147. Ministry announces provisional safety limit for school

The Ministry of Education, Culture, Sports, Science and Technology (MEXT) announced Apr 19 the provisional standard for the utilization of kindergartens, elementary schools and high schools in Fukushima Prefecture after the prefecture was struck with the nuclear crisis. The ministry has come up with a guideline for deciding whether the school grounds and buildings can be used: in order to stay within the 20 millisievert annual exposure safety limit, all outdoor activities need to be stopped when the radiation level at the schoolyard hits above 3.8 microsievert/hr.

Currently, 13 school institutions fall under this restriction. Dosimeters have been distributed to all facilities, and they will monitor the changes (in the radiation level). This provisional standard will be revised at the end of August.

The current guideline was calculated based on the suggestion given by the International Commission on Radiological Protection (ICRP) that “the annual radiation exposure limit after this state of emergency has been brought under control should be (raised to) between 1 to 20 millisievert”. All outdoor activity is to be stopped in the schools if a reading of 3.8 microsievert/hr was recorded in the schoolyard.

If one stays outside for 24 hours when the radiation is at this level, they will be exposed to more than 20 millisievert in a year. However, if a student stays inside the wooden school buildings for 16 hours, the radiation exposure will be reduced to 60%, keeping it below the 20 millisievert limit.

The 13 schools, kindergartens, and nurseries that exceeded this limit are located in Fukushika City, Kooriyama City and Date City, with a total of 3,560 students affected. Outdoor activities in the school grounds and sandboxes are limited to 1 hour in these institutions. Washing hands, gurgling and shaking off the soil from the bottom of their shoes when they arrive at home are some of the suggestions for the children.

Tests on contamination in the school reveal that the effects of internal exposure from breathing in radioactive dust is only 3.5 %, even in schools with high readings of radiation levels, and it was concluded that there was no need to take it into account.

Tests on the radiation level will be held in the facilities every week from now on, and the lift on activity restrictions will be reviewed.

A Nuclear Safety Commission official said in a press conference Apr 13 that when it comes to schools, “the annual radiation exposure safety limit for the children should be half that of adults’ at 10 millisievert,” but withdrew his statement the next day, stating that it was not based on an official decision.

Representative chairman of NRC, Yutaka Kukita, commented Apr 19 that a few reasons, such as the low likelihood of a student remaining outside school buildings for more than 8 hours, means that “we can expect the radiation exposure for each student to remain below 20 millisievert, even if the radiation level exceeds 3.8 microsievert/hr.”

Source: Asahi Shinbun, Apr 20, 1:36
Translated by I. Salim
Edited by English native speaker
Link to original article: http://www.asahi.com/special/10005/TKY201104190598.html

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