VI. RADIATION PROTECTION AND
MONITORINGVI. Radiation Protection and Monitoring
1. Individual Monitoring
Internal and external radiation doses were monitored
for radiation protection, according to the radiation safety
regulations. In this FY 2011, total 550 workers (193
workers registered in this institute and 357 visiting
workers of other institutions) were monitoredindividually. External exposure doses have beenmonitored every month with glass badges sensitive tobeta-, gamma -rays, thermal and fast neutrons for staffs,students and researchers. Digital pocket dosimeters havebeen in use as supplement. The glass badges were used
for monitoring one centimeter dose equivalent and atissue dose equivalent at 70 μm deep. The trend ofannual collective doses was summarized in Table 1.
Internal exposure doses were estimated using theairborne radioactivity in air at work places, so that nointernal doses were detected. The annual collective dose(for total of 193 workers) and the average effective dose
per person were 12.5 man ･ mSv and 0.06 mSv/y,respectively. The maximum individual dose was 1.2mSv/y in a worker of the accelerator. No worker wasexposed to radiation beyond 20 mSv/y, or a dose limit
regulated by the law. According to the law and orders by
the regulation authorities, necessary reports wereprepared and submitted.
2. Indoor Radiation Control
The Section of Indoor Radiation Control monitored theexternal radiation dose, the airborne radioactivity in air
and the surface contamination in the controlled areas,regularly. The monitoring for the external radiation dose
rate in the controlled areas was carried out with both
fixed-position monitors and survey meters which canmeasure beta-, gamma-rays and neutrons during theperiod of the reactor operation. Ionization chambers,
NaI scintillation counters and BF3 counters are mainly
used as the detectors for the fixed-position monitoring
systems. The alert level for the radiation dose rate has
been generally set at 20μSv/h in the controlled area.
The external radiation dose accumulated for aweek/month was also measured with glass badges atmore than 30 locations in the KUR, KUCA containmentbuildings and other radiation facilities such as Linac andradioactive waste management.
Fixed-position monitors for radioactive gases and/or
dust are installed both in work areas and exhaust lines.
The dominant radionuclide resulting from the reactor
operation is 41Ar. The concentration of radionuclides
released from facilities was monitored continuously.
There was no significant release, that is beyond theregulation levels.

3. Environmental Radiation Control
The Section of Environmental Radiation Control
worked for assessing the radiation dose in the vicinity of
the nuclear facility and monitoring the radioactivity inenvironmental samples. In FY 2010, the KUR re-started,so we carefully monitor the radiation doses to the public.
The effective dose on the public resulting from exposure
by the effluent gas from reactor was estimated to beenough below the regulation levels.
The environmental monitoring and meteorologicalobservation was continuously performed to obtainsafety assurance data for the other facilities such as
KUCA. Dose rates of the external radiation in the field
were continuously measured by using NaI scintillation
detectors set at five locations inside the KURRI areaand four locations outside. The thermo-luminescence
dosimeters (TLDs) are set up for measuring theradiation dose accumulated during the period of threemonths at locations outside the KURRI. No significant
increase of the radiation level was recognized in relation
to the reactor operation at any monitoring location.
Temporary increases in the dose rate were attributed toevents with the rainfall that entrains radon daughters.
The external radiation doses for every three months atnine locations around the site are shown in Table 2.
Environmental samples including surface water, riverand pond sediments, field soils, dusts and plants werecollected in the vicinity of the KURRI twice a year
during spring and autumn. Typical data on theenvironmental radioactivity are given in Table 3. The
total activities in beta- and gamma-nuclides, which weremeasured with a low background counter using awindowless gas flow and/or a Ge(Li) detector, showed
the ordinary natural radioactivity levels in any samples
mentioned above. The content of 40K in plants has awide variation ranging from 4.0 x 101 to 7.0 x 102
Bq/kg-wet weight. Small amount of 134Cs was detectedin some environmental samples due to the accident ofTEPCO’s Fukushima Daiichi Nuclear Power Stations.
Liquid waste from the radioactive waste managementfacility or KURRI is discharged into a retention pond
(named Imaike) after treatment process. Neither thecontent of radionuclides beyond the regulation level wasobserved in the effluent water, nor radioactivity in any
environmental samples exhibited tendency to increase
with time.

Table 1 Number of radiation workers, collective dose, and average effective dose, per year, in FY 2007-2011.
FY 2007
Collective dose（man・mSv）
Number of registeredradiation workers
Average effective dose(mSv）

FY 2008

FY 2009

FY 2010

FY 2011

12.3

12.0

12.7

13.3

12.5

186188

191

184

193

0.07

0.06

0.07

0.07

0.06

Table 2 External doses accumulated quarterly by using thermo-luminescence detectors at nine locations around theKURRI site
Period(quarter)
Location
KUR meteor. observ. tower
KUR south of groundBozu-Ike pond
KUR transformer station
KUR gate
Kumatori Wada st.
Izumisano Shimogawaraya st.
Izumisano municipal office st.
Izumisano Hieno st.

First

SecondThird(μSv/quarter)
73
74
94
100
54
57
73
75
67
69
89
85
96
94
989076
73

73
99
55
75
7293
96
94
78

Fourth70
92
55
74
65
8910210274

Total(μSv/year)
290
385221297273356388384
301

Table 3 Radioactivity concentration in environmental samples selectedSamples
Sediment(Bq/kg-dry)

Soils(Bq/kg-dry)
Vegetables(Bq/kg-dry)Rain water(Bq/l)

Sanpling locations
Eiraku-dam
Oo-ikeInakura-ike
Ameyama-gawa(Gomon)KUR Hot Lab.
Kumatori-Wada
Hine shrine
Aritoshi shrine
Radish( leaf)
Radish( root)
Butterbur

Lawn
Meteor. observ.
tower at KURRI

Sampling
date(D/M/Y)
12/10/11
04/10/11
04/10/11
05/10/11
05/10/11
04/10/11
04/10/11
04/10/1130/11/11
30/11/11
30/11/11
07/02/12
Sep.11–Feb. 12Man-made nuclides
60

Co
D.L.
D.L.
D.L.
D.L.

65

Zn
D.L.
D.L.
D.L.
D.L.

137

D.L.
D.L.
D.L.
D.L.
D.L.
D.L.
D.L.
D.L.
D.L.

D.L.
D.L.
D.L.
D.L.
D.L.
D.L.
D.L.
D.L.
D.L.

* : D.L. denotes the measured values were below a detection limit.

Natural nuclides
740K
655
534
535
679

208

Tl
1010107

214

1
D.L.
11Be
11
D.L.
D.L.
1014
16
D.L.
D.L.
D.L.
0.2
D.L.

D.L.
D.L.
D.L.
D.L.
D.L.
1.3
6.1
42.2
D.L.

701
613
594
393
58.2
40.4
84.5
159.2
D.L.

13
12118
D.L.
D.L.
D.L.
0.4
D.L.

18
18
15
12
D.L.
D.L.
D.L.
D.L.
D.L.

Cs

Bi
14
171514