6． Outline of decontamination methods, applications and conditions thereof, andexamination of the effects
Chapter 6.1 outlines the decontamination methods and their applications and conditions
for the decontamination works in the Special Decontamination Area as directed by the
Ministry of Environment (MOE). Chapter 6.2 shows some of the verification results ofdecontamination effects in the decontamination works executed.
The methods to apply and their conditions and the decontamination effects depend on
various environmental conditions such as site situations, material properties and surface
conditions of the objects subject to decontamination, and their aging variation with time.
Therefore, the best decontamination methods and conditions are not easy to specify
beforehand, even for a particular item to be decontaminated.
For example, the decontamination methods for the decontamination works have beenchanging with time after the accident. In the early stage, high-pressure water cleaning was
effective in decontaminating paved road surfaces. But after some time, radioactive cesium
has migrated from the surface deep into the materials so that scraping of the paved roadsurfaces by shot-blasting became a practical and effective approach, instead of simply
washing the surfaces.
Meanwhile, weeds have grown in house gardens and on unpaved road surfaces as time
elapsed after the accident. Also underbrush and shrubs have grown in farmland. Weedremoval and underbrush/shrubs cutting are currently being added to the decontamination
work, which had not been practiced in the early stage.

6.1. Outline of Decontamination Methods and Their Applications and Conditions
Outlines of decontamination methods, and their applications and conditions used in thedecontamination works in the Special Decontamination Areas as directed by the MOE aregiven below.
Decontamination methods are specified in the Common Specifications of Decontamination
Works (“Common Specifications” in this report) (7th Edition), and this report summarizes thedecontamination methods for each decontamination object shown in Table 6-1. As mentioned
in Chapter 4.1.3 (4), the Common Specifications (7th Edition) deals with not only (i)decontamination methods for reducing air dose rates, but also (ii) the methods forpre-decontamination works and post-decontamination works for restoration.
It should be noted that the amount of materials removed such as soil is not given in Chapter
6.1. It can be estimated, for instance, the reference soil thickness of about 5 cm set when
scraping farmland (rice fields, dry fields, grassland) is multiplied by the size of thedecontamination area (if the area of 100 m2 is decontaminated by surface scraping, the soil toremove is estimated as 5 m3). In actual cases, it is not possible to scrape the surface land
uniformly. Uncertainties to some degree cannot be avoided. (See the case given later in
Chapter 6.2.1-(4) 2) i).)271

Table 6-1 Methods of decontamination for individual objects subject to decontamination
Classificationofdecontamination
Residential areas,
schools, parks,
large facilities,
roads, etc.

objectssubjecttosediments
Roofs/ rooftops, exterior
walls/outside
walls,
paved
surfaces(concrete, asphalt) andthe like of structures
Weeds, lawns
Gravel, crushed stones
Soil

Garden trees, planted
vegetation and roadside
trees

OthersSlopesRice fields, dry
fields,grassland,
etc.

Weeds

Soil

Waterways
OthersGrassland, lawns

272

Classification of decontamination methods
sediment removal
wipingbrush cleaning
high-pressure water cleaning
shot-blasting
Superhigh pressure water cleaning
Cleaning by road sweepers
Weeding, lawn mowing
deep pruning of lawns
Removal of gravel, crushed stones
Surface soil removal from rainwater
guttering drains, and under-eaves
Scraping of surface soil
Soil surface covering
Deep plowing
Surface soil removal from the bases oftrees
Delimbing of garden trees, planted
vegetation, roadside trees
Logging of garden trees, planted
vegetation
Wiping, cleaning, scraping of playgroundequipment
Removal of bottom sediments and the likein the street drains along the roads
Removal of weeds, fallen leaves, andsediments from the slopes
Weeding the rice fields and dry fields byhands
Weeding the rice fields and dry fields bymachinery
Collection of weeds removed from rice
fields and dry fields
Weeding the grassland
Leveling of unevenness
Spreadingofsurfacesolidificationmaterials
Scraping of surface soil (standard transfer
method)Dual plowing
Deep tillage
Soil replacement
Restoration of soil fertility
Removal of bottom sediments (soil sucking)Removal of bottom sediments (packing into
bags)
Packing into bags (standard transfer
method)Petit transfer on site (standard transfer
method)Weeding (dense shrubs)
Weeding (sparse shrubs)

Forests

Common items to theforests with mixed treesof coniferous evergreen
trees,
deciduous
broad-leaf
trees andothersConiferous
trees

evergreen

273

Removal of deposited organic sediments
Removal of deposited organic sediments(uncontrolled areas)
Prevention of soil secondary dispersion(lining up of sandbags)
Weeding underbrush and shrubs
Removal of organic sediment residues
Pruning of coniferous trees, collection ofslips6.1.1. Residential Areas, Schools, Parks, Large Facilities, Roads, etc.
（1） Sediment
1）Sediment removal
Locations to be
decontaminated137“1.1.1. Roofs (other than concrete)” of “1.1 Roofs/rooftops” in “1.
Residential areas and the like”“1.1.2. Roofs (concrete)” of “1.1 Roofs/rooftops” in “1. Residential areas
and the like”“1.3.1. Roof gutters” of “1.3 Rainwater gutters” in “1. Residential areas
and the like”“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like.”“1.4.2. Paved surfaces” of “1.4. Gardens and the like.” in “1. Residential
areas and the like.”“2.1. Roofs/rooftops” at “2. Schools”“2.3.1. Roof gutters” of “2.3. Rainwater gutters” at “2. Schools”“2.4.1. Sediment” of “2.4. School grounds and the like” at “2. Schools”“2.4.6. Paved surfaces” of “2.4. School grounds and the like” at “2.
Schools”“3.1. Roofs/rooftops” in “3. Parks (small)”“3.3.1. Roof gutters” of “3.3. Rainwater gutters” in “3. Parks (small)”“3.4.1.Sediment” of “3.4. Playgrounds and the like” in “3. Parks (small)”“3.4.6.Paved surfaces” of “3.4. Playgrounds and the like” in “3. Parks(small)”“4.1. Roofs/rooftops” in 4. Parks (large)”“4.3.1. Roof gutters” of “4.3. Rainwater gutters” in “4. Parks (large)”“4.4.1.Sediment” of “4.4. Playgrounds and the like” in “4. Parks (large)”“4.4.6.Paved surfaces” of “4.4. Playgrounds and the like” in “4. Parks(large)”“5.1.1. Roofs/rooftops” of “5.1. Roofs/rooftops” of “5. Large facilities”“5.3.1. Roof gutters” of “5.3. Rainwater gutters” of “5. Large facilities”“5.4.1.Sediment” of “5.4. Playgrounds and the like” of “5. Large
facilities”“5.4.6. Parking lots (concrete, asphalt)” of “5.4. Playgrounds and thelike” of “5. Large facilities”“6.1.1. Sediment” of “6.1. Paved roads” of “6. Roads”“6.2.1. Road surfaces (soil)” of “6.2. Unpaved roads” of “6. Roads”“6.2.2. Road surfaces (gravel, crushed stone)” of “6.2. Unpaved roads” of“6. Roads”“6.5.1. Pedestrian overpasses” of “6.5. Pedestrian overpasses” “6. Roads”“6.6.1. Sediment” of “6.6. Roadside trees” of “6. Roads”

Decontamination

Sediment removal

methods

137

Residential areas and the like,” “1.1 Roofs/rooftops,” “1.1.1. Roofs (other than concrete),” etc. in the“Locations to be decontaminated,” “Outline,” and “Required equipment and materials” correspond to theobjects subject to decontamination shown in Table 4-7 of the Common Specifications (7th Edition). The
same source applies hereafter.

274

Outline

Sediment shall be removed in the following
procedures(i) Removing fallen leaves, moss, mud, etc.
(ii) Packing the removed materials
from roofs/rooftops, roof gutters, gardens,
grounds, parking lots (concrete, asphalt),
roads/sidewalks, pedestrian overpasses, roadsidetrees, etc. in residential areas, schools, parks,
large facilities, roads, etc.

Decontamination processes■ When working on
roofs/rooftops, gardens, etc. of residences,schools, parks (small), parks (large) or large
facilities (1.1.1, 1.1.2, 1.4.1, 1.4.2, 2.1.1, 3.1.1,
4.1.1, 5.1.1);
grounds, paved surfaces, etc. of schools, parks(small), and parks (large) (2.4.1, 2.4.6, 3.4.1,
3.4.6, 4.4.1, 4.4.6); andgrounds of large facilities, parking lots
(concrete, asphalt) (5.4.1, 5.4.6), paved andunpaved roads (6.1.1, 6.2.1, 6.2.2), as well as
pedestrian overpasses (6.5.1) or roadside trees(6.6.1),
Sediment such as fallen leaves, moss andmud shall be collected using rubber hand
gloves, shovels, rakes, etc. and packed intolarge sandbags; andSediment on easily broken roofs shall be
removed with mops or the like, without
getting directly on the roofs, by using aerial
lift work vehicles and the like.
■ When working on roof gutters of residences,schools, parks (small), parks (large) or large
facilities (1.3.1, 2.3.1, 3.3.1, 4.3.1, 5.3.1),
Fallen leaves, moss, mud, etc. shall be
removed using rubber hand gloves, brooms,
brushes, etc. and packed into large
sandbags.

Tools, equipment and the like fordecontamination work

When working on
roofs/rooftops, gardens, etc. of residences,schools, parks (small), parks (large) or large
facilities (1.1.1, 1.1.2, 1.4.1, 1.4.2, 2.1.1,
3.1.1, 4.1.1, 5.1.1);
grounds of parks (small), paved surfaces,
etc. (3.4.1, 3.4.6); andpedestrian overpasses (6.5.1), roadside trees(6.6.1),Tools, equipment to use
Quantity
Rubber gloves, shovels, rakes,－
etc.
Large sandbags－*For the work at an elevated place, aerial lift
work vehicles or scaffolds shall be used.
275

When working on roof gutters of residences,schools, parks (small), parks (large) or large
facilities (1.3.1, 2.3.1, 3.3.1, 4.3.1, 5.3.1),
Tools, equipment to use
Quantity
Rubber gloves, brooms, brushes,－
etc.
Large sandbags－
When working on
grounds, paved surface, etc. of schools, parks(large) or large facilities (2.4.1,2.4.6, 4.4.1,
4.4.6);
grounds, parking lots (concrete, asphalt) oflarge facilities (5.4.1, 5.4.5), andpaved and unpaved roads (6.1.1, 6.2.1,
6.2.2),(per 1,300m2)
Tools, equipment to use
Quantity
Rubber gloves, shovels, rakes,－
etc.
Dump trucks
0.43
service days
Light oil
9.7L
Large sandbags－
Workforce needed■When working on

roofs/rooftops, gardens, etc. of residences,schools, parks (small), parks (large) or large
facilities (1.1.1, 1.1.2, 1.4.1, 1.4.2, 2.1.1, 3.1.1,
4.1.1, 5.1.1);
grounds of parks (small), paved surfaces, etc.
(3.4.1, 3.4.6); andpedestrian overpasses (6.5.1), roadside trees(6.6.1),(per 1,300m2)
Workforce needed
Quantity
Operation leaders
0.5
worker-days
Decontamination workers
3.2
worker-days
When working on roof gutters of residences,schools, parks (small), parks (large) or large
facilities (1.3.1, 2.3.1, 3.3.1, 4.3.1, 5.3.1),(per 1,300m2)
Workforce needed
Quantity
Operation leaders
0.5
worker-days
Decontamination workers
3.2
worker-days276

When working on
grounds, paved surface, etc. of schools, parks(large) or large facilities (2.4.1,2.4.6, 4.4.1,
4.4.6);
grounds, parking lots (concrete, asphalt) oflarge facilities (5.4.1, 5.4.5), andpaved and unpaved roads (6.1.1, 6.2.1,
6.2.2),(per 1,300m2)
Workforce needed
Quantity
Operation leaders
0.5
worker-days
Decontamination workers
3.2
worker-days
Drivers (ordinary
0.37
decontamination)
worker-days
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites
andconstraints regarding
objects and locations
to be decontaminated

In order to prevent contamination fromspreading due to decontamination work, theorder of tasks shall be considered. For
instance, when decontaminating residential
areas and the like, the decontamination
work shall be done starting with roofs
followed by rainwater gutters and thengardens and the like.
When decontaminating for the first timeafter the accident at a certain place,sediment shall be checked as to whether thefallen leaves and the like are from after theaccident or they were there at around thetime of the accident.

Radiation
exposureprotection of workers

Rubber gloves shall be worn.
The removed objects shall be immediately
packed to avoid unwanted exposure bycontact.

General labor safety ofworkers

For work at an elevated place, aerial lift
work vehicles or scaffolds shall be used.
For the work on roads, barricades and traffic
controllers shall be arranged.

Measures to prevent－

secondary wastes
Others－277

（2） Roofs/rooftops, exterior walls, outside walls, paved surfaces (concrete, asphalt), etc. of
structures

1）Wiping
Locations to be
decontaminated“1.1.1. Roofs (other than concrete)” of “1.1 Roofs/rooftops” in “1.
“Residential areas and the like”“1.1.2. Roofs (concrete)” of “1.1 Roofs/rooftops” in “1. Residential areas
and the like”“1.2.1. Other than earthen walls” of “1.2. Exterior walls/outside walls”
in “1. Residential areas and the like”“1.2.2. Earthen walls” of “1.2. Exterior walls/outside walls” in “1.
Residential areas and the like”“1.3.1. Roof gutters” of “1.3 Rainwater gutters” in “1. Residential areas
and the like”“2.1. Roofs/rooftops” at “2. Schools”“2.2. Exterior walls/outside walls” at “2. Schools”“2.3.1. Roof gutters” of “2.3. Rainwater gutters” at “2. Schools”“3.1. Roofs/rooftops” in “3. Parks (small)”“3.2.1. Exterior walls/outside walls” of “3.2. Exterior walls/outside
walls” in “3. Parks (small)”“3.3.1. Roof gutters” of “3.3. Rainwater gutters” in “3. Parks (small)”“4.1. Roofs/rooftops” in “4. Parks (large)”“4.2.1. Exterior walls/outside walls” of “4.2. Exterior walls/outside
walls” in “4. Parks (large)”“4.3.1. Roof gutters” of “4.3. Rainwater gutters” in “4. Parks (large)”“5.1.1. Roofs/rooftops” of “5.1. Roofs/rooftops” of “5. Large facilities”“5.2.1. Exterior walls/outside walls” of “5.2. Exterior walls/outside
walls” of “5. Large facilities”“5.3.1. Roof gutters” of “5.3. Rainwater gutters” of “5. Large facilities”“6.3.1. Guardrails” of “6.3.Guardrails” of “6. Roads”“6.5.1. Pedestrian overpasses” of “6.5. Pedestrian overpasses” of “6.
Roads”

Decontamination

Wipingmethods
OutlineDecontamination processes

Roofs/rooftops, exterior walls/outside walls, roof
gutters, guardrails, pedestrian overpasses, etc. inresidential areas, schools, parks, large facilities,
etc. shall be decontaminated through wiping.
The objects to be decontaminated shall becarefully wiped by using cleaning cloths andthe like moistened with water or the like(including neutral detergents or vinegar). In
wiping, their folded clean faces shall be useduntil repeated wiping gives hardly any
further
reductioninthesurfacecontamination density.

Tools, equipment and the like for278decontamination work

Tools, equipment to use
Quantity
Cleaning cloths and the like－
Brushes (including deck brushes,－
car washing brushes)* For the work at elevated places, adequate safetymeasures shall be taken for scaffolds, aerial lift
work vehicles and fall arresting devices/systems
using fixed ropes/safety belts, etc.

Workforce needed

When working on roofs/rooftops (1.1.1, 1.1.2,
2.1.1, 3.1.1, 4.1.1, 5.1.1) of residential areas,
schools, parks (small), parks (large), large
facilities, etc. and pedestrian overpasses(6.5.1),(per 130m2)
Workforce needed
Quantity
Operation leaders
0.3
worker-days
Decontamination workers
2.2
worker-days
When working on exterior walls/outside walls(1.2.1, 1.2.2, 2.2.1, 3.2.1, 4.2.1, 5.2.1) ofresidential areas, schools, parks (small),parks (large), large facilities, etc.,(per 1,300m2)
Workforce needed
Quantity
Operation leaders
2.6
worker-days
Decontamination workers
17.2
worker-days
When working on roof gutters（1.3.1, 2.3.1,
3.3.1, 4.3.1, 5.3.1 ） of residential areas,
schools, parks (small), parks (large), large
facilities, etc.,(per 130m)
Workforce needed
Quantity
Operation leaders
0.2
worker-days
Decontamination workers
1.1
worker-days
When working on guard rails (6.3.1),(per 100m)
Workforce needed
Quantity
Operation leaders
0.1
worker-days
Decontamination workers
0.8
worker-days

Idea
development,
lessons,

Prerequisites
andconstraints regarding
objects and locations

In order to prevent contamination fromspreading due to decontamination work,
wiping shall be done from top to bottom, for279

points
tokeepinmind, etc.

to be decontaminatedinstance, when wiping residential areas andthe like, starting with roofs first followed by
rainwater gutters and the like.
Surfaces with attached materials like moss or
mud which are difficult to remove by wiping,or clearly visible dirty surfaces shall bedecontaminated by carefully removing theattached dirt using brushes with dry
conditions without damaging the objects.
Folded clean faces of the cleaning cloths shallbe used for each wiping step, in order toprevent contaminants being reattached to thesurfaces.
When decontaminating earthen walls,
brushes and the like shall be used, notcleaning cloths and the like, to remove dirtwith dry conditions without damaging theobjects.
When decontaminating exterior walls/outside
walls other than earthen walls, or when
decontaminating
guardrails,
brushes(including car washing brushes, deckbrushes) and the like shall be used to remove
dirt with dry conditions without damaging
the objects. Surfaces with attached materials
like moss or mud which are difficult toremove, or clearly visible dirty surfaces shallbe decontaminated by carefully removing theattached dirt using metal brushes or brushes
moistened with water or the like without
damaging the objects.
Whendecontaminatingpedestrian
overpasses, their handrails shall bedecontaminated through wiping.
When rust is present, the rust itself shall be
removed through wiping and other means.

Radiation
exposureprotection of workers

Hand gloves and the like shall be worn.
Cleaning cloths and the like shall not bedirectly touched, because they might becontaminated by radiocesium.

General labor safety ofworkers

For the work at elevated places, adequate
safety measures shall be taken for scaffolds,
aerial lift work vehicles and fall arresting
devices/systems using fixed ropes/safety belts
and the like.
For the work on roads, barricades and traffic
controllers shall be arranged.

Measures to prevent－

secondary wastes
Others－2802）Brush cleaning
Locations to be
decontaminated“1.1.1. Roofs (other than concrete)” of “1.1 Roofs/rooftops” in “1.
Residential areas and the like”“1.1.2. Roofs (concrete)” of “1.1 Roofs/rooftops” in “1. Residential areas
and the like”“1.2.1. Other than earthen walls” of “1.2. Exterior walls/outside walls”
in “1. Residential areas and the like”“1.4.2. Paved surfaces” of “1.4. Gardens and the like” in “1. Residential
areas and the like”“2.1. Roofs/rooftops” at “2. Schools”“2.2. Exterior walls/outside walls” at “2. Schools”“2.4.6 Paved surfaces” of “2.4. Grounds and the like” at “2. Schools”“3.1. Roofs/rooftops” in “3. Parks (small)”“3.2.1. Exterior walls/outside walls” of “3.2. Exterior walls/outside
walls” in “3. Parks (small)”“3.4.6. Paved surfaces” of “3.4. Grounds and the like” in “3. Parks(small)”“4.1. Roofs/rooftops” in “4. Parks (large)”“4.2.1. Exterior walls/outside walls” of “4.2. Exterior walls/outside
walls” in “4. Parks (large)”“4.4.6. Paved surfaces” of “4.4. Grounds and the like” in “4. Parks(large)”“5.1.1. Roofs/rooftops” of “5.1. Roofs/rooftops” of “5. Large facilities”“5.2.1. Exterior walls/outside walls” of “5.2. Exterior walls/outside
walls” of “5. Large facilities”“5.4.6. Parking lots (concrete, asphalt)” of “5.4. Grounds and the like” of“5. Large facilities”“6.3.1. Guardrails” of “6.3.Guardrails” of “6. Roads”“6.5.1. Pedestrian overpasses” of “6.5. Pedestrian overpasses” of “6.
Roads”

Decontamination

Brush cleaning

methods
OutlineDecontamination processes

Roofs/rooftops and exterior walls/ outside walls
in residential areas, schools, parks and large
facilities, paved surfaces of gardens, grounds andthe like, parking lots (concrete, asphalt),
guardrails, pedestrian overpasses, etc. shall becleaned using brushes in the following
procedures(i) Cleaning using brushes(ii) Collecting used water
Cleaning by deck brushes or scrubbing
brushes shall be repeated carefully until
there is hardly any further reduction in thesurface contamination densities.
About 4L/m2 of water shall be poured on
surfaces before brushing and also after281

brushing for washing.
The cleaning water discharge lines shall becleaned beforehand for smooth discharge.
The discharge shall be collected in rainwater
cisterns and the like. After collection, it shallbe transferred to on-site or nearby
wastewater treatment facilities.
Tools, equipment and the like fordecontamination work

When working on
roofs/rooftops of residences, schools, parks(small), parks (large) or large facilities(1.1.1, 1.1.2, 2.1.1, 3.1.1, 4.1.1, 5.1.1),(per 130m2)
Tools, equipment to use
QuantityDeckbrushes,scrubbing－brushes, etc.
Sprinkler
trucks(tank
0.6 service
capacity 3,800L)
days
Light oil
9.9L
Water
0.5m3
Temporary systems and the－like for wastewater collection* For the work at elevated places, adequate
safety measures shall be taken for scaffolds,
aerial lift work vehicles and fall arresting
devices/systems using fixed ropes/safety belts,
etc.
When working on exterior walls/outside
walls other than earthen walls of residences
and the like (1,2,1), exterior walls/outside
walls of schools, parks (small), parks (large),
large facilities, etc. (2.2.1, 3.2.1, 4.2.1, 5.2.1),
paved surfaces of grounds and the like, ofresidences and the like, schools, parks(small) and parks (large), parking lots
(concrete, asphalt) of large facilities (5.4.6)
and pedestrian overpasses (6.5.1),(per 1,300m2)
Tools, equipment to use
Quantity
Deck brushes, scrubbing brushes,
－
etc.
Water
5m3
Temporary systems and the like－for wastewater collection* For the work at elevated places, aerial lift work
vehicles and scaffolds shall be used.
When working on guardrails (6.3.1),(per 1,900m)
Tools, equipment to use
Quantity
Deck brushes, scrubbing brushes,
－
etc.

282

WaterTemporary systems and the likefor wastewater collection
Workforce needed

5m3－

When working on
roofs/rooftops of residences, schools, parks(small), parks (large) or large facilities(1.1.1, 1.1.2, 2.1.1, 3.1.1, 4.1.1, 5.1.1),(per 130 m2)
Workforce needed
Quantity
Operation leaders
0.6
worker-days
Decontamination workers
3.6
worker-days
Drivers (ordinary
0.4
decontamination)
worker-days■When working on

exterior walls/outside walls other thanearthen walls of residences and the like
(1,2,1), exterior walls/outside walls ofschools, parks (small), parks (large), large
facilities, etc. (2.2.1, 3.2.1, 4.2.1, 5.2.1),
paved surfaces of grounds and the like, ofresidences and the like, schools, parks(small) and parks (large) (1.4.2, 2.4.6, 3.4.6,
4.4.6), parking lots (concrete, asphalt) oflarge facilities (5.4.6) and pedestrian
overpasses,(per 1,300m2)
Workforce needed
Quantity
Operation leaders
4.2
worker-days
Decontamination workers
28.1
worker-days
When working on guardrails (6.3.1),(per 1,900m)
Workforce needed
Quantity
Operation leaders
4.2
worker-days
Decontamination workers
28.1
worker-days
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedBrush cleaning shall be done from top tobottom in order to prevent contaminationfrom spreading due to decontamination
work,
for
instance,when
cleaning
residential areas and the like, starting withroofs first followed by exterior walls,
gardens, etc.
Cleaning shall be done from above in order
to avoid water being scattered.

283

Rotary brushes shall not be used when
decontaminating thatched roofs or tiled
roofs, as they are not suitable for suchmaterials.
Whendecontaminatingpedestrian
overpasses, their handrails shall be cleaned
with brushes.
Radiation

exposure

Rubber hand gloves, dust masks and otherprotection of workers

protective gear shall be worn.

General labor safety ofworkers

For the work at elevated places, adequate
safety measures shall be taken for scaffolds,
aerial lift work vehicles and fall arresting
devices/systems using fixed ropes/safety
belts, etc.
For the work on roads, barricades and traffic
controllers shall be arranged.

Measures to prevent－

secondary wastes
Others－2843）High-pressure water cleaning
Locations to be
decontaminated“1.3.1. Roof gutters” of “1.3 Rainwater gutters” in “1. Residential areas
and the like”“1.3.2. Rainwater pipes” of “1.3 Rainwater gutters” in “1. Residential
areas and the like”“1.4.2. Paved surfaces” of “1.4. Gardens and the like” in “1. Residential
areas and the like”“2.1. Roofs/rooftops” at “2. Schools”“2.2. Exterior walls/outside walls” at “2. Schools”“2.3.1. Roof gutters” of “2.3. Rainwater gutters” at “2. Schools”“2.3.2 Rainwater pipes” of “2.3. Rainwater gutters” at “2. Schools”“2.4.6. Paved surfaces” of “2.4. Grounds and the like” at “2. Schools”“3.1. Roofs/rooftops” in “3. Parks (small)”“3.2.1 Exterior walls/outside walls” of “3.2. Exterior walls/outside walls”
in “3. Parks (small)”“3.3.1. Roof gutters” of “3.3. Rainwater gutters” in “3. Parks (small)”“3.3.2. Rainwater pipes” of “3.3. Rainwater gutters” in “3. Parks (small)”“3.4.6.Paved surfaces” of “3.4. Playgrounds and the like” in “3. Parks(small)”“4.1. Roofs/rooftops” in “4. Parks (large)”“4.2.1 Exterior walls/outside walls” of “4.2. Exterior walls/outside walls”
in “4. Parks (large)”“4.3.1. Roof gutters” of “4.3. Rainwater gutters” in “4. Parks (large)”“4.3.2. Rainwater pipes” of “4.3. Rainwater gutters” in “4. Parks (large)”“4.4.6.Paved surfaces” of “4.4. Playgrounds and the like” in “4. Parks(large)”“5.1.1. Roofs/rooftops” of “5.1. Roofs/rooftops” of “5. Large facilities”“5.2.1 Exterior walls/outside walls” of “5.2. Exterior walls/outside walls”
of “5. Large facilities”“5.3.1.” of “5.3. Rainwater gutters” of “5. Large facilities”“5.3.2. Rainwater pipes” of “5.3. Rainwater gutters” of “5. Large
facilities”“5.4.6. Parking lots (concrete, asphalt)” of “5.4. Playgrounds and thelike” of “5. Large facilities”“6.1.2. Roads/Sidewalks” of “6.1. Paved roads” of “6. Roads”“6.3.1. Guardrails” of “6.3. Guardrails” of “6. Roads”“6.5.1. Pedestrian overpasses” of “6.5. Pedestrian overpasses” of “6.
Roads”

Decontamination

High-pressure water cleaning

methods
OutlineRoofs/rooftops, exterior walls/ outside walls,
rainwater gutters (roof gutters, rainwater pipes）
in the residential areas, schools, parks and large
facilities; grounds and the like (paved surfaces);parking lots (concrete, asphalt); and paved
roads/sidewalks, guardrails, and pedestrian
overpasses
shallbecleanedbyusing
high-pressure water cleaning in the following
procedures
285

(i) Cleaning by using high-pressurecleaners(ii) Collecting waste water
Decontamination processes

water■When working on roof gutters of residences andthe like, schools, parks (small), parks (large) andlarge facilities (1.3.1, 2.3.1, 3.3.1, 4.3.1, 5.3.1)
The cleaning water discharge lines shall becleaned beforehand for smooth discharge. The
discharge shall be collected in rainwater
cisterns or the like. After collection, it shall betransferred to on-site or nearby wastewater
treatment facilities.
High-pressure water cleaning shall beapplied mainly where, for instance, it is too
narrow for a hand to reach for wiping.
High-pressure water of about 2 L/min below 5
MPa in principle shall be sprayed by using
high-pressure water cleaners, with attention
to avoid damaging rainwater gutters.
The spray nozzle shall be brought near theobjects to be cleaned (about 20 cm) at an
appropriate moving speed for achieving thecleaning effect.
The water cleaning shall be done from theupper stream to the lower stream ofgradients to avoid water scattering to thesurroundings.
■When working on rainwater pipes of residences
and the like, schools, parks (small), parks (large)
and large facilities (1.3.2, 2.3.2, 3.3.2, 4.3.2, 5.3.2),
Sediment, if any, shall be removed before thecleaning.
The cleaning water discharge lines shall becleaned beforehand for smooth discharge. The
discharge shall be collected in rainwater
cisterns and the like. After collection, it shallbe transferred to on-site or nearby
wastewater treatment facilities.
High-pressure water of about 2 L/min below 5
MPa in principle shall be sprayed by using
high-pressure water cleaners, with attention
to avoid damaging rainwater gutters.
■When working on paved surfaces in the gardens
and the like of residences and the like, grounds
and the like of parks (small), and pedestrian
overpasses (1.4.2, 3.4.6, 6.5.1); paved surfaces of
the grounds and the like at schools and parks(large), parking lots (concrete, asphalt) of large
facilities, and paved roads/sidewalks (2.4.6, 4.4.6,
5.4.6, 6.1.2),
High-pressure water of about 20 MPa in
286

principle shall be sprayed in about 20 L/m2 byusing suction-type high-pressure watercleaners.
The cleaning water collected shall betransferred to on-site or nearby wastewater
treatment facilities.
The water cleaning shall be done fromperipheries to inner sides and from the upperstream to the lower stream of gradients toavoid water scattering to the surrounding.
The cleaning shall be done in a shieldedenvironment in order to avoid water
scattering when buildings stand closely next
to each other.
■ When working on roofs/rooftops of schools,
parks (small), parks (large) and large facilities(2.1.1, 3.1.1, 4.1.1, 5.1.1),
The cleaning water discharge lines shall becleaned beforehand for smooth discharge. The
discharge shall be collected in rainwater
cisterns and the like. After collection, it shallbe transferred to on-site or nearby
wastewater treatment facilities.
High-pressure water of about 15 MPa in
principle shall be sprayed in about 20 L/m2
using high-pressure water cleaners.
The spray nozzle shall be brought near theobjects to be cleaned (about 20cm) at an
appropriate moving speed for achieving thecleaning effect.
The water cleaning shall be done fromperipheries to inner sides and from the upperstream to the lower stream of gradients toavoid water scattering to the surrounding.
The cleaning shall be done in a shieldedenvironment by using sheets or the like inorder to avoid water scattering.
Attention shall be paid to protect water-proof
paints or water-proof sheets from damage.
■When working on exterior walls/outside wallsof schools, parks (small), parks (large) and large
facilities (2.2.1, 3.2.1, 4.2.1, 5.2.1), or guardrails ofroads (6.3.1),
The cleaning water discharge lines shall becleaned beforehand for smooth discharge. The
discharge shall be collected in rainwater
cisterns and the like. After collection, it shallbe transferred to on-site or nearby
wastewater treatment facilities.
High-pressure water of about 15 MPa in
principle shall be sprayed in about 20 L/m2
using high-pressure water cleaners.
287

The spray nozzle shall be brought near theobjects to be cleaned (about 20 cm) at an
appropriate moving speed for achieving thecleaning effect.
The water cleaning shall be done fromperipheries to inner sides and from the upperstream to the lower stream of gradients toavoid water scattering to the surrounding.
Tools, equipment and the like fordecontamination work

■When working on roof gutters of residences andthe like, schools, parks (small), parks (large) andlarge facilities (1.3.1, 2.3.1, 3.3.1, 4.3.1, 5.3.1)(per 130m)
Tools, equipment to use
Quantity
Sprinkler
trucks(Tank
0.6 service
days
capacity 3,800L）
High-pressurecleaners
1.9 service
days(Motor-driven, Output 3.7kw）
Enginegenerators(rated1.9
17/20kvA,
exhaustgas service days
suppression type (primaryside))
Light oil
36.4 LWater
0.3 m3
Temporary systems and the－like for wastewater collection■When working on rainwater pipes of residences

and the like, schools, parks (small), parks (large)
and large facilities (1.3.2, 2.3.2, 3.3.2, 4.3.2, 5.3.2),(per 130m)
Tools, equipment to use
Quantity
Sprinkler
trucks(Tank
1.7 service
days
capacity 3,800 L）
High-pressurecleaners
1.4 service
days(Motor-driven, Output 3.7 kw）
Engine generators (rated 17/20
1.4 service
kvA, exhaust gas suppression
days
type (primary side))
Light oil46.1 LWater
0.3 m3
Temporary systems and the－like for wastewater collection■When working on paved surfaces in the gardens

and the like of residences and the like and parks(small), pedestrian overpasses (1.4.2, 3.4.6, 6.5.1),(per 300 m2)
Tools, equipment to use
Quantity
Suction-typehigh-pressure 1 service day
cleaners (discharge pressure
20.5MPa, vacuum pump）

288

Rotary-type water
vehicles (φ300)

collecting

1 service day

Sprinkler trucks (tank capacity
3,800L)
Crane trucks (load capacity 2 t,suspension weight 2.9 t)
Sewage filters (200 L)
Sewagetank(1m3
polyethylene)
Feedwater
tank
(1
m3
polyethylene)
Light oilWater

1 service day
1 service day
1 service day
6 service days
1 service day
53.3 L
6 m3■ When working on roofs/rooftops of schools,

parks (small), parks (large) and large facilities(2.1.1, 3.1.1, 4.1.1, 5.1.1),(per 1,300 m2)
Tools, equipment to use
Quantity
High-pressurecleaners
4.2(Engine-driven, output 18 kw)
service days
Streetdraincleaner4(Blower-type, hopper capacity service days
3.1m3, air-flow 20m3/min)
Sprinkler trucks (tank capacity
4.9
3,800 L)
service days
Engine-generators(Rated
4.2
17/20
kvA,
exhaustgas service days
suppression
type(primaryside))
Submersible motor pumps for
4.2
construction work (50 mm service days
caliber, total head 20 m)
Water tanks (for general
4.2
construction work, 3 m3)
service days
Light oil
196.2 LWater
27 m3
Temporary systems and the－like for wastewater collection■When working on exterior walls/outside wallsof schools, parks (small), parks (large) and large
facilities (2.2.1, 3.2.1, 4.2.1, 5.2.1),(per 1,300 m2)
Tools, equipment to use
Quantity
High-pressurecleaners
4.2(Engine-driven, output 18kw)
service days
Streetdraincleaners
4(Blower-type, hopper capacity service days
3.1 m3, air-flow 20 m3/min)289

Sprinkler trucks (tank capacity
3,800 L)
Light oil
Water
Temporary systems and thelike for wastewater collection

4.9
service days
183.9 L
27 m3－

■When working on paved surfaces in the school

grounds and the like and parks (large), parking
lots (concrete, asphalt) of large facilities, andpaved roads/sidewalks (2.4.6, 4.4.6, 5.4.6, 6.1.2),(per 350 m2)
Tools, equipment to use
Quantity
Suction-typehigh-pressure1
water
cleaners(discharge service day
pressure 20.5 MPa, vacuum
pump）
Rotary-type water collecting
1
serviceday
vehicles (φ450)
Sprinkler trucks (tank capacity
3,800L)
Crane trucks (load capacity 2t,
suspension weight 2.9t)
Sewage filters (200 L)
Sewage tank (1 m3 polyethylene)
Feedwatertankpolyethylene)
Light oil
Water

(1

m3

1
service day
1service day
1service day
7
service days
1
service day
53.3 L
7 m3■When working on road guardrails (6.3.1),

Tools, equipment to use
High-pressurecleaners(Engine-driven, output 18 kw)
Streetdraincleaners(Blower-type, hopper capacity
3.1 m3, air-flow 20 m3/min)
Sprinkler trucks (tank capacity
3,800 L)
Light oil
Water
Temporary systems and the likefor wastewater collection

Workforce needed(per 1,900 m)
Quantity
4.2
service days
4
service days
4.9
service days
183.1 L
27 m3－

■When working on roof gutters of residences andthe like, schools, parks (small), parks (large) and290

large facilities (1.3.1, 2.3.1, 3.3.1, 4.3.1, 5.3.1)(per 130 m)
Workforce needed
Quantity
Operation leaders
0.4
worker-days
Decontamination workers
2.1
worker-days
Drivers (ordinary
0.4
decontamination)
worker-days■When working on rainwater pipes of residences

and the like, schools, parks (small), parks (large)
and large facilities (1.3.2, 2.3.2, 3.3.2, 4.3.2, 5.3.2)(per 130 m)
Workforce needed
Quantity
Operation leaders
0.5
worker-days
Decontamination workers
2.2
worker-days
Drivers (ordinary
1.1
decontamination)
worker-days■When working on paved surfaces in the gardens
and the like of residences and the like and parks(small), pedestrian overpasses (1.4.2, 3.4.6, 6.5.1),(per 300 m2)
Workforce needed
Quantity
Operation leaders
1.0
worker-day
Specialized decontamination
1.0
workers
worker-day
Decontamination workers
3.0
worker-days
Drivers (ordinary
1.0
decontamination)
worker-day■ When working on roofs/rooftops of schools,
parks (small), parks (large) and large facilities(2.1.1, 3.1.1, 4.1.1, 5.1.1), exterior walls/outside
walls of schools, parks (small), parks (large) andlarge facilities (2.2.1, 3.2.1, 4.2.1, 5.2.1),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
2.1
worker-days
Decontamination workers
7.9
worker-days
Drivers (ordinary
6.2
decontamination)
worker-days■When working on paved surfaces in the school
grounds and the like and parks (large), parking
lots (concrete, asphalt) of large facilities, and291

paved roads/sidewalks (2.4.6, 4.4.6, 5.4.6, 6.1.2),(per 350 m2)
Workforce needed
Quantity
Operation leaders
1.0
worker-day
Specialized decontamination
1.0
workers
worker-day
Decontamination workers
3.0
worker-days
Drivers (ordinary
1.0
decontamination)
worker-day■When working on road guardrails (6.3.1),(per 1,900 m)
Workforce needed
Quantity
Operation leaders
2.1
worker-days
Decontamination workers
7.9
worker-days
Drivers (ordinary
6.2
decontamination)
worker-days
Idea
development,
lessons,
points to
keep inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

In order to prevent contamination fromspreading due to decontamination work, theorder of works shall be considered. For
instance, when decontaminating residential
areas and the like, the decontamination work
shall be done starting with roofs followed by
rainwater gutters and then gardens and thelike. If residences and the like stand closely
next to each other, the cleaning shall be donein a shielded environment by using sheets
and the like in order to avoid water scatteringover surrounding residences and the like.
No risk of damaging the objects by
high-pressure water cleaning shall bechecked beforehand. Attention shall be paid
to the possibility of damaging objects bystripping off the surface.
Soil shall be cleaned at low pressures first inorder to prevent soil dispersion. The pressure
shall be increased gradually by confirming
the cleaning water flows and dispersion
conditions.
Special attention shall be paid when cleaning
the overlapping sections of roofs, places
where the metal is corroded, and around thedrains for rooftops. At these places large
amounts of sediment are attached.
Paved surfaces shall not be cleaned whenfrozen or snow covered.
Suction-type high-pressure water cleaners
shall be used when cleaning paved surfaces ofgardens and the like of residences and the292like, grounds and the like, of parks (small),pedestrian overpasses (1.4.2, 3.4.6, 6.5.1),
those of school grounds and the like, parks(large), parking lots (concrete, asphalt) oflarge facilities, or paved roads/sidewalks(2.4.6, 4.4.6, 5.4.6, 6.1.2). When cleaningother objects, the discharge water shall becollected in the rainwater cisterns and thelike.
Cleaning conditions for decontaminating
respective objects shall be as follows in
principle.
Objects to be
decontaminatedRoofgutters(1.3.1,
2.3.1, 3.3.1, 4.3.1, 5.3.1)
and rainwater pipes(1.3.2, 2.3.2, 3.3.2, 4.3.2,
5.3.2) of residences andthe like, schools, parks(small), parks (large)
and large facilities
Roofs/rooftops(2.1.1,
3.1.1, 4.1.1, 5.1.1) andexterior
walls/outside
walls (2.2.1, 3.2.1, 4.2.1,
5.2.1) of schools, parks(small), parks (large),
and large facilities, androad guardrails (6.3.1)
Paved
surfacesofgardens and the like ofresidences and the like,groundsofparks(small), and pedestrian
overpasses (1.4.2, 3.4.6,
6.5.1), those of school
grounds and the like,parks (large), parking
lots (concrete, asphalt)of large facilities, andpaved roads/sidewalks(2.4.6, 4.4.6, 5.4.6, 6.1.2)
Radiation

exposure

Conditions(principle)
Cleaning with highpressure water ofabout 5 MPa in
about 2 L/m2, inprinciple, by using ahigh-pressure watercleaner
Cleaning with highpressure water ofabout 15 MPa in
about 20 L/m2, inprinciple, by using ahigh-pressure watercleaner
Cleaning with highpressure water ofabout 20 MPa in
about 20 L/m2, inprinciple, by using asuction-typehigh-pressure watercleaner

Safety glasses, dust masks, hand gloves, etc.

protection of workers

shall be worn

General labor safety ofworkers

For the work at elevated places, adequate
safety measures shall be taken for scaffolds,
aerial lift work vehicles and fall arresting
devices/systems using fixed ropes/safety
belts, etc.
For the work on roads, barricades and traffic
293controllers shall be arranged.
Measures to prevent－

secondary wastes
Others－2944）Shot-blasting
Locations to be
decontaminated“1.4.2. Paved surfaces” of “1.4. Gardens and the like” in “1. Residential
areas and the like”“2.4.6. Paved surfaces” of “2.4. Grounds and the like” at “2. Schools”“3.4.6.Paved surfaces” of “3.4. Grounds and the like” in “3. Parks(small)”“4.4.6.Paved surfaces” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.6. Parking lots (concrete, asphalt)” of “5.4. Grounds and the like” of“5. Large facilities”“6.1.2. Roads/Sidewalks” of “6.1. Paved roads” of “6. Roads”

Decontamination

Shot-blasting

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Paved surfaces of gardens/grounds in theresidential areas, schools, parks and large
facilities, etc.,, parking lots (concrete, asphalt),
and paved roads/sidewalks shall be cleaned by
shot-blasting in the following procedures(i) Scraping off object
surfaces withshot-blasters(ii) Packing scrapped materials
Scraping shall be done in a fairly wide paved
place.
Abrasive materials such as steel shot shallbe shot on the surface with a shot-blaster for
scraping away the said surface uniformly.
Scrapped materials, asphalt and the like,shall be collected by a dust collector
connected to the shot-blaster.
Collected scrapped materials shall bepacked in large sandbags.
Fine particles generated shall be prevented
from dispersion to the surroundings bycovers and shall be collected.
A small amount of abrasive materials left
behind on the surfaces shall be collected by amanual magnet car and cleaning.
■When working on paved surfaces of gardens

and the like, of residences and the like (1.4.2),(per 350 m2)
Tools, equipment to use
Quantity
Shot-blasters(scraping/
6.5
suction width 700 mm)
service hours
Engine-generators(Rated1.09
100/125 kvA, exhaust gas service days
suppression type (primaryside))

295

Dust collectors (suction width
700/1000 mm, wind velocity
75 m3)
Crane trucks (load capacity 4t, suspension weight 2.9 t)
Trucks (load capacity 4 t)
Light oil
Large sandbags

6.5
service hours
1.23
service days
1.13
service days
192 L-

■ When working on paved surfaces in the

grounds of schools, parks (small), and parks(large) (2.4.6, 3.4.6, 4.4.6,), parking lots
(concrete, asphalt) of large facilities (5.4.6), andpaved roads/sidewalks (6.1.2),(per 500 m2)
Tools, equipment to use
Quantity
Shot-blasters(scraping/
6.5
suction width 1,000 mm)
service hours
Engine-generators(Rated1.03
125/150 kvA, exhaust gas service days
suppression type (primaryside))
Dust collectors (suction width
6.5
700/1000 mm, wind velocity service hours
75 m3)
Crane trucks (load capacity 8
1.23t, suspension weight 2.9 t)
service days
Trucks (load capacity 8 t)
1.13
service days
Light oil
255 L
Large sandbags-

Workforce needed■When working on paved surfaces of gardens

and the like, of residences and the like (1.4.2),(per 350 m2)
Workforce needed
Quantity
Operation leader
1.0
worker-day
Decontamination worker
2.0
worker-days
Driver (special
2.0
decontamination)
worker-days
Driver (ordinary
1.0
decontamination)
worker-day■ When working on paved surfaces in the
grounds of schools, parks (small), and parks(large) (2.4.6, 3.4.6, 4.4.6,), parking lots296

(concrete, asphalt) of large facilities (5.4.6), andpaved roads/sidewalks (6.1.2),(per 500 m2)
Workforce needed
Quantity
Operation leader
1.0
worker-day
Decontamination worker
2.0
worker-days
Driver (special
2.0
decontamination)
worker-days
Driver (ordinary
1.0
decontamination)
worker-day
Idea
development,
lessons,
points to
keep inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

Paved surfaces shall not be cleaned whenfrozen or snow covered.
Work shall be halted when raining or roads
are wet because working and collecting ofscrapped materials is difficult.
It should be noted that the decontamination
effect by scraping is lowered when ruts or
cracks are present on the paved surfaces
relative to smooth surfaces.
This cleaning method is not effective when
the road unevenness or crack depths exceed
5 mm.
At the edges of blasted area, 5 – 10 cm
overlapping is needed for removing surface
irregularity.
High-pressure water cleaning and the likeshall be used in place of the shot-blasting
method at the edges of paved surfaces 15 –30 cm from adjacent buildings or otherstructures.

Radiation

Safety glasses, dust masks, hand gloves, etc.

exposureprotection of workers

shall be worn.

General labor safety ofworkers

For the work on roads, barricades and traffic
controllers shall be arranged.

Measures to prevent－

secondary wastes
OthersFor the work in narrow spaces of less thanabout 10 m2 of paved surfaces in residential
areas, unit space of 350 m2 shall be read as
50 m2 (tools, equipment, workforce needed).

2975）Superhigh pressure water cleaning
Locations to be
decontaminated“2.4.6. Paved surfaces” of “2.4. Grounds and the like” at “2. Schools”“4.4.6.Paved surfaces” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.6. Parking lots (concrete, asphalt)” of “5.4. Grounds and the like” of“5. Large facilities”“6.1.2. Roads/Sidewalks” of “6.1. Paved roads” of “6. Roads”

Decontamination

Superhigh pressure water cleaning

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Paved surfaces of schools, parks (large) and large
facilities, parking lots (concrete, asphalt), andpaved roads/sidewalks shall be cleaned bysuperhigh pressure water in the following
procedures(i) Scraping off object surfaces with superhigh-pressure water cleaners(ii) Collecting wastewater from decontamination
Paved surfaces shall be scraped off by about
5mm with superhigh pressure watercleaners (cleaning water recovery-type) of
150 MPa or higher.
Wastewater collected shall be separated toscrapings (sludge) and water by the
coagulating sedimentation process, or othermeans.
Tools, equipment to use
Shovels , brooms and the likeSuperhigh pressure watercleaners (240MPa maximum
pressure (including powerful
vacuum trucks)
Streetdraincleaners(Capacity 5.1 m3)
Engine-generators (Rated 3
kvA, Low-noise type)Air
compressor(Portable,
Exhaust gas suppression type(Primary side) 3.5-3.7 m3/min)
Sprinkler
trucks(Tank
capacity 3,800 L)
Light oil
Gasoline
Large sandbags

298(per 1,300 m2)
Quantity
3.7
service days
3.5
service days
2.9
service days
4.7
service days
4.3
service days
1,207.2 L
9.5 L-

Workforce needed
Workforce needed
Operation leaders
Specialized decontamination
workers
Decontamination workers
Drivers (special
decontamination)
Drivers (ordinary
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 1,300 m2)
Quantity
2.8
worker-days
5.8
worker-days
4.8
worker-days
2.7
worker-days
5.4
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

Paved surfaces shall not be cleaned whenfrozen or snow covered.
Superhigh pressure water cleaners may be
not appropriate for scraping near curbs.
Handy-type/edge-scraping type cleaners or
high-pressure water cleaners can be usedinstead (costs of handy-type cleaners shallbe reviewed). When non-water-recovery-type
cleaners are used, the work shall be done
under covers to prevent water dispersion
and the cleaning water shall be collectedfrom street drains.
Radiation dose after decontamination shallbe measured after the road surfaces are
dried.

Radiation exposure
protection of workers

Rainwear, safety glasses, dust masks, hand

General labor safety ofworkers

For the work on roads, barricades and traffic
controllers shall be arranged.

Measures to prevent
secondary wastes

Scrapings (sludge) collected by coagulating
sedimentation
shallbethoroughly
dehydrated and packed in large sandbags.

Othersgloves, etc. shall be worn.

－

2996）Cleaning by road sweepers
Locations to be“6.1.2 Roads/sidewalks” of “6.1 Paved roads” of “6. Roads”

decontaminatedDecontamination

Cleaning by road sweepers

methods
OutlineDecontamination processes

Tools, equipment for decontamination
work

Paved roads/sidewalks shall be cleaned by roadsweepers
Paved roads/sidewalks shall be cleaned byroad sweepers in preparation for the work bydecontamination workers or for maintenance.
Trash collected shall be packed in flexible
containers.
(per 1 km)
Quantity*3(service hours)

Tools, equipment to use
Shovels, brooms, brushes, etc.
Road sweepers (Brush-type,
Hoppercapacity
3.1m3,
4-wheeled)
Light oil
12 x *3 (L)Note) The estimate shall be changed, if sprinkler
trucks are needed.

Workforce needed
Workforce needed
Operation leaders
Decontamination workers
Drivers (ordinary
decontamination)
Assistants todecontamination workers*1: 0.8×T1/T×1/L*2: 1.2×T1/T×1/L*3: T1/L(per 1 km)
Quantity*1( worker-hours)*2(worker-hours)*3 x 0.14(worker-hours)*3 x 0.13(worker-hours)

T1=L/V1＋ℓ/V2
T1= Time required for work (h)L= Cleaning distance (km)V1= Cleaning speed (km/h)= 6.0 km/h (time forcarrying away trash included)ℓ= Distance of journey (km) =ℓ1＋ℓ2＋ℓ3＋ℓ4ℓ1= Distance between the workplace and surplus
soil repository (km)ℓ2= Distance between the workplace and water300

supply point (km)ℓ3= Distance between the workplace to the next
workplace (km) (assuming no need to clean in thesection and the section is longer thanℓ4= Distance between the workplace and the base(km)
In calculating the distance of journey (ℓ) above,following factors shall be considered.
Δ L= Cleaning distance per hopper of street
sweepers (km) = hopper capacity x hopper
coefficient/amountoftrash=(3.10×0.61)/0.1=18.91(km)V2= Driving speed (km/h) =30.0 km/h
T= Road sweeper operation time per day =7.6
h/day
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

Paved surfaces shall not be cleaned whenfrozen or snow covered.
Packing work of the contaminated materials
removed and collected into flexible containers
shall be done under covers to prevent dust
from dispersion.

Radiation exposure
protection of workers

Safety glasses, dust masks, rubber gloves,etc. shall be worn when working outdoors.

General labor safety ofworkers

Barricades and traffic controllers shall bearranged, as the work is done on the roads.

Measures to prevent－

secondary wastes
Others－301

（3） Weeds/lawns
1）Weeding, lawn mowing
Locations to be
decontaminated“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like.”“2.4.2. Weeds/lawns” of “2.4. Grounds and the like” at “2. Schools”“3.4.2. Weeds/lawns” of “3.4. Grounds and the like” in “3. Parks (small)”“4.4.2.Paved surfaces” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.2. Weeds/lawns” of “5.4. Grounds and the like” of “5. Large
facilities”“6.6.2. Weeds” of “6.6. Roadside trees” of “6. Roads”

Decontamination

Weeding, lawn mowing

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Weeds/lawns of residences, schools, parks, large
facilities, and roadside trees, etc. shall be mowed in
the following procedures(i) Weeding and mowing by mowers and the like((ii) Collecting/transferring mowed weeds/grass)(iii) Packing of mowed weeds/grass
Prior to removing sediment and surface soil,
weeds that may hinder the work shall be
removed or weeded by shoulder-type mowers
or by hand.
Packing of weeds/grass removed in large
sandbags■When working on unpaved surfaces of gardens
and the like of residences and the like (1.4.1) andgrounds and the like of parks (small) (3.4.2),(per 1,300 m2)
Tools, equipment to use
Quantity
Mowers (shoulder-type, cutter
18.9
edge 255mm)
service days
Gasoline
46.2 L
Large sandbags■ When working on grounds and the like, of
schools, parks (large) and large facilities, etc.
(2.4.2, 4.4.2, 5.4.2),(per 1,300 m2)
Tools, equipment to use
Quantity
Dump trucks (load capacity 2t)
0.1(2t)
service days
Mowers (shoulder-type, cutter
19.0
edge 255mm)
service days
Light oil
2.6 L

302

Gasoline
Large sandbags

46.2 L-■When weeding roadside trees (6.6.2),(per 1,300 m2)
Tools, equipment to use
Quantity
Mowers (shoulder-type, cutter
6.0
edge 255mm)
service days
Light oil
3.8 L
Gasoline
14.5 L
Large sandbags
Workforce needed■When working on unpaved surfaces of gardens
and the like of residences and the like (1.4.1) andgrounds and the like of parks (small) (3.4.2),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
1.8
worker-days
Specialized decontamination
10.2
workers
worker-days
Decontamination workers
1.5
worker-days■ When working on grounds and the like, of
schools, parks (large) and large facilities, etc.
(2.4.2, 4.4.2, 5.4.2),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
1.8
worker-days
Specialized decontamination
10.2
workers
worker-days
Decontamination workers
1.5
worker-days
Drivers (ordinary
0.1
decontamination)
worker-days■When working on roadside trees (6.6.2),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
1.3
worker-days
Specialized decontamination
3.2
workers
worker-days
Decontamination workers
5.5
worker-days
Drivers (special
0.1
decontamination)
worker-days

Idea
development,
lessons,

Prerequisites
andconstraints regarding
objects and locations

Decontamination work shall be halted when
the weeds/lawns to be decontaminated arefrozen or snow covered.
303

points
tokeepinmind, etc.

to be decontaminatedRadiation exposure
protection of workers

Safety glasses, masks, gloves, etc. shall be

General labor safety ofworkers

For the work on road shoulders, barricades
and traffic controllers shall be arranged.
Mowers are simple machines, but it is easy for
operators to be hurt. Measures shall be taken
to prevent minor collisions with machines.
<Major safety measures>
・ Availability of protective covers shall bechecked.
・ Proper mounting of protective covers shallbe checked.
・ Knife-proof gloves shall be worn.
・ A no-access area shall be set around theweed cutter (5 m).
・ Distance shall be reserved between weed
cutters (15 m).

Measures to prevent
secondary wastes

Cut weeds/grass shall be collected quickly inorder to prevent scattering by wind and rain.

Others

worn.

－

304

2）Deep mowing of lawns
Locations to be
decontaminated“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like.”“2.4.2. Weeds/lawns” of “2.4. Grounds and the like” at “2. Schools”“3.4.2. Weeds/lawns” of “3.4. Grounds and the like” in “3. Parks (small)”“4.4.2.Paved surfaces” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.2. Weeds/lawns” of “5.4. Grounds and the like” of “5. Large
facilities”

Decontamination

Sod cutting

methods
OutlineWeeds and lawns of unpaved surfaces of gardens
and the like of residences and the like, andgrounds of schools, parks, large facilities shall be
removed by sod cutting in the following
procedures(i) Lifting of lawns by sod cutters and the like((ii) Collecting mowed weeds/grass, roots and soil(iii) Packing of removed materials

Decontamination processes■ When working on weeds/lawns of unpaved
surfaces of gardens and the like of residences andthe like (1.4.1) and grounds and the like of parks(small) (3.4.2),
Lawns shall be removed (reproducible
shallow scraping of about 3 cm depth) using
manually-guided sod cutters and the likeafter mowing. Root mat layers shall bepreserved.
Removed materials shall be packed in large
sandbags.
Bumps shall be covered with soil, and soil of 3
– 6 mm depth shall be scattered over them.
■When working on weeds/lawns of grounds andthe like of schools, parks (large) and large
facilities and the like (2.4.2, 4.4.2, 5.4.2),
Large sod cutters, where possible, shall cut
deeply (reproducible shallow scraping ofabout 3 cm depth).
Where large sod cutters cannot gain access,manually-guided sod cutters and the likeshall cut deeply (about 3 cm).
Root mat layers shall be preserved.
Removed materials shall be packed in large
sandbags.
Bumps shall be covered with soil, and soil of 3
– 6mm depth shall be scattered over them.

305

Tools, equipment and the like fordecontamination work

■ When working on weeds/lawns of unpaved
surfaces of gardens and the like of residences andthe like (1.4.1), and grounds and the like of parks(small) (3.4.2),(per 1,300 m2)
Tools, equipment to use
Quantity
Manually-guided sod cutters18.8(cutting path 55 – 65 cm)
service days
Gasoline
63.0 LFresh soil for scattering over
6.5 m3lawns
Large sandbags■When working on weeds/lawns of grounds andthe like of schools, parks (large) and large
facilities, etc. (2.4.2, 4.4.2, 5.4.2),(per 1,300 m2)
Tools, equipment to use
Quantity
Backhoes (Excavators) (Crawler
2.1
type, Exhaust gas suppression service days
type
(secondary),
Standard
bucket capacity 0.28 m3 whenheaped (0.2 m3 when flatly
filled))Dump trucks (load capacity 2 t)
0.7
service day
Manually-guided sod cutters1.1(cutting path 55 – 65 cm)
service days
Light oil
73.5 L
Gasoline
3.7 L
Fresh soil for scattering over
6.5 m3lawns
Large sandbags-

Workforce needed■ When working on weeds/lawns of unpaved
surfaces of gardens and the like of residences andthe like (1.4.1), and grounds and the like of parks(small) (3.4.2),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
3.8
worker-days
Specialized decontamination
10.0
workers
worker-days
Decontamination workers
15.0
worker-days■When working on weeds/lawns of grounds andthe like of schools, parks (large) and large
facilities, etc. (2.4.2, 4.4.2, 5.4.2),

306

Workforce needed
Operation leaders
Specialized decontamination
workers
Decontamination workers
Drivers
decontamination)
Drivers (ordinary
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(special(per 1,300 m2)
Quantity
0.6
worker-days
0.6
worker-days
1.3
worker-days
1.3
worker-days
0.6
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedDecontamination work shall be halted when
the weeds/lawns to be decontaminated arefrozen or snow covered.

Radiation exposure
protection of workers

Safety glasses, masks and gloves shall be

General labor safety ofworkers(When mowers, sod cutters and heavy machinery
are used,)
Setting of color cones or cone bars is
recommended to designate working areas
in order to prevent minor accidents byworker-machine collisions or being caught
in a machine (Driver is in charge). (Whenmowers are used,)
Mowers are simple machines, but it iseasy for operators to be hurt. Measures
shall be taken to prevent accidents due tominor collisions.
<Major safety measures>
・ Availability of protective covers shall bechecked・ Proper mounting of protective covers
shall be checked.
・ Knife-proof gloves shall be worn.
・ A no-access area shall be set around theweed cutter (5 m).
・ Distance shall be reserved between weed
cutters (15 m).

Measures to prevent

－

worn.

secondary wastes
Others－307

（4） Gravel, crushed stones
1）Removal of gravel, crushed stones
Locations to be
decontaminated“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like.”“2.4.3. Gravel, crushed stone” of “2.4. Grounds and the like” at “2.
Schools”“3.4.3 Gravel, crushed stone” of “3.4. Grounds and the like” in “3. Parks(small)”“4.4.3. Gravel, crushed stone” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.3. Gravel, crushed stone” of “5.4. Grounds and the like” of “5. Large
facilities”“6.2.2. Road surfaces (roads of gravel, crushed stone)” of “6.2. Unpaved
roads” of “6. Roads”

Decontamination

Removal of gravel, crushed stone

methods
OutlineGravel, and crushed stone of unpaved surfaces ofgardens and the like of residences and the like, ofgrounds of schools, parks, large facilities, andunpaved road surfaces (roads of gravel or crushedstones) shall be removed in the following
procedures(i) Removing gravel and crushed stone(ii) Packing removed gravel and crushed stone

Decontamination processes■When working on gravel and crushed stone ofunpaved surfaces of gardens and the like ofresidences and the like (1.4.1), and of grounds andthe like of parks (3.4.3),
Gravel and crushed stone shall be uniformly
removed (to about 5 cm depth) with shovels
and the like, and packed in large sandbags.
When the existing gravel or crushed stone isless than 5 cm deep, the top layer about 5 cm
deep and including the soil underneath shallbe uniformly removed and be packed in large
sandbags.
■ When working on gravel and crushed stone
from grounds and the like of schools, parks(large), large facilities, etc. (2.4.3, 4.4.3, 5.4.3),
Gravel and crushed stone shall be uniformly
removed (to about 5 cm depth) with backhoes
and the like, and packed in large sandbags.
When the existing gravel or crushed stone isless than 5 cm deep, the top layer about 5 cm
deep and including the soil underneath shallbe uniformly removed and be packed in large308

sandbags.
■When working on gravel and crushed stone ofunpaved road surfaces (roads of gravel andcrushed stone) (6.2.2),
The top surface layer shall be scraped away
in a uniform thicknesses (about 5 cm from thetop) by backhoes and the like, and packed inlarge sandbags.
Tools, equipment and the like fordecontamination work

■When working on gravel and crushed stone ofunpaved surfaces of gardens and the like ofresidences and the like (1.4.1), and of grounds andthe like of parks (3.4.3),(per 1,300 m2)
Tools, equipment to use
Quantity
Shovels and the like
Large sandbags■ When working on gravel and crushed stone
from grounds and the like of schools, parks(large), large facilities, etc. (2.4.3, 4.4.3, 5.4.3),(per 1,000 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes(Crawler
type,
1.4
Exhaust gas suppression type service days
(secondary), Bucket capacity
0.45 m3 when heaped (0.35 m3
when flatly filled))
Backhoes(Crawler
type,
3.9
Exhaust gas suppression type service days
(secondary), Bucket capacity
0.28 m3 when heaped (0.2 m3
when flatly filled))
Backhoes(Crawler
type,
2.8
Exhaust gas suppression type service days
(secondary), Bucket capacity
0.13 m3 when heaped (0.10 m3
when flatly filled))
Light oil360.1 L
Large sandbags■When working on gravel and crushed stone ofunpaved road surfaces (roads of gravel andcrushed stones) (6.2.2),(per 1,300 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes(Crawler
type,
11.2
Exhaust gas suppression type service days
(secondary), Bucket capacity309

0.28m3 when heaped (0.20 m3
when flatly filled))
Vibratory rollers (Combined
type, 3.0 – 4.0 t weight)
Light oil
Large sandbags
Workforce needed

5.6
service days
565.2 L-

■When working on gravel and crushed stone ofunpaved surfaces of gardens and the like ofresidences and the like (1.4.1), and of grounds andthe like of parks (3.4.3),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
7.7
worker-days
Decontamination workers
51.4
worker-days■ When working on gravel and crushed stone
from grounds, and the like, of schools, parks(large), large facilities, etc. (2.4.3, 4.4.3, 5.4.3),(per 1,000m2)
Workforce needed
Quantity
Operation leaders
1.7
worker-days
Decontamination workers
11.1
worker-days
Drivers (special
8.1
decontamination)
worker-days■When working on gravel and crushed stone ofunpaved road surfaces (roads of gravel andcrushed stones) (6.2.2),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
2.7
worker-days
Decontamination workers
17.9
worker-days
Drivers (special
16.8
decontamination)
worker-days

Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedHeavy machinery (small backhoes and thelike) are preferable to the extent possible forbetter construction efficiency.

Radiation exposure
protection of workers

Masks, gloves and the like shall be worn
when working with shovels and the like.

310

General labor safety ofworkers

Setting of color cones or cone bars is
recommended to designate working areas inorder to prevent minor accidents byworker-machine collisions or being caught ina machine (Driver is in charge).
For the work on roads, barricades and traffic
controllers shall be arranged.

Measures to prevent

Attention is needed to prevent excessive
digging by machinery. Digging depth
indicators shall be set for construction.

secondary wastes
Others－311

（5） Soil
1）Surface soil removal from rainwater gutter drains, under-eaves, etc.
Locations to be
decontaminated■Surface soil removal from rainwater gutter drains, under-eaves, etc.
“2.4.4. Soil” of “2.4. Grounds and the like” at “2. Schools”“4.4.4. Soil” of “4.4. Grounds and the like” in “4. Parks (large)”“5.4.4. Soil” of “5.4. Grounds and the like” of “5. Large facilities”■Surface soil removal from the bases of trees such as roadside trees
and the like
“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like”“2.4.5. Planted vegetation” of “2.4. Grounds and the like” at “2. Schools”“3.4.5 Planted vegetation” of “3.4. Grounds and the like” in “3. Parks(small)”“4.4.5. Planted vegetation” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.5. Planted vegetation” of “5.4. Grounds and the like” of “5. Large
facilities”“6.6.3. Roadside trees” of “6.6. Roadside trees” of “6. Roads”

Decontamination
methods

Soil sediment removal from rainwater gutter drains, under-eaves, etc.
Surface soil removal near the bases of trees and roadside trees

OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Soil sediment of rainwater gutter drains,
under-eaves, etc. of schools, parks, large facilities,
etc. shall be removed in the following procedures.
Similarly, surface soil of gardens and the like ofresidences and the like, and grounds of schools,
parks, large facilities, etc., and soil near the basesof planted vegetation on the roads, trees, roadsidetrees, etc. shall be removed in the following
procedures,(i) Removing surface soil(ii) Packing removed soil
Fallen leaves and soil sediment shall becollected using a shovel or rake, etc. andpacked in large sandbags.
Tools, equipment to use
Shovels, rakes, etc.
Large sandbags

Workforce needed
Workforce needed
Operation leaders
Decontamination workers

312

Quantity(per 1,300 m2)
Quantity
2.0
worker-days
13.3
worker-daysIdea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

The work site could be a high dose level place(hereafter hot spot) depending on the rainfall
conditions. The work flow to designate a hot
spot and monitoring threshold criteria shallbe prescribed in advance in consultation withthe supervisory personnel by referring to theradiation levels around the hot spot.

Radiation
exposureprotection of workers

Masks and gloves shall be worn under dust
handling conditions
Protective gear shall be considered and ahalf-face mask and hand gloves (cotton,
rubber) shall be worn if the radiocesium
concentration is high in the soil to handle,
and if the work corresponds to the work
under high dust concentrations as designatedin relevant guidelines of the Ministry of
Health, Labour and Welfare(MHLW).
If the work site is a hot spot, color cones andthe like shall be arranged, as appropriate, forindicating the hot spot in order to facilitate
reducing the long-term exposure of workers.

General labor safety ofworkers

Safety measures shall be taken for the workwith heavy machinery (proper arrangement
for preventing minor collisions of adjacently
working heavy machinery, and adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)

Measures to prevent－

secondary wastes
Others－313

2）Scraping of surface soil
Locations to be
decontaminated“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like”“2.4.4. Soil” of “2.4. Grounds and the like” at “2. Schools”“3.4.4. Soil” of “3.4. Grounds and the like” in “3. Parks (small)”“4.4.4. Soil” of “4.4. Grounds and the like” in “4. Parks (large)”“5.4.4. Soil” of “5.4. Grounds and the like” of “5. Large facilities”“6.2.1. Road surfaces (soil)” of “6.2. Unpaved roads” of “6. Roads”

Decontamination

Scraping of surface soil

methods
OutlineSoil of unpaved gardens and the like of residences
and the like, of grounds and the like of schools,
parks, large facilities, etc. and the unpaved roadsurface (soil) shall be scraped off in the following
procedures,(i) Scraping off surface soil(ii) Packing scraped soil

Decontamination processes■ When working on the unpaved surfaces ofgardens and the like of residences and the like
(1.4.1), and of grounds and the like of parks(3.4.4),
The garden topsoil shall be uniformly scraped
away (about 5 cm deep) by using bamboo
rakes or similar instruments, and packed inlarge sandbags.
Work breakdown shall be standardized andworkers shall be instructed prior to the workin order to avoid non-uniformity of scraping
thicknesses among workers.
■When working on the soil of grounds and thelike of schools, parks (large), large facilities, etc.
(2.4.4, 4.4.4, 5.4.4),
The surface soil shall be uniformly scraped(about 5 cm deep) with backhoes and the like,and packed in large sandbags.
■ When working on the soil of unpaved roadsurfaces (6.2.1),
The surface soil shall be uniformly scraped(about 5 cm deep) with backhoes and the like,and packed in large sandbags.

Tools, equipment and the like fordecontamination work

■ When working on the unpaved surfaces ofgardens and the like of residences and the like
(1.4.1), and of grounds and the like of parks(3.4.4),314

Tools, equipment to use
Bamboo rakes and the like
Large sandbags

Quantity-■When working on the soil of grounds and thelike of schools, parks (large), large facilities, etc.
(2.4.4, 4.4.4, 5.4.4),(per 1,000 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoe (Crawler type, Exhaust
2.7
gas
suppression
type service days
(secondary), Bucket capacity
0.45 m3 when heaped (0.35 m3
when flatly filled))
Backhoe (Crawler type, Exhaust
2.0
gas
suppression
type service days
(secondary), Bucket capacity
0.28 m3 when heaped (0.20 m3
when flatly filled))
Backhoes(Crawler
type,
0.2
Exhaust gas suppression type service days
(secondary), Bucket capacity
0.13 m3 when heaped (0.10 m3
when flatly filled))
Light oil360.1 L
Large sandbags■ When working on the soil of unpaved roadsurfaces (6.2.1),(per 1,300 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes(Crawler
type,
8.0
Exhaust gas suppression type service days
(secondary), Bucket capacity
0.28 m3 when heaped (0.2 m3
when flatly filled))
Light oil
362.9 L
Large sandbags
Workforce needed■ When working on the unpaved surfaces ofgardens and the like of residences and the like
(1.4.1), and of grounds and the like of parks(3.4.4),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
5.0
worker-days
Decontamination workers
33.4
worker-days■When working on the soil of grounds and the315like of schools, parks (large), large facilities, etc.
(2.4.4, 4.4.4, 5.4.4),(per 1,000 m2)
Workforce needed
Quantity
Operation leaders
1.0
worker-days
Decontamination workers
6.5
worker-days
Drivers (special
4.9
decontamination)
worker-days■ When working on the soil of unpaved roadsurfaces (soil) (6.2.1),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
1.8
worker-days
Decontamination workers
11.8
worker-days
Drivers (special
8.0
decontamination)
worker-days
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

The scraping thickness shall be set before thework. During the work, the scraping
thickness shall be properly confirmed for suredose reduction.

Radiation exposure
protection of workers

Masks and hand gloves shall be worn.

General labor safety ofworkers

Safety measures shall be taken for the workwith heavy machinery (proper arrangement
for preventing minor collisions of adjacently
working heavy machinery, and adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)

Measures to prevent－

secondary wastes
Others－3163）Soil surface covering
Locations to be
decontaminated“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like”“2.4.4. Soil” of “2.4. Grounds and the like” at “2. Schools”“3.4.4. Soil” of “3.4. Grounds and the like” in “3. Parks (small)”“4.4.4. Soil” of “4.4. Grounds and the like” in “4. Parks (large)”“5.4.4. Soil” of “5.4. Grounds and the like” of “5. Large facilities”“6.2.1. Road surfaces (soil)” of “6.2. Unpaved roads” of “6. Roads”

Decontamination

Soil surface covering

methods
OutlineSoil of unpaved gardens and the like of residences
and the like, of grounds and the like of schools,
parks, large facilities, etc. and the unpaved roadsurface (soil) shall be covered in the following
procedures,(i) Covering of surface soil uniformly with fresh
uncontaminated soil,((ii) Short distance transfer of fresh soil to small
places for spreading)(iii) Compacting

Decontamination processes■ When working on the unpaved surfaces ofgardens and the like of residences and the like
(1.4.1), and of grounds and the like of parks(3.4.4),The surface, if its topsoil is scraped away,
shall be covered by fresh soil of similar
quality as before to a similar height.
The new topsoil shall be spread, leveled andcompacted back to the original height andsimilar porosity.
■When working on the grounds and the like ofschools, parks (large), large facilities, etc. (2.4.4,
4.4.4, 5.4.4),
The surface, if its topsoil is scraped away,
shall be covered by fresh soil of similar
quality as before to a similar height by using
backhoes and the like.
The new topsoil shall be spread, leveled andcompacted back to the original height andsimilar porosities.
■When working on the unpaved road surfaces(soil) (6.2.1),
The surface, if its topsoil is scraped away,
shall be covered by fresh soil of similar
quality as before to a similar height using
backhoes and the like.
317

The new topsoil shall be spread, leveled andcompacted back to the original maximum
height and similar porosity.
Tools, equipment and the like fordecontamination work

■ When working on the unpaved surfaces ofgardens and the like of residences and the like
(1.4.1), and of grounds and the like of parks(3.4.4),(per 1,300 m2)
Tools, equipment to use
Quantity
Shovels and the like.
Vibratory rollers (hand guide
15.8
type, 0.8 – 1.1 t weight)
service days
Light oil
56 L
Fresh soil for covering
72.2 m3■When working on the grounds and the like ofschools, parks (large), large facilities, etc. (2.4.4,
4.4.4, 5.4.4),(per 1,000 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes(Crawler
type,
1.1
Exhaust gas suppression type service days
(secondary), Bucket capacity
0.28 m3 when heaped (0.20 m3
when flatly filled))
Vibratory roller (Exhaust gas
1.5
suppression type (primary), service days
Combined type, 3 – 4 t)
Vibratory rollers (Exhaust gas
0.4
suppression
type, service days
manually-guided type, 0.5 – 0.6t)Dump trucks (load capacity 2 t)
1.8
service days
Light oil106.6 LFresh soil for covering
55.5 m3■When working on the unpaved road surfaces(soil) (6.2.1),(per 1,300 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes(Crawler
type,
19.0
Exhaust gas suppression type service hours(secondary), 0.28 m3 whenheaped (0.20 m3 when flat))Vibratory rollers (Exhaust gas
2.0
suppression type (primary),rollers per
Combined type, 3 – 4 t)
day

318

Light oil
Fresh soil for covering
Workforce needed

156.0 L72.2 m3■ When working on the unpaved surfaces ofgardens and the like, of residences and the like
(1.4.1) and of grounds and the like of parks (3.4.4),(per 1,300m2)
Workforce needed
Quantity
Operation leaders
3.3
worker-days
Specialized decontamination
11.5
workers
worker-days
Decontamination workers
10.7
worker-days■When working on the grounds and the like ofschools, parks (large), large facilities, etc. (2.4.4,
4.4.4, 5.4.4),(per 1,000 m2)
Workforce needed
Quantity
Operation leaders
0.7
worker-days
Specialized decontamination
0.4
workers
worker-days
Decontamination workers
4.7
worker-days
Drivers (special
2.6
decontamination)
worker-days
Drivers (ordinary
1.5
decontamination)
worker-days■When working on the unpaved road surfaces(soil) (6.2.1),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
3.5
worker-days
Specialized decontamination
6.9
workers
worker-days
Decontamination workers
1.4
worker-days
Drivers (special
3.0
decontamination)
worker-days

Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedIt was hard to secure similar soil/stones as
the original ones for the gardens of private
residences. Occasionally, it was difficult toobtain their consent to the materials evenwhen similar ones were offered.

Radiation
exposureprotection of workers

The work is often done combined withscraping work. Protective gear such as masks
shall be worn even though the dose decreases

319once fresh soil is spread.
General labor safety ofworkers

Measures to prevent

Safety measures shall be taken for the workwith heavy machinery (proper arrangement
for preventing minor collisions of adjacently
working heavy machinery, and adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)－

secondary wastes
Others－3204）Deep plowing
Locations to be
decontaminated“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like”“2.4.4. Soil” of “2.4. Grounds and the like” at “2. Schools”“3.4.4. Soil” of “3.4. Grounds and the like” in “3. Parks (small)”“4.4.4. Soil” of “4.4. Grounds and the like” in “4. Parks (large)”“5.4.4. Soil” of “5.4. Grounds and the like” of “5. Large facilities”“6.2.1. Road surfaces (soil)” of “6.2. Unpaved roads” of “6. Roads”

Decontamination

Deep plowing

methods
OutlineSoil of unpaved gardens and the like of residences
and the like, of grounds and the like of schools, parks,
large facilities, etc. and the unpaved road surface(soil) shall be plowed deeply in the following
procedures,(i) Excavating surface soil for temporary storage,(ii) Excavating sub-surface soil for temporary storage,(iii) Spreading and compacting of surface soil (in the
sub-surface layer)(iv) Spreading and compacting of sub-surface soil (inthe surface layer)(v) Leveling the top surface

Decontamination processes■When working on the unpaved surfaces of gardens
and the like of residences and the like (1.4.1), and ofgrounds and the like of parks (3.4.4),
The surface soil to about 10 cm depth shall be
uniformly scraped away by hand using shovels
and the like and be placed temporarily on plastic
sheets and the like.
The sub-surface soil to about 20 cm depth shallbe uniformly scraped away and be placed
temporarily apart from the surface soil storage.
The surface soil shall be spread in the
sub-surface layer using shovels. The sub-surface
soil shall be spread over it, leveled andcompacted to the original level with similar
porosity.
■ When working on the grounds and the like ofschools, parks (large), large facilities, etc. (2.4.4,
4.4.4, 5.4.4), and the unpaved road surfaces (soil)(6.2.1),The surface soil to about 10 cm depth shall be
uniformly scraped away by using backhoes andbe placed temporarily on plastic sheets and thelike.
The sub-surface soil to about 20 cm depth shallbe uniformly scraped away and be placed321temporarily apart from the surface soil storage.
The surface soil shall be spread with shovels byhand or using backhoes. The sub-surface soil
shall be spread over it, leveled and compacted tothe original level with similar porosity
Tools, equipment and the like fordecontamination work

■When working on the unpaved surfaces of gardens
and the like of residences and the like (1.4.1), and ofgrounds and the like of parks (3.4.4),
Tools, equipment to use
Quantity
Shovels and the like
Compactors (Dumpers)
Plastic sheets■ When working on the grounds and the like ofschools, parks (large), large facilities, etc. (2.4.4,
4.4.4, 5.4.4), and the unpaved road surfaces (soil)(6.2.1),(per 1,300 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes (Crawler type, Exhaust
7.9
gas suppression type (secondary), service days
Bucket capacity 0.28 m3 whenheaped (0.20 m3 when flat))
Backhoes (Crawler type, Exhaust
6.1
gas suppression type (secondary), service days
Bucket capacity 0.45 m3 whenheaped (0.35 m3 when flat))Vibratory rollers (Exhaust gas
7.9
suppression
type(primary), service days
combined type, 3 – 4 t)
Light oil
549.9 L
Plastic sheet-

Workforce needed■When working on the unpaved surfaces of gardens
and the like of residences and the like (1.4.1), and ofgrounds and the like of parks (3.4.4),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders26.0 worker-days
Decontamination workers
173.0
worker-days■ When working on the grounds and the like ofschools, parks (large), large facilities, etc. (2.4.4,
4.4.4, 5.4.4), and the unpaved road surfaces (soil)(6.2.1),

322

Workforce needed
Operation leaders
Specialized decontamination
workers
Decontamination workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 1,300 m2)
Quantity
1.3 worker-days
6.2 worker-days
8.5 worker-days

Prerequisites andconstraints
regarding objects
and locations to be
decontaminatedIn many cases, especially in residential areas,
this method is often not accepted because thecontaminated soil is not removed.

Radiation exposure
protectionofworkers

Dust masks and rubber gloves shall be worn
when working by hands using shovels and thelike.
Contaminated surface soil collected and piled up
forms temporary hot spots. Early backfill isdesirable before the radiation dose becomes high.

General labor safetyof workers

Safety measures shall be taken for the work withheavy machinery (proper arrangement for
preventing minor collisions of adjacently working
heavy machinery, and adequate instructions andsupervision, as well as thorough control for
preventing access to the machinery)

Measures to prevent－

secondary wastes
Others－323

（6） Garden trees, planted vegetation, roadside trees1）Surface soil removal from bases of trees and the like
The same as the soil sediment removal from rainwater gutter drains, under-eaves, etc. in
the residential areas, schools, parks, large facilities, roads, etc. explained in (5) 1).

2）Delimbing of garden trees, planted vegetation and roadside trees
Locations to be
decontaminated■Delimbing of garden trees“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like”■Delimbing of planted vegetation“2.4.5. Planted vegetation” of “2.4. Grounds and the like” at “2. Schools”“3.4.5. Planted vegetation” of “3.4. Grounds and the like” in “3. Parks(small)”“4.4.5. Planted vegetation” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.5. Soil Planted vegetation” of “5.4. Grounds and the like” of “5.
Large facilities”■Delimbing of roadside trees“6.6.3. Roadside trees” of “6.6. Roadside trees” of “6. Roads”

Decontamination

Delimbing of garden trees, planted vegetation and roadside trees

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Garden trees of residences and the like, planted
vegetation of the grounds of schools, parks, large
facilities, etc., and roadside trees shall bedelimbed in the following procedures.
(i) Delimbing of garden trees, hedges, planted
vegetation((ii) Collecting fallen leaves and the like and small
amount transfer of collected materials)(iii) Packing collected materials
Garden trees, hedges, planted vegetation androadside trees shall be delimbed or pruned byusing pruners and branch cutters, to an
extent that does not cause significant harm totheir growth according to the tree species andtheir delimbing period.
Branches trimmed off shall be packed inlarge sandbags. Too long branches for large
sandbags shall be chopped into short lengths
for packing■When working on garden trees of unpaved
surfaces of gardens and the like of residences andthe like (1.4.1), planted vegetation of the grounds
324and the like of schools, parks, large facilities, etc.
‘2.4.5, 3.4.5, 4.4.5, 5.4.5),
Tools, equipment to use
Rakes and the like
Chain saws (Edge length 350
mm, exhaust 34 cc))
Gasoline
Large sandbags

Quantity
6.5
service days
7.0 L-

■When working on roadside trees (6.6.3),(per 1,300 m2)
Tools, equipment to use
Quantity
Bamboo rakes and the like
Aeriallift
work
vehicles
11.2(Lift-mounted truck, beam-type, service days
work floor elevation 9.7 m)
Chain saws
20.0
(Edge length 350 mm, exhaust service days
34 cc))
Crane trucks (Load capacity 4 t,
3.3
Suspension weight 2.9 t)
service days
Light oil259.9 L
Gasoline
21.6 L
Large sandbags
Workforce needed■When working on garden trees of unpaved
surfaces of gardens and the like of residences andthe like (1.4.1), planted vegetation of the grounds
and the like of schools, parks, large facilities, etc.
‘2.4.5, 3.4.5, 4.4.5, 5.4.5),(per 1,300 m2)
Workforce needed
Quantity
Operation leaders
2.1
worker-daysPlant decontamination
11.5
workers
worker-days■When working on roadside trees (6.6.3),(per 1,300m2)
Workforce needed
Quantity
Operation leaders
4.2
worker-days
Specialized decontamination
9.0
workers
worker-days
Decontamination workers
8.0
worker-days
Drivers (special
10.7
decontamination)
worker-days

Idea
development,
lessons,

Prerequisites
andconstraints regarding
objects and locations

Subject to the heights of garden trees,
planted vegetation and roadside trees thedelimbing work becomes the same as the325points
tokeepinmind, etc.

to be decontaminatedpruning work of coniferous trees (11.1.3.1).
Some municipalities set rules to unify thepruning heights. Such cases shall be checkedin advance, and preparatory consultation
shall be carried out as needed.

Radiation

Safety glasses, dust masks, hand gloves, etc.

exposureprotection of workers

shall be worn.

General labor safety ofworkers

Workers shall wear safety glasses, whendelimbing and pruning, to prevent chips/dust
from getting into their eyes.
Work areas shall be clearly indicated and ano-access area shall be set.
Pruning with chain saws shall be done in astanding and stable posture.
When carrying a chain saw in the hands, theengine shall be switched off, braked, andcarried using both hands.
Allowable time for use shall be indicated oneach chain saw on a sticky tape and the like(to prevent vibration hazard)
For delimbing higher branches by using
branch-cutters and the like, working
positions shall be appropriately chosen toprevent the cut branches from hitting theworkers.

Measures to prevent－

secondary wastes
OthersRequests from some municipalities shall beconsidered to shake down twigs and leaves
stuck on the branches around the pruning
area.

326

3）Cutting of garden trees and planted vegetation
Locations to be
decontaminated■Cutting of garden trees“1.4.1. Unpaved surfaces” of “1.4. Gardens and the like” in “1.
Residential areas and the like”■Cutting of planted vegetation“2.4.5. Planted vegetation” of “2.4. Grounds and the like” at “2. Schools”“3.4.5. Planted vegetation” of “3.4. Grounds and the like” in “3. Parks(small)”“4.4.5. Planted vegetation” of “4.4. Grounds and the like” in “4. Parks(large)”“5.4.5. Soil Planted vegetation” of “5.4. Grounds and the like” of “5.
Large facilities”

Decontamination

Cutting of garden trees and planted vegetation

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Garden trees of residences and the like andplanted vegetation of the grounds of schools,
parks, large facilities, etc. shall be cut in thefollowing procedures.
(i) Cutting garden trees and hedges(ii) Pruning and cross-cutting(iii) Packing collected materials
Garden trees, hedges and planted vegetation
shall be cut using chain saws and the like.
Branches pruned and the like shall be packed
in large sandbags. Too long branches for large
sandbags shall be chopped into short lengths
for packing.
(per 13 trees)
Tools, equipment to use
Quantity
Chain saws
2.5
(Edge length 350 mm, exhaust service days
34 cc)
Gasoline
2.7 L
Large sandbags*Applicable when the diameter at the chest levelexceeds 6 cm.
*Rough terrain cranes, if needed, shall be selectedwhich meet the codes for field conditions.

Workforce needed
Workforce needed
Operation leaders
Plant decontamination
workers

327(per 13 pieces)
Quantity
0.9
worker-days
1.0
worker-day

Decontamination workers

4.9
worker-days*Applicable when the diameter at the chest levelexceeds 6 cm.
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

Trees to be cut shall be confirmed withstakeholders in presence and duly marked forpreventing possible trouble.

Radiation exposure
protection of workers

Safety glasses, masks, rubber gloves, etc.

General labor safety ofworkers

Workers shall wear safety glasses, whendelimbing and pruning, to prevent chips/dust
from getting into their eyes.
Work areas shall be clearly indicated and ano-access area shall be set.
Commencement of the cutting work shall besignaled to nearby workers in the
pre-arranged method.
Chain saws shall be operated in a stableposture.
When carrying a chain saw in the hands, theengine shall be switched off, braked andcarried using both hands.
Allowable time for use shall be indicated oneach chain saw on a sticky tape and the like(to prevent vibration hazard).

Measures to prevent

shall be worn.

－

secondary wastes
Others－328

（7） Other objects to be decontaminated
1）Wiping, cleaning and scraping of playground equipment
Locations to be
decontaminatedDecontamination“2.5.1. Playground equipment and the like”
equipment and the like” at “2. Schools”“3.5.1. Playground equipment and the like”
equipment and the like” in “3. Parks (small)”“4.5.1. Playground equipment and the like”
equipment and the like” in “4. Parks (large)”“5.5.1. Playground equipment and the like”
equipment and the like” of “5. Large facilities”

of “2.5. Playgroundof “3.5. Playgroundof “4.5. Playgroundof “5.5. Playground

Wiping, cleaning and scraping of playground equipment and the likemethods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Workforce needed

Playground equipment and the like of schools,
parks, large facilities, etc. shall be wiped, cleaned
or scraped.
Surfaces of playground equipment shall becleaned with water by using brushes,
cleaning cloths and the like. Neutral
detergents, vinegar (diluted acetic acid), etc.
shall be used as needed.
In wiping, cleaning cloths and the likemoistened with water and the like (including
neutral detergents, vinegar) shall be usedwith each face of the folded cloths used until
repeated wiping gives hardly any further
reduction in the surface contamination
density.
Tools, equipment to use
Cleaning cloths and the like
High-pressure water cleaners
Sand paper, grinders, etc.
Brushes, sand paper, electric
tools, etc.
Large sandbags

Quantity-(per piece of playground equipment)
Workforce needed
Quantity
Operation leaders
0.1
worker-days
Decontamination workers
0.4
worker-days* Applicable to two-seat swings (2.0 m high, 3.0 mwide), one way slides (2.0 m high, 40 cm wide x
4.0 m long slide face), etc.

329

Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

A fresh wiping face of the cloth shall be used
for each wiping step, in order to prevent
contaminants being reattached to theequipment.
Paper towels and the like shall be used forwiping of flat surfaces of painted equipment(horizontal bars, jungle gyms, etc.). Drybrushes shall be used on uneven surfaces
such as monuments at schools and the like.
Possibilities of paint stripping upon wiping
and brushing of playground equipment at
schools shall be discussed with theeducational committee in advance.

Radiation
exposureprotection of workers

Paper towels used for wiping shall not betouched with the bare hands, because they
may be contaminated with radiocesium.
The air dose rate in the working area shall beclearly indicated and the workers notified.
The dose rates in the decontamination
working area shall be measured in advanceand, if the dose rate is high, the area shall beclearly indicated by color cones, color conebars, etc.
Daily and accumulated exposure doses ofindividual workers shall be indicated in aneasily understandable way and kept undercontrol.
Unnecessary access to large packed sandbags
shall be restricted because of high dose rate
risk.
Protective equipment such as disposable
masks, rubber gloves, etc. shall be disposed ofat the pre-designated spots when the work isfinished.

General labor safety ofworkers

Protective equipment (masks, gloves, etc.)
shall be properly worn.
Stability and safety of work floors shall beensured for the work in high places such as 2m high swings.

Measures to prevent
secondary wastes

For volume reduction of secondary wastes,
paper towels and other disposable items usedin wiping work shall be pressed, or
suction-compressed by vacuum cleaners intosealed storage bags.

OthersWhenleavingtheworking
areas,
contamination on body surfaces shall bechecked as lower than 1,300 cpm
byscreening, which is stricter than theallowable limit of 13,000 cpm.

3302）Removal of bottom sediment from street drains and the like of roads
Locations to be
decontaminatedDecontamination“6.4.1. Street drains and the like” of “6.4. Street drains and the like” of“6. Roads”
Removal of bottom sediment from street drains and the like of roads

methods
OutlineBottom sediment of street drains and the like ofroads shall be removed in the following
procedures:(i) High-pressure water cleaning of bottom
sediment(ii) Suctioning up sediment(iii) Transfer of wastewater to a wastewater
treatment facility

Decontamination processes

Tools, equipment and the like fordecontamination work

High-pressure water of about 14 MPa fromdrainage pipe cleaners and the like shall be
used for cleaning in about 20 L/m3. The
wastewater shall be collected.
Sediment removed shall be packed in large
sandbags. The wastewater collected shall betransported to an on-site or nearby
wastewater treatment facility.
Tools, equipment to use
Shovels, brooms, etc.
Drainagepipecleaners(Floor-type, hopper capacity
10.3m3, air-flow 40m3/min)
Drainagepipecleaners(Floor-type, hopper capacity
3.1 m3, air-flow 40 m3/min)
Drainage pipe cleaner (Tank
capacity
2m3,
pressure
14MPa)
Light oil
Water

Workforce needed
Workforce needed
Operation leaders
Decontamination workers
Drivers (ordinary
decontamination)
Idea
development,

Prerequisites andconstraints regarding(per 1,300 m)
Quantity
4.0 service days
1.2 service days
5.3 service days
457.6 L
9.0 m3(per 1,300 m)
Quantity
4.1
worker-days
19.2
worker-days
8.1
worker-days

Sediment easily removable such as fallen
leaves, moss or mud shall be removed in331lessons,
pointstokeep
inmind, etc.

objects and locations
to be decontaminatedadvance by shovels and the like.
When the concrete joint gaps of street drains are
deep, a spatula or the like shall be used to remove
the sediment from the joint gaps.
The cleaning shall be done under covers to
avoid water scattering when buildings standclosely next to each other.
When cleaning covered street drains by using
high-pressure water, the cleaner shall beequipped with a spray nozzle forhigh-pressure water that is inserted in thestreet drains of the roads in order to clean thebottom, sides and top (backside of the cover)of the covered drains.
When a spray nozzle cannot be equipped on
the high-pressure water cleaner for covered
street drains, for instance when much sandhas flowed from mountains and slopes into
the street drains, the cover shall be removed
temporarily and cleaning shall be done byhand.
When removing sediment with hand by using
shovels and the like from street drains
without a cover, wheelbarrows shall be used
for transferring sediment removed to a
nearby spot for collection, as the road surface
is smooth.
Before commencing the high-pressure watercleaning of street drains, the wastewater
discharge lines shall be checked, and small
sandbags shall be lined up to dam the street
drains downstream. The wastewater shall becollected by a street drain cleaner. Small
sandbags containing zeolites shall be placeddownstream to prepare for possible overflow
incidents.

Radiation
exposureprotection of workers

The dose rates in the working area shall be
indicated clearly and the workers notified.
The dose rates in the decontamination
working area shall be measured in advanceand, if the dose rate is high, the area shall beclearly indicated by color cones, color conebars, etc.
Daily and accumulated exposure doses ofindividual workers shall be indicated in aneasily understandable way and kept undercontrol.
Unnecessary access to large packed sandbags
shall be restricted because of their high dose
rate risk.
Protective equipment such as disposable
masks, rubber gloves, etc. shall be disposed of332

at the pre-designated spots when the work isfinished.
General labor safety ofworkers

Measures to prevent

Protective equipment (masks, gloves, etc.)
shall be properly worn.
No one shall stand in the water jet zones at
the time of high-pressure water cleaning.
Attention shall be paid not to cut the fingers
when cleaning street drains by hand using
spatulas or the like.
－secondary wastes

OthersWhenleavingtheworkingarea,
contamination on body surfaces shall bechecked as lower than 1,300 cpm
byscreening, which is stricter than theallowable limit of 13,000 cpm.

333

6.1.2. Slopes
1）Removal of weeds, fallen leaves and sediment on slopes
Locations to be“7.1.1. Weeds, fallen leaves, sediment” of “7.1. Slopes” of “7. Slopes”

decontaminatedDecontamination

Removal of weeds, fallen leaves and sediment on slopes

methods
OutlineWeeds, fallen leaves and sediment on slopes shallbe removed in the following procedures:(i) Branches and leaves, shrubs, weeds, etc. which
can impede decontamination work shall be
removed (weeding, cutting) with shoulder-type
mowers, sickles, etc.
(ii) Weeds, fallen leaves and sediment shall be
removed.
(iii) Transferring removed materials(iv) Packing removed materials

Decontamination processes

Tools, equipment and the like fordecontamination work

Sediment such as fallen leaves, moss, mud,etc. shall be removed by rakes and other tools
and packed in large sandbags.
Tools, equipment to use
Mowers (shoulder-type, cutter
diameter 255 mm)
Light oil
Sand paper, grinder, etc.
Gasoline
Large sandbags

Workforce needed
Workforce needed
Operation leaders
Specialized decontamination
workers
Decontamination workers
Drivers (special
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated(per 1,300 m2)
Quantity
6.5
service days
0.2
service days
7.4 L
18.6 L(per 1,300 m2)
Quantity
1.8
worker-days
3.5
worker-days
8.2
worker-days
0.2
worker-days

Before sediment removal, weeds, which can
impede the work, shall be removed by using ashoulder-type mower or by hand.
The amount of sediment removal (depth to be
removed) shall be determined by test trials.
When decontaminating slopes with a cut

334surface, the conditions of any nets shall bechecked before the work.
When working on long and big slopes, thearea within about 20 m from the living spaceshall be covered with due attention to theusage status and other conditions ofsurrounding areas.
When the slopes need protective measures ofvegetation, appropriate construction methods
shall be chosen in accordance with the“Guidelines of road construction methods for
slope protection and stabilization (June 2009,
Japan Road Association)
Radiation exposure
protection of workers

Safety glasses, dust masks, gloves, etc. shall

General labor safety ofworkers

When working on steep slopes and badfooting slopes, slip prevention measures shallbe ensured by using fixed ropes, safety belts,
sliding devices on fixed ropes, etc.
For work on roadside slopes, barricades andtraffic controllers shall be arranged.

be worn.

Measures to prevent
secondary wastes－

Others

The following points shall be noted whencollecting contaminated objects on slopes:
Transfer methods of large sandbags
containing contaminated materials removed
on the slopes (especially transfer upward)
Crossing methods of rivers, brooks and thelikeNecessary consultations with supervisors onthese collection methods335

6.1.3. Rice Fields, Dry Fields, Pastures, etc.
（1） Weeds
1）Weeding by hand in rice fields and dry fields
Locations to be
decontaminated“8.1.1. Weeds” of “8.1. Rice fields” in “8. Farmland”“8.2.1. Weeds” of “8.2. Dry fields” in “8. Farmland”

Decontamination

Weed removal in rice fields and dry fields

methods
OutlineRice fields and dry fields shall be weeded using
shoulder-type mowers or the like

Decontamination processes

Weeds in rice fields and dry fields shall be
removed by using shoulder-type mowers or
the like

Tools, equipment and the like fordecontamination work

Tools, equipment to use
Mowers (Shoulder-type, cutter
diameter 255 mm)

Workforce needed
Workforce needed
Operation leaders
Specialized decontamination
workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

Quantity(per 100 m2)
Quantity
0.02
worker-days
0.23
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedWeeds in narrow places, slopes and the like
where large mechanized weeding equipment
is not applicable.

Radiation
exposureprotection of workers

Protective equipment such as dust masks
shall be properly worn to protect against dust
blown up by mowers.

作業員の一般労働安全対策

Non-associated personnel shall be kept fromthe working place, as accidents often occur
due to insufficient education on machinery
use or kickbacks by mowers.
To prepare for flying stones, protective
equipment shall be properly worn, forexample, wearing safety goggles and the like,or placing protective nets.

Measures to prevent－

secondary wastes
Others－3362）Weeding by machines in rice fields and dry fields
Locations to be
decontaminated“8.1.1. Weeds” of “8.1. Rice fields” in “8. Farmland”“8.2.1. Weeds” of “8.2. Dry fields” in “8. Farmland”

Decontamination

Weeding by machines in rice fields and dry fields

methods
OutlineWeeding by machines in rice fields and dry fields

Decontamination processes

Weeds in rice fields and dry fields shall be
removed using farm tractors or the like.

Tools, equipment and the like fordecontamination work(per 1,000 m2)
Tools, equipment to use
Quantity
Farm
tractors(110PS,
0.27
wheel-type)service hours
Off-set shredders
0.04(working width 200 cm)
service days
Light oil
3.0 L

Workforce needed
Workforce needed
Operation leaders
Drivers (special
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 1,000 m2)
Quantity
0.01
worker-days
0.05
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

The work shall be done in areas which exceed
a certain size (more than 1,000 m2) andwhere machinery has no risks of overturning.

Radiation
exposureprotection of workers

Protective equipment such as dust masks
shall be properly worn to protect against dust
blown up.

General labor safety ofworkers

Safety measures shall be taken for the workwith heavy machinery (proper arrangement
for preventing minor collisions of adjacently
working heavy machinery, and adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)

Measures to prevent－

secondary wastes
Others－3373）Collection of weeds removed from rice fields and dry fields
Locations to be
decontaminated“8.1.1. Weeds” of “8.1. Rice fields” in “8. Farmland”“8.2.1. Weeds” of “8.2. Dry fields” in “8. Farmland”

Decontamination
methods

Collection of contaminated weeds removed from rice fields and dryfieldsOutlineWeeds removed from rice fields and dry fields
shall be collected

Decontamination processes

Tools, equipment and the like fordecontamination work

Weeds removed shall be collected by using
hay collectors, packing machines for weeding,and other machines.
(per 1,000 m2)
Tools, equipment to use
Quantity
Hay collectors
0.63 service(Hand guided-type, 120cm)
days
Packing machines for weeding 0.59 service
days
(Hand
guided-type,φ
500x700))
Gasoline
21.3 L

Workforce needed
Workforce needed
Operation leaders
Drivers (special
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 1,000 m2)
Quantity
0.06
worker-days
1.16
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

The work shall be done in areas exceeding acertain size (more than 1,000 m2) and wheremachinery has no risks of overturning.

Radiation
exposureprotection of workers

Protective equipment such as dust masks
shall be properly worn to protect against dust
blown up.

General labor safety ofworkers

Safety measures shall be taken for work withheavy machinery (proper arrangement for
preventing minor collisions of adjacently
workingheavy
machinery,adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)

Measures to prevent－

secondary wastes
Others－3384）Weeding of grassland
Locations to be“8.3.1. Weeds” of “8.3. Grassland” in “8. Farmland”

decontaminatedDecontamination

Weeding of grassland

methods
OutlineWeeding of grassland

Decontamination processes

Weeds in grassland shall be removed by using
farm tractors or the like.
Weeds removed shall be formed in roll bales.

Tools, equipment and the like fordecontamination work

Tools, equipment to use
Farm tractors (Riding-type,wheel-type, four-wheel drive,
52 -59kw class (70 – 80PS))
Flail mowers (Direct mounttype) (1.5 m wide)
Roll balers (1.0 m wide, 1.0 m
tall)
Rake (3.6 m wide)
Beam sprayers (600 L, 12.3m
Wide)
Trucks (Load capacity 4.0 – 4.5
t)Light oil
Herbicide
Water

Workforce needed
Workforce needed
Operation leaders
Drivers (ordinary
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per ha)Quantity
5.3
service hours
0.5
service days
0.1
service days
0.1
service days
0.1
service days
0.3
service hours
39.7L
5.0L
0.6m3
(per ha)Quantity
0.17
worker-days
1.1
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

The work shall be done in areas exceeding acertain size (more than 1,000 m2) and wheremachinery has no risks of overturning.

Radiation
exposureprotection of workers

Protective equipment such as dust masks
shall be properly worn to protect against dust
blown up from weeding and roll discharging.

General labor safety ofworkers

Safety measures shall be taken for the workwith heavy machinery (proper arrangement
for preventing minor collisions of adjacently339

working heavy machinery, and adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)
Measures to prevent－

secondary wastes
Others－340

（2） Soil
1）Leveling of unevenness
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”

Decontamination

Leveling of unevenness in rice fields and dry fields

methods
OutlineUnevenness of soil in rice fields and dry fields
shall be leveled.

Decontamination processes

Unevenness of surface soil shall be leveled byusing vibratory rollers or the like.

Tools, equipment and the like fordecontamination work

Tools, equipment to use
Vibratory rollers (Riding-type
combined roller 3 t, Exhaustgas
suppression
type(primary))
Light oilWorkforce needed
Workforce needed
Operation leaders
Drivers (special
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 1,000 m2)
Quantity
1.25
service hours
3.8 L(per 1,000 m2)
Quantity
0.02
worker-days
0.29
worker-days

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedCombined rollers shall not be used in flooded
rice fields, because rollers sink in the fields
and lose mobility
Mobility of combined rollers shall be checkedin advance.
Basically no decontamination work shall bedone during rain storms or in pooled water
areas, because the surface layer of the arable
land will be kneaded.

Radiation

Dust masks, gloves, etc. shall be worn

exposureprotection of workers
General labor safety ofworkers

No one other than the operation leader andthe designated driver is allowed to enter thefields to level the unevenness with combinedrollers.
Existing access routes, if suitable, shall be
used for entering the field for leveling theunevenness.
If no access route is available, the combined341

roller shall enter the field slowly at a rightangle to the ridge along the field. This is to
avoid the roller overturning.
If the slope of the entry route crossing theridge along the field is too steep, a new entry
route shall be constructed in order to preventthe roller from overturning.
It shall be checked that no new big holes weremade by wild bores or the like after weeds
were removed and collected.
Measures to prevent－

secondary wastes
Others－3422）Spreading surface solidifiers
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”

Decontamination

Spreading surface solidifiers

methods
OutlineSurface solidifiers shall be spread on the soil of rice
fields and dry fields

Decontamination processes

Tools, equipment and the like fordecontamination work

Solidifier solution shall be spread on the soil
by using a seed scatterer or the like. The
surface soil shall be checked as firmly
solidified.
The following conditions are assumed forsurface soil solidification: the amount ofsolidifier 15 t/ha, the depth of solidification 2 –3 cm, solidification time required 7 days
(consecutive dry days).
The water to prepare the solidifier solution(solvent) shall be checked in advance that noradioactive materials can be detected in it.
(per 1,000 m2)
Tools, equipment to use
Quantity
Seeders (Riding-type , 1.0 m3)
2.14
service hours
Air compressors (25PS, 0.7 MPa,
0.36
3
2.5 m /min)service days
Crane truck (Load capacity 4 t,
3.25
suspension weight 2.9 t)
service hours
Sprinkler truck
1.11(Tank capacity 3,800 L)
service hours
Light oil
36.9 L
Surface solidifier (neutral)
1.5 t

Workforce needed
Workforce needed
Operation leaders
Specialized decontamination
workers
Decontamination workers
Drivers (special
decontamination)
Drivers (ordinary
decontamination)
Idea

Prerequisites and(per 1,000 m2)
Quantity
0.26
worker-days
0.62
worker-days
0.31
worker-days
0.56
worker-days
0.22
worker-days

No work shall be done in winter, as the343

development,
lessons,
pointstokeep
inmind, etc.

constraints regarding
objects and locations
to be decontaminatedsolidifier does not work.
Weather conditions affect the time required forsolidification.
No spreading of solidifier shall be allowed onwater retaining spots.

Radiation

Safety glasses, dust masks, etc. shall be worn.

exposureprotection of workers
General labor safety ofworkers

The worker controlling the nozzle and theassistant must wear safety glasses to prevent
solidifiers from entering the eyes.
The nozzle shall be firmly held so as not to bewhipped about by the hose pressure.
After the hose is firmly held, the signal shallbe given to start spreading of solidifiers.
The moving parts of the seed scatterer shall becovered to prevent the operator from beingcaught in them.

Measures to prevent

The solidifiers shall be procured in flexible

secondary wastes

containers.

Others－3443）Scraping the surface soil
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Scraping of surface soil (standard transfer method)

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Surface soil of rice fields, dry fields and grasslandshall be scraped away (standard transfer method)
The surface soil shall be scraped away byusing backhoes or the like (to about 5 cm
depth)
When scraping the surface soil in big areas of morethan 30a,(per 100 m2)
Tools, equipment to use
Quantity
Backhoes(Crawler-type,
0.48
exhaustgas
suppression service hours(primary), Bucket capacity 0.45
m3 when heaped (0.35 m3, when
flatly filled))
Light oil
5.3 L
*This applies when topography and field conditions
are relatively favorable and the area has about
30a in regular shape.
■When scraping the surface soil in small areas ofless than 30a,(per 100 m2)
Tools, equipment to use
Quantity
Backhoe (Crawler-type, exhaust
0.56
gas
suppression(primary), service hours
Bucket capacity 0.45 m3 whenheaped (0.35 m3, when flatly
filled))Light oil
6.2 L
*This applies when the field conditions are notfavorable, e.g., the field is not regular in shape.

Workforce needed■When scraping the surface soil in big areas ofmore than 30a,(per 100 m2)
Workforce needed
Quantity
Operation leaders
0.03
worker-days
Decontamination workers
0.18
worker-days345

Drivers (special
0.08
decontamination)
worker-days*This applies when topography and field conditions
are relatively favorable and the area is about 30ain regular shape.
■When scraping the surface soil in small areas ofless than 30a,(per 100 m2)
Workforce needed
Quantity
Operation leaders
0.09
worker-days
Decontamination workers
0.26
worker-days
Driver (special decontamination)
0.09
worker-days*This applies when the field conditions are notfavorable, e.g., the field is not regular in shape.
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedNo work shall be done in flooded rice fields.

Radiation

Masks, gloves, etc. shall be worn.

exposureprotection of workers
General labor safety ofworkers

Measures to prevent

The working areas shall be marked with color
cones, color cone bars, etc. for access control inorder to prevent minor collisions between
backhoes.
－secondary wastes
OthersBanners or the like shall indicate where aerial wires
run above farm roads or farmland, and a traffic
controller shall be arranged in order to prevent
damaging aerial wires when passing under them.

3464）Deep plowing
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Deep plowing

methods
OutlineSoil in rice fields and grassland shall be plowed
deeplyDecontamination processes

Tools, equipment and the like fordecontamination work

The base mat shall be flattened by double
plowing of surface soil by rotary tillers or the
like.
Tools, equipment to use
Farm tractors (Riding-type,wheel-type, four wheel driven
22kW-class (30PS)
Light oilWorkforce needed
Workforce needed
Drivers (ordinary
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 10,000 m2)
Quantity
26.0
service hours
67.6 L(per 10,000 m2)
Quantity
5.0
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedNo work shall be done in flooded rice fields
where the tractors may not be operable.
Mobility of wheel-type tractors shall bechecked in advance.

Radiation exposure
protection of workers

Masks, gloves, etc. shall be worn.

General labor safety ofworkers

No one other than the designated driver shallbe allowed to enter the fields to plow deeply.
Existing access routes, if suitable, shall be
used for entering the fields.
If no access route is available, the tractor shallenter the field slowly moving forward at aright angle to the ridge along the field. This is
to avoid the tractor overturning.
If the slope of the entry route crossing theridge along the field is too steep, a new entry
route shall be constructed in order to preventthe tractor from overturning.
It shall be checked that no new big holes weremade by wild bores or the like after weeds
347were removed and collected.
Counter weights shall be attached to thetractor with a mounted rotary tiller, as
appropriate, according to the instruction
manual of the tractor when it enters or leaves
the field (ascends or descends a ridge along thefield), because the center of gravity of the
tractor moves backward and the tractor issusceptible to overturning.
A rotary tiller shall be mounted or demounted
on a flat place such as a farm road with thetractor engine switched off.
When doing maintenance on the rotary tiller,
for example its cutting edges, not only theengine shall be switched off, but the rotary
shall be locked and held from below by a tableor the like to avoid its dropping suddenly.
Measures to prevent－

secondary wastes
Others－3485）Deep tillage
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Deep tillage

methods
OutlineSurface soil of rice fields, dry fields and grasslandshall be tilled deeply.

Decontamination processes

The fields shall be tilled twice (tillage depthof about 30 cm) by using a deep tilling rotary
tiller.

Tools, equipment and the like fordecontamination work(per 10,000 m2)
Tools, equipment to use
Quantity
Farm tractors (Riding-type,4.3
wheel-type four wheel driven 52 service days
- 59kw-class (70 - 80PS),
22kw-class (30PS)
Light oil
60.0 L

Workforce needed
Workforce needed
Drivers (ordinary
decontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 10,000 m2)
Quantity
4.0
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminated

The farmland where the soil was stirred byplowing after the accident shall be tilled inreverse or deeply.
Deep tillage may damage the roots inorchards, tea plantations and other farmland
where perennial produce is planted.
If the ground below the tilling depth isrudaceous, precautions shall be taken, forexample, to remove the gravel beforehand
because the gravel may come up in the tilling
layer by deep tillage.
The underground water level shall bemeasured, if required, so necessary
precautions may be taken in deep tilling.
When the surface soil is frozen due to lowtemperatures, small-size tractors may not be
sufficient for deep tilling.

Radiation

Safety glasses, dust masks, rubber gloves,

exposureprotection of workers

etc. shall be worn.

General labor safety ofworkers

No one other than the designated driver shallbe allowed to enter the fields to till deeply.

349

Existing access routes, if suitable, shall be
used for entering fields.
If no access route is available, the tractor
shall enter the field slowly moving forward at
a right angle to the ridge along the field. This
is to avoid the tractor overturning.
If the slope of the entry route crossing theridge along the field is too steep, a new entry
route shall be constructed in order to preventthe tractor from overturning.
It shall be checked that no new big holes weremade by wild bores or the like after weeds
were removed and collected.
Counter weights shall be attached to thetractor with a mounted rotary tiller, as
appropriate, according to the instruction
manual of the tractor when it enters or leaves
the field (ascends or descends a ridge along
the field), because the center of gravity of the
tractor moves backward and the tractor issusceptible to overturning.
A rotary tiller shall be mounted or demounted
on a flat place such as a farm road with thetractor engine switched off.
When doing maintenance on the rotary tiller,
for example its cutting edges, not only theengine shall be switched off, but the rotary
shall be locked and held from below by a tableor the like to avoid its dropping suddenly.
Measures to prevent－

secondary wastes
Others－3506）Soil replacement
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Soil replacement

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Surface soil of rice fields, dry fields and the likeshall be replaced with fresh soil in the following
procedures.
(i) Bringing in and spreading fresh soil(ii) Short transferring of fresh soil to narrowplaces and spreading.
(iii) Compacting
After scraping the soil off the surface, heavymachinery shall be used for replacing,spreading and leveling the fresh soil back to
the original elevation.
The MOE supervisory personnel shall be
consulted for determining the quality of
replacing fresh soil.
Results of soil tests including grain sizes andradioactive material concentration
measurement in the replacement fresh soil
shall be reviewed and approved before use by
the MOE supervisory personnel.

(per 1,000 m2)
Tools, equipment to use
Quantity
Shovels and the like
Backhoes(Crawler-type,1.1
exhaustgas
suppression service days
(secondary), Bucket capacity
0.28 m3 when heaped (0.20m3,
when flatly filled))
Vibratory rollers (Exhaust gas
1.5
suppression (primary), combined service days
type 3 – 4 t)
Vibratory rollers (Exhaust gas
0.4
suppression (primary), combined service day
type 3 – 4 t)
Dump trucks (Load capacity 2 t)
1.8
service days
Light oil106.6 LFresh soil
55.5 m3

351

Workforce needed

Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 1,000 m2)
Workforce needed
Quantity
Operation leaders
0.7
worker-days
Specialized
decontamination
0.4
workers
worker-days
Decontamination workers
4.7
worker-days
Drivers (special
2.6
decontamination)
worker-days
Drivers (ordinary
1.5
decontamination)
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedDifferences shall be noted between thesurface soil stirred by plowing and that notplowed after the accident. Even if theradioactive concentration is equal, the air
dose rate is higher above the unplowed soil
which keeps the surface as it was.
The soil replacement and other measuresneeded shall be implemented after
decontamination, soil analysis and diagnosis.

Radiation

Safety glasses, dust masks, rubber gloves,

exposureprotection of workers

etc. shall be worn.

General labor safety ofworkers

Existing access routes, if suitable, shall be
used for entering the fields.
If no access route is available, the heavymachinery shall enter the field slowly moving
forward at a right angle to the ridge along thefield. This is to avoid the heavy machinery
overturning.
If the slope of the entry route crossing theridge along the field is too steep, a new entry
route shall be constructed in order to preventthe heavy machinery from overturning.
It shall be checked that no new big holes weremade by wild bores or the like by which theheavy machinery might be overturned.

Measures to prevent－

secondary wastes
Others－3527）Restoration of soil fertility
Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Restoration of soil fertility

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Soil fertility of rice fields, dry fields and grasslandshall be restored by spreading soil conditioners or
zeolite.
Soil conditioners shall be sprayed by asprinkler mounted on a tractor.
Soil conditioners shall be those reported to
the Governor of Fukushima Prefecture as
special fertilizers pursuant to the Fertilizer
Control Law (Law No. 127, 1950) and thosewhich can increase soil fertility by integrated
improvement of physicochemical andbiological properties of the soil.
The soil conditioners shall be approved by thesupervisory MOE personnel in advancethrough test results.
Zeolite may be used in place of the soil
conditioners.
When spraying soil conditioners,(per 10,000 m2)
Tools, equipment to use
Quantity
Construction
tractors
1.1(Ordinary type, load capacity 9 service hourst)
Lime spreaders 138(Towing
1.1
capacity 800 L, spray span 3 m service hours
class)
Light oil
13.0 L
Soil
conditioner(calcium Depending oncarbonate)soil
properties
Soil conditioner (potassium
0.8 t
silicate)*Machinery for spraying soil conditioners
When spraying zeolite,
Tools, equipment to use
Farm tractor (Crawler-type,
40PS)

138

Machines for dispersion of fertilizer and soil improving agent

353(per 1,000 m2)
Quantity
0.56 service
hours

Lime spreaders (Spray span 1.8
m class)
Light oil
ZeoliteWorkforce needed

When spraying soil conditioners,(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
0.2
worker-days
Decontamination workers
0.77
worker-days
Drivers (special
0.17
decontamination)
worker-days
When spraying zeolite,
Workforce needed
Operation leaders
Specialized decontamination
workers

Idea
development,
lessons,
pointstokeep
inmind, etc.

0.1 service
days
4.3 L
0.5 t

(per 1,000 m2)
Quantity
0.15
worker-days
0.09
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedUpon completion of decontamination andanalysis, the amount of soil conditioners or
zeolite shall be determined.

Radiation

Safety glasses, dust masks, rubber gloves,

exposureprotection of workers

etc. shall be worn.

General labor safety ofworkers

Existing access routes, if suitable, shall be
used for entering the farmland.
If no access route is available, the heavymachinery shall enter the field slowly moving
forward at a right angle to the ridge along thefield.
If the slope of the entry route crossing theridge along the field is too steep, a new entry
route shall be constructed in order to preventthe heavy machinery from overturning.
It shall be checked that no new big holes weremade by wild bores or the like by which theheavy machinery might be overturned.

Measures to prevent－

secondary wastes
Others－354

（3） Waterways
1）Removal of bottom sediment (soil suctioning)
Locations to be“8.4.1. Waterways” of “8.4. Waterways” in “8. Farmland”

decontaminatedDecontamination

Removal of bottom sediment (soil suctioning ) from waterways inmethods

farmland

OutlineBottom sediment in waterways of farmland shallbe removed (soil suctioning)

Decontamination processes

Tools, equipment and the like fordecontamination work

Sediment easily removable such as fallen
leaves, moss, mud, etc. shall be removed byusing shovels and the like.
Tools, equipment to use
Shovels and the like

Workforce needed
Workforce needed
Operation leaders
Decontamination workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

Quantity(per 10 m３)
Quantity
0.21
worker-days
8.37
worker-days

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedMost work for removing bottom sediment inwaterways of farmland is done in narrow
spaces and shall be done by hand. The bottom
sediment collected shall be immediately
packed in small bags nearby and transferredby hand. The small bags shall be such that
hand-carry belts may be used for easytransfer in bad footing spaces (570×530×H550).
If the waterway has flow, the working zone
shall be dammed upstream and downstream
to
block
the
flow.
A
hand-carrywater-immersed
pump(2B, discharge
amount 0.1 – 0.12 m3/min) shall be used sothat the removal work can be done in no-flow
conditions.

Radiation
exposureprotection of workers

The air dose rate in working areas shall beclearly indicated to the workers.
The air dose rate in the working areas fordecontamination shall be measured inadvance, and if the dose rate is high, the area
shall be so indicated by using color cones,
color cone bars and the like.

355

Daily and accumulated exposure doses ofindividual workers shall be indicated in aneasily understandable way and kept undercontrol.
Unnecessary access to places with large
packed sandbags shall be restricted becauseof their high dose rate risk.
Protective equipment such as disposable
masks, rubber gloves, etc. shall be disposed ofat the pre-designated spots when the work isfinished.
General labor safety ofworkers

Measures to prevent

Protective equipment (masks, gloves and thelike) shall be appropriately worn.
Special attention shall be paid to footwear of
workers transferring packed bags and thelike, since the waterways in farmland are
muddy and there are slopes or ridges along
fields where workers may slip.
－

secondary wastes
OthersWhenleavingtheworking
areas,
contamination on body surfaces shall bechecked as lower than 1,300 cpm
byscreening, which is stricter than theallowable limit of 13,000 cpm.

3562）Removal and the like of bottom sediment (Packing)Locations to be“8.4.1. Waterways” of “8.4. Waterways” in “8. Farmland”

decontaminatedDecontamination

Removal of bottom sediment in waterways of farmland (Packing)methods
OutlineBottom sediment in waterways in farmland shallbe removed (and packed).

Decontamination processes
Tools, equipment and the like fordecontamination work

Workforce needed

Bottom sediment collected shall be packed inlarge sandbags by hand.
Tools, equipment to use
Large sandbags
Workforce needed
Operation leaders
Decontamination workers

Idea
development,
lessons,
pointstokeep
inmind, etc.

Quantity(per 10 bags)
Quantity
0.11
worker-days
1.68
worker-days

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedLarge sandbags may lose their shape, whenbeing packed with collected sediment, due todifficulty of uniform filling. For shapekeeping and easy packing, large sandbags
shall be filled on a dedicated table.
Bottom sediment has high water content. In
order to prevent contaminated water fromleaking, an inner bag shall be placed in thelarge sandbags, or water-proof flexible
containers shall be used.

Radiation
exposureprotection of workers

The air dose rate in working areas shall beclearly indicated to the workers.
The air dose rate in the area fordecontamination shall be measured inadvance, and if the dose rate is high, thearea shall be so indicated by using color
cones, color cone bars and the like.
Daily and accumulated exposure doses ofindividual workers shall be indicated in aneasily understandable way and kept undercontrol.
Whenever sand or the like is attached(deposited) on workers’ clothing or protective
equipment, sand or the like shall be wipedaway immediately in order to prevent
contamination from spreading.
Unnecessary access to places with large
357

packed sandbags shall be restricted becauseof their high dose rate risk.
Protective equipment such as disposable
masks, rubber gloves, etc. shall be disposedof at the pre-designated spots when thework is finished.
General labor safety ofworkers

Measures to prevent

Protective equipment (masks, gloves and thelike) shall be appropriately worn.
Special attention shall be paid to footwear of
workers transferring packed bags and thelike, since the waterways in farmland are
muddy and there are slopes or ridges along
fields where workers may slip.
Safety systems and equipment shall bechecked before commencing the day’s work.
When using backhoes for packing, access to
the rotating range shall be prohibited inorder to prevent minor collisions.
－secondary wastes
OthersWhenleavingtheworking
areas,
contamination on body surfaces shall bechecked as lower than 1,300 cpm
byscreening, which is stricter than theallowable limit of 13,000 cpm.

358

（4） Others
1）Packing (standard transfer process)Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Packing (standard transfer process)methods
OutlineSoil removed from rice fields, dry fields or
grassland in farmland shall be packed for transfer(standard transfer process)Decontamination processes

The soil removed shall be collected andpacked in large sandbags by using backhoesor the like.

Tools, equipment and the like fordecontamination work

Tools, equipment to use
Backhoes(Exhaust
gas
suppression (primary), crawler
type, Bucket capacity 0.45 m3
when heaped up, 0.35 m3 when
flatly filled)
Light oil
Large sandbags

Workforce needed
Workforce needed
Operation leaders
Specialized
decontamination
workers
Decontamination workers
Driverdecontamination)
Idea
development,
lessons,
pointstokeep
inmind, etc.

(special(per 10 bags)
Quantity
1.42
service hours

16.0 L(per 10 bags)
Quantity
0.06
worker-days
0.21
worker-days
0.24
worker-days
0.23
worker-days

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedSpecial attachments shall be fabricated for
packing into large sandbags.
Lined up heights of large sandbags after
being filled shall be leveled.

Radiation

Safety glasses, dust masks, gloves, etc. shall

exposureprotection of workers

be worn.

General labor safety ofworkers

The work proceeds next to heavy machinery.
The working range of the heavy machineryshall be clearly indicated and supervising
personnel shall be arranged.
359

Safety education shall be provided to theworkers on nearby parallel work with heavymachinery.
Measures to prevent
secondary wastes

OthersTwigs, protrusions or the like in the sedimentcollected shall be removed before being
packed in large sandbags to prevent bag
breaks.
－3602）Small transfer within the working fields (standard transfer process)Locations to be
decontaminated“8.1.2. Soil” of “8.1. Rice fields” in “8. Farmland”“8.2.2. Soil” of “8.2. Dry fields” in “8. Farmland”“8.3.2. Soil” of “8.3. Grassland” in “8. Farmland”

Decontamination

Small transfer (standard transfer process)methods
OutlineContaminated soil removed from farmland (ricefields, dry fields and grassland) shall betransferred short distances in small amounts(standard transfer process) within the working
fields.

Decontamination processes

Crane backhoes, rough terrain haulers or the
like shall be used for small and shorttransfers in the working fields (loading,unloading)Tools, equipment and the like fordecontamination work(per 10 bags)
Tools, equipment to use
Quantity
Crane backhoes (Exhaust gas
1.3
suppression (primary), crawler service hours
type, Bucket capacity 0.28 m3
when heaped up (0.25 m3 when
flatly filled))
Crane backhoes (Exhaust gas
0.28
suppression (primary), crawler service hours
type, Bucket capacity 0.45 m3
when heaped up (0.35 m3 when
flatly filled))Roughterrainhaulers
0.18(Exhaust
gas
suppression service days
(primary), crawler type, load
capacity 4 t)
Light oil
31.5 L* per short transfer distance L=100 m (round trip)

Workforce needed(per 10 Bags)
Workforce needed
Quantity
Operation leaders
0.06
worker-days
Specialized decontamination
0.23
workers
worker-days
Drivers(special
0.44
decontamination)
worker-days* per short transfer distance L=100 m (round trip)

Idea
development,

Prerequisites
andconstraints regarding

Transfer paths easily get muddy in rain. Iron
sheets or the like shall be needed to cover the361

lessons,
pointstokeep
inmind, etc.

objects and locations
to be decontaminatedmuddy paths used for transfer.

Radiation

Safety glasses, dust masks, gloves, etc. shall

exposureprotection of workers

be worn.

General labor safety ofworkers

Clear indication of transfer paths.
The work proceeds next to heavy machineryor vehicles. The working range of the heavymachinery shall be clearly indicated andsupervising personnel shall be arranged.
Safety education shall be provided to theworkers on nearby parallel work with heavymachinery and vehicles.

Measures to prevent－

secondary wastes
Others－362

6.1.4. Grassland, Lawns
1）Cutting down shrubs (dense)
Locations to be“9.1.1. Shrubs (dense)” of “9.1. Shrubs (dense)” in “9. Grassland, lawns”

decontaminatedDecontamination

Cutting down shrubs (dense)

methods
OutlineShrubs (dense) in grassland and lawns shall be
cut down in the following procedures.
(i) Cutting down shrubs(ii) Small amount and short distance transfer inthe working fields(iii) Packing of cut shrubs

Decontamination processes

Tools, equipment and the like fordecontamination work

Large weeds, shrubs and the like shall be cut
down by chainsaws and the like and be
packed in large sandbags.
Cut shrubs and the like too large to pack inlarge sandbags shall be chopped into
packable sizes, or cut in about 2 m long pieces
after removing leaves with a hatchet and tied
using strings or the like in about 30 cm
diameter bundles. The removed leaves shallbe packed in large sandbags.
Tools, equipment to use
Cutters (Chainsaw, edge 600
mm long (80 cc))
Gasoline
Large sandbags

Workforce needed
Workforce needed
Operation leaders
Specialized
decontamination
workers
Decontamination workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated(per 1,000 m2)
Quantity
13.3
service days
16.8 L(per 1,000 m2)
Quantity
3.6
worker-days
5.3
worker-days
16.7
worker-days

The geometry of grassland and lawns isdiverse. Depending on the work site
situation, the spot for packing into large
sandbags, transfer paths, loading stations,etc. shall be chosen and designated. Flat
spaces shall be chosen for packing andtemporary storage in order to ensure working
safety.
Worker safety shall be ensured before
363

starting cutting by designating safe working
and transfer paths.
Basically chainsaws shall be used for cutting
in dense shrub areas. Shrubs cut down shallbe pruned to carriable sizes and be carriedout for collection after removing branches.
When cutting down tall bamboo trees, the cut
bamboo may be impediments to working. The
cut bamboo trees shall be carried out as they
are and be pruned elsewhere.
When packing, branches or the like may
damage the large sandbags. To prevent
sandbags being damaged, shrubs shall be cut
so that no sharp cut ends are left.
Large sandbags may lose shape, when being
packed with collected cut materials, due todifficulty of uniform filling. For shapekeeping and easy packing, the large sandbags
shall be filled on a dedicated table.
Radiation exposure
protection of workers

The air dose rate in working areas shall beclearly indicated to the workers.
The air dose rate in the area fordecontamination shall be measured inadvance, and if the dose rate is high, the area
shall be indicated by using color cones, color
cone bars and the like.
Daily and accumulated exposure doses ofindividual workers shall be indicated in aneasily understandable way and kept undercontrol.
When collecting cut branches and leaves,rakes or the like shall be used in order toprevent direct handling to the extent
possible.
Unnecessary access to places with large
packed sandbags shall be restricted becauseof their high dose rate risk.
Protective equipment such as disposable
masks, rubber gloves, etc. shall be disposed ofat the pre-designated spots when the work isfinished.

General labor safety ofworkers

Protective equipment (masks, gloves and thelike) shall be appropriately worn.
Safety systems and equipment shall bechecked before commencing the day’s work.
When using backhoes for packing, the accessto the rotating range shall be prohibited inorder to prevent minor collisions.
Safety glasses shall be properly worn, whenpacking, to prevent branches from poking the
eyes.

364

When cutting, flying stones or rotating edges
may hurt nearby workers. To prevent the, theworking zones shall be set apart with aninterval of about 10 to 15 m, and the work
shall be done under a foreman’s supervision.
When working on vibratory machines such as
chain saws and weed cutters, a rest of morethan 5 min shall be taken each 30 min inorder to prevent vibration hazard.
When working with hatchets for cutting, a
suitable distance shall be kept fromneighboring workers.
Measures to prevent－

secondary wastes
OthersWhenleavingtheworking
areas,
contamination on body surfaces shall bechecked as lower than 1,300 cpm
byscreening, which is stricter than theallowable limit of 13,000 cpm.

3652）Cutting down shrubs (sparse)
Locations to be
decontaminatedDecontamination“9.2.1. Shrubs (sparse)” of “9.1. Shrubs (sparse)” in “9. Grassland,
lawns”
Cutting down shrubs (sparse) in grassland, lawns

methods
OutlineShrubs (sparse) in grassland and lawns shall be
cut in the following procedures.
(i) Cutting down shrubs(ii) Small amount and short distance transfer inthe working fields(iii) Packing cut shrubs

Decontamination processes

Tools, equipment and the like fordecontamination work

Weeds, shrubs and the like shall be cut downby shoulder-type mowers and the like and be
packed in large sandbags.
(per 1,000 m2)
Tools, equipment to use
Quantity
Mowers (Shoulder-type, cutter
2.0
255 mm, 1.3 kW class)service days
Gasoline
5.7L
Large sandbags-

Workforce needed
Workforce needed
Operation leaders
Specialized
decontamination
workers
Decontamination workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminated(per 1,000 m2)
Quantity
3.1
worker-days
1.1
worker-days
7.0
worker-days

The geometry of grassland and lawns isdiverse. Depending on the field situation, thespot for packing into large sandbags, transfer
paths, loading stations, etc. shall be chosen
and designated. Flat spaces shall be chosen
for packing and temporary storage in order toensure working safety.
Work safety shall be ensured before starting
cutting by designating safe working andtransfer paths.
Shoulder-type mowers shall be used for
cutting in sparse shrub areas. Too large
shrubs to cut by mowers shall be cut by
chainsaws.
When cutting down tall bamboo trees, the cut
bamboo may be impediments to working. The

366

cut bamboo trees shall be carried out as they
are and be pruned elsewhere.
When packing, branches or the like may
damage the large sandbags. To prevent this,shrubs shall be cut so that no sharp cut ends
are left.
Large sandbags may lose their shape, whenbeing packed with collected scrubs, due todifficulty of uniform filling. For shapekeeping and easy packing, the large sandbags
shall be filled on a dedicated table.
Radiation
exposureprotection of workers

The air dose rate in working areas shall beclearly indicated to the workers.
The air dose rate in the area fordecontamination shall be measured inadvance, and if the dose rate is high, theareas shall be so indicated by using color
cones, color cone bars and the like.
Daily and accumulated exposure doses ofindividual workers shall be indicated in aneasily understandable way and kept undercontrol.
When collecting cut branches and leaves,rakes or the like shall be used in order toprevent direct handling to the extent
possible.
Unnecessary access to places with large
packed sandbags shall be restricted becauseof their high dose rate risk.
Protective equipment such as disposable
masks, rubber gloves, etc. shall be disposed ofat the pre-designated spots when the work isfinished.

General labor safety ofworkers

Protective equipment (masks, gloves and thelike) shall be appropriately worn.
Safety systems and equipment shall bechecked before commencing the day’s work.
When using backhoes for packing, the accessto the rotating range shall be prohibited inorder to prevent minor collisions.
Safety glasses shall be properly worn, whenpacking, to prevent branches from poking theeyes.
When cutting, flying stones or rotating edges
may hurt nearby workers. To prevent this,the working zones shall be set apart with aninterval of about 10 to 15 m, and the work
shall be done under a foreman’s supervision.
When working on vibratory machines such as
mowers and weed cutters, a rest of more than
5 min shall be taken each 30 min in order toprevent vibration hazard.

367

When working with hatchets for cutting, a
suitable distance shall be kept fromneighboring workers.
Measures to prevent－

secondary wastes
OthersWhenleavingtheworking
areas,
contamination on body surfaces shall bechecked as lower than 1,300 cpm byscreening, which is stricter than theallowable limit of 13,000 cpm.

368

6.1.5. Forests（1） Items common to the forests with mixed trees of coniferous evergreen trees, deciduous
broad-leaf trees and others

1）Removal of sediment (organic materials)
Locations to be
decontaminated“11.1.1. Sediment (organic materials)” of “11.1. Coniferous evergreen
trees” in “11. Forests”“11.2.1. Sediment (organic materials)” of “11.2. Deciduous broad-leaf
trees” in “11. Forests”“11.3.1. Sediment (organic materials)” of “11.3. Forests with mixed
trees” in “11. Forests”

Decontamination

Removal of Sediment (organic materials)

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work
Workforce needed

Sediment(organic
materials)offorests(coniferous evergreen trees, deciduous broad-leaf
trees, other mixed trees, etc.) shall be removed in
the following procedures.
(i) Removing organic materials such as fallen
leaves(ii) Small and short transfer in working fields(iii) Packing removed organic materials
Fallen leaves, fallen branches and the like ina layer about 5 cm deep from the surface
shall be collected and carried by rakes or the
like to the bottom edge of slopes and be
packed in large sandbags. The removal
should not be as deep as to reach the mineralsoil layer.
Fallen branches or the like too big to pack inlarge sandbags as they are shall be chopped
into packable sizes, or cut into about 2 m longpieces and bundled using strings or the likein about 30 cm diameter bundles.
Tools, equipment to use
Rakes or the like
Large sandbags■ WhenQuantity-

working on cedar trees amongconiferous evergreen trees,(per 10,000 m2)
Workforce needed
Quantity
Operation leader
21.1
worker-days
Decontamination workers (for86.1
removing organic materials)
worker-days
Decontamination workers (small
31.6transfer)
worker-days369

Decontamination
workers(packing into large sandbags)

22.8
worker-days

When working on Japanese cypress amongconiferous evergreen trees(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
15.6
worker-days
Decontamination workers (for57.4
removing organic materials)
worker-days
Decontamination workers (small
31.6transfer)
worker-days
Decontamination
workers
15.2(packing into large sandbags)
worker-days
When working on Japanese red pine and thelike among coniferous evergreen trees, andother mixed trees,(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
20.5
worker-days
Decontamination workers (for83.2
removing organic materials)
worker-days
Decontamination workers (small
31.6transfer)
worker-days
Decontamination
workers
22.0(packing into large sandbags)
worker-days
When working on Japanese emperor oak andthe like among coniferous evergreen trees,(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
21.5
worker-days
Decontamination workers (for88.1
removing organic materials)
worker-days
Decontamination workers (small
31.6transfer)
worker-days
Decontamination
workers
23.3(packing into large sandbags)
worker-days
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedSafety measures are occasionally difficult totake on steep slopes and the like. In suchcases, decontamination work has been
implemented, upon consultation with theordering party, for individual working areas(for example, 2 m from the top of slopes or 2
m from the bottom of slopes).

Radiation

Safety glasses, masks and gloves shall be

exposureprotection of workers

worn.

370

General labor safety ofworkers

Measures to prevent

In case general safety measures are
insufficient to secure working safety, forexample, on steep slopes, safety measures
shall be strengthened depending on
individual working conditions.
Where risks of falling down or sliding down
are present, safety measures shall be needed,
for instance, installing fixed ropes and using
fall arresting devices.
If there are roads along the forest edge,
barricades and traffic controllers shall bearranged.
－secondary wastes
OthersAs a preparatory measure for small transfer,
workers shall be instructed to carry small
empty sandbags when collecting organic
materials.

3712）Removal of Sediment (organic materials) (non-control areas)
Locations to be
decontaminatedDecontamination“11.1.1. Sediment (organic materials)” of “11.1. Coniferous evergreen
trees” in “11. Forests”“11.2.1. Sediment (organic materials)” of “11.2. Deciduous broad-leaf
trees” in “11. Forests”“11.3.1. Sediment (organic materials)” of “11.3. Forests with mixed
trees” in “11. Forests”
Removal of Sediment (organic materials) (non-control areas)

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Workforce needed

Sediment (organic materials) of forests(coniferous evergreen trees, deciduous broad-leaf
trees, forests with mixed trees, etc.) in
non-control areas shall be removed in thefollowing procedures.
(i) Removing organic materials such as fallen
leaves(ii) Small amount and short-distance transfer inworking fields(iii) Packing removed organic materials
Fallen leaves, fallen branches and the like ina layer about 10 cm deep from the surface
shall be collected and carried using rakes or
the like to the bottom edge of slopes and be
packed in large sandbags. The removal
should not be so deep as to reach the mineralsoil layer.
Fallen branches or the like too large to packin large sandbags shall be chopped into
packable sizes, or cut in about 2 m longpieces and bundled using strings or the likein about 30 cm diameter bundles
Tools, equipment to use
Rakes or the like
Large sandbags

Quantity-(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
28.2
worker-days
Decontamination workers (for133.3
removing organic materials)
worker-days
Decontamination
workers
31.6(small transfer)
worker-days
Decontamination
workers
22.8(packing into large sandbags)
worker-days*This applies when the organic material layer372thickness exceeds 10 cm, irrespective of the tree
types.
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedSafety measures are occasionally difficult totake on steep slopes and the like. In suchcases, decontamination work has been
implemented, upon consultation with theordering party, for individual working areas(for example, 2 m from the top of slopes or 2
m from the bottom of slopes).

Radiation exposure
protection of workers

Safety glasses, masks and gloves shall be

General labor safety ofworkers

In case general safety measures are
insufficient to secure working safety, forexample, on steep slopes, safety measures
shall be strengthened depending on
individual working conditions.
Where risks of falling down or sliding down
are present, safety measures shall beneeded, for instance, installing fixed ropes
and using fall arresting devices.
If there are roads along the forest edge,
barricades and traffic controllers shall bearranged.

Measures to prevent

worn.

－

secondary wastes
OthersAs a preparatory measure for small transfer,
workers shall be instructed to carry small
empty sandbags when collecting sediment.

3733）Prevention of secondary dispersion of contaminated soil (lining up of sandbags)
Locations to be
decontaminated“11.1.2. Soil” of “11.1. Coniferous evergreen trees” in “11. Forests”“11.2.2. Soil” of “11.2. Deciduous broad-leaf trees” in “11. Forests”“11.3.2. Soil” of “11.3. Forests with mixed trees” in “11. Forests”

Decontamination

Prevention of secondary dispersion of contaminated soil (lining up of

methods

sandbags)

OutlineSecondary dispersion of contaminated soil inforests (coniferous evergreen trees, deciduous
broad-leaf trees, other mixed trees, etc.) shall be
prevented by lining up sandbags.

Decontamination processes

When removing fallen leaves from steep
slopes, sandbags shall be lined up at theforest edges in order to prevent soil frombeing eroded.
Sandbags shall be lined up with their small
tied end in front unless otherwise
instructed.
Sandbags of 48cm x 62cm (No. 2) shall be
used and when packed shall measureapproximately about 50cm x 40cm x 10cm.

Tools, equipment and the like fordecontamination work

Tools, equipment to use
Shovels and the like
Sandbags (jute, 48 x 62 cm)
mountain sandWorkforce needed
Workforce needed
Operation leaders
Decontamination workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 50 spots)
Quantity
200 bags
4.0 m3(per 50 spots)
Quantity
0.2
worker-days
1.5
worker-days

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedSandbags shall be lined up at the forest edgein order to prevent soil from eroding, whenorganic materials such as fallen leaves are
removed from steep slopes in forests, orwhen soil erosion by rainfall is possible after
the removal of sediment organic materials

Radiation

Dust masks, rubber gloves and the like shall

exposureprotection of workers

be worn.

General labor safety ofworkers

Protective measures shall be taken toprevent sliding down, such as fixed ropes,
safety belts and sliding devices on fixedropes.

374

Measures to prevent－

secondary wastes
Others－3754）Cutting down underbrush and shrubs
Locations to be
decontaminated“11.1.4. Underbrush cutting” of “11.1. Coniferous evergreen trees” in“11. Forests”“11.2.4. Underbrush cutting” of “11.2. Deciduous broad-leaf trees” in“11. Forests”“11.3.4. Underbrush cutting” of “11.3. Forests with mixed trees” in “11.
Forests”

Decontamination

Cutting down underbrush and shrubs

methods
OutlineDecontamination processes

Tools, equipment and the likefor decontamination work
Workforce needed

Underbrush and shrubs in forests (coniferous evergreen
trees, deciduous broad-leaf trees, other mixed trees, etc.)
shall be cut down.
Underbrush and shrubs shall be cut down by using
shoulder-type mowers and the like. The cut materials
shall be collected at the forest edge and packed inlarge sandbags.
Pieces too big to pack in large sandbags as they are
shall be chopped into packable sizes, or cut into lessthan 2 m long pieces and tied using strings or the likein about 30 cm diameter bundles. The bundles shall becollected and piled up at the forest edge forsubsequent processes (transfer to volume reduction
facilities or volume reduction by wood crushers).
Tools, equipment to use
Sandbags

Quantity-

When the objects to be cut down are sparsely
distributed, less than 17,000 pieces/ha (good visibility
in the forests and easy to walk around),(per 10,000 m2)
Quantity
Workforce
Slope
Slope
Slope
needed0 to 20°
21 to 30°
> 31°
Operation
leaders
Decontaminatio
n workers376

1.1
worker-days
7.1
worker-days

1.2
worker-days
7.7
worker-days

1.3
worker-days
8.6
worker-days

When the objects to be cut down are intermediate indistribution, between 17,000 and 28,000 pieces/ha,(per 10,000 m2)
Quantity
Workforce
Slope
Slope
Slope
needed0 to 20°
21to 30°> 31°
Operation
leaders
Decontamination
workers

1.5
1.6
1.6
worker-days worker-days worker-days
10.0
10.4
10.9
worker-days worker-days worker-days

When the objects to weed are densely distributed,
more than 28,000 pieces/ha (lots of underbrush, poor
visibility in the forests and hard to walk around),(per 10,000 m2)
Quantity
Workforce
Slope
Slope
Slope
needed0 to 20°
21 to 30°
> 31°
Operation
leaders
Decontamination
workers

Idea
development, lessons,points to
keep inmind, etc.

1.9
2.1
2.2
worker-days worker-days worker-days
12.9
13.7
14.5
worker-days worker-days worker-days

Prerequisites
and constraints
regardingobjects andlocations to be
decontaminatedThis work is to improve visibility at the bases of trees
in forests.

Radiation
exposureprotection
workers

Dust masks, rubber gloves and the like shall be worn.
The underbrush and shrubs are likely to have grownafter the accident. The spot to place the cut materials
collected shall be chosen carefully, because the air
dose rate may increase after the cutting work

Generalsafetyworkers
Measures

of

labor
of
to

The mower edge may be hidden in the underbrush
during cutting. Due attention shall be paid to the feetso as not to get cuts or injuries from the blade edges－

prevent
secondarywastesOthers－3775）Removal of residual sediment (organic material)
Locations to be
decontaminated“11.1.5. Removal of residual sediment (organic materials)” of “11.1.
Coniferous evergreen trees” in “11. Forests”“11.2.5. Removal of residual sediment (organic materials)” of “11.2.
Deciduous broad-leaf trees” in “11. Forests”“11.3.5. Removal of residual sediment (organic materials)” of “11.3.
Forests with mixed trees” in “11. Forests”

Decontamination

Removal of residual leaf litter and woody materials (organic materials)

methods
OutlineResidual sediment (organic materials) in forests(coniferous evergreen trees, deciduous broad-leaf
trees, other mixed trees, etc.) shall be removed.

Decontamination processes

Tools, equipment and the like fordecontamination work

Where residual organic materials are left
behind after removal work, they shall becollected by rakes or the like and be packed inlarge sandbags after being transferred to thebottom of the slope.
The removal of residual organic materials
should not be so deep as to reach the mineralsoil layer, the same as in removing theorganic materials originally.
Tools, equipment to use
Rakes or the like
Large sandbags

Workforce needed
Workforce needed
Operation leaders
Decontamination workers
Idea
development,
lessons,
pointstokeep
inmind, etc.

(per 10,000 m2)
Quantity(per 10,000 m2)
Quantity
3.6
worker-days
24.0
worker-days

Prerequisites
andconstraints regarding
objects and locations
to be decontaminatedExposed roots of trees and low areas on theslopes may induce surface water streams,
causing deterioration of forests. Prior tocommencing the work of removing organic
materials,
theforestmanagerandsupervisory personnel shall be closely
consulted on designating the area of work.

Radiation
exposureprotection of workers

Dust masks, rubber gloves and the like shallbe worn.
Precautions shall be taken to prevent
inhaling fine organic materials scatteredwhen the residue is being collected378

General labor safety ofworkers

Measures to prevent

Safety measures shall be taken for the workwith heavy machinery (proper arrangement
for preventing minor collisions of adjacently
working heavy machinery, and adequate
instructions and supervision, as well as
thorough control for preventing access to themachinery)－

secondary wastes
Others－379

（2） Coniferous evergreen trees
1）Pruning coniferous trees and collecting pruned branches
Locations to be“11.1.3. Trees” of “11.1. Coniferous evergreen trees” in “11. Forests”

decontaminatedDecontamination

Pruning coniferous trees and collecting pruned branches

methods
OutlineDecontamination processes

Tools, equipment and the like fordecontamination work

Workforce needed

Coniferous evergreen trees in the forests shall be
pruned and the pruned branches shall becollected in the following procedure.
(i) Pruning(ii) Collecting pruned branches
Branches of living coniferous evergreen
trees (cedar, Japanese cypress, and the like)of more than 3 year old class shall be cut off
using saws or the like up to the height ofabout 4 m from the ground, if they standwithin about 5 m from the forest edge (about
1 or 2 rows). But the tree canopies of morethan half of their original size shall be left. If
branches and leaves of living trees
considerably hang above buildings, theyshall be cut off using saws and the like.
Branches too long to pack in large sandbags
as they are shall be chopped into packablesizes, or cut into less than 2 m long pieces
and tied using strings or the like in about 30
cm diameter bundles. The bundles shall becollected and piled up at the forest edge forsubsequent processes (transfer to volume
reduction facilities or volume reduction bywood crushers).
Tools, equipment to use
Saws or the like
Large sandbags

Quantity-■When cutting cedars,(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
16.1
worker-days
Decontamination
workers
77.5(for pruning)
worker-days
Decontamination
workers
29.7(for bundling)
worker-days*In cases pruned branches and fallen leaves arebundled and transferred to the bottom of slopes.

380

When cutting Japanese cypress,(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
19.4
worker-days
Decontamination
workers
99.3(for pruning)
worker-days
Decontamination
workers
29.7(for bundling)
worker-days*In cases pruned branches and fallen leaves arebundled and transferred to the bottom of slopes.
When cutting Japanese red pine and thelike,(per 10,000 m2)
Workforce needed
Quantity
Operation leaders
16.9
worker-days
Decontamination
workers
99.3(for pruning)
worker-days
Decontamination
workers
13.2(for bundling)
worker-days*In cases pruned branches and fallen leaves arebundled and transferred to the bottom of slopes.
Idea
development,
lessons,
pointstokeep
inmind, etc.

Prerequisites andconstraints regarding
objects and locations
to be decontaminatedThis method may be applied to windbreaktrees around housing areas

Radiation
exposureprotection of workers

Dust masks, rubber gloves and the like shallbe worn.
At the top of untreated trees, radioactive
materials are likely to have attached.
Maximum attention shall be paid not totouch materials falling from above(branches, leaves, dust, etc.)

General labor safety of

Cautions shall be taken to prevent workers

workers

being hit with objects dropped during
pruning.

Measures to prevent－

secondary wastes
Others－381

6.2. Verification of Decontamination Effects
Chapter 6.2 shows some of the verification results of decontamination effects in thedecontamination works done under various test conditions in the Special Decontamination
Areas as arranged by the MOE.
It should be noted that the decontamination effects depend on various environmental
conditions such as material properties or surface conditions of the objects subject todecontamination, or their aging variation with time, and therefore, the same decontamination
effects cannot be necessarily expected even if the same decontamination methods for aparticular item are applied. There are also some cases which showed different results fromthose of model projects conducted by the Cabinet Office and Japan Atomic Energy Agency(JAEA) or those experienced in the first stage decontamination work in relatively high doseareas in Fukushima Prefecture (mainly in JFY 2011).
It should be also noted that the decontamination methods and application conditions cannot
be decided solely by the test decontamination results. The specific decontamination methods
and application conditions have been decided for individual communities upon the residents’consent with consideration to workability, preservation of functions of the item to be
decontaminated, and the like.
The verification results are shown below for individual decontamination methods tested in
two groups of Special Decontamination Areas, i.e., relatively low dose areas ofresiding-restricted areas (the areas in which residing is restricted) and the evacuation orderlifting preparation areas (the areas in which the evacuation orders are being prepared forlifting), and relatively high dose areas of difficult-to-return areas (the areas where it isexpected that the residents have difficulties in returning for a long time).
The decontamination effects are shown basically in terms of the changes in surface
contamination densities (cpm). But for farmland, where penetrated contamination is likely,
rather than surface contamination, the decontamination effects are expressed in terms of thechange in dose equivalent (μSv/h).

382

6.2.1. Residing-restricted Areas (Areas in Which Residing is Restricted) or Evacuation

Orders Lifting Preparation Areas (Areas in Which Evacuation Orders are Being
Prepared for Lifting)
The following are the results of decontamination effects under various test conditions
obtained from the decontamination work model projects authorized by the MOE in theresiding-restricted areas and the evacuation order lifting preparation areas.

（1） Residential areas and the like1）Roofs/rooftops
A) Wiping
After removing sediment on roofs when present, one to three wiping operations wereconducted using disposable paper wipes.
The test decontamination was conducted on roofs facing east, south, west and north. Roofs
facing east had mostly higher values of air dose rates and surface contamination densities
than the other roofs. This will be attributed to the wind direction and the source ofradioactive materials.
Higher surface contamination densities (3,000 to 5,000 cpm) have been experienced on
roofs with seams such as batten-seamed roofs and folded-plate roofs or metallic roofs withrust such as galvanized steel sheets, while lower densities have been experienced on roofs
with flat surface materials or fewer seams. This indicates that radioactive materials tend
to be attached and remained on roof surfaces with uneven configurations, while from flat
surface roofs radioactive materials may be washed away by rainfall even if attached once.
The air dose rate was reduced by about -13 to +28% (about 9 to 11% on the average) by
wiping the roofs after removing sediment, and the surface contamination densities werereduced by about -13 to +79% (average about 27 to 39%).
There were variations in the radiation reduction effects by wiping. Even 10 wiping
operations did not lower the dose to the lowest level. Once the contamination is reduced toseveral hundred [cpm], the data variation becomes big. The radiation reduction effects ata particular place remained almost unchanged even if wiping operations were repeated(once, twice, three times and ten times).

383

Table 6-2 Example results in residential areas, etc. of wiping roofs and rooftops
Air dose rate139 at 1
cm away from thesurface(μSv/h)Surfacecontamination
density(without
shielding cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom the surface(%)

Decontamination
rate of Surface
contamination
density(%)

Before wiping

1.2

1.32×103－－

After first wiping
AftersecondwipingAfter third wiping

1.0

6.00×102

11

33

1.1

5.57×102

9

36

1.0

5.00×10211

39

After tenth wiping

1.0

5.20×10210

27Work Schedule※ Dose equivalent rate, surface contamination density and reduction rate are the average of theirmeasurements.
※ Even if the reduction rate was negative at a measuring point, the reduction rate of the concerned point
was not considered to be zero, and was calculated using the raw value (negative value).
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method2）Exterior walls/outside walls
A) Wiping, brushing
Glass surfaces, siding walls, wooden walls, mortar walls, earthen walls, and galvanizedsteel sheet walls, corrugated sheet walls and metal walls were wiped or brushed once tothree times (both for mortar walls, but only brushing for earthen walls and only wiping forothers).
Whatever the material was, the surface contamination densities were confirmed to belower than those on the roofs or in the rainwater gutters.
The dose rate was basically low, and the dose rate change was minimal even when wiped
or brushed, irrespective of moss presence, the wall materials, and the numbers of wiping
and brushing operations.

3）Rainwater guttersA) Sediment removal, wiping
Sediment causes high dose rates. There is a case in which the maximum dose rate before
decontamination was 10 μSv/h and the surface contamination density was 17,000 cpm.
The reduction effects by removing sediment was about 3 to 78% (average 42%) for air dose
rates and about 20 to 59% (average 35%) for surface contamination densities. The effects
by wiping were about –11 to +18% (average about 7 to 11%) for air dose rates and about–30 to +52% (average about –1 to +11%) for surface contamination densities.
In decontaminating rainwater gutters, sediment removal is most effective. This is because
the sediment includes most of the radioactive contaminants.

139

Air dose rate measured 1 cm away from the ground or 1 cm away from the surface of target.

384

Table 6-3 Example results in residential areas, etc. of removing sediment from rainwater
gutters followed by wiping

Work Schedule

Air dose rate at 1
cm away fromsurface(μSv/h)Surfacecontamination
density(without
shielding cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom surface(%)

Decontamination
rate of Surface
contamination
density(%)

Before removing
5.2
1.03×104－－
sediments
After removing
2.0
5.87×103
42
35
sediments
After first wiping
1.9
6.07×1037(-1)
3
After second wiping
1.8
5.27×10911After third wiping
1.8
5.27×103
11
6※ The effect of decontamination depends on the various factor such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

3854）Street drains
A) Sediment removal
In street drains the maximum air dose rate of 2.4 μSv/h and surface contamination
density of 1,310 cpm were observed before decontamination.
The reduction in the surface contamination density reached as high as 47%. The concrete
covers of street drains lowered the surface contamination density to as low as 290 cpm.
Table 6-4 Example results in residential areas, etc. of removing sediment from side
ditchesWork Schedule

Air dose rate at 1
cm away fromsurface(μSv/h)Surfacecontamination
density(without shielding
cpm)

Decontamination
rate of Air dose rate
at 1 cm away fromsurface(%)

Decontamination
rate of surface
contamination
density(%)

With cover－－
1.4
4.10×102(before work)
Without cover－－
2.4
1.31×103(before work)
After removing
1.4
6.90×102
42
47
sediments
After cleaning
1.4
5.10×102
42
61
side ditches
With cover
1.1
2.90×102
54
78(after work)※ The reducing rate is the value after the cover was removed.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and etc.The results shown above are theresults which have been examined for the specific target to be decontaminated. Therefore, it does notassure that the equivalent effect can be attained by using the same decontamination method.

5）Outdoor equipment and the likeA) Wiping
Wiping operation was done one to three times.
The maximum air dose rate and surface contamination density of outdoor equipment andthe like have been measured as 0.80 μSv/h and 920 cpm, respectively.
The reduction rate of air dose rates was about -6 to +6% on the average and that of surface
contamination densities was about 44 to 85% on the average.
By repeating the wiping operation, the surface contamination densities decreased386

Table 6-5 Example results in residential areas, etc. by wiping outdoor equipment and thelikeWork Schedule

Air dose rate at 1
cm away fromsurface(μSv/h)Surfacecontamination
density(without shielding
cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom surface(%)

Decontamination
rate of surface
contamination
density(%)

Before wiping

8.0×10-1

9.20×102－－

8.5×10-1

5.20×102(-6)

44

7.5×10-1

2.10×102

6

77

7.5×10-1

1.40×1026

85

After first
wipingAfter second
wipingAfter third
wiping※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

387

（2） Schools1）Roofs of a swimming poolA) Wiping
The top part and the lower part of the roofs of a swimming pool were wiped.
The surface contamination density at the top was 340 to 440 cpm (average 400 cpm)
before decontamination. At the lower part it was 560 to 630 cpm (average 600 cpm). The
surface contamination density at the lower part was slightly higher than that at the top.
The reduction rate of air dose rates by wiping was –4 to +4% on the average, while that of
surface contamination densities was about 27% to 36% on the average.
Table 6-6 Example results in schools of wiping swimming pool roofs
Work Schedule

Upper

Lower

BeforewipingAfter wiping
BeforewipingAfter wiping

Air dose rate at 1
cm away fromsurface(μSv/h)Surfacecontamination
density(with shielding
cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom surface(%)

Decontamination
rate of surface
contamination
density(%)

1.2

4.00×102

－

－

1.2

2.60×102

4

36

1.8

6.00×102

－

－

1.9

4.30×102(-4)

27※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore、it does not assure that the equivalent effect can be attained by the same decontamination
method.

388

2）Pool sides
A) High-pressure water cleaning
High-pressure cleaning (vacuum collection 15 MPa, discharge flow rate of 12.7 L/min and
20 L/m2) were done one to three times.
The surface contamination density was 6,550 to 11,000 cpm, and the average was 9,330
cpm before decontamination. The pool side surface material was rubbery and black dirt
was recognized on the surface and roughness was locally observed in the area to be
decontaminated.
After the first high pressure cleaning, unevenness of the cleaning was visually observedon the pool side surfaces. After the second high pressure cleaning, hardly any cleaning
unevenness was visible on the surface. After the third high pressure cleaning, it was
visually confirmed that the dirt was almost uniformly removed from the surface.
As a result of implementing high-pressure water cleaning, the rate of reduction in the air
dose rate was approximately 76 to 79% on average, and the percent decrease in surface
contamination density was approximately 93 to 98% on average.

Table 6-7 Example results in schools for high-pressure water cleaning of swimming poolsides

Work Schedule

Before high pressurecleaning
After first cleaning
After second cleaning

Air dose rate at 1
cm away fromsurface(μSv/h)Surfacecontamination
density(with shielding
cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom surface(%)

Decontamination
rate of surface
contamination
density(%)

3.4

9.33×103－－

8.1×10-1

6.50×102

76

93

-1

2

79

97

6.9×102.70×10

7.0×10-1
1.90×102
79
98
After third cleaning※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

389

3）Exterior walls (with minor staining)A) Brushing (dry)The decontamination effect by brushing in dry conditions was checked on the test target
portion of the exterior wall surface with minor staining.
When shielding was used for more reliable measurement, the surface contamination
density was 100 to 110 cpm and the average was 100 cpm before decontamination.
The surface contamination density after dry brushing was 90 to 150 cpm and the average
was 130 cpm.
Little change was observed, since the contamination before decontamination was low
enough.
Table 6-8 Example results of (dry) brushing school external walls (with minor staining)Work Schedule

Air dose rate at
1 cm awayfrom surface(μSv/h)Surfacecontamination
density(without
shielding cpm)

Decontamination
rate of Air dose rate
at 1 cm away fromsurface(%)

Decontamination
rate of surface
contamination
density(%)

Before brushing

9.1×10-1

1.00×102－－

8.6×10-1
1.30×1026(-24)
After brushing※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore、it does not assure that the equivalent effect can be attained by the same decontamination
method.

4）Exterior Wall (with major staining)A) Brushing (wet)The decontamination effect by one-time brushing or twice brushing in wet conditions waschecked on the test target portion of the exterior wall surface with major staining.
When shielding was used for more reliable measurement, the surface contamination
density was 310 to 620 cpm and the average was 430 cpm before decontamination.
The surface contamination density after the first brushing was 180 to 430 cpm and theaverage was 280 cpm. The surface contamination rate after the second brushing was 230
to 420 cpm and the average was 320 cpm, slightly higher than those after the firstbrushing. It was interpreted that uncertainties were included in the data due to low
contamination. Because of the low values before decontamination for the wall, the average
reduction rate in the second brushing was 24 %.

390

Table 6-9 Example results of (wet) brushing school external walls (major staining)Work Schedule

Air dose rate at 1
cm away fromsurface(μSv/h)Surfacecontamination
density(with shielding
cpm)

Decontamination
rate of Air dose rate
at 1 cm away fromsurface(%)

Decontamination
rate of surface
contamination
density(%)

Before brushing

1.2

4.30×102－－

After first
1.1
2.80×102
6
35
brushing
After second
1.2
3.20×102(-5)
24
brushing※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and etc.The results shown above are theresults which have been examined for the specific target to be decontaminated. Therefore, it does notassure that the equivalent effect can be attained by using the same decontamination method.

391

5）Slopes in School PlaygroundA) Weeding and lawn scraping
Slopes in a school playground were weeded and the lawns were scraped away.
The surface contamination density was 1,490 to 1,970 cpm, and the average was 1,580
cpm before decontamination.
The surface contamination density was 1,920 to 2,710 cpm and the average was 2,380 cpm
after weeding, higher than that before weeding. After scraping lawns away by a backhoe,
the surface contamination density dropped to 170 to 280 cpm and the average to 230 cpm.
(The average reduction rate of surface contamination densities was about 85%).
Table 6-10

Example results of implementing weeding and lawn scraping on slopes in aschool playground

Work Schedule

Air dose rate
at 1 cm awayfrom surface(μSv/h)Air doserate at 1 m
away fromsurface(μSv/h)Surfacecontaminationdensity(withshieldingcpm)

Before weeding

4.8

3.2

1.58×103

Decontamination rate ofAir doserate at 1 cm
away fromsurface(%))

Decontamination rate ofAir doserate at 1 m
away fromsurface(%)

Decontaminationrate ofsurfacecontaminationdensity
(%)

－

－

－

4.5
2.8
2.38×1036
12(-53)
After weeding
After scrapping
1.4
2.1
2.30×102
72
35
85
lawn
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

6）Pavement (berm140 concrete)A) Abrasive vacuum blasting
The abrasive vacuum blasting effect for berm concrete was checked. The blasting speed
was set at 4 min/m2.
Berm concrete surfaces are often found under the eaves at schools or large size facilities.
Hot spots were frequently generated there caused by rain dripping from roofs.
The reduction rate of surface contamination densities by abrasive vacuum blasting wasabout 81% on the average.

140Berm concrete is an earthen-based concrete surface often found on the ground under eaves in order toprevent water intrusion into buildings.

392

Table 6-11 Example results of implementing abrasive vacuum blasting of pavement surfaces(berm concrete) in schools
Air doserate at 1 cm
Work Schedule away fromsurface(μSv/h)BeforeblastingAfterblasting

Surface
Air dose
Decontamination Decontamination Decontamination
contamination
rate at 1 mrate of Air dose rate of Air dose rate of surface
density
away fromrate at 1 cm away rate at 1 m away contamination(withsurfacefrom surface
from surface
densityshielding(μSv/h)
(%))
(%)
(%)
cpm)

－

－

2.00×103

－

－

－

－

－

3.80×102－－

81※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

393

（3） Roads
1）Paved surfaces
A) High-pressure water cleaning.
Test cleaning was executed on a paved road at three different flow rates of 10 L/m2, 15
L/m2 and 20 L/m2. The discharge pressure of high pressure water cleaning was set at 15
MPa.
The dose rates before decontamination were 1.0 to 1.1 μSv/h at 1 cm from the surface and1.1 to 1.2 μSv/h at 1m above the ground, and the surface contamination density was 310 to530 cpm.
The reduction rates of doses rate in all cases were 26 to 29% at 1cm from the surface and 9
to 11% at 1m above ground, and those of surface contamination densities were 55 to 66%.
The decontamination effect was evident. Concerning the effect of cleaning water flow
rates, no significant difference was observed.
Table 6-12

Example results of implementing high-pressure water cleaning of roadpavement surfaces

Water flow rate

10L/m2

15L/m2

20L/m2

Beforecleaning
Aftercleaning
Beforecleaning
Aftercleaning
Beforecleaning
Aftercleaning

Decontaminationrate of Air
dose rate
at 1 cmaway fromsurface(%))

Decontaminationrate of Air
dose rate
at 1 maway fromsurface(%)

Decontaminationrate ofsurfacecontaminationdensity(%)

Air doserate at 1 cm
away fromsurface(μSv/h)Air doserate at 1 m
away fromsurface(μSv/h)Surfacecontamination
density(withshielding
cpm)

1.1

1.1

1.18×103－－－

7.8×10-1

1.0

5.30×102

29

11

55

1.0

1.1

9.90×102－－－

7.2×10-1

9.8×10-1

4.50×102

29

9

55

1.0

1.2

9.10×102－－－

7.4×10-1

1.0

3.10×102

26

11

66

※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

394

2）Street drains
A) High-pressure cleaning
Decontamination effects of the air dose rate and surface contamination density were
measured at the two removable grating covers.
The reduction rates were about 64% for both of dose rates (at 1 cm from the surface) andsurface contamination densities, while the reduction rate for the dose rates at 1 m above
the ground was about 14%.
Table 6-13

Example results of implementing high-pressure water cleaning of road side
ditchesWork
Schedule

Air doserate at 1 cm
away fromthe surface(μSv/h)Air doserate at 1 m
away fromthe surface(μSv/h)Surfacecontamination
density(withshieldingcpm)

Decontamination rate ofAir doserate at 1 cm
away fromthe surface(%))

Decontamination rate ofAir doserate at 1 m
away fromthe surface(%)

Decontamination rate ofsurfacecontaminati
on density(%)

Before
－
－
－
1.7
1.0
5.30×102
cleaning(※)
After
6.1×10-1
9.0×10-1
1.90×10264
1464
cleaning(※)※ The measurement which was measured using a collimator.at one location.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

（4） Farmland
1）Rice fields
A) Leveling unevenness
The uneven topsoil was leveled by using a vibratory roller (combined roller). After levelingthe unevenness, irregularity of the test area was checked for the measurements.
The maximum difference in elevation of unevenness in rice fields was 40 to 60 mm before
leveling. In areas with many wild boars, it was confirmed that the difference had
increased to 95 to 110 mm.
It could be seen that the unevenness was reduced to 20 to 43 mm by leveling and theground surface looked generally smooth. In the rice fields of areas with many wild boars,
the unevenness was 57 to 97mm after leveling. It was visually confirmed that leveling byvibratory rollers could reduce the unevenness. The big unevenness caused by wild boars
could have been certainly reduced, but the change was minimal.
If the surface soil hardness was more than approximately 10 mm (by Yamanaka’
durometer), leveling work was possible. If there were many consecutive rainy days, thesoil hardness was less than 10 mm, and the leveling work was hard to do. The accessconditions (the access route, road widths or other conditions) of heavy machinery should
be checked in advance. Only roads with the gradient of 20 degrees or less were accessibleby heavy machinery.

3952）Dry fields
A) Off-scraping of topsoil
Topsoil was scraped off, after spraying surface solidifiers, by soil skimmers141.
The reduction rate of dose rates at 1 cm from the surface and at 1 m above the ground wasabout 36 to 37% and the reduction rate of surface contamination densities was about 47%.
The amount of soil carried out from dry fields by skimmers was 41 flexible container bags,
weighing 37.2 tons. When the area of 400 m2 was scraped uniformly to the depth of 5 cm,
the theoretical amount should have been 30 tons (specific gravity: 1.5). Actually, 7.2 tons(about 24%) more topsoil was scraped off than the planned amount.
Skimmers with rubber caterpillars could run smoothly for scraping. The surface finish
after scrapping topsoil was also good. The topsoil scraping approach by skimmers isappropriate for application in large flat fields.
Table 6-14

Work
Schedule

Example results of scraping topsoil in fields

Surface
Air dose
Air dose
Decontamination Decontamination Decontamination
contamination
rate at 1 cm rate at 1 mrate of Air dose rate of Air dose rate of surface
density
away from away fromrate at 1 cm away rate at 1 m away contamination(withsurfacesurfacefrom surface from surface
densityshielding(μSv/h)(μSv/h)
(%))
(%)
(%)
cpm)

Before
－
－
－
2.1
2.4
5.70×102
scrapping
After
1.3
1.5
2.70×10237
36
47
scrapping※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

141

Topsoil scrapping and recovering machine396

（5） Forests
A) Surface layer removal and topsoil scraping
The air dose rate was measured before weeding and surface layer (dry leaves) removal.
After weeding and removing dry leaves, the level obtained was defined as the reference
level (DL-0cm). The dose rate and the surface contamination density were measured at
1cm intervals in the depth direction from the reference level. The measurement was
terminated when hard soil layers appeared at the depth of DL-3cm to DL-4cm.
Measurements were implemented at three locations; on the southern slope of a forest of
deciduous trees, on the southern slope of a forest of evergreen trees, and on the western
slope of a forest of deciduous trees.
Occasionally the dose rate increased by weeding and dry leaf removal. The surface
contamination density decreased by removing the surface topsoil as seem in themeasurements made at 1cm intervals. By removing the surface topsoil by about DL-2 toDL-3cm from the reference level, the surface contamination density decreased to about
200 to 950 cpm. The reduction rate of surface contamination densities reached about 25 to
63% (about 36 to 53% on the average). The higher the initial surface contamination
density was, the higher the reduction rate was achieved.
It was understood that removing surface soil as deep as DL-2 to -3cm was appropriate forthe site conditions and the viewpoints of radiation reduction and soil erosion.
Table 6-15

Example results in a forest for surface layer removal and topsoil scraping

Work
Schedule

Air doserate at 1
cm away
from thesurface(μSv/h)Beforeremoving
surfacelayer
Afterremoving
surfacelayer
DL-1 cm

Surface
Air dose
Decontamination Decontamination
contamination
Decontamination
rate at 1 mrate of Air dose rate of Air dose
densityrate of surface
away fromrate at 1 cm
rate at 1 m away(with
contamination
the surface
away from the from the surface
shieldingdensity (%)(μSv/h)surface (%)
(%)
cpm)
－

－

2.5

2.3

9.2×102

2.5

2.0

9.7×102

(-1)

10

(-2)

2.4

2.0

9.9×102

5

12

(-5)

DL-2 cm

1.9

2.0

6.1×102

25

12

36

DL-3 cm
DL-4
cm(※)

1.5

1.9

4.4×102

39

14

53

1.8

2.9

4.0×102

53

26

68

－

※ DL-4cm was measured at one location.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which habe been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

397

6.2.2. Difficult-to-return Area (Areas Where It Is Expected That the Residents Have Difficulties
in Returning for a Long Time)The following are the results of decontamination effects under various test conditions
obtained from the decontamination work model projects authorized by the MOE in the
difficult-to-return area.
The surface contamination densities were always measured in terms of the radiation doseat 1cm from the surface. Beta rays from the surface contamination were measured as thedifference between the values with a collimator and the acrylic shielding plate and with only acollimator.

（1） Residential areas and the like1）RoofsA) Wiping
Test decontamination was executed for two types of roofing materials (ceramic tiles andgalvanized steel sheets) in District A and only ceramic tiles in District B.
In District A, the surface contamination densities showed big variation in data, probably
due to different surface configurations. The decontamination effect was evaluated interms of the dose equivalent rate.
The reduction rate of air dose rates (at 1cm from the surface, with a collimator) in District
A was 0 to 12%, showing no visible decontamination effects. Such results were also foundat other test cases. Significant reduction effects could not be confirmed even for different
wiping methods.
In District B, no significant reduction effects could be confirmed in evaluating the air dose
rates (at 1cm, with a collimator). On the other hand, in the evaluation of surface
contamination densities, some reduction effects could be confirmed by the first wiping, but
no further effects were confirmed by further wiping.
Wiping by disposable paper towels was chosen as the standard method, by which
improvement in decontamination workability could be expected.
In consideration of workability, wiping more than once, and finishing work by the second
wiping operation was chosen as the standard decontamination method for roofs.

398

Table 6-16 Example results of wiping roofs on residential land, etc. (District A residences,
ceramic tiles)

Work Schedule

BeforewipingAfterwipingBeforeWet paper wiping
towel
After
wipingDry paper
towel

Air dose rate at
1 cm away fromthe surface(μSv/h)Surfacecontamination
density (without
shielding cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom the surface(%)

Decontamination
rate of Surface
contamination
density (%)

7.7×10-1－－－

7.8×10-1

－

(-2)

－

7.5×10-1－－－

7.7×10-1

－

(-3)

－

※ The value shown in the table is the average of the value (s) measured at 3 locations.
※ The decontamination rate is the average value of decontamination rate at each measurement point.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

Table 6-17 Example results of wiping roofs on residential land, etc. (District A residences,
galvanized steel sheet plate roofs)

Work Schedule

Dry
paper
towelsWet
paper
towels

BeforewipingAfterwipingBeforewipingAfterwipingAir dose rate at 1
cm away fromthe surface(μSv/h)Surfacecontamination
density (without
shielding cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom the surface(%)

Decontamination
rate of Surface
contamination
density (%)

1.1

－

－

－

1.1

－

6

－

1.2

－

－

－

1.1

－

7

－

※ The value shown in the table is the average of the value (s) measured at 3 locations.
※ The decontamination rate is the average value of decontamination rate measured at each point.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been executed in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

399

Table 6-18

Example results of wiping roofs on residential land, etc. (District B, ceramic tiles)
Air dose rate at 1
cm away fromthe surface(μSv/h)Surfacecontamination
density (without
shielding cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom the surface(%)

Decontamination
rate of Surface
contamination
density (%)

Before wiping

1.1

1.41×103－－

After first wiping

1.2

1.25×103(-3)

11

After second wiping

1.1

1.23×1034

12After third wiping

1.1

1.20×1032

15Work Schedule※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

400B) Brushing
Test decontamination of cement tile roofs in District A was conducted by using a deckbrush.
Generally decontamination is believed to be ineffective on cement tiles.
The decontamination effect was checked by two ways of brushing, in one direction or
back-and-forth directions ten times. However, it was confirmed that the reduction rate ofsurface contamination densities was 0%, showing no decontamination effects.
The poor decontamination effect was understood to be due to rough surfaces of cement
tiles, on which fine grains containing radioactive materials were easily deposited into theporous structure of the surface layer.
It was found that brushing had no decontamination effects at all.
Table 6-19

Example results of brushing cement tile roofs on residential land, etc.

Work Schedule

One waybrushingRoundbrushing

Beforewiping
After
two
times
wiping
After
four
times
wipingBeforewipingAfter tentimes
wipingAir dose rate at 1
cm away from thesurface (μSv/h)

Surfacecontamination
density (without
shielding cpm)

Decontamination
rate of Air dose
rate at 1 cm awayfrom the surface(%)

Decontamination
rate of Surface
contamination
density (%)－

1.12×104－－－

1.12×1040－－

1.12×1040－－

1.00×104－－－

1.00×1040－※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

401

2）Exterior Walls
A) WipingFor exterior walls, wiping effects were tested on the wall materials such as soft
lysine-sprayed walls, pea gravel-washed walls and metallic siding. In many cases thedecontamination effect had little correlation with the wall materials.
Although no big difference was recognized depending on different wiping methods, wiping
by wet paper towels was chosen as the standard decontamination method for external
walls, in consideration of the test results on the roofs and workability.
The decontamination rate of the third wiping from the second wiping was -1% in District
C and +12% in District D. The improvement of decontamination in the third wiping was
not significant when compared with those of the first two wiping steps.
For the exterior wall decontamination, twice wiping (finishing work by the second wiping)
was chosen as the standard decontamination method.
Table 6-20

Example results of wiping external walls on residential land, etc.

Work Schedule

Ceramic
siding,wiping by
dry paper
towel
Metallic
siding,[wiping
by
wet
paper
towel

Before wiping
After
first
wipingAftersecondwipingAfter
thirdwipingBefore wiping
After first
wipingAftersecondwipingAfter
thirdwipingDecontamination
Decontamination
rate of Air dose
rate of Surface
rate at 1 cm away
contaminationfrom the surface
density (%)(%)

Air dose rate at 1
cm away from thesurface (withshielding, μSv/h)

Surfacecontamination
density (withshielding cpm)－

7.84×102－－－

6.43×102－18－

5.52×102－30

5.60×102

29

2.2

－

－

－

1.8

－

18

－

1.7

－

25

1.5

35

※ For metallic siding, many discrepancies due to impact to be considered that surface shape affected on
surface contamination density were confirmed. Therefore, the effect was evaluated by dose equivalentrate.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

402

3）GuttersA) Sediment removal and wiping
Test decontamination of gutters were done by wiping, the standard method, changing thenumber of wiping operations under two conditions of wet wiping and dry wiping.
Collimators could not be used for the air dose rate measurements due to narrow gutter
openings.
For the surface contamination density, the first wiping after removing sediment gave ahigh decontamination rate. No further big decrease could be observed even if wiping was
repeated. Wet wiping gave a higher decontamination rate than dry wiping.
A combination of wiping by wet paper towels and wiping once or more after removing
sediment was chosen as the standard decontamination method for gutters.
Table 6-21

Example results in residential areas of removing sediment from roof gutters
followed by wiping

Work ScheduleDrywiping(wiping
by
dry
paper
towel)

Wet
wiping(wiping
by
wet
paper
towel)

Before wiping
Afterremoving
sediments
After
first
wipingAfter second
wipingAfter
thirdwipingAfter fourth
wipingAfter
fifthwipingAfter
sixthwipingBefore wiping
Afterremoving
sediments
After
first
wipingAfter second
wipingAfter
thirdwipingAfter fourth
wipingAfter
fifthwipingAfter
sixthwiping.

Decontamination
Decontamination
rate of Air dose
rate of Surface
rate at 1 cm
contamination
away from thedensity (%)
surface (%)

Air dose rate at 1
cm away fromthe surface (withshielding, μSv/h)

Surfacecontamination
density (withshielding cpm)

3.0×10－－－1.2×102.25×104

61

－

9.2

2.31×104

69

(-3)

8.7

1.74×104

71

23

9.0

1.26×104

70

44

8.9

1.55×104

70

31

8.8

1.35×104

71

40

8.8

1.35×10471

40

3.0×10－－－1.2×102.25×10461－

1.0×109.75×103

66

56

1.0×107.30×103

66

67

1.0×105.60×103

66

74

1.0×107.20×103

66

67

1.0×107.00×103

66

68

1.0×107.00×103

66

68

403

※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

4044）Paved surfaces
A) High-pressure water cleaning and shot-blasting
Test decontamination of paved surfaces were executed by the following three methods; i)high-pressure water cleaning with vacuum collection of water (water pressure of 20 MPa,
2 times cleaning), ii) shot-blasting (discharge pressure of steel shot, 5M Pa by thestandard decontamination method in accordance with the decontamination guidelines)
and iii) shot-blasting (discharge pressure of steel shot, 7M Pa). The decontamination
rates were compared, the damaged condition of paved surfaces was checked and theapplicable scope of each decontamination method was verified.
The highest decontamination rate was obtained by the standard method of shot-blasting(discharge pressure of steel shot 7 MPa), but shot-blasting marks remained on the paved
surface and the road surface markings were even erased.
The high-pressure water cleaning with vacuum collection of water was appropriate toapply in narrow gaps and on the paved surfaces where damage should be avoided. The
shot-blasting at 7 MPa could basically be applied to flat places over a certain distance forcontinuous working. The lines on the roads and the locations vulnerable to damage
should be blasted at 5 MPa.
Table 6-22

Example results in residential areas, etc. of implementing high-pressure watercleaning and shot-blasting of pavement surface (Asphalt pavement)

Work Schedule

Suction Before
type high cleaningpressure Afterwatercleaning
BeforeShot
blasting
blasting
After
5mpa
blasting
BeforeShot
blasting
blasting
After
7mpa
blasting

Decontamination
Air dose rate Air dose
Surface
Decontamination Decontamination
rate of Air doseat 1 cm away rate at 1 m contamination
rate of Air dose rate of surface
rate at 1 cm
from theaway fromdensityrate at 1 m away contamination
away from thesurfacethe surface(withfrom the surface
densitysurface(μSv/h)(μSv/h) shielding cpm)
(%)
(%)
(%))
－

－

7.51×103

－

－

－

－

－

3.45×103

－

－

53

－

－

6.16×103

－

－

－

－

－

3.89×103

－

－

37

－

－

8.08×103

－

－

－

－

－

1.25×103－－

84※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The decontamination rate is the average value of decontamination rate at each measurement point.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

405

Table 6-23

Example results in residential areas, etc. of implementing high-pressure watercleaning and shot-blasting of pavement surface (Concrete pavement)

Work Schedule

Suction Before
type high cleaningpressure Afterwatercleaning
BeforeShot
blasting
blasting
After
7 MPa
blasting

Surface
Decontamination
Decontamination Decontamination
contamination rate of Air dose
rate of Air dose rate of surface
densityrate at 1 cm
rate at 1 m away contamination(withaway from thefrom the surface
densityshieldingsurface
(%)
(%)
cpm)
(%))

Air doserate at 1 cm
away fromthe surface(μSv/h)Air doserate at 1 m
away fromthe surface(μSv/h)－－2.45×104

－

－

－

－

－

1.06×104

－

－

56

－

－

2.08×104

－

－

－

－

－

7.92×103－－

63※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The decontamination rate is the average value of decontamination rate at each measurement point.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

406

（2） Schools1）Rooftops
A) High-pressure water cleaning.
Test decontamination was conducted on the rooftop of a kindergarten building covered bywater proof sheets using high-pressure water cleaning with vacuum water collection. The
discharge flow rate of 20 Lm3/m2 was used at two water pressure conditions of 10 MPa
and 15 MPa in the test.
No big difference in decontamination rates was observed for the two pressure conditions,
10 MPa and 15 MPa. No further significant decrease of decontamination rates was foundby the second and further cleaning, regardless of the cleaning pressure.
The standard cleaning method for rooftops was set as “one time cleaning at 15MPa.
Table 6-24

Example results of implementing high-pressure water cleaning of school roofs

Work Schedule

Cleaning
water
pressure(10mpa)Cleaning
water
pressure(15mpa)Beforecleaning
After
first
cleaning
Aftersecondcleaning
After
third
cleaning
Beforecleaning
After
first
cleaning
Aftersecondcleaning
After
third
cleaning

Air dose rate at 1
cm away fromthe surface(with shielding
μSv/h)

Surfacecontamination
density(with shielding
cpm)

Decontamination
rate of Air dose
rate at 1 cm
away from thesurface(%)

Decontamination
rate of Surface
contamination
density(%)－

3.12×102－－－

5.80×10－81－

3.40×10－89－

9.00×10－71－

3.90×102－－－

7.80×10－80－

7.80×10－80－

5.80×10－85※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

407

（3） Parks
1）Playgrounds and the likeA) Scraping topsoil and earth covering
Topsoil in a playground in a kindergarten facility was scraped and the scraped surface
was covered afterward with fresh soil. Two scraping depths of 5 cm and 10 cm were used.
It was found that even 5 cm scraping could obtain a decontamination rate of more than90%.
The standard decontamination method for parks (playgrounds) was set as scrapping
topsoil by 5 cm and earth covering by 5 cm.
Table 6-25

Example results of scraping topsoil followed by earth covering on park
playgrounds, etc.

Work schedule

Beforescraping
Scraping After
depth scraping
(5cm)
After
covering
Beforescraping
Scraping Afterdepthscraping(10cm)
Aftercovering

Air dose
Air dose
Surface
Decontamination
rate at 1 cm rate at 1 m
Decontamination Decontamination
contamination rate of Air doseaway from away fromrate of Air dose rate of surface
densityrate at 1 cm
the surface the surface
rate at 1 m away contamination(withaway from the
(with
(with
from the surface
densityshieldingsurfaceshielding shielding
(%)
(%)
cpm)
(%))
,μSv/h)μSv/h)－－

8.76×102

－

－

－

－

－

4.00×10

－

－

95

－

－

2.80×10

－

－

97

－

－

1.10×103

－

－

－

－

－

1.40×10

－

－

99

－

－

3.40×10－－97※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

408

（4） Large size facilities
1）Rooftops
A) High-pressure water cleaning
The standard method of high-pressure water cleaning was tested for the rooftop of a
hospital covered by waterproof sheets and cinder concrete. The discharge flow rate of 20
Lm3/m2 was used at two water pressure conditions of 10 MPa and 15 MPa in the test.
Higher decontamination rates were obtained by 15 MPa cleaning than 10 MPa cleaning.
For the waterproof sheet rooftops, the decontamination rate of 3% was obtained by thesecond cleaning. Therefore, the most effective decontamination method was twice
cleaning at 15MPa water pressure. For the cinder concrete rooftops, no significant
decontamination rate could be observed regardless of the number of cleaning times andwater pressure.
The standard decontamination method was set as one-time cleaning at 15MPa waterpressure for both types of rooftops of large size facilities, in due consideration of
workability and overlapping of work areas.
Table 6-26

Example results of implementing high-pressure water cleaning of roofs onlarge-size facilities (waterproof sheeting)Work Schedule

Cleaning waterpressure(10mpa)Cleaning waterpressure(15mpa)Beforecleaning
After firstcleaning
Aftersecondcleaning
Beforecleaning
After firstcleaning
Aftersecondcleaning
After thirdcleaning

Air dose rate at 1
cm away fromthe surface(with shielding
μSv/h)

Surfacecontamination
density(with shielding
cpm)

Decontamination
rate of Air dose
rate at 1 cm
away from thesurface(%)

Decontamination
rate of Surface
contamination
density(%)－

2.98×102－－－

1.48×102－50－

1.34×102－55－

2.04×102－－－

1.10×102－46－

6.80×10－67－

6.20×10－70※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

409

Table 6-27

Example results of implementing high-pressure water cleaning of roofs onlarge-size facilities (cinder concrete)

Work Schedule

Cleaning waterpressure(10mpa)Cleaning waterpressure(15mpa)Beforecleaning
After firstcleaning
Aftersecondcleaning
Beforecleaning
After firstcleaning
Aftersecondcleaning

Air dose rate at 1
cm away fromthe surface(with shielding
μSv/h)

Surfacecontamination
density(with shielding
cpm)

Decontamination
rate of Air dose
rate at 1 cm
away from thesurface(%)

Decontamination
rate of Surface
contamination
density(%)－

5.77×103－－－

2.54×103－56－

2.33×103－60－

6.50×103－－－

2.32×103－64－

1.98×103－70※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

4102）Paved surfacesA) Shot-blasting
The shot-blasting for paved surfaces in a hospital premise was tested with different
discharge pressures of steel shot, 7 MPa (the standard decontamination method) and 5
MPa. The low discharge pressure was tested in order to consider preventing the paved
surface from being damaged. The decontamination effect was also tested on the asphalt
surface and road surface markings (drawn by the thermoplastic method).
Decontamination rates and the degree of damage were compared between
decontamination methods.
The highest decontamination rate was obtained by the standard decontamination methodof shot-blasting (7 MPa discharge pressure of steel shot). But marks due to steel shot
remained on the paved surfaces and the white surface marking were erased.
It is necessary to lower the discharge pressure to about 5 MPa or to consider analternative method for places with road surface markings.
Table 6-28

Work schedule

7MPawith lap

7MPa
withoutlap

Example results of implementing shot-blasting on pavement surface(conventional pavement surface) of large-size facilities
Air dose rate Air dose rate
Surface
Decontamination
Decontamination Decontamination
at 1 cm away at 1 m away contamination rate of Air dose
rate of Air dose rate of surface
from thefrom thedensityrate at 1 cm
rate at 1 m away contamination
surface (with surface (with(withaway from thefrom the surface
densityshieldingshieldingshieldingsurface(%)(%),μSv/h)μSv/h)
cpm)(%))

Beforeblasting

－

－

After
blasting－－

Beforeblasting

－

－

After
blasting－－

5.86×103
5.02×102 ※1

5.86×103 ※2

6.15×102 ※3

－

－

－

－

－

91 ※1

－

－

－

－

－

90 ※3

※1 The average of the values of measured at 5 locations※2 Since the value before decontamination was not consistent with the value after decontamination, it
was compared using the average of measurements in a decontamination targets.
※3 The average of the values of measured at 4 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be
decontaminated. Therefore, it does not assure that the equivalent effect can be attained by the samedecontamination method.

411

Table 6-29

Example results of implementing shot-blasting on pavement surface (whitesurface markings) of large-size facilities

Work schedule

Before5MPablasting
withoutAfterlapblasting
Before7MPablasting
withoutAfterlapblasting

Air dose rate Air dose rate
Surface
Decontamination
Decontamination Decontamination
at 1 cm away at 1 m away contamination rate of Air dose
rate of Air dose rate of surface
from thefrom thedensityrate at 1 cm
rate at 1 m away contamination
surface (with surface (with(withaway from thefrom the surface
densityshieldingshieldingshieldingsurface(%)(%),μSv/h)μSv/h)
cpm)
(%))
－

－

7.83×103 ※1

－

－

－

－

－

4.50×103 ※1

－

－

43 ※1

－

－

2.68×103 ※2

－

－

－

－

－

3.83×102 ※2

－

－

84 ※2

※1 The measurement were implemented at 3 locations. But, these data was abandoned, due to widelydiscrepancies.
※2 The average of 3 measurements. The decontamination rate is the average of the decontamination rate
which was calculated in every location.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be
decontaminated. Therefore, it does not assure that the equivalent effect can be attained by the samedecontamination method.

3）Wood decks
A) Wiping, high-pressure water cleaning and superhigh-pressure water cleaning
Wood decks of large facilities were decontaminated by wiping, high-pressure watercleaning and superhigh-pressure cleaning for tests.
The decontamination rate by wiping with wet cleaning cloths was about 10%. Both thedecontamination rates by superhigh-pressure water cleaning and high-pressure watercleaning were about 95%.
The superhigh-pressure water cleaning caused splinters on the wood deck surfaces due tothe high water pressure. Therefore, the high-pressure water cleaning was chosen as thestandard decontamination method for wood decks.

412

Table 6-30 Example results of implementing high-pressure water cleaning andsuperhigh-pressure water cleaning of wood decks of large-size facilities
Air dose
Air dose
Surface
Decontamination
rate at 1 cm rate at 1 m
Decontamination Decontamination
contamination rate of Air doseaway from away fromrate of Air dose rate of surface
densityrate at 1 cm
Work schedule the surface the surface
rate at 1 m away contamination(withaway from the
(with
(with
from the surface
densityshielding,surfaceshielding, shielding,
(%)
(%)
cpm)
(%)
,μSv/h)μSv/h)
BeforeWipingwipingby wetAfterragwipingBeforeHighcleaningpressure
After
15 mpacleaning
Superhi Before
cleaning
ghpressure After
70mpa cleaning－－

3.89×103

－

－

－

－

－

3.29×103

－

－

15

－

－

8.99×103

－

－

－

－

－

4.32×102

－

－

95

－

－

7.70×103

－

－

－

－

－

4.32×102－－

94※ The value shown in the table is the average of the value (s) measured at 5 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

413

（4） Roads
1）Paved surfaces
A) Superhigh-pressure water cleaning
Decontamination by the superhigh-pressure water at the standard water pressure of 150
MPa may damage the road surface and erase road surface markings on it (center lines,
outer lines), just as occurred by the shot-blasting. To set the appropriate cleaningpressure, test decontamination was conducted by changing the water pressures as 15, 30,
50, 100 and 150 MPa, while observing damage conditions of the road surface and thedecontamination effect.
The standard pressure for superhigh-pressure water cleaning is 150 MPa. The working
pressure of 100 MPa does not show significant deterioration of decontamination rates.
Concerning the damage on the surface, no big damage was observed below 30 MPa. But
at 50 MPa, loosened materials were blown out and above 100 MPa, the lines (center lines
and outer lines) were erased.
It is necessary to consider lowering the water pressure below 100 MPa when working onroad marking areas and portions where noticeable damage was found on the pavement.
Table 6-31 Example results of implementing superhigh-pressure water cleaning of road pavement
surfaces
Air dose
Air dose
Surface
Decontamination
cleaning water rate at 1 cm rate at 1 m
Decontamination Decontamination
contamination rate of Air dosepressure of away from away fromrate of Air dose rate of surface
densityrate at 1 cm
superhighthe surface the surface
rate at 1 m away contamination(withaway from thepressure water
(with
(with
from the surface
densityshieldingsurfacecleaning
shieldingshielding
(%)
(%)
cpm)
(%))
,μSv/h)μSv/h)
Beforecleaning
15
MPa After
cleaning
Beforecleaning
30
MPa After
cleaning
Beforecleaning
50
MPa After
cleaning
Before100 cleaning
MPa After
cleaning
Before150 cleaning
MPa After
cleaning－－

4.09×103

－

－

－

－

－

1.99×103

－

－

51

－

－

5.11×103

－

－

－

－

－

2.08×103

－

－

60

－

－

4.32×103

－

－

－

－

－

1.21×103

－

－

72

－

－

4.58×103

－

－

－

－

－

7.20×102

－

－

83

－

－

3.10×103

－

－

－

－

－

6.30×102－－80※ The value shown in the table is the average of the value (s) measured at 3 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.
414

415

（5） Farmland
1）Rice fields
A) Scraping topsoil, covering by fresh soil, leveling of unevenness and double plowing
Topsoil of rice fields in relatively high dose areas in the target area was scraped off by soil
skimmers142, and plowed after being covered by fresh soil. Prior to the scraping, the field
was mowed, the cut materials were removed, the top soil was scraped and the unevenness
was leveled by rolling compaction followed by double plowing to a depth of 3 cm.
According to present knowledge, the radiocesium concentration in the layer below 5 cm
from the surface is less than 5,000 Bq/kg in most farmland, even if the radiocesium
concentration in the surface layer of about 5 cm exceeds 5,000 Bq/kg. The scraping
thickness is set as 5 cm. But according to the sampling survey of the radiocesium
concentration as a function of depth, there were cases in District D in which theconcentration below 5 cm from the surface still exceeded 5,000 Bq/kg. Therefore, three
scraping depths of 5 cm, 7 cm and 10 cm were applied in this test decontamination.
The cases in which decontamination rates of 7 cm scraping were lower (higher
contamination densities) than those of 5 cm scraping were considered to be due tolocalized conditions (a similar trend was noticed in the radiocesium concentration
analysis in the layer, i.e. higher radiocesium concentrations when scraped by 7 cm thanby 5 cm).
The evaluation based on decontamination rates using surface contamination densities isgenerally considered appropriate for surface contamination. But such results were notalways obtained in farmland. Contamination in farmland may not be surface
contamination, but penetration contamination. In this case, the evaluation using dose
equivalent rates would be more appropriate.
Based on a proposal by the decontamination business operator, test measurements in ahigh dose area were conducted using a collimator and placing lead blocks on the ground,in order to shield from the surrounding radiation and preclude the influence of radiation
sources other than those on the surface. The difference of air dose rates between the caseswith shielding and without shielding is equivalent to the dose rate due to only gamma
rays. This approach gave better (more accurate) values. But the difference was just a few
percent and lead blocks are needed for measurement. In view of the workload required,ordinary measurements using a collimator of air dose rate at 1 cm from the surface isconsidered appropriate for measurements related to decontaminating farmland.
Even with the scraping depth of 5 cm, the decontamination rate of more than 90% after
plowing was obtained in the air dose rates as well as in the surface contamination
densities.

142

Topsoil scrapping and recovering machine

416

Table 6-32

Example results of scraping topsoil, bringing topsoil from another place, leveling
unevenness, and implementing double plowing of rice fields

Work Schedule,
Scraping depth

Scraping
5 cm

Scraping
7cm

Scraping
10 cm

Beforescraping
Afterscrapping
Afterbringing
topsoilfromanotherplace
Afterplowing
Beforescraping
Afterscraping
Afterbringing
topsoilfromanotherplace
Afterplowing
Beforescraping
Afterscraping
Afterbringing
topsoilfromanotherplace
Afterplowing

Air dose
Air dose
Surface Decontamination
rate at 1 cm rate at 1 m
Decontamination Decontamination
contamination rate of Air doseaway from away fromrate of Air dose rate of surface
densityrate at 1 cm
the surface the surface
rate at 1 m away contamination(withaway from the
(with
(with
from the surface
densityshieldingsurfaceshieldingshielding
(%)
(%)
cpm)
(%))
,μSv/h)μSv/h)
8.1

－

－

－

1.6

－

－

77

5.6×10-1

－

－

90

－

92

6.0×10-1

－

－

89

－

91

6.4

－

－

－

－

－

1.6

－

－

71

－

70

6.0×10-1－－

88

7.6×10-1

－

－

87

－

88

8.1

－

－

－

－

－

2.6×10-1

－

－

92

－

91

2.0×10-1－－

95

1.0×10-1

－

－

96

－

－
73

91

94

－

95

※ The value shown in the table is the average of the value (s) measured at 3 locations.
※ The effect of decontamination depends on the various factors such as the material and the surface
condition of decontamination target, their deterioration status and so on. The results shown above are
the results which have been implemented in a tentative way for the specific target to be decontaminated.
Therefore, it does not assure that the equivalent effect can be attained by the same decontamination
method.

417