There was an irradiation incident on June 15, 2007 involving, a radiation therapist at the radiation therapy centre Georges François Leclerc at Dijon, France. This event occurred during the treatment of a patient in radiation therapy. The irradiation of the patient was started as a radiation therapist was still present in the treatment room. The irradiation was interrupted in emergency after around ten seconds. The radiation therapist (occupational worker) who was staying near the accelerator has been exposed to a part of the radiation beam delivered to the patient. An assessment of the dose received by the radiation therapist could confirm that the dose received was in excess of the annual regulatory dose limit allowed for a worker of 20 mSv, the effective dose received was about 30 mSv. No health effects are expected for this person from this exposure. Investigation of the incident is being performed to determine the chronology and causes of the incident and to assess the corrective actions taken by the centre. It has been found that the incident resulted from human errors and a lack of proper procedure.
It is reported that the centre has taken immediate corrective administrative measures and committed itself to perform an in-depth risk identification analysis. Due to the overrun of one of the regulatory exposure limits (effective dose in excess of the yearly limit of 20 mSv), the Nuclear Safety Authority of France (ASN) ASN rates this incident at level 2 on the International Nuclear Event Scale. – Source IAEA News
Monday, July 30, 2007
Saturday, July 21, 2007
EARTHQUAKE IN JAPAN TIPPED OVER 100 NUCLEAR WASTE BARRELS
It was reported that a powerful earthquake of 6.8 magnitude on July 16, 2007 at the Kashiwazaki-Kariwa facility run by Tokyo Electric, Japan caused tipping over of about 100 barrels of low-level nuclear waste at waste storage building of a nuclear power plant. Some of the barrels were found with the lids open. The earthquake also caused some contaminated water from the Tokyo Electric's plant to escape into the sea.
Water which is thought to be from the spent fuel storage pool spread on the operation floors 3 and 3M of the reactor building (non-controlled zone) of unit #6. It was recognized that some leaked water was discharged into sea through draining route. Discharged water activity (after dilution) is reported to be fully less than legislative criteria (0.2Bq/cm^3). It is claimed the discharging had already stopped.
Radionuclides such as I-131, I-133, I-135, Cr-51 and Co-60 were detected on July 17, 2007 in the main ventilation duct (Unit # 7). The ventilation ducts were found bent at the connections to the main stack. The total amount of radioactivity (release?) was estimated to be 3x10^8 Bq. The main stack radiation monitors (units # 1to 6) and monitoring posts in the power station has shown no significant indication of radiation.
Just after the earthquake on July 16th, fire broke out in the unit #3 house transformer that supplies electricity to the reactor facility. It was extinguished at 11:58 AM. The regulator requested licensee to review its fire protection and preparedness system.
The four operating reactors at Kashiwazaki-Kariwa were shut automatically after the earthquake, and the other three had already been halted for routine maintenance, Tokyo Electric said on its Web site. The plant is 9 kilometers (5.6 miles) from the epicenter of the quake. The trade ministry and Kashiwazaki town authorities ordered Tokyo Electric to keep the seven nuclear reactors idle pending safety checks. The government criticized the company for being slow to disclose the radioactive leaks.
The Kashiwazaki-Kariwa plant was not designed to withstand an earthquake as powerful as the magnitude 6.8 tremor. The Trade ministry last year updated regulations to make the nation's nuclear power stations more earthquake resistant. Japan has 55 reactors that generate about one-third of the country's power, making the nation the third-largest nuclear producer in the world. Tokyo Electric operates 17 reactors.
On July 19, Shares of Tokyo Electric Power Co. dropped to a nine-month low on concern that the company's nuclear facility in central Japan, the world's biggest, may be shut for a year after the earthquake caused radioactive leaks.
Water which is thought to be from the spent fuel storage pool spread on the operation floors 3 and 3M of the reactor building (non-controlled zone) of unit #6. It was recognized that some leaked water was discharged into sea through draining route. Discharged water activity (after dilution) is reported to be fully less than legislative criteria (0.2Bq/cm^3). It is claimed the discharging had already stopped.
Radionuclides such as I-131, I-133, I-135, Cr-51 and Co-60 were detected on July 17, 2007 in the main ventilation duct (Unit # 7). The ventilation ducts were found bent at the connections to the main stack. The total amount of radioactivity (release?) was estimated to be 3x10^8 Bq. The main stack radiation monitors (units # 1to 6) and monitoring posts in the power station has shown no significant indication of radiation.
Just after the earthquake on July 16th, fire broke out in the unit #3 house transformer that supplies electricity to the reactor facility. It was extinguished at 11:58 AM. The regulator requested licensee to review its fire protection and preparedness system.
The four operating reactors at Kashiwazaki-Kariwa were shut automatically after the earthquake, and the other three had already been halted for routine maintenance, Tokyo Electric said on its Web site. The plant is 9 kilometers (5.6 miles) from the epicenter of the quake. The trade ministry and Kashiwazaki town authorities ordered Tokyo Electric to keep the seven nuclear reactors idle pending safety checks. The government criticized the company for being slow to disclose the radioactive leaks.
The Kashiwazaki-Kariwa plant was not designed to withstand an earthquake as powerful as the magnitude 6.8 tremor. The Trade ministry last year updated regulations to make the nation's nuclear power stations more earthquake resistant. Japan has 55 reactors that generate about one-third of the country's power, making the nation the third-largest nuclear producer in the world. Tokyo Electric operates 17 reactors.
On July 19, Shares of Tokyo Electric Power Co. dropped to a nine-month low on concern that the company's nuclear facility in central Japan, the world's biggest, may be shut for a year after the earthquake caused radioactive leaks.
Monday, July 16, 2007
ICRP PUBLICATION NO. 95
The International Commission on Radiological Protection (ICRP) has brought out recently a CD containing the ICRP publication no. 95. The publication is a complementary report to other earlier publications which provided age-specific bio-kinetic models and dose coefficients (dose per unit intake of radioactive substance) for members of the public (Publications 56, 67, 69, 71, and 72).
The ICRP-95 provides information on radiation doses to the infant due to intakes of radionuclides in maternal milk. Intakes by female members of the public and female workers are addressed, and dose coefficients per unit intake by the mother (Sv per Bq) are given for radioisotopes of 35 elements including sodium, magnesium, phosphorus, and potassium. The CD provides all the dose coefficients in Publication 95 in a handy electronic format, and includes a considerable amount of additional information. Thus, committed equivalent doses to the various organs and tissues of the offspring are provided. Dose coefficients are also given for inhalation for ten aerosol sizes (0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, 5, and 10 µm AMAD) as well as for ingestion. Effective doses and equivalent doses for all important tissues for a range of post-natal integration times (1, 5, 10, and 20 years) are given, together with the dose coefficients to age 70 years. All intake scenarios are considered.
The ICRP-95 provides information on radiation doses to the infant due to intakes of radionuclides in maternal milk. Intakes by female members of the public and female workers are addressed, and dose coefficients per unit intake by the mother (Sv per Bq) are given for radioisotopes of 35 elements including sodium, magnesium, phosphorus, and potassium. The CD provides all the dose coefficients in Publication 95 in a handy electronic format, and includes a considerable amount of additional information. Thus, committed equivalent doses to the various organs and tissues of the offspring are provided. Dose coefficients are also given for inhalation for ten aerosol sizes (0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, 3, 5, and 10 µm AMAD) as well as for ingestion. Effective doses and equivalent doses for all important tissues for a range of post-natal integration times (1, 5, 10, and 20 years) are given, together with the dose coefficients to age 70 years. All intake scenarios are considered.
Saturday, July 14, 2007
WHAT IS ACCEPTABLE LEVEL OF RISK ?
The health risk considered here is the fatal cancer, the ultimate end effect of exposure to carcinogens, which is also used as the basis for establishing the radiation dose limits for workers and the public. It is often said that “Nothing is poison but the dose makes it so”. Many substances (such as chemicals) which are toxic at high doses are beneficial to health in small doses, as medicines, to cure diseases. There is no credible scientific evidence that low-dose radiation is harmful. It is also widely reported that low-dose ionizing radiation is harmless and often beneficial to health.
Life is evolved, over millions of years in an environment of ionizing radiation. Even today, there are many radioactive elements existing in the nature. The variation in the background radiation exposures due to these radioactive isotopes is in the range of about 2 to 6 milli-Sievert and more per year in various countries and areas. No adverse health effects are found amongst people living in High Background Radiation Areas (HBRAs).
Public perception of acceptability of risk is based on the benefits that can be derived by taking or accepting the risk. For example, the risk of radiation exposure to much higher levels is accepted by the people in diagnostic and therapeutic radiological procedures. Whereas, the general exposure levels of occupational radiation workers fall in the same range of variation of natural background radiation doses.
For the purpose of regulation of public exposures, a numerical value for the acceptable risk is arrived at in accordance with the principle of protection optimization. In line with the US-Nuclear Regulatory Commission, one can accept a risk of fatality from cancer of one in a million per year, corresponding to the annual public exposure of 0.01 mSv (exposure which can be considered as of below regulatory concern) may be adopted. In case of annual exposures of 1 mSv (dose limit to the public) of small population (like critical group), one can accept a conservative lifetime (75 years) risks to individuals as high as five cancer fatalities in a thousand exposed.
Radiation exposures of the individual members of the public which result in risks below these limits are considered to be safe and acceptable.
Life is evolved, over millions of years in an environment of ionizing radiation. Even today, there are many radioactive elements existing in the nature. The variation in the background radiation exposures due to these radioactive isotopes is in the range of about 2 to 6 milli-Sievert and more per year in various countries and areas. No adverse health effects are found amongst people living in High Background Radiation Areas (HBRAs).
Public perception of acceptability of risk is based on the benefits that can be derived by taking or accepting the risk. For example, the risk of radiation exposure to much higher levels is accepted by the people in diagnostic and therapeutic radiological procedures. Whereas, the general exposure levels of occupational radiation workers fall in the same range of variation of natural background radiation doses.
For the purpose of regulation of public exposures, a numerical value for the acceptable risk is arrived at in accordance with the principle of protection optimization. In line with the US-Nuclear Regulatory Commission, one can accept a risk of fatality from cancer of one in a million per year, corresponding to the annual public exposure of 0.01 mSv (exposure which can be considered as of below regulatory concern) may be adopted. In case of annual exposures of 1 mSv (dose limit to the public) of small population (like critical group), one can accept a conservative lifetime (75 years) risks to individuals as high as five cancer fatalities in a thousand exposed.
Radiation exposures of the individual members of the public which result in risks below these limits are considered to be safe and acceptable.
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