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A report on the accident at windscale, published as a white paper last week, shows that no harm to anyone's health is to be expected, though it points to certain short comings in organization. An operation for the controlled release of wigner energy, which is a routine procedure in uranium-graphite piles, was being carried out at the time the accident occurred. No harm to any person resulted or is likely to result from the episode, and the devotion to duty and prompt and efficient actions of all those concerned in dealing with the accident deserve the highest praise. The members of the various expert committees have produced so promptly a report which makes available to the public all the relevant facts, and interprets them.
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moon, that its e one hand we have those often depict e which fit the fcrnale hand, we have the opi believes that. '* Ifhu .Haber. of the Space work i n the vacuum ust do it i n solidlong controvcrsy whcther all those in num tr able cralers werc formed by meteoric bombardment or by volcanic scopes where n o alniospheric unsteadiness will blur Tiriics of November the report. for h e bega to know what is in n s to learn that the future entry into medi hools. Will the rot student doctors int ACCIDENT AT WINDSCALE A report on Ihc accident at Windscale,' published as a Whitc Papcra lasr week, shows that no harm to anyone's health is to be cxpeclcd, though i t points to certain shorltrolled rclcasc of Wigncr energy, which i c a roulinc procedure in uranium-graphite piles. was bcing carricd
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Nov. 16, 1Y57 ACCIDENT AT WINDSCALE Burnsw 1167M CDICA LJovnuAL out at thc timc thc accidcnt occurrcd. A standard pile consists of a large block o f graphite somcwhai Iargcr than a house, with hundrcds of cylindrical holcs passing from onc side to :he other, plirallcl to the ground. Cartridgcs composed of uranium and uranium oxidc containcd in a case of aluminium o r zirconium alloy are inscncd into thc centre of thc pile through the holes at one side. and, whcn cxpendcd. a r c pushcd out from thc other by frcsh cartridges similarly inscrted. T h c surrounding graphite is known as the moderator and slows down the ncutron emission from thc uranium to a suiiablc levcl. This results in some of thc atoms of carbon bccoming displaccd from stable to unstablc positions, Wigncr' postulatcd that this would occur, and thc phcnomcnon is known a s thc Wigncr cficct. Thc Wigner eRcct is progressive and can result in a spontancous rclcasc of cncrgy. T h i s occurred in the Windscale pilc in 195: Artificial hcating of the graphite undcr controlled conditions causcs a reversal of the Wigncr cfTcct, and this opcration. which had becn succcssfully accomplishcd on eight previous occasions, was in progrcss when Controlled rclcase of stored Wigner cncrgy is accornplishcd by shutting off the air cooling systems which arc normally in opcration and allowing the tempcraturc of thc pilc I O risc. T h e progress of the opcration is asscsscd by observation of the tcmpcraturcs which arc rccordcd by rhcrmocouplcs. but on this occasion, owing partly to lack of adcquatc knowlcdgc of the Wigncr cliect at the timc thc pile was built, unduly high Iempcratures were being attained at points in the graphitc wherc thermocouples wcrc not installed. T h c physicist in charge of thc operation, handicapped by insufficient data and inadtquatc instructions for thc procedure, repeated the hcating prpccss too soon and too quickly, causing failure of thc uranium cartridgcs and oxidation of the uranium. On Octohcr 9 it was realized that thc graphite tcrnperaturc readings wcrc unusually high, and thc cooler fans ' wcrc turncd on intermittently. Early on the next day rncters in the chimncy recorded incrcascd radioactivity, but thc lcvcls wcrc considcred to he within normal limits. The fans wcre turned o n again. and again the mcasurcd radioactivity increased. As a rcsult of thcsc obscrvations tbc operators concluded that onc o r more uranium cartridgcs had failed. Special apparatus is installed to assist in the dctection of burst cartridgcs, but on this occasion the scanning gear was found to be jammed. although it had becn rcccntly rcpaircd. It was necessary ihercforc to arrangc for visual inspection through the pile face, and four channels revcalcd cartridgcs a t red was not possiblc to cjcct them i n the normal way through the opposite face of thc graphite pile, and thc firc was thercforc localized by rcmoving a number of ncighbouring cartridgcs. Carbon dioxide foam was applicd but failcd to rcducc thc tcmpcraturc, andit was dccidcd thcn to usc watcr to quench the fire. ?'his was bcgun at 6 . 5 s a.m. on October JI.adequate nicasures having been taken to ensure the safcty of the staff, a/nd continucd for 24 hours, at the end of which time the pilc was cold. Although the Committee of Inquiry was u n - able to endorse thc conclusion that the obscrvcd ternpcrature .recordings indicated the nccd for a second heating. i t agreed that both the instrumentation in the quatc. T h c Atomic Energy Authority has accepted full responsibility for the accidcnt a n d is detcrrnincd to d o all it can to avoid a similar occurrcncc elseAs to the mepsurcs takcn to deal with the conscquenccs of thc accidcnt, the commit kc appointed by the Medical Rcsearch Council agreed that thcsc wcrc cssentially right, and. once they were brought fully into vent ill clTects. The International Commission o n ' Radiological Protection' ha: recommended a maximum permissible cxposure for life for any fission producfs longed exposure this value should bc divided by 10, but f o r short periods of exposure, similar to those occurring as a rcsult of this accident, m a y be rnultiplicd by IO. I f lo-' p c per C.C. is considered to be one unit, then thc air contamination ovcr the factory site from thc afternoon of October 10 to midday October 1 1 varied bctween 2 and IO units. All mcasures neccssary to safeguard the members of the emergency squad working on t h e damaged pile were taken, and n o cases of scvcrc cxccssive exposure occurred. T h e acccptcd permissible dose of radiation in a n y 13-week period Is 3 r. For the relevant J3-wcek pcriod including the accidcnt thc 3 r maximum was cxcccdcd by only 14 workcrs, and the highcst rccordcd lcvel was 4.66 r. Thesc findings were checked and found to be accurate by personal cmcrgency recording cquipmcnt used ticc these workmcn have bccn removed from furthcr radiation risk and will not rcsumc until i t is safe to d o so. N o worker was detained for spccial trcatmcnt, and i n only one case was there a n y dificulty in decontaminating hands a n d hcads of exposed pcrsons. Suitablc protection was providcd f o r this .workman whcn he returned to his home. and t h e dccontamination was complcted ncxt day. Thc procedure is strict and thc monitoring scnsitive, so that no risk remains for this man or for thc persons with whom he comes thought that thc risk f r o m inhalation of radioactivc maierjals outside the works might b c significant. hlcasurcmcnts rnadc o n the hair and clothing of pcrsons who cyclcd in the vicinity s h o w that, evcn if thcy ncithcr washcd nor changcd thcir clorhcs in ten days. the exposure would still havc been negligible. As prcviously stated in thcsc columns.' the main potential hazard was from absorption of radioiodinc. Thc report con-
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firms this view and states that. except for the need to milk o f catilc grazed o n certain specilicd arcas. n o risk exists from cither radiostrontium o r radiocaesium a \ a result o f the accident. Having agrecd that absorption rnittcc has prescnted data which indicate that no harm - f u l cliccts arc likcly to result either to plant pcrsonncl or to mcmbcrs of the public. A thyroid iodine survey h a s been made among workers and among local inhabitants round Ihc works. T h e lntcrnational Commission on Radiological Protcction recommended a lcvcl of 0.1 pc for safe con!inuous and constant activity in thc adult thyroid. T h c highest thyroid activity recorded among thc staff is 0.5 pcand among thc local population 0.28 p c in a child. These lcvcls are well within the permissiblc lcvcl for short exposure, which is acccptcd a s tcn timcs the recommcndcd lcvcl of 0.1 /IC Thc dccision IO suspcnd di.;tribution of milk from c\~:~hlislicdto1cr;incc for r;tdioiodinc in milk cxists, but a limit of 0.3Y p c per litrc for nd k given to infants had bccn suggcsted. T h e first milk analyses revealed levels up to 0.S p c per litre. a n d milk distribution was stopped. Aftcr consultations hctween thc medical and physics experts it was agreed that niilk from the area should not be consumcd until thc levels had decrcascd to not more than 0.1 pc per litre. Examination o f water, meat. eggs, a n d vegctables in the area revealed that n o haz:ird cxistcd in relation to ingestion of thesc itcnis. T h e committec of the Medical Rescarch Council cxpresscd the opinion that the delay bctween recognition of thc accidcnt and the instiiution of an cxtensivc and rapid milk-sampling programme throughout the arca of possiblc risk was a weakness in the organization apparcnt only ' aftcr thc cvcnl, and that the investigations had rcvcalcd certain gaps in scientific knowledge which rcquirc early attcntion. enccs bctwecn the Windscalc plant and t h e more modern installations already working at Caldcr Hall and under construc:ion for thc electricity authorities in other parts of the country. T h c new pilcs not only have bcttcr controlling equipment hut opcrate at a higher Icmpcraturc. The laticr modification will allo ~ rcleasc of much of the Wigner cncrgy a s i t is formed. So that opcrations to rcleasc stored cncrgy will bc requircd lcss frcquently. Morcovcr, i n the ncwcr piles failure of a fuel cartridge would be dctcctcd immediately and thc amount of radioactive m;ttcritll which l o constitulc ;I. hawrd. In thc words of Sir Edwln Plowdcn, chairman of Ihc United Kingdom Atomic Energy Authority, this accident causcd disturbancc and anxicty to many pcople. No harm to any person has rcsultcd or is likely to result from the episode, a n d thc devotion to duty a n d prompt and cfficient actions of all thosc conccrned in dcaling with the accident deservc Lhc highest praise. Wc should be grateful, too. to t h e mcmbcrs of thc various expert commitices who have produced so promptly a rcport which makes available I O Ihc public all thc rclcvant facts, a n d intcrprets thcni hit by a lightning flash or a highlvol organs afeu ccnti of this accident often svcrsc myelitis or currents can make t r fibrillatc. A condition of profound ' pparenl suppression of all nervous activi o r two hours after ing disabilitics. Minor scquclac arc frcqucnt, and headaches and paracsthcsiacsccm to bc the commonest effects