Spatial distributions of atmospheric concentrations of radionuclides on 15 March 2011 discharged by the Fukushima Dai-Ichi Nuclear Power Plant Accident estimated from NaI(Tl) pulse height distributions measured in Ibaraki Prefecture

Figures & data

Table 1. List of the monitoring stations and the estimation methods applied to them. H is by the hybrid method of the present study and T by the method of Terasaka et al. [13].

No.	MS	Latitude/°N	Longitude/°E	Altitude/m [27]	Estimation Method
Northern Coastal (NC) sector
1	Kuji	36.5044	140.6101	36	H
2	Ishigami	36.4872	140.5715	19	H
3	Toyooka	36.4787	140.6020	3	H
4	Funaishikawa	36.4676	140.5544	30	H
5	Oshinobe	36.4502	140.5696	31	H
6	Muramatsu	36.4495	140.5962	13	H, T
Northern Inland (NI) sector
7	Isobe	36.5161	140.5383	8	H
8	Kadobe	36.4887	140.4840	35	H
9	Yokobori	36.4655	140.5200	34	H
Central Coastal (CC) sector
10	Mawatari	36.4116	140.5717	31	H
11	Hitachinaka	36.3967	140.5925	30	H
12	Ajigaura	36.3873	140.6076	29	T
Central Inland (CI) sector
13	Sugaya	36.4446	140.5000	34	T
14	Horiguchi	36.3866	140.5149	22	H
15	Ishikawa	36.3921	140.4257	39	T
Southern Coastal (SC) sector
16	Ohba	36.3297	140.5195	25	H
17	Ohnuki	36.3085	140.5524	31	T
18	Hiroura	36.2933	140.5107	29	H
19	Araji	36.2301	140.5474	42	T
20	Tsukuriya	36.2385	140.5108	17	H
Southern Inland (SI) sector
21	Ebisawa	36.2588	140.4595	27	H
Dose rate measurements
K	Kume	36.5379	140.4775	26	–
N	Nemoto	36.5269	140.4367	21	–

Figure 1. Locations of the estimated monitoring stations, numbered as in Table 1. The two monitoring stations Kume (K) and Nemoto (N) referred to their dose rate records and the two meteorological stations Hitachi (H) and Mito (M) operated by Japan Meteorological Agency are also shown.

Table 2. The setting of the bins and the values of factor Γ determined by calculation with the EGS5 code. The values of Γ less than 10⁻⁷ cps (Bq m⁻³)⁻¹ are expressed as zero.

			Γ/cps (Bq m^−3)^−1
BIN No.	Aimed Gamma Ray (Energy, Emission Rate)	Width/keV *	Xe-133	Te-132	I-131	I-133	Cs-137	Cs-134	I-132	Cs-136
1	Xe-133 (81keV, 38.0%)	56–102	1.459E-03	4.995E-03	5.542E-03	5.656E-03	4.814E-03	1.252E-02	1.574E-02	1.545E-02
2	Te-132 (228keV, 88.0%)	205–257	0	1.571E-03	9.043E-04	1.128E-03	1.021E-03	2.658E-03	3.388E-03	2.973E-03
3	I-131 (364keV, 81.7%)	329–408	0	0	8.464E-04	3.670E-04	3.534E-04	9.213E-04	1.147E-03	1.153E-03
4	I-133 (530keV, 87.0%)	494–577	0	0	1.402E-05	5.257E-04	1.277E-04	5.188E-04	6.110E-04	4.505E-04
5	Cs-137 (662keV, 85.1%)	628–721	0	0	3.048E-05	1.949E-05	3.727E-04	2.078E-04	6.895E-04	2.755E-04
6	Cs-134 (796keV, 85.5%)	742–845	0	0	1.212E-06	1.183E-05	0	3.197E-04	3.145E-04	4.656E-04
7	I-132 (955keV, 17.6%)	912–1036	0	0	0	7.883E-06	0	5.240E-06	7.107E-05	8.140E-05
8	Cs-136 (1048keV, 80.3%)	1036–1072	0	0	0	3.788E-06	0	4.195E-06	2.080E-05	2.911E-04

* for the pulse height distribution of Muramatsu.

Figure 2. Comparison of atmospheric concentrations of the five radionuclides at Muramatsu estimated by the hybrid method (solid circles) and by the method of Terasaka et al. [13] (open circles) with the measured concentrations by Ohkura et al. [1] (solid squares).

Figure 3. Temporal variations in the estimated atmospheric Xe-133 activity concentrations. The mark (T) following MS name in the legends denotes the results of Terasaka et al. [13].

Figure 4. Same as Figure 3 but for Te-132.

Figure 5. Same as Figure 3 but for I-131.

Table 3. The highest concentrations of the nuclides in each plume. Bold figures are maxima among the monitoring stations. The mark (T) following monitoring stations name means the estimation by Terasaka et al. [13].

		Xe-133/Bq m^−3			Te-132/Bq m^−3			I-131/Bq m^−3			I-133/Bq m^−3			I-132/Bq m^−3
No.	MS	P2A	P2B	P2C	P2A	P2B	P2C	P2A	P2B	P2C	P2A	P2B	P2C	P2A	P2B	P2C
	Northern Coastal (NC) sector
1	Kuji	2300	61,600	75,600	110	2930	2670	190	2820	1960	40	240	370	150	4040	3680
2	Ishigami	1600	66,700	48,700	100	1770	1580	180	2210	1550	30	240	340	130	2750	2810
3	Toyooka	4200	129,200	106,100	150	2870	3030	290	3360	2660	70	920	1040	160	2940	3190
4	Funaishikawa	2100	91,500	64,500	70	1770	1400	170	2300	1710	60	850	810	60	1100	1000
5	Oshinobe	5700	134,000	122,000	130	2170	2700	320	2760	2640	70	640	820	220	2720	3520
6	Muramatsu	3400	44,700	72,700	140	1100	1850	220	1310	1980	50	160	430	190	1760	3990
	Northern Inland (NI) sector
7	Isobe	5900	83,500	48,900	130	3440	1370	510	3590	1460	70	320	190	450	5620	2060
8	Kadobe	6700	68,200	48,800	260	6000	1840	350	5400	940	110	1620	450	180	4650	950
9	Yokobori	3200	127,700	48,300	110	2950	1520	260	3120	1110	100	1450	780	90	1700	690
	Central Coastal (CC) sector
10	Mawatari	6300	21,800	111,000	210	500	3190	400	540	2920	100	140	1120	210	420	3110
11	Hitachinaka	300	-	6100	200	-	2840	450	-	3720	120	-	980	300	-	4620
12	Ajigaura(T)	5600	-	85,800	190	-	1840	280	-	2000	60	-	390	230	-	2710
	Central Inland (CI) sector
13	Sugaya (T)	2600	81,400	48,800	100	1720	920	140	1310	850	30	290	190	110	1390	960
14	Horiguchi	2500	17,600	46,300	60	140	750	170	380	1060	40	60	400	90	350	1370
15	Ishikawa (T)	2000	57,900	42,000	100	1400	800	120	1150	820	30	270	180	90	1110	870
	Southern Coastal (SC) sector
16	Ohba	5600	-	80,200	230	-	2710	340	-	2600	70	-	510	310	-	4260
17	Ohnuki (T)	6500	-	102,100	160	-	1950	250	-	1860	60	-	540	190	-	2460
18	Hiroura	6300	-	107,300	150	-	3280	450	-	3180	150	-	1580	220	-	3570
19	Araji (T)	6100	-	105,500	290	-	2320	380	-	2300	80	-	670	270	-	2900
20	Tsukuriya	4100	-	74,700	230	-	2580	340	-	2990	80	-	890	270	-	4470
	Southern Inland (SI) sector
21	Ebisawa	3000	-	61,500	120	-	2720	170	-	3240	50	-	890	70	-	3700

Count overflows occurred at Isobe and Kadobe for Plume P2B.

Figure 6. The spatial distribution of atmospheric concentrations of Xe-133, Te-132 and I-131 in Plume P2A.

Figure 7. Same as Figure 6 but in Plume P2B.

Figure 8. Same as Figure 6 but in Plume P2C.

Table 4. The activity ratios calculated from time-averaged concentrations for each plume.

		Xe-133/I-131			Te-132/I-131			I-133/I-131			I-132/I-131
No.	MS	P2A	P2B	P2C	P2A	P2B	P2C	P2A	P2B	P2C	P2A	P2B	P2C
	Northern Coastal (NC) sector
1	Kuji	10.9	28.0	37.4	0.737	1.10	1.39	0.158	0.090	0.170	0.816	1.47	1.84
2	Ishigami	10.5	32.0	36.3	0.645	0.831	1.19	0.172	0.110	0.183	0.724	1.26	2.14
3	Toyooka	15.7	43.9	39.5	0.569	0.904	1.06	0.286	0.260	0.370	0.550	0.891	1.21
4	Funaishikawa	11.6	42.2	36.0	0.394	0.815	0.772	0.329	0.367	0.439	0.323	0.469	0.567
5	Oshinobe	19.2	50.4	50.4	0.465	0.813	1.08	0.233	0.228	0.321	0.653	4.28	1.45
6	Muramatsu	15.2	39.8	35.9	0.698	0.828	0.903	0.172	0.125	0.128	0.816	1.45	1.96
	Northern Inland (NI) sector
7	Isobe	13.2	44.6	34.3	0.281	0.856	0.979	0.179	0.095	0.130	0.870	1.55	1.62
8	Kadobe	19.0	41.6	63.1	1.08	1.01	2.65	0.446	0.295	0.680	0.486	0.853	1.04
9	Yokobori	13.7	40.9	49.2	0.605	0.923	1.67	0.422	0.449	0.836	0.329	0.539	0.556
	Central Coastal (CC) sector
10	Mawatari	16.0	39.9	38.8	0.580	0.874	1.05	0.279	0.240	0.358	0.529	0.766	1.09
11	Hitachinaka	0.898	-	1.15	0.488	-	0.729	0.276	-	0.244	0.627	-	1.27
12	Ajigaura(T)	20.7	-	50.5	0.627	-	0.901	0.212	-	0.196	0.821	-	1.36
	Central Inland (CI) sector
13	Sugaya (T)	13.6	60.8	57.9	0.580	1.20	0.908	0.220	0.211	0.204	0.778	1.05	1.07
14	Horiguchi	15.1	45.2	43.9	0.411	0.420	0.594	0.246	0.195	0.366	0.582	0.923	1.22
15	Ishikawa (T)	15.2	50.8	50.6	0.703	1.11	0.845	0.226	0.225	0.199	0.708	0.966	0.988
	Southern Coastal (SC) sector
16	Ohba	15.2	-	35.3	0.749	-	1.09	0.241	-	0.136	0.828	-	1.63
17	Ohnuki (T)	24.3	-	60.7	0.487	-	1.03	0.221	-	0.257	0.653	-	1.26
18	Hiroura	12.2	-	37.9	0.439	-	1.06	0.346	-	0.481	0.483	-	1.14
19	Araji (T)	16.5	-	49.2	0.595	-	1.09	0.216	-	0.264	0.636	-	1.23
20	Tsukuriya	12.9	-	28.4	0.870	-	1.15	0.284	-	0.285	0.839	-	1.61
	Southern Inland (SI) sector
21	Ebisawa	19.4	-	21.5	0.942	-	0.852	0.301	-	0.277	0.414	-	1.15
Geometric Mean		13.2	42.3	35.0	0.589	0.876	1.04	0.250	0.199	0.272	0.617	1.07	1.24
Estimated (Terasaka et al. [13])		18.1	57.1	53.7	0.61	1.1	0.95	0.22	0.22	0.23	0.59	0.96	1.2
Measured (Ohkura et al. [1])		-	-	-	0.403	0.818	0.702	0.171	0.149	0.140	0.484	0.841	0.899

Figure 9. Temporal variations in the 10-min activity ratio of Xe-133/I-131. The mark (T) following each monitoring station name in the legends means calculations from the results of Terasaka et al. [13].

Figure 10. Same as Figure 9 but of Te-132/I-131.

Figure 11. The spatial distribution of Xe-133/I-131 and Te-132/I-131 in Plume P2A.

Figure 12. Same as Figure 11 but in P2B.

Figure 13. The spatial distribution of Te-132/I-131 in Plume P2C.

Terasaka Y, Yamazawa H, Hirouchi J, et al. Air concentration estimation of radionuclides discharged from Fukushima Daiichi Nuclear Power Station using NaI(Tl) detector pulse height distribution measured in Ibaraki Prefecture. J Nucl Sci Technol. 2016;53:1919–1932.

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Ohkura T, Oishi T, Taki M, et al. Emergency monitoring of environmental radiation and atmospheric radionuclides at Nuclear Science Research Institute, JAEA following the accident of Fukushima Daiichi Nuclear Power Plant. Tokai-mura (Japan): Japan Atomic Energy Agency; 2012. ( JAEA-Data/Code 2012-010).

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