appears to be included in references (e.g., 23, 50) rather than in the topical report itself.
c.
In draft topical report section 1.5, Outcome Objectives, it states that X-energy is requesting the NRC staffs concurrence with X-energy graphite test plan in section 5. The NRC staff does not concur on test plans. The NRC staff performs evaluations to determine whether the information provided by the applicant complies with, or can support the compliance with, the applicable regulatory requirements.
X-energy should clarify if it is requesting the NRC staff to make a regulatory finding regarding the test plan and, if so, provide the basis for that finding.
d.
X-energy states in the topical report that it is requesting NRC approval of the design methodology for the life of the plant. X-energy should clarify this request given that the methodology does not appear to cover the life of the plant, for example, monitoring and surveillance programs that would be developed under a Reliability and Integrity Management (RIM) program to supplement the existing and planned data to show that the graphite core assembly will perform its safety functions for the entire design envelope.
2.
X-energy should ensure all cited references are available to support a potential NRC audit.