Nuclear Energy

International RELAP5 User Group (IRUG)

IRUG supports licensed RELAP5-3D users with software access, training, technical collaboration and governance to advance reactor safety and engineering analysis.

IRUG members

International RELAP5 User Group

The International RELAP5 User Group (IRUG) comprises organizations licensed to use the RELAP5 nuclear power plant safety analysis code, developed at Idaho National Laboratory (INL) since 1979. The objective of IRUG is to serve industry, government, and academia by providing and maintaining a versatile RELAP5 package for safety and engineering analyses of nuclear power reactors. IRUG oversees RELAP5–3D improvements, ensuring it remains a leading reactor safety systems code.

What does IRUG provide?

IRUG provides access to RELAP5-3D on INL's supercomputers, auxiliary software, user group meetings, training, and support for input design and debugging. Members can report issues via User Trouble Reports. Annual meetings, held at INL or member facilities, feature training, technical presentations, business updates, and voting on code and group matters.

Who can be an member?

Membership is open to individuals and organizations, including governmental entities, commercial companies, and academic institutions. Requests for access must be vetted by the Nuclear Computational Resource Center (NCRC). Membership fees, based on usage level (from basic to superuser), are charged annually and adjusted as needed.

Who leads IRUG?

IRUG is led by a chairman, vice-chairman, and secretary. Voting rights are based on membership level, and meeting minutes are distributed prior to each meeting.

International RELAP5 User Group (IRUG) Meeting 2027

May 2027 | Idaho Falls, Idaho

The 2027 International RELAP5 User Group (IRUG) Meeting is planned for May 2027 at the Idaho State University Center for Higher Education in Idaho Falls. Final meeting dates and registration information will be posted when available.

Past IRUG Seminars

International RELAP5 User Group (IRUG) Meeting 2026
May 18–21, 2026 | Idaho Falls, Idaho

The 2026 IRUG Meeting featured RELAP5-3D beginner and intermediate training workshops, followed by the IRUG Technical Seminar and Business Meeting.

Links to presentations will be available soon.

View Flyer

The 2025 IRUG meeting was held on July 28 – August 1, 2025 in Idaho Falls, ID.

The 2025 International RELAP5-3D User Group (IRUG) Meeting will feature the release of RELAP5-3D version 4.6.2 and the new RELAP5-3D/MOOSE Coupling.

The 2024 IRUG meeting was held on Sept. 9-13 in Park City, Utah.

Links to presentations will be available soon.

The 2023 IRUG meeting was held on December 4 – 8, 2023 in Idaho Falls, ID. 

Links to presentations will be available soon. 

The 2021 RELAP5-3D Training Workshop and Users Group Seminar was held virtually on September 13 – 17, 2021. There were 15 technical presentations and the meeting included basic and advanced RELAP5-3D training classes. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter part of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
The 2019 RELAP5-3D Training Workshop and Users Group Seminar was held in Idaho Falls, Idaho USA from April 15 – 19 2019. There were 20 technical presentations. The meeting also included an advanced RELAP5-3D training class. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
2018 RELAP5-3D Training Workshop and Users Group Seminar The 2018 RELAP5-3D Training Workshop and Users Group Seminar was held in Idaho Falls, Idaho USA from April 30 – May 4 2018. There were 20 technical presentations. The meeting also included an introductory RELAP5-3D training class and a half day of training on RAVEN. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
2016 RELAP5-3D Training Workshop and Users Group Seminar The 2016 RELAP5-3D Training Workshop and Users Group Seminar was held in Idaho Falls, Idaho USA from October 3-7 2016. There were 19 technical presentations. The meeting also included an Advanced RELAP5-3D training class and a day of training on RAVEN. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
International RELAP5 Users Group (IRUG) Seminar and Meeting The 2015 RELAP5 Users Group Meeting was held from August 13 – 14, 2015 in Idaho Falls, ID. There were over 20 technical presentations. The meeting was preceded by an Advanced RELAP5-3D training class. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
International RELAP5 Users Group (IRUG) Seminar and Meeting The 2014 RELAP5 Users Group Meeting was held from September 11-12 2014 in Idaho Falls, ID. There were 20 technical presentations. The meeting was preceded by an Advanced RELAP5-3D training class. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
International RELAP5 Users Group (IRUG) Seminar and Meeting The 2013 RELAP5 Users Group Meeting was held from September 12-13 2013 in Idaho Falls, ID. There were over to attendees at the meeting and 25 technical presentations. The meeting was preceded by an Introductory RELAP5-3D training class that had over 30 in attendance. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.
International RELAP5 Users Group (IRUG) Seminar and Meeting The 2012 International RELAP5 Users Group (IRUG) Seminar and Meeting was held October 23-24 in Sun Valley, Idaho. The meeting provided a forum for RELAP5 users from around the globe to share their experiences in developing models and performing analyses using the code. In addition, the latter portion of the seminar was set aside for an executive meeting of the International RELAP5 Users Group. Membership in the User Group was not a condition for attendance at the seminar, and technical papers were encouraged based on any version or application of RELAP5.

Papers and Presentations from the Salt Lake City Meeting

The 2011 RELAP5 International Users Seminar July 26-28, 2011 Salt Lake City, UT. The following list of presentations that were presented at the conference. 

Presentations coming soon. 

Papers and Presentations from the West Yellowstone Meeting

The 2010 RELAP5 International Users Seminar September 20-23, 2010 West Yellowstone, Montana. 

For additional information please contact:

James R. Wolf
RELAP5-3D Program Manager
Idaho National Laboratory
P.O. Box 1625
Idaho Falls, ID 83415-3870
USA
Tel: (208)526-7725
Fax: (208)526-0528
Email: James.Wolf@inl.gov

Papers and Presentations from the Idaho Falls Meeting

Papers and Presentations from the Park City Meeting

The 2009 International RELAP5 Users Seminar was held August 10 – 12th in Park City, Utah. The following is a list of presentations from the conference. 

Presentations coming soon. 

For additional information please contact:
Dr. James R. Wolf
RELAP5 Program Manager
Idaho National Laboratory
PO Box 1625
Idaho Falls, ID 83415
Email: James.Wolf@inl.gov 
Phone: (208) 526-7725

Papers and Presentations from the Idaho Falls Meeting

The 2008 International RELAP5 Users Seminar was held November 18 – 20, 2008 in Idaho Falls, Idaho. 

Presentations coming soon. 

For additional information please contact:
Dr. James R. Wolf
RELAP5 Program Manager
Idaho National Laboratory
PO Box 1625
Idaho Falls, ID 83415
Email: James.Wolf@inl.gov
Phone: (208) 526-7725

Papers and Presentations from the Idaho Falls Meeting

The 2007 International RELAP5 Users Seminar was held November 7-8, in Idaho Falls, Idaho. 

Presentations coming soon. 

For additional information please contact:

James R. Wolf
RELAP5-3D Program Manager
Idaho National Laboratory
P.O. Box 1625
Idaho Falls, ID 83415-3870
USA
Tel:(208)526-7725
Fax:(208)526-0528
Email: James.Wolf@inl.gov

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