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 tow 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. <ref>http://public-blog.nrc-gateway.gov/2011/05/17/putting-the-axe-to-the-scram-myth/</ref>

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Scram lists

[Table View]

[last 90 days]

Loading map...
  • 2022: 31
  • 2021: 30
  • 2020: 40
  • 2019: 49
  • 2018: 46
  • 2017: 39
  • 2016: 44
  • 2015: 55

Automatic Scram

 Start dateSiteRegion
ENS 5621610 November 2022 12:44:00CookNRC Region 3
ENS 5618930 October 2022 10:53:00HarrisNRC Region 2
ENS 560916 September 2022 04:45:00Comanche PeakNRC Region 4
ENS 5607628 August 2022 17:48:00CookNRC Region 3
ENS 560283 August 2022 17:58:00FarleyNRC Region 2
ENS 5600518 July 2022 23:03:00Wolf CreekNRC Region 4
ENS 5598812 July 2022 13:03:00DresdenNRC Region 3
ENS 5596425 June 2022 03:38:00FermiNRC Region 3
ENS 5596325 June 2022 01:12:00WaterfordNRC Region 4
ENS 5590923 May 2022 21:16:00SusquehannaNRC Region 1
ENS 5589916 May 2022 19:52:00Peach BottomNRC Region 1
ENS 5584314 April 2022 13:28:00North AnnaNRC Region 2
ENS 558215 April 2022 06:23:00Nine Mile PointNRC Region 1
ENS 557335 February 2022 08:57:00OconeeNRC Region 2
ENS 556843 January 2022 17:23:00Calvert CliffsNRC Region 1
ENS 5552816 October 2021 09:28:00DresdenNRC Region 3
ENS 5551411 October 2021 17:21:00SusquehannaNRC Region 1
ENS 555075 October 2021 10:32:00Beaver ValleyNRC Region 1
ENS 553469 July 2021 01:54:00Davis BesseNRC Region 3
ENS 5532021 June 2021 05:51:00BraidwoodNRC Region 3
... further results

Manual Scram

 Start dateSiteRegion
ENS 562104 November 2022 19:00:00Quad CitiesNRC Region 3
ENS 5617724 October 2022 12:57:00CatawbaNRC Region 2
ENS 5612026 September 2022 07:38:00LaSalleNRC Region 3
ENS 560873 September 2022 02:48:00Saint LucieNRC Region 2
ENS 5607528 August 2022 07:29:00HarrisNRC Region 2
ENS 559754 July 2022 06:04:00Quad CitiesNRC Region 3
ENS 5597330 June 2022 19:45:00Grand GulfNRC Region 4
ENS 5594315 June 2022 11:24:00Beaver ValleyNRC Region 1
ENS 5591024 May 2022 08:14:00CookNRC Region 3
ENS 5589411 May 2022 22:14:00FermiNRC Region 3
ENS 558753 May 2022 19:41:00VogtleNRC Region 2
ENS 5586829 April 2022 08:05:00HarrisNRC Region 2
ENS 5585623 April 2022 06:24:00CatawbaNRC Region 2
ENS 5575022 February 2022 03:07:00OconeeNRC Region 2
ENS 5574818 February 2022 09:59:00McGuireNRC Region 2
ENS 5567929 December 2021 20:52:00HatchNRC Region 2
ENS 5564110 December 2021 15:24:00Saint LucieNRC Region 2
ENS 5559721 November 2021 15:46:00Calvert CliffsNRC Region 1
ENS 5558617 November 2021 18:13:00Beaver ValleyNRC Region 1
ENS 5558015 November 2021 22:28:00SummerNRC Region 2
... 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 1 [Cleveland Electric 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 2 [DTE Energy events] [RSS]
Dairyland Power Cooperative 0 [Dairyland Power Cooperative events] [RSS]
Dominion 2 [Dominion events] [RSS]
Duke Energy 10 [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 7 [Entergy events] [RSS]
Eversource Energy 0 [Eversource Energy events] [RSS]
Exelon 0 [Exelon events] [RSS]
FirstEnergy 5 [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 2 [Luminant events] [RSS]
NextEra Energy 5 [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 1 [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 3 [Southern Nuclear events] [RSS]
Talen Energy 2 [Talen Energy events] [RSS]
Tennessee Valley Authority 1 [Tennessee Valley Authority events] [RSS]
WEC Energy Group 0 [WEC Energy Group events] [RSS]
Wolf Creek Nuclear Operating Corporation 2 [Wolf Creek Nuclear Operating Corporation events] [RSS]

by site - 24 months

Site#Man#AutoCompanyEvent lists
Almaraz 0 0 Iberdrola [Almaraz events] [RSS]
Arkansas Nuclear 1 1 Entergy [Arkansas Nuclear events] [RSS]
Asco 0 0 Endesa [Asco events] [RSS]
Beaver Valley 3 1 FirstEnergy [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 0 Tennessee Valley Authority [Browns Ferry events] [RSS]
Brunswick 0 0 Duke Energy [Brunswick events] [RSS]
Byron 0 0 Constellation [Byron events] [RSS]
Callaway 0 0 Ameren [Callaway events] [RSS]
Calvert Cliffs 2 1 Constellation [Calvert Cliffs events] [RSS]
Catawba 2 1 Duke Energy [Catawba events] [RSS]
Chernobyl 0 0 [Chernobyl events] [RSS]
Clinton 0 0 Constellation [Clinton events] [RSS]
Cofrentes 0 0 Iberdrola [Cofrentes events] [RSS]
Columbia 0 0 Energy Northwest [Columbia events] [RSS]
Comanche Peak 0 2 Luminant [Comanche Peak events] [RSS]
Cook 2 2 American Electric Power [Cook events] [RSS]
Cooper 0 0 Entergy [Cooper events] [RSS]
Dampierre 0 0 Électricité de France [Dampierre events] [RSS]
Davis Besse 0 1 Cleveland Electric [Davis Besse events] [RSS]
Diablo Canyon 1 0 Pacific Gas & Electric [Diablo Canyon events] [RSS]
Dresden 0 2 Constellation [Dresden events] [RSS]
Duane Arnold 0 0 NextEra Energy [Duane Arnold events] [RSS]
Dungeness 0 0 EDF Energy [Dungeness events] [RSS]
Farley 0 1 Southern Nuclear [Farley events] [RSS]
Fermi 1 1 DTE Energy [Fermi events] [RSS]
FitzPatrick 0 0 Constellation [FitzPatrick events] [RSS]
Flamanville 0 0 Électricité de France [Flamanville events] [RSS]
Ginna 0 0 Constellation [Ginna events] [RSS]
Grand Gulf 1 1 Entergy [Grand Gulf events] [RSS]
Harris 2 2 Duke Energy [Harris events] [RSS]
Hartlepool 0 0 EDF Energy [Hartlepool events] [RSS]
Hatch 1 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 1 0 Duke Energy [McGuire events] [RSS]
Millstone 0 0 Dominion [Millstone events] [RSS]
Monticello 0 0 Xcel Energy [Monticello events] [RSS]
Nine Mile Point 0 1 Constellation [Nine Mile Point events] [RSS]
Nogent 0 0 Électricité de France [Nogent events] [RSS]
North Anna 1 1 Dominion [North Anna events] [RSS]
Oconee 1 1 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 1 1 Constellation [Peach Bottom events] [RSS]
Perry 1 0 FirstEnergy [Perry events] [RSS]
Point Beach 1 0 NextEra Energy [Point Beach events] [RSS]
Prairie Island 0 0 Xcel Energy [Prairie Island events] [RSS]
Quad Cities 3 0 Constellation [Quad Cities events] [RSS]
River Bend 1 1 Entergy [River Bend events] [RSS]
Rivne 0 0 Energoatom [Rivne events] [RSS]
Robinson 0 0 Duke Energy [Robinson events] [RSS]
Saint Lucie 2 1 NextEra Energy [Saint Lucie events] [RSS]
Salem 0 0 PSEG [Salem events] [RSS]
Seabrook 0 0 NextEra Energy [Seabrook events] [RSS]
Sequoyah 0 1 Tennessee Valley Authority [Sequoyah events] [RSS]
Sizewell 0 0 EDF Energy [Sizewell events] [RSS]
South Texas 0 1 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 0 2 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 0 1 NextEra Energy [Turkey Point events] [RSS]
Vandellos 0 0 Endesa [Vandellos events] [RSS]
Victoria 0 0 Exelon [Victoria events] [RSS]
Vogtle 1 0 Southern Nuclear [Vogtle events] [RSS]
Waterford 0 1 Entergy [Waterford events] [RSS]
Watts Bar 0 0 Tennessee Valley Authority [Watts Bar events] [RSS]
Wolf Creek 0 2 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 (0) 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) 7 (7) [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) 37 (3.7) [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) 14 (7) [GE-2 events] [RSS]
GE-3 (7) 21 (3) [GE-3 events] [RSS]
GE-4 (13) 43 (3.3) [GE-4 events] [RSS]
GE-5 (5) 15 (3) [GE-5 events] [RSS]
GE-6 (5) 37 (7.4) [GE-6 events] [RSS]
P4 REP 1300 (2) 0 (0) [P4 REP 1300 events] [RSS]
Pool (4) 0 (0) [Pool events] [RSS]
TRIGA (0) 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 (2) 0 (0) [TRIGA Mark III events] [RSS]
VVER-1000 (4) 0 (0) [VVER-1000 events] [RSS]
W-AP1000 (1) 0 (0) [W-AP1000 events] [RSS]
Westinghouse PWR 2-Loop (4) 7 (1.8) [Westinghouse PWR 2-Loop events] [RSS]
Westinghouse PWR 3-Loop (13) 47 (3.6) [Westinghouse PWR 3-Loop events] [RSS]
Westinghouse PWR 4-Loop (20) 102 (5.1) [Westinghouse PWR 4-Loop events] [RSS]