1、1Lost Source Accident in NanJing,ChinaBaowei CHEN1)，Qipu ZHOU2)1)China Institute for Radiation Protection2)Nuclear and Radiation Safety Center(Affiliated to Chinese Department of the Environment)2Contentsv Sourcev Accident Processv Dose Calculationv Clinical Manifestation SourcevSource:Ir-192vUsage:
2、industrical defect detectionvActivety:about 0.94TBq(25.5Ci)3Process4v On 7th,May Four workers had done industrial defect detection work in a workshop of a factory which locates in NanJing,a big city in the southeast of the China.The work had been finished,the detection instruments needed to be colle
3、cted and taken away from the workshop.5Processv 7th May,about 3:00 a.m.When the workers collected the instruments,they found that the remote control cable cant be unloaded.According to the machines design,only when the radiation source locates in the machine,t h e r e m o t e c a b l e c a n b e unl
4、oaded.Otherwise,the cables unloading is impossible.6 So,the radiation source was suspected still had located in the source guide tube,yet.The workers shook the guide tube wanted to find the source,but there wasnt source in the tube.(Indeed,the source had slid off tube when they had picked the tube u
5、p,before they shook it.)ProcessGuide Tube7Process One worker took a dosimeter to detect the dose near the surface of the machine.The dose rate indication was high,so he thought the source must be located in the machine.(indeed,if there had been a source in the machine,the dose rate near the machine
6、cant be so high.The machines radiation shield is thick enough.The exposure actually came from the radiation source near the machine.)8Process Because the workers believed that the source had located in the machine,they took the machine with the unloaded cable away from the workshop.About at 7:00 a.m
7、.,7th,May Other employees went into the workshop and begun their work.One worker found the source.He picked it up,looked it carefully.He didnt know what it was,then he thrown it out of the workshop.9ProcessAbout at 8:00 a.m.,7th,May Another worker,named Wang(who received the most r a d i a t i o n d
8、 o s e i n t h i s accident),found the source near the workshops door.He thought it was beautiful and attractive,so he picked it and put it into his pocket.Then Wang took a rest with source in his pocket in a rest room about one hour.There was a workmate of Wang in the room,The workmate was also irr
9、adiated.10ProcessAbout at 9:00 a.m.,7th,May Wang had done his normal work till 11:30,some his workmates near him had been irradiated.Wang had finished his work and went his home with the source in his pocket at about 11:30.Then he put the source in a warehouse locates in his backyard.11ProcessAt nig
10、ht,8th,May The formal four workers took the inspection instruments into the workshop again.The film wasnt photo sensitized after the“exposure”.So the radiation source was found lost!12ProcessAt 2:00,9th,May The radiation source lost accident was reported to environment protection bureau and police b
11、ureau of NanJing city.At 3:00,9th,May Environment protection bureaus employees went to the workshop where the source was lost.At 8:00,9th,May The policemen went to the workshop and asked everyone worked in the factory.They promised 20,000 RMB Yuan to the people who provided the corresponding informa
12、tion.But the policemen didnt tell that the lost item is harmful.13Process Mr.Wang felt fearful.He had not the knowledge about radiation source,and he thought the item he had picked up must be very expensive,otherwise the policemen cant provide so much money for its information.He thought policemen m
13、aybe regard him as thief who stolen the“very expensive treasure”.So he didnt tell policemen the truth,and he telephoned his wife to transfer the source to his parents home.Mr.Wang feared and feared at that night.The next morning(10th,May),he went to his parents home,wrapped the source with a dark bl
14、ue plastic bag and thrown it to a grass 100 meters away from his parents home.1415vFinding the source The approximate position of the source was found through gamma-ray detection instruments at morning 9:00 a.m.on 10th May,after Wang had thrown it 3 hours late.But the precise positions determination
15、 was difficult,because the source was too small and the radiation was too strong near the source.Finally,a metal-detector was used to find the precise position of the source.16Process171819Calculation Mr.Wangs DoseLocal DoseLocal Dose：v ThighThigh：D=157Gy (t=3.5h,r=5cm,D5cm=50Gy/h)v Hands Hands：(pic
16、ked up and looked up the source,loaded the source,took the source)D=D1+D2+D3=14.33Gyv Whole Body Dose Whole Body Dose：2.55 Sv（Bladder,gonad,red marrow and skin are mainly considered.）20Calculation Other Peoples DoseWangs Wife：vHands Dose(Carrying source)：0.16Gy;vWhole Body Dose(Carrying source and c
17、lose contact source at home）：270mSvThe person who first picked up the source：vHands Dose：0.83Gy;vWhole Body Dose：8.3mSv。21Other people working in workshop：9 person（3-5m from source），Dose：2.5-6.25mSv 4 person（6m from source），Dose：1.74mSv 7 person（15m from source)，Dose：0.28mSv 20 person(20-40m from so
18、urce)，Average Dose：0.07mSvThe road construction workers near the warehouse:20 person(10-20m from source)Dose：0.78 3.125mSv22Calculation Other Peoples DoseThe workmate rested along with Wang in rest room Average range from source：3meters，Dose：13mSvWangs family and tenant:Dose：2537.5mSvWangs parents a
19、nd sister:Wangs Father：0.09mSv;Wangs Mother：1.22mSv Wangs Sister：0.22mSv23Calculation Other Peoples Dose Two tenants lived in second floor up the sources room Dose：5.12-6.4mSv;The constructors near the place where the source was found 11 constructors（30-80m from the source），Maximum Dose：0.42mSv24Cal
20、culation Other Peoples DoseConclude of the calculationvNear 100 people(More than 80)had been irradiated in Near 100 people(More than 80)had been irradiated in this source lost accident.this source lost accident.vThe person who accepted the most dose is Wang.His The person who accepted the most dose
21、is Wang.His local dose are more than 100 Cy,and his whole body local dose are more than 100 Cy,and his whole body dose is about 2.5Sv.This dose is very harmful,but dose is about 2.5Sv.This dose is very harmful,but not fatal.not fatal.vWangs wife had once carried the source and close to Wangs wife ha
22、d once carried the source and close to the source long time at home,her dose maybe about 270 the source long time at home,her dose maybe about 270 mSv.mSv.vAll of the other peoples dose are little than 50mSv.All of the other peoples dose are little than 50mSv.vThese data come from calculation used b
23、y physical These data come from calculation used by physical method,the uncertainties of the data maybe large.method,the uncertainties of the data maybe large.25Clinical Manifestation26 W a n g i s i n t h e hospital and undergoing treatment at present.An abscess had been taken placed on his right thigh.No life threatening temporarily.27ThanksThanks！
