Scram

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A scram is a rapid plant shutdown through the insertion of all control rods

  • A automatic scram is the type of scram which is triggered by automatically detecting various plant conditions (or even invalid signal).
  • A manual scram means that the control rod insertion was trigger by a plant operators.

SCRAM is an acronym for Safety Control Rod Ax Man. Scram refers to the automatic rapid insertion of control rods in response to the detection of undesirable conditions.

Crud Burst

Corrosion product spiking in the reactor coolant during the reactor shutdown has been observed in practically all operating boiling water reactors (BWRs or PWRs). However, the spiking magnitude and the total released activities may vary from reactor to reactor, depending on the activity inventory and the characteristics of the deposit on the fuel cladding surfaces. The corrosion product deposit on the fuel cladding surfaces is known to have two distinguishable layers: the inner tenacious layer and the loosely attached outer layer. The characteristics of the deposit depend largely on the thickness of the deposit and the metallic elemental composition in the deposit (or metallic impurity level in reactor water). There are at least three major causes for the release of the corrosion product deposit from the fuel cladding surfaces during power transients:

(1) Mechanical and/or hydraulic disturbance.
(2) Coolant chemistry change caused by temperature and radiation field changes.
(3) Decreasing temperature which increases the solubilities of some corrosion product oxides in the deposit.

It is obvious that immediately after a reactor shutdown or scram, the crud burst occurs due to mechanical and/or hydraulic disturbance in the core. A portion of the outer layer (made up of fission and corrosion by-products) is believed to be easily shaken off by the mechanical disturbance. Smaller crud spikes can also continue for some time after the reactor shutdown. Such small spikes may be attributed to continued water boiling at lower pressure and/or water chemistry upset at lower temperatures. Since the crud deposition on cladding surfaces may be partially due to a weak interaction between the charged particles and the stationary surface, when a slight change in water chemistry occurs, the weak attraction force may be broken and particles released from the surface.

The corrosion product spiking is not limited to the release of insoluble crud. The spiking of soluble species can sometimes account for the majority of the released activities. The decrease in the reactor water temperature is probably responsible for the release of soluble species, which is normally observed long after the first crud spike and the temperature is about 200°C. Based on the known solubilities of many corrosion product oxides (or mixed oxides) in water, it is predictable that most of the activities in the fuel deposit should become more soluble at lower temperatures. However, there are two factors (thermodynamics and kinetics) that control the dissolution rate of the corrosion product oxide during the cooling down process. At lower temperatures, the solubility is high but the dissolution process may be fast enough but equilibrium is in favor of the insoluble form.

History

The name Scram isn't an acronym. It is simply a colorful slang term for "run-away".

Common Myth:

The name comes from the first nuclear reactor (called a pile, because it was made up of a large square pile of graphite blocks with uranium tubes running through it), which was under the stands at the University of Chicago football stadium. After the reactor went critical (sustained a nuclear chain reaction), if the chain reaction could not be controlled, then everyone was to "scram" (run away) except for a man with an ax, who was to cut through a rope that would allow a boron containing safety control rod to drop into the pile. The control rod would stop the nuclear chain reactor, i.e., shut down the shutdown the reactor. The SCRAM has since been used to mean an automatic or rapid shutdown of a nuclear reactor. [1]

Scram lists

[Table View]

[last 90 days]

Loading map...
  • 2023: 27
  • 2022: 32
  • 2021: 30
  • 2020: 40
  • 2019: 49
  • 2018: 46
  • 2017: 39
  • 2016: 44
  • 2015: 55

Automatic Scram

 Start dateSiteRegion
ENS 5722110 July 2024 11:28:00Peach BottomNRC Region 1
ENS 5717516 June 2024 17:33:00WaterfordNRC Region 4
ENS 5714123 May 2024 16:46:00Quad CitiesNRC Region 3
ENS 571075 May 2024 08:38:00BraidwoodNRC Region 3
ENS 5709025 April 2024 03:15:00Browns FerryNRC Region 2
ENS 5704623 March 2024 04:04:00FermiNRC Region 3
ENS 5704222 March 2024 04:37:00WaterfordNRC Region 4
ENS 5703317 March 2024 20:15:00Comanche PeakNRC Region 4
ENS 570044 March 2024 00:42:00Nine Mile PointNRC Region 1
ENS 570033 March 2024 17:42:00Prairie IslandNRC Region 3
ENS 5689416 December 2023 09:50:00Grand GulfNRC Region 4
ENS 5688713 December 2023 07:02:00River BendNRC Region 4
ENS 5685616 November 2023 07:27:00Calvert CliffsNRC Region 1
ENS 568397 November 2023 21:17:00Calvert CliffsNRC Region 1
ENS 5681325 October 2023 01:59:00Turkey PointNRC Region 2
ENS 567319 September 2023 15:43:00GinnaNRC Region 1
ENS 567102 September 2023 10:32:00Nine Mile PointNRC Region 1
ENS 5658522 June 2023 14:35:00RobinsonNRC Region 2
ENS 5658016 June 2023 23:32:00Comanche PeakNRC Region 4
ENS 5654430 May 2023 08:46:00MillstoneNRC Region 1
... further results

Manual Scram

 Start dateSiteRegion
ENS 572159 July 2024 01:25:00VogtleNRC Region 2
ENS 5719527 June 2024 12:04:00CookNRC Region 3
ENS 5718722 June 2024 11:28:00VogtleNRC Region 2
ENS 5717718 June 2024 07:17:00Saint LucieNRC Region 2
ENS 571645 June 2024 20:48:00VogtleNRC Region 2
ENS 571614 June 2024 17:52:00Saint LucieNRC Region 2
ENS 5713219 May 2024 04:30:00Beaver ValleyNRC Region 1
ENS 5712815 May 2024 08:27:00CookNRC Region 3
ENS 5703317 March 2024 20:15:00Comanche PeakNRC Region 4
ENS 5703216 March 2024 19:49:00WaterfordNRC Region 4
ENS 5702111 March 2024 17:37:00HatchNRC Region 2
ENS 570147 March 2024 19:42:00Reed College (Reed)NRC Region 0
ENS 5699124 February 2024 20:46:00Calvert CliffsNRC Region 1
ENS 5697116 February 2024 11:34:00FarleyNRC Region 2
ENS 5686318 November 2023 05:55:00River BendNRC Region 4
ENS 5685214 November 2023 16:41:00FarleyNRC Region 2
ENS 5684610 November 2023 08:14:00SusquehannaNRC Region 1
ENS 568261 November 2023 10:48:00HatchNRC Region 2
ENS 5679013 October 2023 01:27:00GinnaNRC Region 1
ENS 567691 October 2023 03:14:00Diablo CanyonNRC Region 4
... further results

by company - 24 months

... further results
Allied-General Nuclear Services 0 [Allied-General Nuclear Services events] [RSS]
AmerGen 0 [AmerGen events] [RSS]
Ameren 0 [Ameren events] [RSS]
American Electric Power 4 [American Electric Power events] [RSS]
Arizona Public Service 1 [Arizona Public Service events] [RSS]
Carolina Power & Light Company 0 [Carolina Power & Light Company events] [RSS]
Cincinnati Gas & Electric Company 0 [Cincinnati Gas & Electric Company events] [RSS]
Cleveland Electric 0 [Cleveland Electric events] [RSS]
Cleveland-Cliffs 0 [Cleveland-Cliffs events] [RSS]
Connecticut Yankee Atomic Power Co 0 [Connecticut Yankee Atomic Power Co events] [RSS]
Constellation 13 [Constellation events] [RSS]
Consumers Energy 0 [Consumers Energy events] [RSS]
DTE Energy 1 [DTE Energy events] [RSS]
Dairyland Power Cooperative 0 [Dairyland Power Cooperative events] [RSS]
Dominion 1 [Dominion events] [RSS]
Duke Energy 5 [Duke Energy events] [RSS]
Duquesne Light Company 0 [Duquesne Light Company events] [RSS]
EDF Energy 0 [EDF Energy events] [RSS]
Energy Northwest 0 [Energy Northwest events] [RSS]
Entergy 9 [Entergy events] [RSS]
Eversource Energy 0 [Eversource Energy events] [RSS]
Exelon 0 [Exelon events] [RSS]
FirstEnergy 0 [FirstEnergy events] [RSS]
GEH Hitachi 0 [GEH Hitachi events] [RSS]
GPU Nuclear 0 [GPU Nuclear events] [RSS]
Houston Lighting and Power Company 0 [Houston Lighting and Power Company events] [RSS]
Illinois Power Company 0 [Illinois Power Company events] [RSS]
Jiangsu Nuclear Power Corporation 0 [Jiangsu Nuclear Power Corporation events] [RSS]
LaCrosseSolutions 0 [LaCrosseSolutions events] [RSS]
Long Island Lighting Company 0 [Long Island Lighting Company events] [RSS]
Luminant 3 [Luminant events] [RSS]
NextEra Energy 6 [NextEra Energy events] [RSS]
Niagara Mohawk 0 [Niagara Mohawk events] [RSS]
Northeast Nuclear Energy 0 [Northeast Nuclear Energy events] [RSS]
Omaha Public Power District 0 [Omaha Public Power District events] [RSS]
Ontario Power Generation 0 [Ontario Power Generation events] [RSS]
PSEG 0 [PSEG events] [RSS]
Pacific Gas & Electric 1 [Pacific Gas & Electric events] [RSS]
Pennsylvania Power and Light Company 0 [Pennsylvania Power and Light Company events] [RSS]
Portland General Electric 0 [Portland General Electric events] [RSS]
Power Authority of the State of New York 0 [Power Authority of the State of New York events] [RSS]
Progress Energy 0 [Progress Energy events] [RSS]
Rochester Gas and Electric 0 [Rochester Gas and Electric events] [RSS]
STP Nuclear Operating Company 0 [STP Nuclear Operating Company events] [RSS]
South Carolina Electric & Gas Company 1 [South Carolina Electric & Gas Company events] [RSS]
Southern California Edison 0 [Southern California Edison events] [RSS]
Southern Nuclear 12 [Southern Nuclear events] [RSS]
Talen Energy 1 [Talen Energy events] [RSS]
Tennessee Valley Authority 1 [Tennessee Valley Authority events] [RSS]
WEC Energy Group 0 [WEC Energy Group events] [RSS]

by site - 24 months

Site#Man#AutoCompanyEvent lists
Almaraz 0 0 Iberdrola [Almaraz events] [RSS]
Arkansas Nuclear 0 1 Entergy [Arkansas Nuclear events] [RSS]
Asco 0 0 Endesa [Asco events] [RSS]
Beaver Valley 1 0 Vistra [Beaver Valley events] [RSS]
Belleville 0 0 Électricité de France [Belleville events] [RSS]
Blayais 0 0 Électricité de France [Blayais events] [RSS]
Braidwood 0 1 Constellation [Braidwood events] [RSS]
Browns Ferry 0 1 Tennessee Valley Authority [Browns Ferry events] [RSS]
Brunswick 0 1 Duke Energy [Brunswick events] [RSS]
Byron 0 0 Constellation [Byron events] [RSS]
Callaway 0 0 Ameren [Callaway events] [RSS]
Calvert Cliffs 1 2 Constellation [Calvert Cliffs events] [RSS]
Catawba 1 0 Duke Energy [Catawba events] [RSS]
Chernobyl 0 0 [Chernobyl events] [RSS]
Clinch River 0 0 [Clinch River events] [RSS]
Clinton 0 1 Constellation [Clinton events] [RSS]
Cofrentes 0 0 Iberdrola [Cofrentes events] [RSS]
Columbia 0 0 Energy Northwest [Columbia events] [RSS]
Comanche Peak 1 3 Luminant [Comanche Peak events] [RSS]
Cook 2 2 American Electric Power [Cook events] [RSS]
Cooper 1 0 Entergy [Cooper events] [RSS]
Dampierre 0 0 Électricité de France [Dampierre events] [RSS]
Davis Besse 0 0 Cleveland Electric [Davis Besse events] [RSS]
Diablo Canyon 1 0 Pacific Gas & Electric [Diablo Canyon events] [RSS]
Dresden 0 0 Constellation [Dresden events] [RSS]
Dungeness 0 0 EDF Energy [Dungeness events] [RSS]
Farley 2 2 Southern Nuclear [Farley events] [RSS]
Fermi 0 1 DTE Energy [Fermi events] [RSS]
FitzPatrick 0 0 Constellation [FitzPatrick events] [RSS]
Flamanville 0 0 Électricité de France [Flamanville events] [RSS]
Ginna 1 1 Constellation [Ginna events] [RSS]
Grand Gulf 1 1 Entergy [Grand Gulf events] [RSS]
Harris 1 1 Duke Energy [Harris events] [RSS]
Hartlepool 0 0 EDF Energy [Hartlepool events] [RSS]
Hatch 3 0 Southern Nuclear [Hatch events] [RSS]
Heysham 0 0 EDF Energy [Heysham events] [RSS]
Hinkley Point 0 0 EDF Energy [Hinkley Point events] [RSS]
Hope Creek 0 0 PSEG [Hope Creek events] [RSS]
Hunterston 0 0 EDF Energy [Hunterston events] [RSS]
Khmelnytskyi 0 0 Energoatom [Khmelnytskyi events] [RSS]
LaSalle 1 0 Constellation [LaSalle events] [RSS]
Lee 0 0 Duke Energy [Lee events] [RSS]
Limerick 0 0 Constellation [Limerick events] [RSS]
McGuire 0 0 Duke Energy [McGuire events] [RSS]
Millstone 0 1 Dominion [Millstone events] [RSS]
Monticello 0 0 Xcel Energy [Monticello events] [RSS]
Nine Mile Point 0 2 Constellation [Nine Mile Point events] [RSS]
Nogent 0 0 Électricité de France [Nogent events] [RSS]
North Anna 0 0 Dominion [North Anna events] [RSS]
Oconee 0 0 Duke Energy [Oconee events] [RSS]
Olkiluoto 0 0 Teollisuuden Voima [Olkiluoto events] [RSS]
Palisades 0 0 Entergy [Palisades events] [RSS]
Palo Verde 0 1 Arizona Public Service [Palo Verde events] [RSS]
Peach Bottom 0 1 Constellation [Peach Bottom events] [RSS]
Perry 0 0 FirstEnergy [Perry events] [RSS]
Point Beach 0 0 NextEra Energy [Point Beach events] [RSS]
Prairie Island 0 1 Xcel Energy [Prairie Island events] [RSS]
Quad Cities 1 1 Constellation [Quad Cities events] [RSS]
River Bend 1 1 Entergy [River Bend events] [RSS]
Rivne 0 0 Energoatom [Rivne events] [RSS]
Robinson 0 1 Duke Energy [Robinson events] [RSS]
Saint Lucie 3 0 NextEra Energy [Saint Lucie events] [RSS]
Salem 0 0 PSEG [Salem events] [RSS]
Seabrook 1 0 NextEra Energy [Seabrook events] [RSS]
Sequoyah 0 0 Tennessee Valley Authority [Sequoyah events] [RSS]
Sizewell 0 0 EDF Energy [Sizewell events] [RSS]
South Texas 0 0 STP Nuclear Operating Company [South Texas events] [RSS]
South Ukraine 0 0 Energoatom [South Ukraine events] [RSS]
Summer 1 0 South Carolina Electric & Gas Company [Summer events] [RSS]
Sundesert 0 0 San Diego Gas & Electric Compnay [Sundesert events] [RSS]
Surry 0 0 Dominion [Surry events] [RSS]
Susquehanna 1 0 Talen Energy [Susquehanna events] [RSS]
Taishan 0 0 China Guangdong Nuclear Power Group [Taishan events] [RSS]
Trillo 0 0 Iberdrola [Trillo events] [RSS]
Turkey Point 1 1 NextEra Energy [Turkey Point events] [RSS]
Vandellos 0 0 Endesa [Vandellos events] [RSS]
Victoria 0 0 Exelon [Victoria events] [RSS]
Vogtle 5 0 Southern Nuclear [Vogtle events] [RSS]
Waterford 1 2 Entergy [Waterford events] [RSS]
Watts Bar 0 0 Tennessee Valley Authority [Watts Bar events] [RSS]
Wolf Creek 0 0 Wolf Creek Nuclear Operating Corporation [Wolf Creek events] [RSS]
Zaporizhzhia 0 0 Enerhodar [Zaporizhzhia events] [RSS]


by Reactor type - 10 Years

type (#)# (ratio)listfeed
Advanced Boiling Water Reactor (1) 0 (0) [Advanced Boiling Water Reactor events] [RSS]
B&W-L-LP (5) 9 (1.8) [B&W-L-LP events] [RSS]
B&W-R-LP (1) 4 (4) [B&W-R-LP events] [RSS]
CANDU (4) 0 (0) [CANDU events] [RSS]
CANDU-6 (1) 0 (0) [CANDU-6 events] [RSS]
CANDU-9 (0) 0 (0) [CANDU-9 events] [RSS]
CE (10) 36 (3.6) [CE events] [RSS]
CP0 (0) 0 (0) [CP0 events] [RSS]
CP1 (2) 0 (0) [CP1 events] [RSS]
CP2 (0) 0 (0) [CP2 events] [RSS]
Economic and Simplified Boiling Water Reactor (0) 0 (0) [Economic and Simplified Boiling Water Reactor events] [RSS]
Evolutionary Power Reactor (4) 0 (0) [Evolutionary Power Reactor events] [RSS]
GE Pool (2) 0 (0) [GE Pool events] [RSS]
GE-1 (1) 0 (0) [GE-1 events] [RSS]
GE-2 (2) 9 (4.5) [GE-2 events] [RSS]
GE-3 (7) 14 (2) [GE-3 events] [RSS]
GE-4 (13) 38 (2.9) [GE-4 events] [RSS]
GE-5 (5) 13 (2.6) [GE-5 events] [RSS]
GE-6 (5) 32 (6.4) [GE-6 events] [RSS]
P4 REP 1300 (2) 0 (0) [P4 REP 1300 events] [RSS]
Pool (5) 0 (0) [Pool events] [RSS]
TRIGA (1) 0 (0) [TRIGA events] [RSS]
TRIGA Mark I (10) 0 (0) [TRIGA Mark I events] [RSS]
TRIGA Mark II (4) 0 (0) [TRIGA Mark II events] [RSS]
TRIGA Mark III (3) 0 (0) [TRIGA Mark III events] [RSS]
VVER-1000 (4) 0 (0) [VVER-1000 events] [RSS]
W-AP1000 (1) 3 (3) [W-AP1000 events] [RSS]
Westinghouse PWR 2-Loop (4) 9 (2.3) [Westinghouse PWR 2-Loop events] [RSS]
Westinghouse PWR 3-Loop (13) 40 (3.1) [Westinghouse PWR 3-Loop events] [RSS]
Westinghouse PWR 4-Loop (20) 84 (4.2) [Westinghouse PWR 4-Loop events] [RSS]