ML23319A239
| ML23319A239 | |
| Person / Time | |
|---|---|
| Site: | 99902071 |
| Issue date: | 11/30/2023 |
| From: | Hernandez J Office of Nuclear Reactor Regulation |
| To: | Michael Wentzel Office of Nuclear Reactor Regulation |
| References | |
| EPID L-2018-LRM-0076 | |
| Download: ML23319A239 (1) | |
Text
November 30, 2023 MEMORANDUM TO:
Michael Wentzel, Chief Advanced Reactor Licensing Branch 2 Division of Advanced Reactors and Non-power Production and Utilization Facilities Office of Nuclear Reactor Regulation FROM:
Jorge Hernandez, Project Manager
/RA/
Advanced Reactor Licensing Branch 2 Division of Advanced Reactors and Non-power Production and Utilization Facilities Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF THE OCTOBER 5, 2023, PUBLIC MEETING WITH X ENERGY, LLC. (X-ENERGY), APPROACH FOR GRAPHITE QUALIFICATION FOR THE XE-100 HIGH TEMPERATURE GAS REACTOR (EPID NO. L-2018-LRM-0076)
Meeting Information:
Applicant: X ENERGY, LLC. (X-energy)
Docket/Project No.(s): 99902071 Public Meeting Notice Agencywide Documents Access and Management System (ADAMS)
Accession No.: ML23264A852 Applicant Presentation Slides ADAMS Accession No.: ML23244A273 Meeting Attendees: See the enclosure for a list of meeting attendees.
CONTACT:
Jorge Hernandez, NRR/DANU 301-287-9096
Background:
The X ENERGY, LLC (X-energy) Xe-100 reactor is a high-temperature graphite-moderated gas-cooled reactor. The graphite core structure performs three primary safety functions: (1) control of reactivity via inherent reactivity feedback and moveable poisons, (2) heat removal from fuel to vessel wall, and (3) limit stress under design basis accidents. These functions are achieved by maintaining reactor core geometry, providing channels for control rod insertion, and ensuring a flow path for core cooling. The graphite core structure also supports the following safety significant functions: (1) control (active) heat removal, and (2) radionuclide retention during anticipated operational occurrences.
Additionally, the graphite reflector provides thermal insulation and neutron shielding for the metallic reactor pressure vessel. The material properties of irradiated graphite are specific to each individual grade and while graphite has been used in earlier high temperature gas-cooled reactors, there is limited experimental data and operational experience with more recently developed grades.
The purpose of this series of pre-application meetings is to introduce specific aspects of X-energys graphite qualification plan for the Xe-100 design, to the U.S. Nuclear Regulatory Commission (NRC) staff. The American Society of Mechanical Engineers (ASME) requirements for graphite qualification are covered by the ASME Boiler and Pressure Vessel Code Section III Division 5, Subsection HH, Subpart A.
By letter dated October 31, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22304A197), X-energy submitted a licensing topical report (LTR)
Xe-100 Licensing Topical Report: Graphite Qualification Methodology, for NRC staff review.
The LTR describes the method for qualification of graphite core structures used by X-energy for the Xe-100 reactor.
On December 14, 2022, the NRC staff held a partially closed public meeting with X-energy to request clarification on certain aspects of the LTR. During the meeting, the NRC staff made various observations and identified technical deficiencies, which are documented in the meeting summary (ML23040A141). During the meeting, X-energy stated that it was very likely that they would withdraw the LTR. On December 20, 2022, Xenergy told the NRC staff that they planned to withdraw the report.
By letter dated January 3, 2023 (ML23003A803), X-energy requested to withdraw the LTR. By letter dated February 1, 2023 (ML23023A248), the NRC staff (1) acknowledged the request to withdraw the LTR, (2) confirmed the cessation of the review, and (3) documented the issues identified by the NRC staff as enclosures to the letter. The NRC staff indicated that X-energy should address these issues if they intended to re-submit the LTR.
On April 24, 2023 (ML23207A188) the NRC staff held a partially closed meeting with X-energy.
The topics included identification of materials for top and bottom reflectors, ASME Boiler and Pressure Vessel Code requirements, and current/future activities to qualify graphite components.
X-energy proposed a series of public meetings, some of which would be partially closed, to discuss specific aspects of graphite qualification for the Xe-100 design.
By letter dated July 31, 2023 (ML23212B211), X-energy transmitted a regulatory engagement plan focused on material qualification of graphite and other graphite-related matters, along with the proposed schedule for the meetings.
Prior to this meeting, the following meeting has been held, in accordance with the aforementioned regulatory engagement plan:
August 24, 2023 (ML23271A128): partially closed meeting to discuss scope of graphite qualification and methodologies that will be included in the Preliminary Safety Analysis Report (Construction Permit) for the Xe-100 and referenced technical documentation and means of addressing finality by the Final Safety Analysis Report (Operating License) stage.
Meeting Summary:
The NRC staff conducted the meeting in accordance with NRC Management Directive 3.5, Attendance at NRC Staff-Sponsored Meetings (ML21180A271).
This meeting was the second meeting included in X-energys regulatory engagement plan for graphite components.
The X-energys staff presentation discussed the following topics:
A proposed method of modelling irradiated graphite, including a discussion on why modeling is necessary.
Principles and process used to develop the material model for structural integrity analysis. X-energy noted the use of Regulatory Guide 1.203, Transient and Accident Analysis Methods, (ML053500170) as guidance for development of the model.
Various irradiated graphite properties considered within the model, e.g., Youngs modulus, the coefficient of thermal expansion, etc., with an explanation for the causes, trends, and equations selected.
How irradiation creep will be considered as a combination of primary creep, secondary creep, and recoverable creep and how irradiation creep will be considered within the broader context of influencing graphite properties.
The development of the model framework, and the process of fitting and calibrating the model to grade specific data, with examples of fitting and calibration of the model with historical grades of graphite. Historical graphite data was used to create the model, which will then be fitted to the proposed grades. The model will be updated as additional data becomes available.
In the closed portions of the meeting, X-energy presented (1) a physical layout of graphite reflectors, (2) expected temperature/dose envelopes, and (3) a comparison to existing datasets for various grades.
The NRC staff made the following questions/observations (including X-energys responses):
It was unclear how the model extrapolates and interpolates between the same graphite grade and different grades across temperature. X-energy believes that their semi-empirical model, in combination with the available data, will be able to address these concerns.
The NRC staff asked if the structural analysis of irradiated graphite will require material properties other than those discussed, and if so, what equations will be used to model the effect of irradiation on those properties. X-energy mentioned the change of graphite strength with irradiation would be linked to the underlying model and X-energy will be collecting additional data from testing.
The NRC staff questioned the justification for assuming that the elastic Poissons ratio does not vary with irradiation. X-energy responded that this assumption is linked to convention.
The NRC staff made several questions and observations during the closed portion of the meeting related to quality assurance of test data, considerations for oxidation, internal energy, and low temperature behavior.
No regulatory decisions were made as a result of this meeting.
Project No. 99902071
Enclosure:
List of Meeting Attendees cc: X-energy Xe-100 via GovDelivery
SUBJECT:
SUMMARY
OF THE OCTOBER 5, 2023, PUBLIC MEETING WITH X ENERGY, LLC. (X-ENERGY), APPROACH FOR GRAPHITE QUALIFICATION FOR THE XE-100 HIGH TEMPERATURE GAS REACTOR (EPID NO. L-2018-LRM-0076) DATED: NOV 30, 2023 DISTRIBUTION:
PUBLIC RidsNrrDanuUal1 Resource RidsNrrDanuUal2 Resource RidsNrrDanu Resource AMuniz AChereskin DBeacon GOberson IJung JBass LKingsbury MGordon RIyengar VVoltaggio ADAMS Accession Number: ML23319A239 NRR-001 OFFICE NRR/DANU/UAL2/PM NRR/DANU/UAL2/BC NRR/DANU/UAL2/PM NAME JHernandez MWentzel JHernandez DATE 11 / 15 / 2023 11 / 30/ 2023 11 / 30 / 2023 OFFICIAL RECORD COPY
Enclosure List of Meeting Attendees For the October 5, 2023 Public Meeting With X Energy, LLC. (X-Energy), Approach for Graphite Qualification for the Xe-100 High Temperature Gas Reactor Open Meeting Name Organization Adrian Muniz U.S. Nuclear Regulatory Commission (NRC)
Alexander Chereskin NRC Dan Beacon NRC Greg Oberson NRC Ian Jung NRC Jorge Hernandez Munoz NRC Joseph Bass NRC Lance Kingsbury NRC Matthew Gordon NRC Michael Wentzel NRC Raj Iyengar NRC Ryann Bass NRC Vince Voltaggio NRC Chong Chen X-energy Doug Kalinousky X-energy Emna Sghaier X-energy FJ van Zanten X-energy Jaime A Cano X-energy James Roll X-energy Jasmine Wang X-energy Jon Facemire X-energy Maggie Staiger X-energy Mo Oghbaei X-energy Sam Baylis X-energy Tim Lucas X-energy Travis Chapman X-energy Zach Burns X-energy Gwennael Beirnaert X-energy (contractor)
Michael Saitta X-energy (contractor)
Mark Natale Department of Energy Carl Friesen Department of Energy Jana Bergman Curtiss Wright Sebastian Black Frazer Nash Consultancy Timothy Polich RoPower Dominik Muszynski Unknown Closed Meeting Name Organization Adrian Muniz NRC Alexander Chereskin NRC Dan Beacon NRC Greg Oberson NRC Ian Jung NRC
2 Name Organization Jon Facemire NRC Jorge Hernandez Munoz NRC Joseph Bass NRC Matthew Gordon NRC Michael Wentzel NRC Ryann Bass NRC Vince Voltaggio NRC Chong Chen X-energy Doug Kalinousky X-energy Emna Sghaier X-energy FJ van Zanten X-energy Gwennael Beirnaert X-energy Jaime A Cano X-energy James Roll X-energy Jasmine Wang X-energy Maggie Staiger X-energy Mo Oghbaei X-energy Nico Zucchi X-energy Raja Sekhar Tripuraneni X-energy Ryan Buck X-energy Sam Baylis X-energy Tim Lucas X-energy Tom Braudt X-energy Travis Chapman X-energy Zach Burns X-energy Laura Dawson X-energy (contractor)
Mark Joyce X-energy (contractor)
Michael Saitta X-energy (contractor)