ML21250A385
| ML21250A385 | |
| Person / Time | |
|---|---|
| Issue date: | 09/07/2021 |
| From: | Duane Hardesty NRC/NRR/DANU |
| To: | |
| Hardesty, Duane | |
| References | |
| Download: ML21250A385 (19) | |
Text
U.S. Research Reactor Operating Experience Report 2019 - 2021 Duane Hardesty Senior Project Manager Research and Test Reactors Licensing Branch Office of Nuclear Reactor Regulation (NRR)
US Nuclear Regulatory Commission (NRC)
Events of Interest
- 1) National Institute of Standards and Technology (NIST)
- 2) Purdue University
- 3) Oregon State University 2
3 National Institute of Standards and Technology (NIST)
- 20 MWth reactor, operated 24/7
- Closed, non-pressurized heavy water primary cooling system with helium cover gas
- Carbon and high-efficiency particulate air (HEPA) filtered emergency exhaust ventilation and recirculation cleanup 4
NIST - Sequence of Events
- Timeline of the event*
0910 - During startup, operators raised power from 10 to 20 MW 0911 - Increasing radioactivity on fission product monitor 0912 - Increasing radioactivity on building exhaust stack monitor 0912 - Automatic shutdown due to high stack radiation level 0916 - NIST declared Alert in accordance with procedures 1532 - Event downgraded to Notification of Unusual Event 1935 - Event terminated
- Timeline limited to February 3, 2021
NIST - Event Response
- Emergency Planning Response
- Placed reactor in safe, shutdown condition with cooling maintained
- Evacuated confinement building to control station in adjacent building
- Environmental monitoring performed at confinement exhaust stack and 400-meter emergency planning site boundary (within NIST Gaithersburg campus fence line)
- Environmental sampling for radioactive material releases, as well as radiological surveys, confirmed that release amounts were a small fraction of alert or notification of unusual event criteria, which led to event termination later that day
- Safety System Response
- Radiation monitors and automatic safety system performed as designed
- Additional inspection activities ongoing in this area
NIST - Event Consequences
- Facility Consequences - Exceeded Fuel Temp Safety Limit (842 °F)
- Observed one element not fully seated in normal position
- Observed small amount of once molten material on lower grid plate
- Cladding would melt if temperatures reached 1076°F - 1202°F (580°C - 650°C)
- NIST plans to provide a detailed report on the event to the NRC by the end of the year.
A reportable event - Licensee informed NRC as required GUIDE WORDS:
1.2 Reporting Categories Degradation of barriers and safety related systems 1.2.1 Reporting Categories Fuel cladding failure or fuel damage 1.3.1 Reporting Categories Deficiencies in design 1.3.3 Reporting Categories Deficiencies in operation (maintenance and periodic testing) 1.3.4 Reporting Categories Deficiencies in design, construction, operation (including maintenance and periodic testing) or quality assurance 1.6 Reporting Categories Events of potential safety significance (potential unsafe situation) 5.1 Cause of the event Unknown or other 6.1.1 Effects on Operation Automatic Reactor Scram 6.6.1 Effects on Operation Unanticipated release of radioactive materials 7.1 Characteristics of incident Degraded Fuel 8.2.1 Nature of Failure or error Independent multiple failures or errors 8
Purdue University 9
Purdue University
- 12 KWth reactor, operated for training & education
- Open Pool, light water moderated
- Cooled by natural convection of light water, moderated by light water, and reflected by water and graphite 10
Purdue University Overpower Event
- Purdue performed an initial reactor startup after a digital I&C modification on August 27, 2019
- After the reactor startup, Purdue performed gold foil irradiations to calibrate the nuclear instrument detectors
- An error resulted in actual reactor power being low by a factor of approximately three.
- A radiation area existed at the reactor pool top, but the area was not posted as a radiation area 11
A reportable event - Licensee informed NRC as required GUIDE WORDS:
1.2.4 Reporting Categories Degradation of systems required to control reactivity and shutdown -- incorrect safety system setting 1.3.3 Reporting Categories Deficiencies in operation (including maintenance and periodic testing) -- Personnel errors or procedural deficiencies resulting in loss of reactor capability to perform safety functions 1.3.4 Reporting Categories Deficiencies in quality assurance -- Insufficient verification of accomplished work owing to deficiency 1.4 Generic problem of safety (a) recurring event; (b) event with implication for similar reactor design 12
Guide Words (Continued) 2.1.3 Plant Status Prior to Event Raising Power on startup 3.4. Failed / Affected Systems Instrumentation and control systems 3.4.1 Failed / Affected Systems Reactor shutdown system 3.4.4 Failed / Affected Systems Neutron flux monitoring channels 4.1.9 Failed/affected component Neutron flux (detectors, ion chambers and associated components) 5.1.10 Cause of the event Human factors 5.3.1 Cause of the event Inadequate human action - Maintenance 5.5 Human performance related Lack of control of task, Training, Written procedures causal factors and documents, Skill of the craft less than adequate 6.1.1 Effects on Operation Automatic Reactor Scram 6.10 Effects on Operation Exceeding technical specification limits 7.5 Characteristics of incident Significant degradation of safety function 8.3 Nature of Failure or error Common cause failure 13
Oregon State University TRIGA Reactor 14
Oregon State University Faulty IFE
- The Pulse
- Administratively limited to a max pulse of $2.25
- Performed a $2.20 pulse on 21 May 2018
- The next day, upon reaching full power, the operator discovered the IFE readings had increased by ~ 45 C
- The temperature continued to increase over time
OSU - Event Status
- OSU submitted an application to remove the IFE from the Technical Specifications (OLS).
- The NRC staff is reviewing the application
- If approved, OSU will remove the IFEs from service and the limiting safety setting will be based on reactor power to prevent exceeding safety limit (temperature)
- Target completion is 1st Quarter 2022 16
OSU - Information for License Amendment
- Peak fuel temp
- Confirming limit for proposed pulse limit
- Rod worth measurements
- Need to understand the application of uncertainties
- Sensitivity analysis
- Need to better understand the change of core parameters over life that may impact pulse performance 17
Not a reportable event - Licensee informed NRC as courtesy GUIDE WORDS:
1.2.4 Reporting Categories Degradation of reactivity control system required to shutdown --
failure of the process variable providing safety setting 1.3.1 Reporting Categories Deficiencies in design 1.3.4 Reporting Categories Deficiencies in quality assurance (b) a was not constructed as intended in design 1.4 Generic problem of safety (a) recurring event; (b) event with interest implication for similar reactor design 2.1.6 Plant Status Prior to Event Pulse Operation 3.4.0 Failed / Affected Systems Other monitoring and control system 3.4.1 Failed / Affected Systems Reactor shutdown system 3.4.4 Failed / Affected Systems Process monitoring (Temperature) 4.1.2 Failed/affected component Temperature 5.1.0 Cause of the event Unknown or other 5.1.5 Cause of the event Instrumentation and control failure 6.10 Effects on Operation Exceeding technical specification limit 8.2.1 Nature of Failure or error Independent multiple failures or errors 18
Thank you for your attention Questions?
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