A control rod (CR) or control rod blade (CRB) or Control Rod Drive (CRD) may be inserted into a reactor in order to reduce reactivity by absorbing free neutrons before they react with fuel. During a Scram all control rods are fully inserted to shutdown the reactor as fast as possible.
Their compositions include chemical elements such as boron, cadmium, silver, hafnium, or indium, that are capable of absorbing many neutrons without themselves decaying.
Control Rod vs Control Rod Blade
Both terms may be considered control rods but the distinction is that a Control Rod Blade is Cross-shaped, and slides between 4 fuel bundles. Rather then "rods" which are within a fuel bundles in the place of a fuel pin and these use a guide tube to travel.
Control Rod Drive (CRD)
The control rod drive is the motive force to insert control rods.
Control Rod Notch
Each control rod has a series of positions or notches. Raising and lowering reactor power involves moving control rods in or out 1 notch at a time.
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| | Site | Start date | Title | Description |
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| ML25113A264 | Turkey Point | 31 December 2025 | Benchmark Calculation for Turkey Point, Unit 3, Cycles 1-3 Using the Scale 6.3/Polaris–PARCS v3.4.2 Code Package | | | ML25140A136 | | 9 June 2025 | Natrium Topical Report, Radiological Source Term Methodology Report (NAT-9392, Rev 0) | | | ML25150A335 | | 3 June 2025 | 007834 Xe-100 Licensing Topical Report Transient and Safety Analysis Methodology- NRC Staff Review - ACRS Subcommittee - 060325 | | | ML25150A337 | | 3 June 2025 | Xe-100 GOTHIC-Flownex - NRC Staff Review - ACRS Subcommittee - 060225 | | | IR 05000186/2025201 | University of Missouri-Columbia | 2 June 2025 | The Curators of the University of Missouri - U.S. Nuclear Regulatory Commission Safety Inspection Report 05000186/2025201 | | | NUREG-0090 Volume 47, Report to Congress on Abnormal Occurrences Fiscal Year 2024 | | 31 May 2025 | NUREG-0090, Vol. 47, Report to Congress on Abnormal Occurrences Fiscal Year 2024 | | | ML25150A377 | University of Missouri-Rolla | 30 May 2025 | Annual Progress Report for the Missouri University of Science and Technology Reactor | | | JAFP-25-0034, License Amendment Request for Proposed Changes to the Technical Specification Primary Containment Isolation Instrumentation Tables and New Main Steam Tunnel Area Temperature Technical Specification 3.7.8 | FitzPatrick | 29 May 2025 | License Amendment Request for Proposed Changes to the Technical Specification Primary Containment Isolation Instrumentation Tables and New Main Steam Tunnel Area Temperature Technical Specification 3.7.8 | | | IR 05000298/2024003 | Cooper | 29 May 2025 | Integrated Inspection Report 05000298/2024003, Disputed Non-Cited Violation Revised | | | ENS 57734 | Vogtle | 28 May 2025 16:53:00 | Manual Reactor Trip and Auxiliary Feedwater Actuation | The following information was provided by the licensee via phone and email:
At 1253 EDT, on May 28, 2025, with Unit 1 in mode 1 at 100 percent power, the reactor was manually tripped due to a loss of main feedwater pump `A'. The trip was not complex, with all systems responding normally post-trip.
Operations responded and stabilized the plant. Decay heat is being removed by discharging steam through the steam dumps to the main condenser. Units 2, 3, and 4 are not affected. An automatic actuation of auxiliary feedwater (AFW) also occurred. The AFW auto-start is an expected response from the reactor trip.
Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). This event is also being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the auxiliary feedwater system.
There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
All control rods inserted on the trip. A main feedwater pump lube oil evolution was in progress at the time of the trip. |
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