a sequence of physical events - Three Mile Island

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TABLE 11-25. Occupational dose March 1 to September 30, 1979 1 75MonthNumber of Dosimeters DistributedCollective Dose(person-rem)March 1131 334April 4504 1 40May 5282 350June 2973 1 59July 2500 (approx.) 63August 2500 (approx.) 63September 2472 36TABLE 11-26. Occupational doses in excess of 100 mrem March 1, 1979 to September 30, 1979Dose Range 1 00- 251- 501- 751- 1 001- 2001- 3001- 4001- More than(mrem) 250 500 750 1 000 2000 3000 4000 5000 5000Numberof 648 465 213 118 1 29 16 4Individuals3 0TABLE 11-27. Dose accumulation rate for individuals receiving more than 3000 mrem from March 1,1979 to September 30, 1979 175Dose (mrem)PeriodIndiv.AIndiv.BI ndiv.CI ndiv.DI ndiv.EI ndiv.FIndiv.G03/01-03/31 4100 4120 1785 3575 2230 1785 236004/01-04/30 1 60 10 915 40 990 915 133505/01-06/30 1 5 30 45 220 1 00 45 1 8007/01-09/30 30 15 395 70 345 395 210shortening is largely due to increased cancer mortality.180,181Radiation-induced cancer is detectable only in astatistical sense. A particular case cannot be attributedto radiation 182 .Human evidence for radiogeniccancer comes from epidemiological studiesconducted on relatively large population groups exposedto doses much larger than those experiencedby the population in the vicinity of the Three Mile IslandStation. Numerous animal studies confirm thecarcinogenic properties of radiation, but those studiesalso necessarily involved exposure to relativelylarge doses. Cancers induced by radiation are indistinguishablefrom those occurring from othercauses. Radiogenic cancer thus can only be inferredon the basis of an excess above the expectednatural incidence.Theoretical considerations suggest that at anylevel of radiation, no matter how small, some carcinogenicpotential exists. Thus far, nearly all humandata rely on observations at high dose levels andhigh dose rates (doses generally greater than 50402
em and dose rates on the order of rads per minute)and the risk factors given in most scientific publications183,18a,185are derived from these data. Toquantitatively assess the health consequences ofthe incremental radiation exposure received by thepopulation as a result of the TMI-2 accident, it isnecessary to determine how the risk factors derivedfrom relatively high doses and dose rates can beused in estimations of health effects resulting fromdoses of a few millirads to tens of millirads of lowLET radiation. (LET, linear energy transfer, is theaverage amount of energy lost by particle per unit oftrack length; low LET radiation characteristics ofbeta rays (electrons), X-rays and gamma rays, areradiations to which the population in the vicinity ofTMI was exposed.)One way of determining radiation risk factors,which serves as the basis of current radiation exposurestandards, is to assume that the effects observedat high doses from high dose rates can bedirectly and linearly extrapolated to low dosesdelivered at very much lower dose rates, and thatthere is no dose (or threshold) below which there isno health risk. Applying these assumptions resultsin a linear, nonthreshold, dose-rate independent,dose-effect relationship.The majority of the scientific community considersthat the linear, nonthreshold extrapolationrepresents the upper limit of effects at very lowdoses, and that the risk factors derived using suchan extrapolation probably overestimate the actualrisk 1 86 This view is stated in relevant publicationsof the National Academy of Sciences (BEIR I andBEIR III) 185,187and the United Nations (UNSCEAR77). 188 Both BEIR I and BEIR III indicate that the actualrisk could be appreciably smaller for low levelirradiation, and even zero. However, they also indicatethat, because of the greater killing of cells athigh doses and high dose rates, extrapolationsbased on effects observed under such conditionsmay be postulated to underestimate the risks. Inmost cases, however, the linear hypothesis probablyoverestimates rather than underestimates therisk from low level, low LET radiation.BEIR III further states that it is not known whetherdose rates of gamma or X-radiation of around 100mrad/year are detrimental to exposed people; anysomatic effects would be indistinguishable fromthose occurring naturally or caused by other factors.The observed variations in incidence (fromplace to place and from year to year) are far greaterthan any likely effect of radiation delivered at suchdose rates.The 1977 UNSCEAR report is consistent with theview of BEIR I and BEIR III that the linear nonthresholdextrapolation describes the upper limit of risk.UNSCEAR concluded that at doses of a few rad, theestimates are likely to be too high and the actualrate might be substantially lower. UNSCEAR alsostates that the risk from irradiation due to radionuclidesdeposited within the body is not different fromthat from external radiation, provided that the absorbeddose to a given tissue is the same from bothmodes of irradiation. Thus, the risk from the totalradiation dose received by the population is thesame whether the dose is received from externalexposure or from radioactive materials that mighthave been ingested or inhaled.Upper limits of possible premature cancer deathsresulting from this accident can be estimated usingthe linear, nonthreshold dose-response relationship.However, in addition to dose response relationships,several other assumptions must be made in derivationof risk estimates. The ongoing human studiessuffer from many imperfections: imprecise dosedetermination, limited number of subjects, and inabilityto control variables. Because these studiesare not completed, many assumptions have to bemade, including: (1) the duration of increased riskfollowing irradiation, (2) latent period (time intervalbetween irradiation and detection of effect), and (3)whether the risk following a given population doseshould be expressed by some number of excesscancers, regardless of natural incidence (absoluterisk), or as a fractional increase of the natural risk ina given population (relative risk). Because of thenumerous assumptions that have to be made, therisk coefficients and risk estimation models publishedby various scientific organizations differ. 189The Radiation Health Effects Task Group of thePresident's Commission on the Accident at ThreeMile Island applied risk factors and models publishedby various national and international risk assessmentbodies, as discussed above, to estimatesof doses received by the population as a result ofthe TMI-2 accident. Table 11-28, taken from thisTask Group's report, contains the ranges of projectednumbers of lifetime excess cancer among theoffsite population. 190 This table also shows theranges of the estimated additional risk of developingcancer by the maximally exposed individuals in thevicinity of Three Mile Island Station. Our analysisyields the same values.We find, therefore, that it is extremely unlikelythat any individual will suffer discernible ill effects,during his or her lifetime, from radiation exposureassociated with the TMI accident. The effects onthe population as a whole, if any, will certainly benonmeasurable and nondetectable.403
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COVER:A heat-sensitive DOE photogra
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15. Public Announcements16. Board N
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4. Estimates of Doses and Potential
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7. Effects on Aquatic Biota and Fis
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IV.Safety Management Factors German
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A SEQUENCE OFPHYSICAL EVENTSThe fol
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polisher system are discussed in Se
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FIGURE 11-3. The Makeup and Letdown
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pumps 6 into the RCS. At TMI-2, the
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FIGURE II-5. The Once-Through Steam
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March 28,1979-4:30 a.m.At approxima
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still having trouble stabilizing th
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[The low steam pressure in steam ge
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[Leakage through the PORV had now b
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shut. Closing this valve, with pump
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Each of the two core flood tanks ho
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March 28,1979-3:10 p.m.At 11 hours
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FIGURE 11-8. Gas Venting SystemGase
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perature in the loop A cold leg was
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Up to this time, degassing of the R
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oxygen in the presence of radiation
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B RADIOLOGICALRELEASES AND THEIREFF
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either trapped or chemically bound.
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FIGURE 11-9. Ventilation and Waste
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a representative sample of carbon r
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FIGURE II-10. Liquid Radioactive Wa
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cess radioactive material. The IWTS
Page 57 and 58: FIGURE 11-12. Release PathwaysConti
Page 59 and 60: tective efforts did not provide any
Page 61 and 62: TABLE 11-3. 1-131 releases-Continue
Page 63 and 64: TABLE 11-4. Calculated 1311 release
Page 65 and 66: The cleanup components installed in
Page 67 and 68: was made prior to the large influx
Page 69 and 70: TABLE 11-7. Analysis of TMI-2 conta
Page 71 and 72: TABLE 11-9. Inventories of radioact
Page 73 and 74: a. Offsite Radiological Environment
Page 75 and 76: COLOR PLATE I. LOCATION OF OOSIMETR
Page 77 and 78: These samples were later counted wi
Page 79 and 80: TABLE 11-12. NRC TLD locations-Cont
Page 81 and 82: TABLE II-13. Raw milk sample progra
Page 83 and 84: TABLE 11-14. Source locations for H
Page 89 and 90: TABLE 11-16. EPA milk sampling loca
Page 91 and 92: 0331 3:28 a.m. GE-4; Fence, east Gr
Page 93 and 94: 0331 9:03 p.m. '/4 east ofObservati
Page 95 and 96: April 6, 1979-By April 6, offsite e
Page 97 and 98: TABLE 11-20. Met Ed Teledyne and RM
Page 99 and 100: TABLE 11-21. Net exposures, attribu
Page 101 and 102: Table 11-22 contains daily data fro
Page 103 and 104: SW-1 0.9±0.1 0.8 1.2 ±0.3 1.1 ±0
Page 105 and 106: Other Collective Dose Estimate-Usin
Page 107: not have any discernible effect. Th
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Page 115 and 116: The technical specifications for TM
Page 117 and 118: that facility did not provide suffi
Page 119 and 120: FIGURE 11-17. Actual Organization o
Page 121 and 122: FIGURE II-18. "Normal" Emergency Or
Page 123 and 124: monitoring activities and Dubiel wo
Page 125 and 126: FIGURE 11-21. Emergency Radiation P
Page 127 and 128: clothing was exchanged for paper co
Page 129 and 130: As part of the training conducted b
Page 131 and 132: equipped with Geiger-Muller (G-M) t
Page 133 and 134: TABLE 11-37. Atmospheric monitoring
Page 135 and 136: SAM-2 in another kit was issued eve
Page 137 and 138: Preaccident Personnel Dosimetry-The
Page 139 and 140: ecommendations for correcting them.
Page 141 and 142: nel, reflect the continued inadequa
Page 143 and 144: that have evolved comprehensively a
Page 145 and 146: REFERENCES AND NOTES1 Met Ed, "Fina
Page 147 and 148: term Environmental Radiation Monito
Page 149 and 150: United Nations Scientific Committee
Page 151 and 152: 302NRC, "Investigation into the Mar
Page 153 and 154: the emergency feedwater system, amo
Page 155 and 156: FIGURE 11-22. Pressurizer Surge Lin
Page 157 and 158: k)ss of heat removal from the prima
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main feedwater pumps and turbine ar
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Recommendations-The categorization
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through the break will not result i
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Findings-Under normal circumstances
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psig, 66although some reactor build
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A thorough evaluation should be per
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Shortly after their start the diese
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thereby providing high level coolin
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the service-instrument air cross-se
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Following recovery of hotwell level
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TABLE 11-44. Accident monitoring in
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TABLE 11-47. Information readouts a
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TABLE 11-47. Information readouts a
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2TABLE 11-47. Information readouts
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TABLE 11-49. Errors at most recent
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TABLE 11-51. Estimated data reliabi
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expected to survive environments mo
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TABLE 11-52. Sources of data about
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FIGURE 11-23. TMI-2 Isometric Schem
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FIGURE 11-25. The Pressurizer492
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COLOR PLATE IV. HOT AND COLD LEG TE
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egan to heat up. When the hottest p
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FIGURE 11-26. System Parameters for
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Steaming to Condenser.SRM-count rat
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emained open for more than 1 1 /2 h
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FIGURE II 2'1. Hydrogen Burn at 9.9
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PZR Vent and Spray Valves-closed.De
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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of time, to determine a heat balanc
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locked to steam flow by hydrogen th
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two-phase mixture of water and stea
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e made for two reasons: (1) the act
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FIGURE 11-31. Fuel Temperature Hist
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Additionally, it is estimated that
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15 minutes (3 hours 21 minutes to 3
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system if all of the water removed
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FIGURE 11-32. Reactor Primary Syste
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eleased before melting. In general,
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the decay calculation. Table 11-57
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RadiolysisRadiation absorbed in wat
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principle-the compliance of a liqui
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Error AnalysisAn error analysis of
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Explosive Hazard in Reactor VesselA
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gression was such that a substantia
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TABLE 11-58. Timing of a meltdown a
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vessel steel are matters of conside
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Reactor Building Base Mat Penetrati
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1 Met Ed, "Final Safety Analysis Re
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Injection Signal Reset Following a
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175Id. at 18-21.176Electrical Power
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D ALTERNATIVEACCIDENT SEQUENCESIn t
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• failure of operators to recogni
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Two variations in the flow rates fr
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gression than alternative sequences
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TABLE 11-59. Description of alterna
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FIGURE II-39. Comparison of Base Ca
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lack of emergency feedwater after a
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FIGURE 11-42. Effect of Pump Trips
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egions occurring as the reactor coo
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TABLE 11-61. Typical containment de
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E HUMAN FACTORS1. INTRODUCTIONFrom
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FIGURE 11-44. PORV Indicator Light
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cable to this written procedure and
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FIGURE 11-46. EFW Control Station S
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accident; and (2) these errors resu
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guidance on the use of some very im
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TABLE 11-62. TMI-2 control room key
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FIGURE 11-49. Visual Scan Necessary
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FIGURE 11-51. Relationship of Makeu
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FIGURE 11-53. Typical TMI-2 Alarm P
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than the other two, having only one
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• too many exceptions to the go-n
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tion or production facility," which
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5. classroom training course on TMI
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applicants for CRO licenses for nuc
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6. It took an archaic approach to l
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may be compared to nuclear powerpla
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evaluating the need for operator tr
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• misleading labeling due to viol
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encourage an increased rate of inco
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REFERENCES AND NOTES1 NRC, Investig
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' * Letter from Miller, Met Ed, to
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F ENVIRONMENTAL ANDSOCIOECONOMICIMP
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FIGURE 11-55. Map of Area621
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FIGURE 11-58. Initial Sources of In
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FIGURE 11-59. Percent of Persons Sa
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FIGURE 11-62. Percent of Individual
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FIGURE 11-64. Respondents' Reasons
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FIGURE 11-66. Respondents' Evaluati
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considered changing jobs more frequ
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FIGURE 11-70. Respondent's Concern
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FIGURE II-71. Costs Per Evacuating
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three-tenths of 1% of annual person
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posed by the municipality and appro
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achieved with volunteer labor, addi
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eady done so. Within 15 miles, an e
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APPENDIX 11.1I NTRODUCTION TOSEQUEN
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EventNumberDateTimeafterinitiationE
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EventNumberDateTimeafterinitiationI
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APPENDIX 11.2CARBON PERFORMANCEWITH
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presented in App. Table 11-2. The g
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APP. TABLE 11-4. Physical propertie
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APPENDIX 11.3RADIOLOGICAL ENVIRONME
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Sampling locations are shown in Fig
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APPENDIX 11.4OFFSITE RADIOLOGICALMO
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APP. TABLE 11-7. Field Ge(Li) and H
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APP. FIGURE 11-2. EML Measurement S
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APPENDIX 11.5ATMOSPHERIC RELEASE AD
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they did not have enough familiarit
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APPENDIX 11.6RADIOLOGICAL CHRONOLOG
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ITEM DATE AND TIME EVENT DESCRIPTIO
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REFERENCES AND NOTES1 NRC, "Investi
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The apparent surface area isFor Apr
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APPENDIX 11.8TMIBOIL CODE CALCULATI
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APP. TABLE 11-8.TMIBOIL calculation
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APP. FIGURE II-3. Fuel Temperature
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APP. FIGURE 11-7. Fuel Temperature
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APP. FIGURE II-11. Fuel Temperature
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Memorandum from G. P. Marino and J.
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This equation (which contains no ap
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We have not included the effects of
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APP. FIGURE 11-22. Bubble Volume at
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a) The fugacity coefficient of hydr
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TABLE 1. Hydrogen solubility dataTe
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APP. FIGURE 11-24. Hydrogen Solubil
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APP. FIGURE 11-26. B&W Test #5-Prop
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APP. FIGURE 11-28. B&W Test #7-Prop
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APP. FIGURE 11-30. Reactor Coolant
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2. EXCERPTS FROM TMI-2 SENSITIVITYS
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APP. FIGURE 11-32. Relative SRM Res
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tegration over time dependent varia
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A99 FIGURE D-33 Plots of Input Data
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APP. FIGURE 11-35. Postulated Core
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APP. FIGURE 11-37. Postulated Core
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APP. FIGURE 11-39.SRM Reading Versu
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4. ALTERNATE INTERPRETATION OFTHE A
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etween about 740 and 775 minutes (1
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APP. FIGURE II-43. Hydrogen Pressur
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APP. FIGURE 11-45. Hydrogen Pressur
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APP. FIGURE II-47. Water Flow Rates
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APP. FIGURE 11-49. Water Height in
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APP. FIGURE 11-51. Temperature Leve
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ing fuel (G. W. Parker et al. ORNL-
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a sequence of physical events - Three Mile Island

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