i

まえがき
労働安全衛生法第 65 条に規定する作業環境測定は，事業場の労働衛生管理の基本となるもので，その的確な実施のために，厚生労働大臣の定める「作業環境測定基準」に則して『作業環境測定ガイドブック』が当協会から刊行されています。
『作業環境測定ガイドブック』（以下，ガイドブック）は，作業環境測定法
施行規則別表の作業場の種類に従ってガイドブック 1（粉じん・石綿・RCF），
同 2（電離放射線関係），同 3（金属類を除く特定化学物質），同 4（金属類），
同 5（有機溶剤）に分かれているほか，デザイン，サンプリングおよび測定結果の評価方法等を説明したガイドブック 0（総論編）と同 6（温湿度・騒音・酸欠等関係）の全 7 冊から構成されてきました。
ガイドブック 2 は，作業環境測定基準に則った測定の具体的な実施方法の例を示すことにより作業環境測定の技術水準の向上と測定結果の精度の確保を図るため，1980（昭和 55）年に電離放射線に関する測定を対象としてガ
イドブック 4 として発刊され，その後の改訂を経て，『作業環境測定ガイド
ブック 2 電離放射線関係』として刊行されてきました。
本書は化学物質関係のガイドブック 3，4，5 が 2019（令和元）年に「物質別各論」として改題され発行されたことに伴い，装いを新たに『作業環境測定ガイドブック 2［電離放射線・放射性物質］の測定の実務』として 2020
年に初版発行しました。この第 2 版では用語用字の修正等を行いました。

ii
本書が，作業環境管理に携わる関係各位に広く活用され，作業環境測定・評価の技術水準および精度等の一層の向上に寄与することを期待いたします。
2023 年 3 月(公社)日本作業環境測定協会

iii

目

次
Ⅰ 総 論

1. 目 的 ··················································································· 2
2. 空気汚染の管理······································································ 2
3. 試料採取方法 ········································································· 3
3.1 試料採取方法の種類 ······························································ 3⑴ ろ過捕集方法 ·································································· 3⑵ 液体捕集方法 ·································································· 3⑶ 直接捕集方法 ·································································· 3⑷ 固体捕集方法 ·································································· 4⑸ 冷却凝縮捕集方法 ···························································· 4
3.2 試料採取方法の選定 ······························································ 4
3.3 試料採取方法（サンプリング方式） ········································· 4⑴ ゼネラルサンプリング（室内全体空気のサンプリング） ········· 5⑵ セントラルサンプリング（集中サンプリング） ····················· 6⑶ ローカルサンプリング（局所空気のサンプリング） ··············· 7⑷ スポットサンプリング（特殊作業のサンプリング） ··············· 7⑸ パーソナルサンプリング（個人空気サンプリング） ··············· 7
3.4 試料採取時間および箇所 ························································ 7
3.5 吸引試料空気量 ···································································· 9
3.6 ろ過捕集材の性能 ······························································· 10

4. 分析方法·············································································· 12
4.1 分析方法の種類と選択 ························································· 12
4.2 核種同定の必要性 ······························································· 13
4.3 全放射能計測方法 ······························································· 14

iv
4.3.1 計測器 ········································································ 14⑴ 全α放射能計測器 ·························································· 14⑵ 全β放射能計測器 ·························································· 15⑶ 全γ放射能計測器 ·························································· 15⑷ ガス捕集用電離箱 ·························································· 16
4.3.2 計測器の校正 ······························································· 16〈参考〉標準線源の作製 ·························································· 18
4.4 放射線スペクトル分析方法 ··················································· 19
4.4.1 計測器 ········································································ 19⑴ α線スペクトロメータ ···················································· 19⑵ β線スペクトロメータ ···················································· 20⑶ γ線スペクトロメータ ···················································· 20
4.4.2 計測器の校正 ······························································· 20
4.5 放射化学分析方法 ······························································· 22
4.6 蛍光光度分析方法 ······························································· 24
4.7 分析方法の選定 ·································································· 24
4.8 空気中濃度の計算 ······························································· 24

5. 測定結果の記録···································································· 25

Ⅱ 各 論
第 1 章 使用器具の取扱いと濃度評価上の留意点 ························ 28
1. ろ過捕集方法による空気中放射性物質濃度測定方法 ·············· 28
1.1 適用範囲 ··········································································· 28
1.2 使用器具類 ········································································ 28⑴ ろ過式ダストサンプラまたはろ過式ダストモニタ ················ 28⑵ ろ 紙 ········································································· 29⑶ 放射能計測器 ································································ 29
1.3 試料採取方法 ····································································· 30
1.3.1 吸引試料空気量 ···························································· 30

v
1.3.2 捕集条件 ····································································· 31
1.3.3 流量の補正 ·································································· 31
1.4 放射能計測方法 ·································································· 32⑴ 計数器による場合 ·························································· 32⑵ 計数率計（ダストモニタ）による場合 ······························· 33⑶ 放射線スペクトル分析方法を用いる場合 ···························· 33
1.5 空気中放射性物質濃度の計算 ················································ 34⑴ 計数器による場合 ·························································· 34⑵ 計数率計による場合 ······················································· 35
1.6 記 録 ·············································································· 35〈参考〉ダストモニタによるプルトニウムの連続測定方法 ················ 36

2. 固体捕集方法による放射性ヨウ素など揮発性物質の空気中濃度測定方法 ····························································· 38
2.1 適用範囲 ··········································································· 38
2.2 使用器具類 ········································································ 38⑴ サンプラまたはモニタ ···················································· 39⑵ 捕集材 ········································································· 39⑶ 放射能計測器 ································································ 40
2.3 試料採取方法 ····································································· 40
2.3.1 捕集効率 ····································································· 40⑴ 放射性ヨウ素 ································································ 40⑵ 放射性ヨウ素以外の揮発性物質 ········································ 42
2.3.2 吸引試料空気量 ···························································· 42
2.3.3 捕集条件 ····································································· 42⑴ 平均流量 ······································································ 42⑵ 流 速 ········································································· 44
2.4 放射能計測方法 ·································································· 44⑴ 計数器による場合 ·························································· 44⑵ 計数率計（モニタ）による場合 ········································ 44

vi⑶ γ線スペクトル分析方法による場合 ·································· 45
2.5 空気中濃度の計算 ······························································· 45
2.6 記 録 ·············································································· 46

3. ガス捕集用電離箱を用いた直接捕集方法による
ガス状放射性物質の空気中濃度測定方法 ······························· 46
3.1 適用範囲 ··········································································· 46
3.2 使用器具類 ········································································ 47⑴ ガス捕集用電離箱または流通型電離箱 ······························· 47⑵ 真空ポンプおよび真空計 ················································· 47⑶ 電位計 ········································································· 47
3.3 試料採取方法 ····································································· 47
3.4 放射能計測方法 ·································································· 48
3.5 空気中濃度の計算 ······························································· 50〈参考〉ラドンに対する濃度換算係数 ··········································· 52
3.6 記 録 ·············································································· 52

4. 捕集用ガス容器を用いた直接捕集方法による
ガス状放射性物質の空気中濃度測定方法 ······························· 53
4.1 適用範囲 ··········································································· 53
4.2 使用器具類 ········································································ 53⑴ 捕集用ガス容器 ····························································· 53⑵ 吸引ポンプ ··································································· 53⑶ 放射能計測器 ································································ 53
4.3 試料採取方法 ····································································· 53
4.4 放射能計測方法 ·································································· 55⑴ 計数器による場合 ·························································· 55⑵ 計数率計（モニタ）による場合 ········································ 56
4.5 空気中濃度の計算 ······························································· 56
4.6 記 録 ·············································································· 57

vii

5. 冷却凝縮捕集方法，液体捕集方法および固体捕集方法
によるトリチウム化水蒸気などの空気中濃度測定方法 ··········· 57
5.1 適用範囲 ··········································································· 57
5.2 トリチウム化水蒸気濃度測定方法の比較 ································· 58
5.3 冷却凝縮捕集方法によるトリチウム化水蒸気の
空気中濃度測定方法 ··························································· 59
5.3.1 使用器具類 ·································································· 59
5.3.2 試料採取方法および測定試料の作製 ································· 59⑴ 試料採取の方法 ····························································· 59⑵ 測定試料の作製 ····························································· 60
5.3.3 試料水中のトリチウム放射能計測方法 ······························ 61
5.3.4 空気中濃度の計算 ························································· 61
5.3.5 記 録 ········································································ 62
5.4 液体捕集方法によるトリチウム化水蒸気の
空気中濃度測定方法 ··························································· 62
5.4.1 使用器具類 ·································································· 62
5.4.2 試料採取方法および測定試料の作製 ································· 63⑴ 試料採取の方法 ····························································· 63⑵ 測定試料の作製 ····························································· 64
5.4.3 吸引試料空気量 ···························································· 64
5.4.4 捕集効率の決定 ···························································· 64
5.4.5 試料水中のトリチウム放射能計測方法 ······························ 64
5.4.6 空気中濃度の計算 ························································· 65
5.4.7 記 録 ········································································ 65
5.5 固体捕集方法によるトリチウム化水蒸気の
空気中濃度測定方法 ··························································· 65
5.5.1 使用器具類 ·································································· 65
5.5.2 試料採取方法 ······························································· 66⑴ 吸 着 ········································································· 66

viii⑵ 脱 着 ········································································· 66
5.5.3 試料水中のトリチウム放射能計測方法 ······························ 67
5.5.4 空気中濃度の計算 ························································· 68
5.5.5 記 録 ········································································ 69〈参考〉トリチウムガスの酸化捕集方法 ········································ 69

6. 蛍光光度分析方法による空気中ウラン濃度の測定方法 ··········· 70
6.1 原理および適用範囲 ···························································· 70
6.2 使用器具類 ········································································ 70〈参考〉ウラン標準溶液の調製方法 ·············································· 71
6.3 試料採取方法および採取試料の処理 ······································· 71
6.3.1 試料採取方法 ······························································· 71
6.3.2 採取試料の処理 ···························································· 71
6.3.3 ウランの抽出 ······························································· 72
6.4 溶融体の作製 ····································································· 72
6.4.1 溶融剤の調製 ······························································· 72
6.4.2 溶融体の作製 ······························································· 72
6.5 蛍光光度測定ならびにウランの定量 ······································· 72
6.5.1 蛍光光度測定 ······························································· 72
6.5.2 ウランの定量 ······························································· 73
6.6 空気中濃度の計算 ······························································· 73
6.7 記 録 ·············································································· 74

第 2 章 外部放射線による線量当量率の測定 ······························ 75
1. 目 的 ················································································· 75
2. γ線および X 線の線量当量率の測定 ····································· 75
2.1 測定対象 ··········································································· 75
2.2 測定点の選定 ····································································· 75
2.3 測定機器の型式と特性 ························································· 76
2.3.1 線量当量率計 ······························································· 76

ix
2.3.2 線量当量計 ·································································· 79
2.3.3 測定機器の選択 ···························································· 80
2.4 測定方法 ··········································································· 80
2.5 測定機器の校正および点検 ··················································· 81⑴ 校 正 ········································································· 81⑵ 日常点検 ······································································ 82
2.6 1 cm 線量当量率および 70 µm 線量当量率の算定方法 ··············· 82⑴ 1 cm 線量当量率の算定方法············································· 82⑵ 70 µm 線量当量率の算定方法··········································· 85

3. β線および電子線の線量当量率の測定 ·································· 86
3.1 測定対象 ··········································································· 86
3.2 測定点の選定 ····································································· 86
3.3 測定機器の型式と特性 ························································· 86
3.3.1 線量当量率計 ······························································· 86
3.3.2 線量当量計 ·································································· 87
3.4 測定方法 ··········································································· 87
3.5 測定機器の校正および点検 ··················································· 88⑴ 校 正 ········································································· 88⑵ 日常点検 ······································································ 88
3.6 70 µm 線量当量率の算定方法 ··············································· 88

4. 中性子線の線量当量率の測定················································ 88
4.1 測定対象 ··········································································· 88
4.2 測定点の選定 ····································································· 88
4.3 測定機器の型式と特性 ························································· 89
4.3.1 線量当量率計 ······························································· 89
4.3.2 線量当量計 ·································································· 90
4.4 測定方法 ··········································································· 91
4.5 測定機器の校正および点検 ··················································· 91⑴ 校 正 ········································································· 91

x⑵ 日常点検 ······································································ 91
4.6 1 cm 線量当量率および 70 µm 線量当量率の算定方法 ··············· 91⑴ 1 cm 線量当量率の算定方法············································· 91⑵ 70 µm 線量当量率の算定方法··········································· 92

5. 測定結果の記録···································································· 92〈参考資料〉測定結果の記録用紙 ················································· 94

第 3 章 放射能測定データの精度とその表し方 ·························· 101
1. 基本的事項 ········································································· 101
1.1 精度の表し方 ···································································· 101
1.2 比較測定と絶対測定 ··························································· 101
1.3 トレーサビリティ ······························································ 101

2. 基本的統計分布と統計誤差 ·················································· 102
2.1 ポアソン分布 ···································································· 102
2.2 正規分布 ·········································································· 102
2.3 誤差の伝ぱ ······································································· 102

3. 放射能測定値の統計誤差 ····················································· 103
3.1 全計数および計数率の統計誤差 ············································ 103
3.2 正味計数率の統計誤差 ························································ 103
3.3 最適測定時間の配分 ··························································· 104
3.4 最低検出可能放射能 ··························································· 104

4. 測定装置の不感時間の補正 ·················································· 104〈参考〉核原料物質鉱山の坑内における放射性物質の濃度の測定 ····································································· 106

用語解説··················································································· 108

Ⅰ

総

論

2

Ⅰ

総

論

「Ⅰ 総論」では，作業環境における空気中の粒子状およびガス状の放射性物質の濃度を測定するための試料採取および測定法について述べる。
対象となる放射性物質の種類は非常に多いので，ここではそれらの大部分に共通する測定方法を主として述べ，必要に応じて，特殊な手法を必要とす
る放射性物質の測定方法についても触れる。

1．目

的

作業環境測定の目的の一つは，作業環境における空気中の粒子状およびガ
ス状の放射性物質を採取，定量し，作業場所での空気中の放射性物質の濃度を求めることにより，作業環境管理の適切さを確認するための資料を得ることである。

2．空気汚染の管理
作業環境における空気汚染の発生原因としては，次の場合が考えられる。
⑴ 放射性物質の取扱いにおける操作または反応① 放射性炭素を含む炭酸ガスやトリチウムを含む水素ガスを発生するような化学反応② トリチウム水などの蒸発や放射性ヨウ素などの揮発③ 放射化あるいは汚染した固体の切削または研磨④ 粒子状放射性物質の容器間の移し替え⑤ 放射性廃棄物の詰め替え⑵ 表面汚染物質の再浮遊または飛散① 床や器具類の表面汚染物質が歩行や作業に伴ない微粉末となることによって生じる当該物質の浮遊または飛散② 内部が汚染した器具類の開放や，放射性物質用容器の開封などの操作に伴う，内面に付着している粉末状汚染物質の浮遊または飛散

3．試料採取方法 3えい⑶ 密封系器具類の欠陥などによるガスまたは粉末の漏洩⑷ ウランの採鉱や精錬
このように，放射性物質を非密封の状態で取扱う作業場においては，種々の原因により空気汚染が発生することが考えられるので，放射性物質の封じ込めまたは作業環境への漏洩防止のためにグローブボックスやフード，または局所排気装置付の汚染防止囲い等の使用のほか，部屋の換気や作業場所の
局所排気による空気汚染の低減措置をとることが最も重要である。
これらの施設においては，作業環境における空気汚染を適切に評価し，必要があれば作業環境の改善等を行う必要がある。

3．試料採取方法
3.1 試料採取方法の種類
空気中における放射性物質の状態や放射能測定方法等を考慮して，表Ⅰ.1に示すいろいろな試料採取方法が用いられる。
ここで表Ⅰ.1 の各試料採取方法は，次のように特徴づけられる。
⑴ ろ過捕集方法
試料空気をろ過材，例えばろ紙を通して吸引し，ろ過材に測定対象物質を捕集する方法である。
⑵ 液体捕集方法
試料空気を液体中に通しまたは液体表面と接触させ，溶解，反応，吸収，衝突等を利用して測定対象物質を捕表Ⅰ.1 試料採取方法

集する方法である。
⑶ 直接捕集方法
試料空気を吸収，吸着等の過程を放射性物質の状態
粒

子

状

ガ

ス

状

経ずにそのままガス捕集用電離箱や捕集用ガス容器などの捕集容器に採取する方法である。

試料採取方法ろ過捕集方法
液体捕集方法直接捕集方法
固体捕集方法
液体捕集方法
冷却凝縮捕集方法

4

Ⅰ

総

論

⑷ 固体捕集方法
試料空気を活性炭やシリカゲルなどの固体粒子層を通して吸引するなどにより，固体粒子の上に測定対象物質を捕集する方法である。
⑸ 冷却凝縮捕集方法
試料空気を冷却面に接触させ，凝縮を利用して測定対象物質を捕集する方法である。

3.2 試料採取方法の選定
空気中の放射性物質には，繊維系ろ紙で捕集されるような粒子状の物質と，ヨウ素のような揮発性物質，水蒸気および化学的に不活性な希ガスなどガス状の物質とがある。空気試料の採取の方法は，放射性物質の種類や性状，採取試料の分析方法における検出感度および濃度限度（電離放射線障害防止規則第三条第三項並びに第八条第五項及び第九条第二項の規定に基づく厚生労働大臣が定める限度及び方法（昭和 63 年 10 月 1 日 労働省告示第 93 号，
最終改正：令和 4 年 11 月 17 日 厚生労働省告示第 335 号））との関係を考慮し，適切な方法を選択しなければならない。この場合，原則として検出下限濃度が濃度限度の 1/10 以下となることを目標とする。
表Ⅰ.2 に主な放射性物質の性状と，それに適する試料採取方法および分析方法との関連を示す。
また，放射性物質の性状は，発生条件や作業環境の特性等によっても変化する。性状の異なる放射性物質が混在するおそれのあるときは，それぞれに適した試料採取方法を併用して選別捕集することが必要になる。
この場合，ある方法によって得られる核種の濃度と，その核種の濃度限度との比（ここでは濃度限度比という）が，その他の方法によってそれぞれ得られる濃度限度比の総和に対して十分小さい（0.1 以下）ことが明らかなときは，その方法による試料採取は省略してよい。

3.3 試料採取方法（サンプリング方式）
試料採取方式（以下サンプリング方式という）には，①作業室全体の空気3．試料採取方法 5
表Ⅰ.2 各試料採取方法と放射性物質の性状および分析方法の組み合わせの例
試料採取方法

捕集材，捕集

対象放射性

器具（例）

物質の性状

ろ紙

粒子状

ろ過捕集方法

固体捕集＊1方法

主な核種

放射性物質定量方法＊2

60Co，67Ga，99mTc，全α，全β，全γ放射能計測方法，

147Pm，201Tl，U，

α，β，γ線スペクトル分析方法，

Pu

蛍光光度分析方法＊3

活性炭含浸

気体状（揮

32P，35S

ろ紙

発性物質）

123I，125I，131I
203Hg

全β，全γ放射能計測方法，γ線スペクトル分析方法

活性炭カー

気体状（揮

123I，125I，131I，

トリッジ

発性物質）

203Hg

トル分析方法

シリカゲル

水蒸気

3H

液体シンチレーション計測方

全γ放射能計測方法，γ線スペク

法＊4
ガス捕集用
直接捕集方法

気体状

放射性希ガス，

全β，全γ放射能計測方法（いず3H，14C

れも電離電流計測方法）

気体状

放射性希ガス

全β，全γ放射能計測方法

水蒸気

3H

液体シンチレーション計測方

水蒸気，

3H

液体シンチレーション計測方

ミスト

14C

法＊4

電離箱
捕集用ガス
容器

冷却凝縮捕集

コールドト

方

ラップ

法

液体捕集方法

水バブラー

γ線スペクトル分析方法
法＊4

1 一般には，ろ過捕集方法と併用される。

＊

2 ここには示されていないが，放射化学分析方法は，対象核種の濃縮，分離あるいは計測試料の＊調製の目的ですべての場合に適用することができる。
3 ウランの場合に限る。

＊

4 液体シンチレーション計測方法は，この場合β線スペクトル分析方法とみなされる。

＊

汚染の有無を確認する，②空気中の放射性物質の濃度分布を把握する，③作
業者が吸入する空気中の放射性物質の濃度を知るなどの目的によって次のよ
うな方式がある（図Ⅰ.1 参照）。
⑴ ゼネラルサンプリング（室内全体空気のサンプリング）
放射性物質取扱室全体についての空気汚染の検出を目的とし，空気汚染発生源の位置を確認するためのものではない。試料採取箇所は，空気汚染の発生を確実に検出できる位置とし，例えば，室内の換気用排気口付近や作業場
所の風下とする。