Measurement results of municipal nursery school (Kohoku Ward)

Following the confirmation of "micro spot" around rainwater basin in Kohoku Ward

About measurement results of radiation dose in municipal nursery school in Kohoku Ward

Radiation doses higher than the surrounding area were confirmed around the road gutter in Kohoku Ward, so we urgently measured the radiation dose at a municipal nursery school in Kohoku Ward, which takes care of infants who are likely to be affected by radiation.

(1)　Measurement date

9:30 a.m. on Sunday, September 18, 2011

(2)　Number of facilities and measurement locations

95 municipal nursery schools in Kohoku Ward (10-22 locations each garden)

(3)　Measurement location

Of the places where children may approach in the facility, the places where there is a high possibility of becoming a "micro spot" are categorized and the measurement location is selected. In addition, we measure nursery room and the center of garden to refer to evaluation of measured values.

(1)　The lower part of the vertical gutter (rain gutter) (excluding those directly connected to sewage) and its surroundings
(2)　Gutter and its surroundings (in the gutter where the upper part is open, the gutter lid)
(3)　Surrounds of rainwater basins and sewage basins
(4)　Depots where dead leaves are accumulated (places that fall naturally under trees and hedges, places collected by cleaning, places that naturally gather due to wind and rain, etc.)
(5)　Home garden
(6)　Turf, moss surface
(7)　Places that slide down from slides (for playground equipment, evacuation)
(8)　Rooftops and terraces where people can enter and exit (places where rainwater and dust accumulate)
(9)　Sandbox
(10)　Pool
(11)　Outdoor hand washing area
(12)　The center of the garden
(13)　Nursery room (1 room on the 1st floor)

(4)　Measurement equipment

NaI (TI) scintillation detector TCS-172B (manufactured by Hitachi Aloka Medical, Ltd.)

(5)　Measurement contents

Measurement of spatial gamma (gamma) dose of 1cm, 5cm, and 50cm of the ground surface before and after cleaning

(6)　Measurement results

Measurements were performed mainly in places where children could approach and become "micro spots", but all of them were below 0.59 μSv / h, which is a guideline for re-measurement.

In addition, values exceeding 0.59 μSv / h is measured in a place (one place) where sand was deposited on the rooftop where people do not enter on a daily basis.

List of measurement results (PDF: 73KB)

Regardless of the result of the measurement, at a municipal nursery school that takes care of infants who are likely to be affected by radiation, regardless of the results of the measurement, in order to grasp the effects of cleaning, `` micro spots '' on the premises We carried out cleaning of places that could become.

Cumulatives such as soil, stone, dead leaves, moss, dust, etc. were removed. In addition, the removed items are sealed in double plastic bags, covered with blue sheets, etc., to prevent scattering, and temporarily stored in a place where children do not approach.