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Radioactive Contamination in Scrap and Steel Products G. K. Panda Radiological Safety Division Atomic Energy Regulatory Board
Introduction • In the recent years there were some reported cases of detection of low level radioactive contamination in steel products in India and in other countries as well • Most of the cases were because of inadvertent melting of orphan sources along with the scrap
Challenges or Opportunities? ? ? Definitely- a challenge to the fraternity
Consequences of radioactive contamination • Exorbitant economical loss to Health hazard • and public at large, though most of the time it is low • Anxiety among workers the and public about the health consequences • Bad name to the company • Bad name to the country
Mission of AERB "The mission of AERB is to ensure that the use of ionizing radiation and nuclear energy in India does not cause unacceptable impact on the health of workers and the members of the public and on the environment. "
What AERB is doing • Educate • Alert • Guidance • Interactingwithvarious. Governmental agencies
How radioactive sources look like? • Very small • Doubly encapsulated in SS • Further shielded according to their strength
How radioactive sources look like? Very small Doubly encapsulated in SS Further shielded according to their strength
Radiation warning symbol
Loss of Control of a Radioactive Source Intentional Inadvertent • Loss of, or damage to sources • Misplaced • Forgotten • Accidents Damage (Sabotage) Acquisition • Theft • Illegal purchase • Legal purchase Malevolent Motive • Terrorism • Individual’s intent to harm other(s) Financial Motive • Illegal sale for profit • Avoidance of costs of ownership dumping to avoid disposal fees • Extortion
Flow of radioactive contamination Radioactive material in the Steel metal scrap Gets Melted in the Furnace Rolled/Forging in Steel Mills Manufacture of final consumer product Exported or supplied to a dealer Reaches to end user
Economical impact of contamination. Calculation based on the inputs received from an Indian exporter • material steel grade 304 exported to an European destination and returned to India after detection of contamination at the port of destination • Price index prevailed in steel market in Aug , 2008.
Detection • RAM can be detected in the metal scrap stream by monitoring the metal scrap in the following way. § Administrative Monitoring § Visual Monitoring § Radiation Monitoring
Administrative Monitoring • The following administrative procedures can provide a first indication of whethere is a significant potential for radioactive scrap metal to be present in consignments § Knowledge of the origin of the scrap metal § Knowledge of the scrap metal supplier § The history of previous transactions
Visual Monitoring • Metal scrap should be visually monitored during its handling at scrap yards, melting plants and institutions involved with value addition • Persons handling scrap should be trained to recognize the different types of radiation sources, source housings and radioactivity warning signs.
Radiation Labels on Packages
Supplementary Ionizing Radiation Warning Symbol; from Feb. 2007
Radiation Monitoring • Possible presence of radioactive material in scrap metal and finished products should be checked for radiation using fixed and/or portable monitors.
Important Characteristics of Equipment • Serve the intended purpose (energy independent etc. ) • Optimal utilization (e. g. portability) • Minimal requirements for operation training and ease of operation • Highest efficiency and sensitivity • Reliability • Work in wide temperature and humidity range • Cost effective
Detection Probability Alpha Negligible Beta Very Low Gamma High Neutrons High (with neutron monitors)
Location of Radiation Monitoring • Monitoring outside of a container as a whole while entering the industry • At the time of unloading the scrap • At the time of filling the charge bucket • After manufacturing of products like metal sheets, billets, ingots • In the laboratory while performing the composition analysis • Monitoring of slag and off-gas dust • At the time of containers leaving the industry with finished products
Monitoring of Scrap • Fixed Monitors • Location: weigh bridge/entrance of the institute • Speed of truck carrying the scrap container should be less than 8 km. /h;
Monitoring of Scrap… • Portable Monitors • Location: any accessible place • Speed of the monitor should be less than 0. 2 m/sec. • Weight should be less than 2 kg.
Determination of an instrument threshold • As we all are aware of the fact that background radiation levels at different places are different (in most of the places it is in the range of 5 -15 µRem/h). • Even at a particular location the background radiation level fluctuates • So, it is very difficult, to give a universally acceptable threshold radiation level at which appropriate actions to be initiated
Fluctuation in background readings • It is a common question that up to what background variation it is acceptable. • As a rule of thumb, the fluctuation in the reading is considered to be within two times of square root of an observed reading at any time (say, x µrem/h) i. e. the readings should fall within the range x ± 2 √x µrem/h.
Fluctuation in background readings… • For example, if the observed reading is 9 µrem/h, then the fluctuation can be taken as (2 x 3) µrem/h i. e. 6 µrem/h. This means the expected readings should fall in the range 3 to 15 µrem/h. • For readings to fall with in x ± 2 √x; confidence level is 95 %.
Response to the alarms • Once an alarm is confirmed as genuine alarm, cordon off the area around the container and ensure that the radiation level at cordon does not exceed 0. 1 m. R/h (1 µSv/h) • At the cordoned off area, it is required to display radiation caution symbol and a placard mentioning “RADIATION AREA-KEEP AWAY” at a prominent location
Response to alarms. . (Emergency management) • Very unlikely to get a bare source in the scrap • If any metallic container or object with radiation warning symbol found, or any metallic container with unusually heavy weight w. r. t. its shape, size etc – do not remain near it – cordon off the area – do not allow unauthorised entry nearby – inform AERB immediately @
Emergency management…… Head, Radiological Safety Division Atomic Energy Regulatory Board Anushaktinagar, Mumbai – 400 094 Ph No. 022 25990655/656, Fax No. 25990650 E-mail: sahussain @aerb. gov. in
National/International Trade • Before selling their products, the sellers should ascertain that up to what contamination level it is acceptable to the buyer and to the country.
Summary i. Radiation contamination free certificate ii. Radiation monitoring at various stages
Management Mantra Learning of lessons: i. From own mistakes- may cost crores of rupees to the affected party because of radioactive contamination ii. From other’s mistakes- free of cost
Thanks for your kind Attention!!