Journal of Nuclear and Radiochemical Sciences, Vol. 24, pp. 13-21, 2024

ArticlesUrinary bioassay for the measurement of actinides by alpha spectrometry for rapid
response after radiation emergency
Guosheng Yanga, Masako Ohnoa, Eunjoo Kima, Hatsuho Senoa, Osamu Kuriharaa,*, Jian ZhengaaNational Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-city, Chiba, Japan

Received February 20, 2024; Accepted June 10, 2024; Published online August 1, 2024
In response to an internal contamination accident of five workers at a plutonium (Pu) fuel research facility ofJapan Atomic Energy Agency’s Oarai Research and Development Center in 2017, different sample pretreatment
and chromatographic purification techniques were compared to obtain a feasible and rapid method to measure U,
Pu, and Am in urine samples. The combination of complete organic matter decomposition, iron hydroxide co-precipitation, and chromatographic separation/ purification using the TEVA and DGA resin cartridges followed byanion exchange Dowex 1x8 resin column was selected prior to one day counting using alpha spectrometer. Thisurinary bioassay demonstrated stable and high (~ 80%) yields, and low detection limit (approximately 0.5 mBq
using 500 mL urine sample) for U, Pu, and Am. The turnaround time of 38.5 h allows us to perform urgent
response to a radiological/nuclear emergency. The proposed method was finally validated in the international
comparison program (PROCORAD 2018), with satisfactory results for U, Pu, and Am analysis with all |Z-score|≤2.
Keywords: Internal contamination accident; Urinary bioassay; Actinides; Alpha spectrometry; PROCORAD 2018.

1. Introduction
A Pu/Am internal radiation exposure accident occurred onJune 6th, 2017 in Japan, in which five workers inhaled airborne Pu/Am when inspecting nuclear fuel materials at anuclear research facility in Oarai of the Japan Atomic Energy
Agency (hereafter, we call this the Oarai accident).1 For an
adult, the inhalation dose coefficients applied in the case ofinternal intake are much higher for alpha emitters than that forother radiation emissions: e.g., (1.6−12) × 10 -5 Sv Bq-1 for 239Puor 240Pu, and (1.6−9.6) × 10 -5 Sv Bq-1 for 241Am versus (4.6−39)
× 10 -9 Sv Bq-1 for 137Cs (β- and γ).2 Therefore, internal contamination with alpha-particle emitters, such as 239Pu, 240Pu, 241Am,
is likely to bring a large radiation exposure dose to the tissuesof persons even if the intake amount is small. It is thus of great
importance to timely evaluate the order of magnitude of thedose to the person(s) of concern in order to provide necessary
information for decision-making in radiation emergency medicine.
As the “core advanced radiation emergency medical support
center” designated by the Nuclear Regulation Authority,
Japan, it is one of our missions to accommodate, conduct dose
assessment and medical treatment, and implement long-termmonitoring for the patients accidentally exposed and/or contaminated, such as the case of the Oarai accident.1,3 In terms ofinternal contamination by α particles (e.g. 238U, 239Pu, 241Am), it
would be challenging to use external monitoring techniques(e.g. whole-body counter, lung counter) to confirm low internal contamination level, since α particles will be blocked byour body.4 In that case, rapid bioassay of urinary and fecal
samples should be considered for precise dose assessment.5-7
Although the mass spectrometric methods present advantage
on the rapid measurement, it is more sensitive to measure
short-lived radionuclides with high specific activities by radiometric spectrometry and presently it is of great challenge to*Corresponding author. E-mail: kurihara.osamu@qst.go.jp

measure 238Pu using mass spectrometric methods due to theisobaric interference of 238U.8 As conventional technique, alpha
spectrometric techniques are widely used for the measurementof actinides in bioassay samples.5,9-12 However, the significant
disadvantage of actinide bioassay using alpha spectrometry isthat it is a significantly labor-intensive and time-consuming
work.13 Therefore, it is critical to develop rapid actinide bioassay using alpha spectrometry for emergent response after aradiological/nuclear accident.9,12This work aims to develop a rapid actinide bioassay usingalpha spectrometry in urine with high yield for emergent
response in case of internal contamination accidents occurredin nuclear fuel-related facilities. First, we investigated thesample pretreatment of actinides in urine by wet ash and dry
ash followed by calcium phosphate co-precipitation and ironhydroxide co-precipitation; and then, optimized the purification/separation procedure applicable to the measurement of
actinides in urine samples, for shortening the total turnaroundtime. We finally validated the performance of the optimized
procedure in an international inter-comparison program forbioassay analyses, the 2018 PROCORAD (Association for the
PROmotion of Quality Control in R ADiotoxicological
Analysis) exercise.
2. Experimental
2.1. Materials and Reagents. Analytical grade reagentsincluding HNO3 (65%), HCl (35%), H 3PO 4 (85%), H 2O2 (30–35%), HClO4 (70%), NH4I, NaNO2, NH4Cl, CaCl2, FeCl3·6H2O,
Al(NO3)3·9H 2O, sulfamic acid, ascorbic acid, oxalic acid, andammonium oxalate monohydrate were purchased from
Fujifilm Wako Pure Chemical Corporation (Osaka, Japan).
Ammonium hydroxide (28–30%) was purchased from Kanto
Chemicals (Tokyo, Japan). All the required solutions were prepared with Milli-Q water (18.2 MΩ·cm). The extraction resinsof TEVA and DGA-N in 2 mL cartridges were all obtained© 2024 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 08/01/2024

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J. Nucl. Radiochem. Sci., Vol. 24, 2024

from Eichrom Technologies (50–100 μm, Lyle, IL, USA).
Anion exchange resins employed were DowexTM 1X8 (100–200 mesh, Cl - form) obtained from Fujifilm Wako Pure
Chemical Corporation (Osaka, Japan) and AG® 1-X4 (50–100
mesh, Cl- form) obtained from Bio-Rad (Hercules, CA, USA).
The 242Pu (SRM 4334i) and 232U (SRM 4324b) both obtained
from the National Institute of Standards and Technology(NIST; Gaithersburg, MD, USA), and 243Am (1577–9) obtained
from Eckert & Ziegler Isotope Products (Valencia, CA, USA),
were diluted to approximately 80 mBq/mL and used for themeasurements as yield tracers. Microwave digestion and dry
ash for urine samples were performed using Discover® SP-D
microwave digestion system and microwave muffle furnace of
Phoenix, respectively (CEM Corporation, Matthews, NC,USA).
2.2. Procedure of alpha spectrometric analysis. As shownin Figure 1, after spiking approx. 40 mBq of 242Pu, 243Am, and232
U into each 500-mL urine sample as yield tracers, 100 mLof concentrated HNO3 and 5 mL of concentrated H 2O2 wereadded to the urine sample, followed by wet ash at 300°C until
dryness. The residue added with 10 mL of concentrated HNO3
and 5 mL of concentrated H2O2 was then heated to dryness at
300°C. This process was performed more than one time asnecessary to obtain completely white residue. The remaining
residue was dissolved in 20 mL of 8 M HNO3 and then diluted
to 350 mL with Milli-Q water. After adding 150 mg sulfamicacid, the solution was heated to boiling for 5 min and thencooled for 5 min. After that, iron hydroxide co-precipitation
was processed by adding 1 g of NH4Cl and 20 mg of Fe3+, followed by pH adjustment to ~9.0 with concentrated NH3·H 2O.
After aging for 1 h and then centrifugation at 3,000 rpm for 15
min, the precipitate was dissolved in 15 mL of 8 M HNO3 followed by the addition of 5 mL of 1 M Al(NO3)3-8 M HNO3 tominimize the inf luence of phosphate naturally existing inurine for the next extraction chromatographic separation process.9 After adding 70 mg of sulfamic acid with stirring at
40°C for 5 min, the valence adjustments of Fe to Fe(Ⅱ) and Pu
to Pu (Ⅲ) were performed by adding 300 mg of ascorbic acidwith stirring at 40°C for 5 min, and Pu to Pu(Ⅳ) by adding
500 mg of NaNO 2 with stirring at 80°C for 30 min.9 The
valence adjustment of Pu to Pu(Ⅳ) was then performed again
by adding 500 mg NaNO2 with stirring at 80°C for 10 min.
The sample solution was then passed through a 0.45-μm membrane filter prior to chromatographic separation/purification
with stacked TEVA and DGA resin cartridges. After the sample solution was loaded, the resin cartridges were rinsed with
25 mL of 8 M HNO3. At this stage, Th and Pu were retained in
the TEVA resin, whereas U and Am were retained in the DGA
resin. After the stacked TEVA and DGA cartridges were split,
Pu was eluted with 45 mL of 0.1 M NH4I-8 M HCl from the
TEVA cartridge, after Th removal with rising 40 mL of 9.5 M
HCl. In addition, U and Am in the DGA resin were separately
eluted by 30 mL of 0.2 M HNO3 and 30 mL of 0.01 M HCl,
respectively. The U fraction was further evaporated to dryness
and dissolved in 10 mL of 0.5 M HCl. It was then loaded onto
a 4-mL Dowex 1X8 resin column to remove trace 210Po naturally existing in urine. Finally, U was collected with the combination of drain solution of loading and elution solution using
30 mL of 0.5 M HCl.
After the above separation procedures, the solutions of eachelement fraction (Pu, Am, and U) were evaporated, and thedecomposition of the residual organic matters mainly fromresin was achieved using wet ash with 2 mL of concentrated
HNO3 and 0.2 mL of concentrated HClO4. After redissolving
the residual in 10 mL 0.9 M H 2SO4 by heating to boiling, pH
was adjusted into the range of 1.2–2.8 by a buffer system of
0.9 M H 2SO 4 and 15% ammonia solution with Thymol blue
indicator. Next, electrodeposition (1.0 A, 2 h) was performed
to prepare samples for alpha spectrometry with the use of a

Figure 1. Rapid bioassay method for the measurement of actinides in urine samples by alpha spectrometry.

Urinary bioassay for the measurement of actinides by alpha spectrometry

J. Nucl. Radiochem. Sci., Vol. 24, 2024

15

TABLE 1: The recoveries of U, Pu, and Am in urine measured by alpha spectrometry after different digestion
processes and the required time of different pretreatment and separation/purification processes.
Digestion

Recovery (%)
242

Pu

Am

243

232

U

Required timea) Fast digestion

53±27 (n=7)

66±16 (n=7)

58±6 (n=7)

7.5 hb) One-time wet ash

77±5 (n=31)75±8 (n=31)73±9 (n=6)

9.0 hc) Three-time wet ash

77±7 (n=31)

78±5 (n=31)

79±5 (n=17)

10.5 hspectrometer (Ensemble 8, ORTEC, Oak Ridge, TN, USA)with Si detectors with an active area of 450 mm 2 (AMETEK,Oak Ridge, TN, USA). The counting time for each electrodeposited sample was normally set at 86,400 s (1 day); however,it could be shortened depending on the radioactivity in urine
samples.
3. Results and discussion
Prior to chromatographic purification/separation, it is critical to decompose the organic matter and remove matrix asmuch as possible to avoid the inf luence of separation efficiency of radionuclides.14-17 In the present study, we investigated and compared the recovery yields and required times ofdifferent sample pretreatments, chromatographic separation/
purifications for the determination of actinides in urine inorder to select the optimal procedure for the rapid emergency
bioassay program.
3.1. Sample pretreatment. Figure S1 presents the comparison of the sample pretreatment methods tested in this study.
Calcium phosphate and iron hydroxide were used as the coprecipitation reagents (Figure S1, b-d). Details on each method
are described below.
As shown in Figure S1a, urine samples were evaporated todryness at 300°C, after adding 100 mL of concentrated HNO3
and 5 mL of concentrated H2O2.13 Digestion was performed byrepeatedly adding 20 mL of concentrated HNO3 for complete
decomposition of organic matters until only white residue wasleft. This residue was then dissolved by 35 mL of 8 M HNO3
and allowed to stay overnight to precipitate extra minerals,
which were then removed using MFTM Membrane Filters with
a 0.45μm pore size (Merk Millipore Ltd., Irland).
In terms of the calcium phosphate precipitation methods(Figure S1, b and c), after adding 100 mL of concentrated
HNO3 and 5 mL of concentrated H 2O2, the urine sample was
evaporated at 300°C until the volume was reduced to approximately 200 mL. To obtain calcium phosphate precipitation,
160 mg of Ca 2+ and 125 μL of concentrated H3PO4 were thenadded to the urine sample followed with pH adjustment byconcentrated NH3·H 2O (pH 9–10). After centrifugation (3000rpm, 30 min), the precipitate was kept for subsequent procedure. The following procedures were different between themethods b and c. In the method b, the produced precipitate wasprocessed through two times’ wet ash by adding 10 mL of concentrated HNO3 and 5 mL of concentrated H2O2, and then theresidue was dry ashed (at 150°C for 30 min, 300°C for 60 min,and 450°C for 120 min). In the method c, additional microwave digestion was performed after dissolving the precipitate
with 17 mL of concentrated HNO3. After evaporation of thedigested solution in a beaker, wet ash was performed twice inthe same manner as the method b. The well decomposed urine
samples (left as white residues) from these two methods weredissolved by 20 mL of 8M HCl prepared for the subsequent
separation procedure.
In terms of the iron hydroxide co-precipitation method(Figure 1d), details were described in the section 2.2.

Table S1 summarizes the required time for each pretreatment method prior to chromatographic purification/purification (Figure S1). As shown, the time of 18 h for the calcium
phosphate precipitation method (Figure S1b) was much shorter
than that for the presently recommended method (28 h) (FigureS1a). The former method could be further shortened to 9 h byapplying microwave digestion (Figure S1c). The fastest method
was found to be the iron hydroxide co-precipitation method
requiring only about 7 h (Figure S1d). The iron hydroxide coprecipitation method (Figure S1d) has an advantage over thethird method (Figure S1c) which requires additional sample
transfer for the microwave digestion procedure. With theadvantage of less time consumed and much easier operation,
the pretreatment using iron hydroxide co-precipitation was
thus selected as the optimal technique for the matrix removal
after organic matter decomposition and prior to chromatographic separation/purification.
Prior to co-precipitation for preconcentration of actinides, it
is also of importance to decompose organics naturally exitingin human urine.15 In the present study, we attempted to examine whether further speed-up could be achieved by roughdigestion, as shown in Figure S2. Table 1 provides a comparison of the performance among the fast digestion without wetash, the one-time wet ash, and the three-time wet ash. The
one-time wet ash resulted in large amount of carbonized residues (Figure S3a), and the two-time wet ash resulted in lesscarbonized residues (Figure S3b). After the three-time wetash, the white residues indicated complete organic matterdecomposition (Figure S3c). In addition, the fast digestion
showed lower and unstable yields compared to other two methods, although the turnaround time was shortened by 3 h andthe operations were easier (Table 1). The one-time wet ash hada small advantage only on the required time over the threetime wet ash. Complete decomposition of organic matters was
also beneficial to avoid low flow rate even clogging during thechromatographic separation/purification step. Therefore, thethree-time wet ash was considered to be the best way for complete organic matter decomposition prior to the iron hydroxide
co-precipitation (Figure S1d).
3.2. Chromatographic separation/purification procedures. Several chromatographic separation/purification methods for U, Pu, and Am were tested in this study using
extraction chromatography resins and anion exchange resins(Figure S4). Figure S4a shows the presently recommended
separation method using anion exchange resins in Japan,13
whereas Figure S4b and S4c show the rapid separation methods using extraction chromatography resins and/or anion
exchange resins. A flow rate was adjusted to be 1–2 mL/min
for all separation processes in these methods. Details on eachmethod are described below.
In terms of the presently recommended separation method(Figure S4a), 500 mg of NaNO 2 was added to adjust Pu
valence to Pu(Ⅳ) prior to separation/purification with 7 mL
of AG 1-X4 resin column. The drain solution of loading andelution solution with extra rinse with 80 mL of 8 M HNO3
were then collected for the following Am and U separation

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J. Nucl. Radiochem. Sci., Vol. 24, 2024

processes. After that, Th (trapped by the resins together withPu) was removed by washing with 60 mL of 8M HCl.18 After
that, Pu was eluted with 50 mL of 0.1 M NH4I-8 M HCl solution from the resin. The Am and U fraction was evaporated todryness, and dissolved in 30 mL of 8M HCl solution. The filtration was also conducted if there were precipitates for thesubsequent processes. Subsequently, the sample solution wasthen loaded onto 7 mL of Dowex 1X8 resin column. The drain
solution of loading and elution solution with 50 mL of 8M
HCl, were then used for the following Am separation processes. After that, U trapped in the resin was eluted with 50
mL of 0.2 M HNO3. The Am fraction was then evaporated todryness and dissolved by 50 mL of 8 M HNO3. After dilution
with milli-Q water to a volume of 300 mL, co-precipitation
was performed by adding 10 g of oxalic acid, 10 g of ammonium oxalate monohydrate, and 500 mg of Ca 2+ followed by
pH adjustment using concentrated NH 3·H 2O (to pH 1.8). The
produced precipitate was filtered with membrane filter paperwith a pore size of 3 μm and the precipitate was further processed for dry ash in a furnace with increasing temperature (at150°C for 30 min, 450°C for 60 min and 600°C for 360 min).
The residual was dissolved by 30 mL of 8 M HCl and thendiluted to 200 mL with milli-Q water. Followed by adding 20
mg of Fe3+ and 1 g of NH4Cl, the iron hydroxide co-precipitation was performed through the pH adjustment (pH ~9) using
concentrated NH3·H2O. After aging for 1 h and then centrifugation at 3,000 rpm for 15 min, the precipitate was then dissolved in 20 mL of 8 M HCl and loaded onto 7 mL of Dowex
1X8 resin column to remove iron. The combination of drain
solution from the loading and elution solution with the rinse ofadditional 50 mL of 8 M HCl were then evaporated to dryness
and dissolved by 20 mL of 8 M HNO3, followed by loading
onto another 7 mL of Dowex 1X8 resin column to remove any
interfering isotopes such as 210Po. Finally, Am was collectedwith the drain solution of loading and elution solution with 50
mL of 8 M HNO3. The final fractions (containing Am, Pu, andU, respectively) were used for the following process for alphasource preparation.
In the first rapid separation/purification method (FigureS4b), the anion exchange Dowex 1x8 resin column and theextraction DGA resin cartridge were used. Pu in the pretreatedsample solution was adjusted to Pu(Ⅳ) by adding 500 mg of
NaNO2, and the solution was loaded onto 7 mL of Dowex 1x8
resin column. The drain solution from the loading and elution
solution with the rinse of 50 mL of 8 M HCl were collected forthe following Am separation processes. Subsequently, the U
fraction was eluted by using 50 mL of 0.5 M HNO3, following
eluting the Pu fraction by using 50 mL of 0.1 M NH4I- 8 M

HCl. The Am fraction was evaporated to approximately 5 mL
and dissolved in 20 mL of 8 M HCl, then loaded onto 2 mL of
DGA resin column. After rinse with 25 mL of 8 M HCl, Am
was eluted by 35 mL of 0.01 M HCl.
In terms of the second rapid separation/purification method(Figure S4c) using the stacked TEVA and DGA resin cartridges combined with anion exchange Dowex 1x8 resin column for the separation of U, Pu and Am, details were
described in the section 2.2.
Table S2 summarizes the required time for each chromatographic separation method (Figure S4). The presently recommended method (Figure S4a) required more than 1 day (37 h),
whereas the rapid separation/purification method using anionexchange and DGA resin columns significantly shortened therequired time to 6.5 h (Figure S4b). Using the stacked TEVA
and DGA resin cartridges followed by anion exchange Dowex
1x8 resin column enabled to further shorten the required timeto 3.5 h (Figure S4c).
With the combination of three-time wet ash, iron hydroxide
co-precipitation, and separation/purification using stacked
TEVA and DGA resin cartridges followed by anion exchange
Dowex 1x8 resin column, stable and sufficient chemical yields(nearly 80%) for U, Pu and Am could be obtained, as shown in
Table 1. Based on the above results, we considered that thiscombination, as shown in Figure 1, was the best bioassay
method available at our laboratory for the rapid measurementof actinides in urine using alpha spectrometry in emergency
situations. This method was characterized by low detection
limits of approximately 0.5 mBq for U, Pu, and Am analysis in
500 mL urine, in the case of a counting time of 86,400 s byalpha spectrometry. The required time for the pretreatment
and separation/purification (Pu, Am and U) was 10.5 h intotal, and 14.5 h including the sample preparation of electrodeposition for alpha spectrometric analys
3.3. Method validation and application. Finally, the developed actinide bioassay was validated by participating 2018
PROCORAD international comparison, and our results aredemonstrated in Table 2 (actinides in urine) and Table 3 (U inurine). This exercise offers various test samples containing
various radionuclides, such as actinides, and participants canselect samples that one wants to test.
Exploitation of results and performance evaluation are conducted in accordance with ISO standard 13528 and IUPAC
2006.19,20 In the PROCORAD program, the performance index
of Z-score was used to check the performance of the laboratories if the number of participants were ≥ 7, and the equation
was listed as follows:

TABLE 2: Actinide results in urine during 2018 PROCORAD program.
Sample18ACTUA

18ACTUB

18ACTUCND: not detected.

Recovery (%)

Isotope

Concentration(mBq/sample)

Assigned value(mBq/sample)

Z-scoreBias (%)

Pu

2.07±0.71

2.23±0.13

-0.5

-7

-1.0

-14

76±6

238

76±6

239

79±7

241

76±6

238

76±6

239

85±8

241

73±6

238

73±6

239

85±8

241

Pu

1.93±0.67

2.24±0.13

Am

ND

ND

Pu

4.70±0.11

4.96±0.23

-0.4

-5

Pu

5.01±1.09

4.98±0.23

0.0

1

Am

9.38±1.50

8.82±0.42

0.4

6

Pu

ND

ND

Pu

ND

ND

Am

ND

ND

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Urinary bioassay for the measurement of actinides by alpha spectrometry

17

TABLE 3: Uranium results in urine during 2018 PROCORAD program.
SampleRecovery (%)

Isotope

Concentration(mBq/sample)

Assigned value(mBq/sample)

Z-scoreBias (%)

U

140±13143±11

-0.2

-2

235

U

6.71±1.62

6.87±0.54

-0.1

-2

238

U

147±13

142±9

0.4

4

234

18UA

87±7

U

35.2±4.3

37.1±3.7

-0.5

-5

235

U

1.22±0.64

1.81±0.18

-1.9

-33

238

U

39.5±4.7

36.7±3.3

1.0

8

234

18UB

82±6

U

584±48527±18

1.4

11

235

U

11.8±2.3

12.6±1.4

-0.3

-6

238

U

ND

2.92±2.17

234

18UC

76±6

ND: not detected.

Z-score =X lab − XS*

(1)where X lab is the laboratory’s result; X is the assigned value;
S* is the robust standard deviation calculated from the resultsof participants. |Z-score| ≤2 indicates satisfactory performance; 2< |Z-score| ≤3 indicates questionable result withwarning; |Z-score| >3 indicates unsatisfactory performance,
requiring corrective action.
In the 2018 exercise, we obtained satisfied results with all|Z-score| ≤2, as shown in Table 2 and Table 3. In terms of bias
X −X
(Bias = lab), all data were within the relative bias of 15%
X
for all tested items excluding 235 U (-33% compared to theassigned values) in the 18UB and 238U (not be detected) in the
18UC. The relatively large discrepancy for 235U in the 18UB
was turned out to be due to a miscalculation of the overlappedpeak affected by the peak tailing from 234U. The recalculation
improved the result for 235U (only -6% bias). In terms of the238
U in the 18UC, even the assigned value was 2.92±2.17 mBq/
sample (500 mL/sample), with a relative standard deviation of
74%. The 238U assigned value in the 18UC was corresponding
to be 0.469±0.349 μg L -1, which were in the range of those in
the occupationally unexposed persons (0.0008−3.70 μg L -1).21
All these results mentioned above indicated that the developed
urinary bioassay method could be applied to the actinide measurement in urine.
4. Conclusions
A new rapid bioassay method to determine actinides inurine samples using alpha spectrometry was developed in thiswork. By performing acid digestion and iron hydroxide coprecipitation, 28 h process time for the pretreatment of urine
samples in the presently recommended method was reduced to
7 h. In the chromatographic separation/purification process,by optimizing the use of extraction resin cartridges followedby anion exchange resin column, the required time was
reduced to 3.5 h compared to the presently recommended
method which took 37 h. The whole turnaround time for thisnew method, including alpha source preparation process(about 4 h) and measurement time (24 h), was approximately
38.5 h. The significant reductions in time required allow us toprovide timely information for decision-making in radiation
emergency medicine. The average recoveries of Pu, Am and U
were approximately 80% and the detection limit was approximately 0.5 mBq using 500 mL urine sample with a counting

time of 86,400 s. The application of the new rapid bioassay
method demonstrated satisfactory performance in the international comparison program (PROCORAD 2018).
5. Conflict of interest
The authors declare that they have no conflict of interest.
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Supporting Information
TABLE S1. The required times of the pretreatments for urine samples.
Pretreatmenta) Presently recommended methodb) Calcium phosphate co-precipitationc) Calcium phosphate co-precipitation with microwave digestiond) Iron hydroxide co-precipitation

Required time
28 h
18 h
9h
7h

TABLE S2. The required times for the chromatographic purification/separation ofU, Pu, and Am in urine.
Chromatographic purificationa) Presently recommended methodb) Anion exchange resin column and DGA-N resin cartridgec) TEVA and DGA-N resin cartridge, and Dowex 1X8 column

Required time
37 h
6.5 h
3.5 h

Urinary bioassay for the measurement of actinides by alpha spectrometry

J. Nucl. Radiochem. Sci., Vol. 24, 2024

Figure S1. Comparison of the digestion methods for the measurement of actinides in urine samples.

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Kurihara

J. Nucl. Radiochem. Sci., Vol. 24, 2024

Figure S2. Comparison of the digestion methods for the measurement of actinides in urine samples.

a)

b)

c)

Figure S3. a), b): Urine samples with carbonized residues, c): Urine sample with complete organic matter decomposition.

Urinary bioassay for the measurement of actinides by alpha spectrometry

J. Nucl. Radiochem. Sci., Vol. 24, 2024

Figure S4. Comparison of chromatographic purification/separations for the measurement of actinides in urine samples.

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