NUREG-1250, "Report on the Accident at the Chernobyl Nuclear

215 Pages·2007·28.98 MB·English

0UE-1250
Report on the AMcclint' at the'
Chernobyl Nuclear PoWer. Station
(TU.S.) Nuclear Regulatory .Comission
Washington, DC
Jan 87
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BIBL00RPHI DAASHEE
NIJREG- 125-0
1. TITL. ANO S"TITLE I I i3
LIAVI OL8%k
Report on' th~e Acc'ident at the
Chernobyl Nuclear Power Statior I
.............~.................._.._.._.._..._.._4 -.i
I AUT"0(cid:127) IS January 198
Multiple Authors
a Dore ",P1UImO I
MONT" 1.ya"
9 1987
Januar
EDEnelvepicarrtotrnmicme nePtn otawolf e r PERrnoeetrsegeyca tricohn IAnosetnitcuy-tIen st., of Nuclea V wr--,------.. --M %O ft ....-W--P-as-i .------ .ow k
Federal Emergency Managemet, Agency. . - i---
Nuclear Regulatory Commission ._"_._
_ __•
U. S. Nuclear,, RegulatoryE c ot ssnion d.ed r i ilty A cy
WashingtonD. C.ý "20555- ~ ~
'i'.
oSWO"P"A"N~T&ARN OTES
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A5YRAC-I .,.ae
This report presebts the CoiAM~e .,finfogatias obtained by various organ-
iozcactuiorrneds rý.et guairkdtin g4 othfe thaecc-niduecolet ar(M Wpdo w-ethr es ctaotmiosnq8 *aetc eCsb e0r4a:s bthyel ainc ctihdee nUt)S SRth aotn
April 26. 1986. Each organistation baa indepeodently accepted responsibility
for one or more chapters. thre various authors are identified in a footnote to
each chapter. Chapter provides a8 overvieW of the rteprt. Very briefly the
other chapters cover: desi f. teei l nuCclpetracr2 ,tse tation
Uiit 4; Chapter 3, safety analyses for E3t.1 ; .Chaappttse r the accident scenario;
Chapter 5, the role of tbhe operator; Chapter 6, a-a ssesneat of the rad.oactive K
release, dispersion, an tsanport;-Chaterd 7L,2 e a tiLes. associated with
muergency actions; emid-Chte6-ifatiem t-e health and environmental
consequences from the accident. ltes8e subject cover the major aspects of the
a.ccident that have the pote(cid:127) (cid:127)il to'pcOet n;w sjnfe*Mation and less(cid:127)os for the
nuclearlindustry in seomral.et;Z
The task Of evaluatingft''_M '4igo~~u ta6 kaaiiw tedte
-'s
pursue according to the relevace ofmthe suJect to thei o ,. To..s
findings will be Loased" qrtlb h emiatog~''~ The basic
purpose of this report s -to pr(cid:127)vide -the; afomettif ýo wb.kcn such 1ssfsnments
can be
,.ade.
Chernobyl Accident, Russian Reactor, Severe Accident, Core Melt.,
Radioactive Release, Reactivity Accident, Graphite Fire, Unlimited
& Pressure Tube Reactor
OW044sw e"Aft"D, te(cid:127)a~mi $t*l 1.
UnZcl assi fled
Unclassified
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uclar
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a9

Report on,&t Accid-ent
_-th
Chev~iNucdear~
PowerSS tation
SS
U.S. NUCLEAR
..REGULATORY
,COMMLSION
-',Prepared by:
ent ofý Energy
I'.. -Electric Power Research Institute
' :Environmental Protection Agency
Federol Emergency Management Agency
Institute of Nuclear Power Operations
Nuclear Regulatory Commission
-ABSTRACT
_This report presents the compilation of informatix-,*o btained by' various organ-
izations regarding the accident (and the consequences of the accident) that
occurred at Unit 4 of the nuclear power station at CbernobyiL in the USSR on
April 26, 1986. Each organization Ls independentl7 accepted responsibility
for one or more chapters. -The various authors are identified in a footnote to
each chapter. Chapter 1 provides an overview of the report. Very briefly the
other chapters cover: Chapter 2, the design of the Chernobyl nuclear station
Unit,4; Chapter 3, safety analyses for Unit 4; Chapter 4, the accident scenario;
Chapter 5, the role of the operator;Chap-ter6,.an assessment of the radioactive
release, dispersion, sandtruasport;-.Chapter 7, the activities associated with
.emergency actions; and Chapter, infoat:ionm on the health and environmental
consequences from the accident ,(cid:127),(cid:127)(cid:127)These subjects cover the major aspects of the
accident that have pthepont, -pew. information and lessons for the
nuclear industry ,in-.general'.
The task of evaluating .the iufomtioni -obtained in these various areas and the
assessment of the potential Aiplications bas been left to each organization to
pursue according to the relevance.of the subject to their organization. Those
findings will be issued separaLely by the cognizant organizations. The basic
purpose of this report is to provide the information upon which such assessments
can be made.
ttI
Pagte
Abstfract ............................................................ .... iii
Acknowledgments ........................................................ ix
ýýater T:-;
IO verview .......................................................... 1-1
2 Plant Design ......................... 2-
. . . . .
2.1 Reactor, -Fuel,-a nd Fueling z.-achinei i'.... ...4. ............... --
2.2 Fluid and Heat Transport ,Systems............................. 2-18
2.3 Reactor Physics ................................................. 2.24
2.4 Instrumentation ands.Control. ........................... 2-27
2.5 ElectricalPower System................................... .2-36
2.6 Safety Systems .................... ........................... 2-37
2.7 Reactor Operations..................................*.. ..... :2-49
2.8 References ......... .................................. 2-51
3 Safety Analysis .......................... .......................... 3-1
3.1 Introduction.............................. *.. ................ 3-1
3.2 Soviet Safety Analysis of the Chernobyl Unit 4 F.,.;actor ....... 3-3
3.3 Independent Safety. Review .. . 3-27
.3.4 References..................................................... 3-53
4 Accident Scenario... ....... ................ ........................ 4-1
4.1 0,verview... ; --. ;; .... .... . ... -,.. . .. . . . . . . . . .
4.2 -Event.x1ed tbi h4eiAc(cid:127)cdent.. . I ........ 4-2
4.3 EZvents:Vurift.-sa*d Atr(t hel-c~dde. .................. ........ 49;
4.4 References .......... ... . . ........................ 4-12
5 Role of Operating Personnel ........ .................... 5-1
5.1 Operator Actions and Plant Activities Before the Accident... 5-2
5.2 Immediate and Short-Tern Operator Actions ................... 5-3
5.3 Sumary of Key Operational Events and Errors ................ 5-6
5.4 Operator Actioms Following tha Accident ..................... 5-9
5.5 References ................................. 5-10
6 Radionuclide Release and Ataospheric Dispersion arid Transport 6-1
6.1 Radionuclide Release ........................................ 6-1
6.2 Atmospheric Dispersion and Transport ............ ............. 6-8
CO:TENTS (Continued)
Chapter Page
f
6.3 Consistency of Soviet Estimates of Rad'.onuclide, Release
With Observed Data From Other Countries ............... ...... . ,10
References............6-12
7 Emergency Preparedness and Response...... ........................ 7-1
7.1 Emergency Plans. .................................... :7-1
7.2 Emergency Organization and Facilities ....................... 7-6
7.3 Alert and Notification System .............................. .7-7
7.4 Protective Actions Taken........ ............................ 7-8
7.5. Radiological Monitoringand Exposure Control,......... ....... 7-10
-76.- '.ed ical Treatment. ................. 7-14
7.7. Soviet .,Guidance _,on.'Acep ble(cid:127)-i vels. of Public
Eposure..
Radiation 4 .. v :. ............................... 7-16
7.8 Decontandtio.............................7-18
7.9 Site :Recovery. ..... . ............................
7.10 Relocation-and Xeienr (Off Site) .......................... '7-21
7.11 Public.-EducAtionaadImoxmtion Prog(cid:127)rams.....:. ". .....- §7-21
7.12 Training. rram......................................................... 7-22
7.13 Summary. . .. -. .................................. 724
7.14 R7.elf4eRreefrnecnceess .. ...... ............................................ 772-27
8 Health and Environmental Consequences ...................... ....... 81
8.1 Pathways of hNmaaExposure .................................. 8-1
8.2 Health Effects ........................................ 84
8.3 Radiological Effectsa on the Soviet Union .................... 8-6
8. 4 Radiological.Effects on turoFe Outside the Soviet Union ..... 8-11
8.5 Radiological Effects on the Umited Etates ................... 8-14
8.6 Global Effects on Agricultwre and Food ...................... 8-24.
8.7 .-.kological(cid:127)Iffects,(cid:127), ,:........... ......... ....................... 816
8.8 References. ..... .. -.... *...* 8416
Figure Pg
2.1 Cross-sectional vievofR -000 ................................ 2-9
2.2 Fuel channel 2......................................................2-1
2.3 Zirconiui-to-stainless 'steel transition Joint. ................... 210
2.4 Assembly of graphite riags on pressure °ube and graphite block
cooling ......................................... ..............-....... 211
2.5 Cross-sectional view of reactor cavity........................... 2-12
2.6 Cross-sectional view of reactor building elevation, Chernobyl
Units 3 and 4 ................................ 2-14
2.7 Layout of main building of Chernobyl Units 3 and 4 ..................... 2-15
2.8 Scbematic drawing of the 36-rod fuel element ..................... 2-17
2.9 Cross-sectional view of the fueling machine ...................... 2-19
2.10 Grab book of refueling machine ................................... 2-20
vi
'A_,iý,COrflNTS. (Continued)
Figure Page
2.11 Normal and .emergency cooling system of the Chernobyl Unit 4
Leactor. .... .........I ............................. ... .......... ... 2-21
2.12 Schematic drawing of control rod cooling system ................. 2-232
2.13 Gas circuit system .............................................. 2-24
2.14 Effect of reactor Operation on the coolant void, fuel
temperature, and moderator temperature reactivity coefficients... 2-27
2.15 Control rod design ............... ........... i ............... 2-31
-2.16 Schematic drawing of fully withdrawn and fully inserted
control rods......... ................................ 2-32
12.17 Functional diagram of a*.control rod irlyc.. 2-35
of-the reactor:_.ergency. +cooling system...... .... 2-38
2.19 Schematic drawing of themsystem for discharging steam from
the main safety -valves inteo'tepreslure suppression pool of
the accident locAllitlastis .,ta , ...................... 2-41
2.20 Systep .o protect the eactor vault from excess pressure ......... 2-43
I
2.21 Schematic diagram of the accident localization system ........... 2-45
2.22 Evolution of reactorparsmeters during startup ................... 2-50
3.1 Nuclear safety regulatory bodies and docume-ts in the-USSR ........ 3-6
4.1 Chronology of the accident at the Chernobyl Nuclear Power
Station .......................................................... 4-3
4.2 Key reactor parameters for the last five.minutes before the
accident ...................................................... 4-6
4.3 Chernobyl data evaluation of power vs. time during core
destruction phase ............................................. . 4-. 10
4.4 Photographs of the residues from model fuel pins (SPXN rods)
nfter tests in the +CDC.,(capsule driver core) siz/.Iting power
.excursions fnr mre acuivity laseitio c.id......... .... 4-1
5.1 Schema tic diar O0.................... 5-2
6.1 Daily radionuclide release In the ataoephfte from the
- -
damaged unit ....... 6-3......................
Table Z +e
2.1 Development of Soviet-graphbltmodarated, -water-cooled
reactors ............ ............................. ..... 2-2
2.2 Chernobyl Unit 4 design parameters ......... ...................... 2
I
2,3 Fuel assembly desigp parsmeters forCharnobyl Unit 4 ............. 2-18
2.4 Calculated reactivity coefficieuts for R ...................... 2-26
2.5 Types of :ontrol rods ..... ... * .......... . .......................... 2-29
2.6 Control rod specifications ....................................... 2-32
4.1 Chronology of tbh accident at the Chernobyl Nuclear Power
Sta o ........ ................................................. 4-13
~ ~ ~ ~
, •. .. •• ll l eo le l le ll ll 1. ,. l l lll.l4
CONTENTS (Co tined)
:11 .....
Table mage
5.1 Operator violations of ýprocedures .............................. 5-8
6.1 Core inventories and total releases, at he time of the
Chernobyl accident ................................................ .6-2
6.2 Daily release of radioactive substances into the atmosphere
from the damaged unit........... ,;(cid:127)...................................6.
6.3 Radionuclide composition of release from the damaged unit of
Chernobyl Nuclear Power Station .................................. 6-6
6.4 Estimates of percent of core inventory released based on f.
measurements outside the Scviet Union... 6_12
7.1 griultralprouct in-_c'tepermitted: radioactive_
Contamination was-found-to beexceeded.............................. 7-13
•7.2 Levels of 1-131 in milk, Ny 196. .............................. 7-13
7.3 Criteria for makig erProttaibn of thepopulation.. 7-17
8.1 Radionuclide contributions- .to external dose based on
spectrometric measuraemntse lin southern-Finland on
May 6 and 7, 1986. ...... ........................................ 8-2
8.2 Radionuclide deposition in two U.S. areas ........................ 8-3
8.3 Maximum radiation levels found in Europe following the
accident, by country ........................................... 8-12
8.4 Haximum individual doses tosgroups in the United States
due to exposures or-,intakes.,(cid:127)n the first.year after the
accident ...................................................... 8-15
- 1