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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| ENS 57372 | Calvert Cliffs | 10 October 2024 09:57:00 | Automatic Reactor Trip Due to Turbine Generator Loss of Field | The following information was provided by the licensee via phone and email:
At 0557 EDT on 10/10/2024, with Unit 2 in mode 1 at 100 percent power, the reactor automatically tripped due to turbine generator loss of field. The trip was not complex with all systems responding normally post-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).
Operations responded using EOP-0, post trip immediate actions, and stabilized the plant in mode 3. Decay heat is removed by discharging steam to the main condenser using the turbine bypass valves.
Unit 1 is not affected.
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:
The exciter is suspected to being the cause and is under investigation. All control rods fully inserted. | | NUREG-1022, Rev. 3, Supplement 2, Event Report Guidelines 10 CFR 50.72(b)(3)(ii) and 10 CFR 50.73(a)(2)(ii) Final Report | | 30 September 2024 | NUREG-1022, Rev. 3, Supplement 2, Event Report Guidelines 10 CFR 50.72(b)(3)(ii) and 10 CFR 50.73(a)(2)(ii) Final Report | | | ML24270A074 | FitzPatrick | 30 September 2024 | Individual Notice of Consideration of Issuance of Amendments to Renewed Facility Operating Licenses, Proposed No Significant Hazards Consideration Determination, & Opportunity for a Hearing (EPID L-2024-LLA-0134) - LTR | | | NL-24-0320, License Amendment Request Proposing a New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods That Exceed the Linear Heat Generation Rate Limit Detailed in Regulatory Guide 1.183, Table 3,. | Farley | 27 September 2024 | License Amendment Request Proposing a New Set of Fission Gas Gap Release Fractions for High Burnup Fuel Rods That Exceed the Linear Heat Generation Rate Limit Detailed in Regulatory Guide 1.183, Table 3,. | | | ML24270A145 | FitzPatrick | 26 September 2024 | Notice of Enforcement Discretion for James A. Fitzpatrick Nuclear Power Plant | | | ML24257A058 | Palisades | 26 September 2024 | Summary of August 1, 2024, Hybrid Public Meeting on the Potential Palisades Nuclear Plant Restart | | | JAFP-24-0047, License Amendment Request – Temporary Addition to TS 3.3.2.1 Condition C, Control Rod Block Instrumentation to Support Upgrade to Rod Worth Minimizer Software | FitzPatrick | 25 September 2024 | License Amendment Request – Temporary Addition to TS 3.3.2.1 Condition C, Control Rod Block Instrumentation to Support Upgrade to Rod Worth Minimizer Software | | | ML24254A255 | Seabrook | 25 September 2024 | Alternative Request No. 4A-01 for the Fourth 10-Year Inservice Inspection Interval | | | RBG-48306, Report of Changes and Errors to 10CFR50.46 | River Bend | 24 September 2024 | Report of Changes and Errors to 10CFR50.46 | | | ENS 57333 | FitzPatrick | 23 September 2024 11:20:00 | Automatic Reactor Scram Due to Generator Trip | The following information was provided by the licensee via phone and email:
At 0720 EDT on September 23, 2024, James A. FitzPatrick was at 100 percent power when an automatic scram occurred as a result of a main turbine trip due to an automatic trip of the generator output breakers; the cause is still under investigation.
The scram was not complex. The automatic scram inserted all control rods. A subsequent reactor pressure vessel (RPV) low water level resulted in a group 2 isolation and initiation of high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems. RCIC did inject, but HPCI did not inject, as expected, based on RPV water level recovery with the feedwater system. Reactor pressure is being maintained by main steam line bypass valves. The plant is stable in Mode 3 with the 'A' reactor feed pump maintaining RPV water level.
The initiation of the reactor protection system (RPS) due to the automatic scram signal while critical is reportable per 10 CFR 50.72(b)(2)(iv)(B). The general containment Group 2 isolations and HPCI and RCIC system actuations are reportable per 10 CFR 50.72(b)(3)(iv)(A).
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:
The group 2 containment isolation affects multiple systems.
- * * UPDATE ON 9/23/2024 AT 1540 EDT FROM RYAN PERRY TO SAMUEL COLVARD * * *
On 9/23/2024 at 1156 EDT Constellation communications provided a media statement to Oswego area news media contacts summarizing the events that had occurred at Nine Mile Point Unit 2 and FitzPatrick Unit 1. This is a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(xi). The NRC Senior Resident Inspector has been notified.
Notified R1DO (Dimitriadis) |
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