Journal of Nuclear and Radiochemical Sciences, Vol. 6, No. 3, pp. 265-266, 2005

Investigation of Analytical Method for Technetium-99 in Liquid Effluent Discharged fromTokai Reprocessing Plant
M. Takeishi,*,†, a Y. Hiyama,b T. Mizutani,a H. Watanabe,a and Y. MaruocaJapan Nuclear Cycle Development Institute(JNC), Tokai-Works, Tokai, Ibaraki 319-1194, Japan
Zuiho Co., Tokai, Ibaraki 319-1111, Japanc
Japan Nuclear Cycle Development Institute(JNC), Fugen-Station, Tsuruga, Fukui 914-8510, Japanb

Received: July 31, 2005; In Final Form: September 30, 2005Analytical method for technetium-99 in liquid effluent was investigated and had been applied for measurement ofliquid effluents discharged from the Tokai reprocessing plant in Japan. The quarterly averaged concentrations of99
Tc in liquid effluents from 1990 to 2000 were ranged from N.D. (< 5 × 10−7 Bq·cm−3) to 6.7 × 10−5 Bq· cm−3. The
average of the normalized annual release of 99Tc was 7.4 × 10−4 GBq·(GWa) −1and it was approximately one fiftyfifth of Iodine-129, which was one of the typical nuclides to have difficulty to remove from liquid effluent. The
committed effective dose by intake of seaweed was evaluated to be less than 3 × 10−10 mSv·a−1.

99

1. Introduction
The low level radioactive liquid effluent from the Tokai
Reprocessing Plant (TRP) is discharged in batch mode at 24 m
beneath the sea surface through the 3.7 km long pipeline fromthe shoreline.
The radioactivity concentrations in liquid effluent are certified to be less than discharge limits set. The concentrations ofgross-alpha and gross-beta radioactivity, gamma–ray radionuclides and tritium are measured prior to discharge in every
batch of discharge. The Pu(α) isotopes (238Pu, 239+240Pu), 90Srand 129I in liquid effluent are measured by radiochemical analysis in a composite sample for a month.
Technetium-99 can be measured as part of the gross-beta
radioactivity with approximately ten percent counting efficiency for a sample mounted on the stainless steel plate. Assalts and solid materials in liquid effluents were almost
removed by duplicated distillation process, the beta-ray counting method was available for measurement of 99Tc without selfabsorption. Accordingly, the concentration of 99Tc in discharge
water had been certified to be less than the discharge limit by
the beta-ray counting method with other beta-nuclides. The
measured gross beta-radioactivity was assumed to be 99 Tc
radioactivity conservatively and confirmed below the 99Tc discharge limit.
As the results of these monitoring, the concentrations of 99Tc
in the effluents were implied to be very low compared with the129
I and other detected nuclides. However, we could not determine fluctuation of 99Tc concentration by these monitoring.
Therefore, it was needed to develop a more sensitive methodfor 99Tc in the liquid effluent. Consequently, the analyticalmethod1 of 99Tc for environmental water was applied for liquid
effluent2 and concentration level of 99Tc in liquid effluent from
TRP was investigated.
2. Analytical Method for 99Tc
A known 95mTc activity was added to a sample as chemicalyield tracer at first. However, the measurement of beta-ray of*Corresponding author. E-mail: takeishi.minoru@jaea.go.jp.
FAX: +81-29-282-3838.
†Present affiliation: Nuclear Fuel Cycle Engineering Laboratory,
Japan Atomic Energy Agency.

Tc was disturbed by gamma-ray of the 95mTc tracer. The chemical yields of samples in the same batch of analysis were almost
similar among them. Accordingly, the yield of the sample (reference sample) to which 95mTc was added had applied for theothers without adding 95mTc tracer. The 8-litter of sample wasanalyzed after homogenizing. The chemical separation of 99Tc
was adopted with the same procedure both the sample and thereference sample as follow.
After FeSO4 with HCL(2+1) and FeCL3 were added to thesample, the 99Tc in the sample was co-precipitated with Fe(OH)2by adjusting over pH 9 by ammonia. The precipitate was dissolved by H2SO4(1+5) and K2S2O8 was added to it. The 99Tc inthe sample was extracted by 15 mL of TBP with 2 mL of HF
using a separation funnel and the organic phase was washed byusing H2SO4(1+5) with 0.5 mL of HF in twice. After discarded
aquatic phase, the 45 mL of Xylene and 15 mL of NaOH(8w/v%) were added to it and shaken. The 99Tc in organic phase wasre-extracted to aquatic phase. The solution was neutralized by
H2SO4 and H2SO4(1+5) was more added. The process from theTBP extraction to the re-extracted procedure was repeated.
Finally, the 99Tc was electoroplated onto stainless steel disk for2-hour at 0.3 A current. The beta-ray emitted from 99Tc on thisdisk was measured by the low background gas-flow counter.
3. Results and Discussion
The chemical yield of this procedure was examined using aknown 99Tc activity tracer. A 9.33Bq of 99Tc was added to the500 mL test water and analyzed. The values of 80% to 90%
were obtained as chemical yield by the six times tests. Furthermore, the chemical yields of 8-litter of real samples were almost
constant as 70 ± 7% in the eleven quarters from 1990 to 1993.
The difference of the chemical yields between the test samples
and the real samples were attributed to the amount of chemicalcomponents in the samples.
Decontamination factor (DF) were also examined by using thetracers of 106Ru, 54Mn, 60Co, 90Sr, 137Cs, 152Eu. The DF of 106Ru
was measured as 102 and 90Sr was obtained 1.6 × 103. The DF’sof other nuclides were measured more than 103.
Detection limit of this method was approximately 5 × 10 −7
Bq·cm−3 using 8 litter of sample, which was more sensitive than
1.8 × 10−4 Bq·cm−3 by the beta-ray counting method using 1 litter of sample.
Subsequently, we have investigated for the concentration© 2005 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 12/28/2005

Takeishia
99-3

T

10

C=-4

10-510-610

5x10-7

D.L.:-710using the safety assessment of TRP. The diffusion equation
was introduced by the field experiments offshore JNC Tokai
Works. The diffusion equation can be described as:

1990

1992

1994

1996

1998

2000

Fiscal year (Apr.–Mar.)

Where C is the concentration of radionuclide in sea water(Bq·m−3), q is the discharge rate (Bq·s−1), u is the current speed
as 0.1 (m·s−1), H is the vertical mixing layer as 6.9 (m), Y is thehorizontal width of vertical mixing layer as 2 (m), α is theexperimentally obtained constant as 0.1415, χ is the distancefrom the discharge point, and erf is the error function as:erf (y) =99

Figure 1. Quarterly Averaged Concentrations of Tc in Liquid effluent from TRP.

level of 99 Tc in liquid effluent from TRP using this method
since 1990. The quarterly averaged concentrations of 99Tc inliquid effluents from 1990 to 2000 were ranged from N.D. (< 5× 10−7 Bq·cm−3) to 6.7 × 10−5 Bq·cm−3. The maximum concentration was approximately one ten thousandth of the discharge
concentration limit of 99 Tc for liquid effluent as 1 Bq·cm −3(Figure 1), which is authorized by Japanese law for nuclear
facilities.
On the other hand, annual releases of 99Tc were ranged from
1.3 × 10 −5 GBq·a−1 to 1.5 × 10 −3 GBq·a−1 and the normalized
releases of 99Tc, which were normalized by annual energy generated (GWa) derived from the treated spent fuels, were ranged
from 1.3 × 10−6 GBq·(GWa) −1 to 2.1 × 10−3 GBq·(GWa) −1. They
were smaller than that of other detected radionuclides (Table 1).
TABLE 1: Normalized Annual Releases of Nuclides/GBq(GWa) –1
Range~ 2.1 × 10

Average

Tc-99

1.3 × 10−3

(7.4 × 10−4)

H-3

7.2 × 104 ~ 3.3 × 105(2.1 × 105)

I-129

2.0 × 10−2 ~ 8.3 × 10−2

(4.1 × 10−2)Pu(α)

2.7 × 10−3 ~ 1.1 × 10−2

(5.1 × 10−3)−6

1990–2000
The release rates of 99Tc to the inventory of 99Tc in the treatedspent fuel were estimated below 10−7 from 1990 to 2000. However, the release rate of 99Tc was not so consistent with the inventory of it. The release rate was depended on both the storage
and the operation of the treatment process of liquid waste.
Based on these data, the concentrations of 99Tc in the sea
water and seaweed were evaluated by the diffusion equation

qYuerfuHY
4 αχ

13-2

1031

Concentration of 99Tc / Bq ·cm-3

266 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

2πy∫ exp(–t )dt.
20The radioactivity concentrations of 99Tc in the sea water near
the discharge point and the shore where seaweed lives, 5km
apart from discharge point, were calculated. The maximum
value of annual concentration of 99Tc in the sea water near thedischarge point and the shore could be estimated approximately
9 × 10−11 and 1 × 10−11 Bq·cm−3, respectively. The concentrationof 99Tc in seaweed (as Eisenia bicyclis) was evaluated as 3 × 10−5
Bq·kg−1-fresh by using bioaccumulation factor3 as 2600 in Bq·g−1
per Bq·cm−3 based on the experiment by 95mTc tracer. The committed effective dose of intake of the seaweed was evaluated to
3 × 10 −10 mSv·a−1 using a consumption rate 4 of seaweed as 40g·d−1 for adult and the dose factor (6.4 × 10−7 mSv·Bq−1 as f1 =0.5) based on the ICRP publication 72.
On the other hand, the evaluation of committed effective dosethrough food chain due to intake of all nuclides discharged tothe sea from TRP were ranged from 2 × 10−6 to 8 × 10−5 mSv·a−1
during the ten year, which were lower than the dose limit for thepublic as 1 mSv·a−1.
Consequently, the committed effective dose by intake of seaweed for the public due to release of 99Tc was negligibly smaller
than the dose due to all nuclides.
Reference(1) E. Holm, J. Rioseco, and M. Garcia-Leon, Nucl. Instrum.
Methods 223, 204 (1984)(2) Manual of Standard Procedures for Sampling and Analysisof Radioactive Effluents and Gases Discharged into
Environment, PNC N8520 93-003 (1994) (in Japanese).
(3) Radioactive Waste Management Center, RWMC-96-P-18,
Environmental Parameter Series 6, 372(1996) (in Japanese).
(4) Nuclear Safety Commission of Japan, “Guideline to Evaluate Dose Objectives of LWRs”, (1976, reveised in 2001) (inJapanese).