On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods
A practical possibility of specific alpha-activity measurement of the radioactive waste (RAW) as much as thousands tons placed in the 4-th Chornobyl wrecking unit is demonstrated by means of determination of the helium content (on the account of Pu, Am decay) in the hermetic containers filled with t...
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| Cite this: | On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods / N.P. Dikiy, A.N. Dovbnya, L.K. Myakushko, L.V. Reprintsev, A.Eh. Tenishev, V.L. Uvarov // Вопросы атомной науки и техники. — 2002. — № 2. — С. 64-65. — Бібліогр.: 6 назв. — англ. |
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Dikiy, N.P. Dovbnya, A.N. Myakushko, L.K. Reprintsev, L.V. Tenishev, A.Eh. Uvarov, V.L. 2015-04-12T06:24:14Z 2015-04-12T06:24:14Z 2002 On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods / N.P. Dikiy, A.N. Dovbnya, L.K. Myakushko, L.V. Reprintsev, A.Eh. Tenishev, V.L. Uvarov // Вопросы атомной науки и техники. — 2002. — № 2. — С. 64-65. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 06.60.Mr, 07.30.Hd, 07.77.-n, 81.70.-q https://nasplib.isofts.kiev.ua/handle/123456789/80117 A practical possibility of specific alpha-activity measurement of the radioactive waste (RAW) as much as thousands tons placed in the 4-th Chornobyl wrecking unit is demonstrated by means of determination of the helium content (on the account of Pu, Am decay) in the hermetic containers filled with the RAW. The method using application of helium filter is acceptable but filterless one seems to be more economical. The latter is based on a constraint of all gases into choused gaseous medium but helium. The appraisal of necessary time for passive helium accumulation up to partial pressure of ~10⁻⁷ Pa (a value to be measured by mass-spectrometer) is of ~1000 hours using a scheme with real helium filter and of ~10 hours in the case without filter for specific alpha-activity of ~10⁵ Bq/kg. (a threshold level for the RAW disposition). en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Application of the nuclear methods On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods О возможности измерения α-активности радиоактивных отходов большой толщины методами высоковакуумной техники Article published earlier |
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On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods |
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On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods Dikiy, N.P. Dovbnya, A.N. Myakushko, L.K. Reprintsev, L.V. Tenishev, A.Eh. Uvarov, V.L. Application of the nuclear methods |
| title_short |
On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods |
| title_full |
On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods |
| title_fullStr |
On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods |
| title_full_unstemmed |
On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods |
| title_sort |
on possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods |
| author |
Dikiy, N.P. Dovbnya, A.N. Myakushko, L.K. Reprintsev, L.V. Tenishev, A.Eh. Uvarov, V.L. |
| author_facet |
Dikiy, N.P. Dovbnya, A.N. Myakushko, L.K. Reprintsev, L.V. Tenishev, A.Eh. Uvarov, V.L. |
| topic |
Application of the nuclear methods |
| topic_facet |
Application of the nuclear methods |
| publishDate |
2002 |
| language |
English |
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Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
О возможности измерения α-активности радиоактивных отходов большой толщины методами высоковакуумной техники |
| description |
A practical possibility of specific alpha-activity measurement of the radioactive waste (RAW) as much as thousands tons placed in the 4-th Chornobyl wrecking unit is demonstrated by means of determination of the helium content (on the account of Pu, Am decay) in the hermetic containers filled with the RAW. The method using application of helium filter is acceptable but filterless one seems to be more economical. The latter is based on a constraint of all gases into choused gaseous medium but helium. The appraisal of necessary time for passive helium accumulation up to partial pressure of ~10⁻⁷ Pa (a value to be measured by mass-spectrometer) is of ~1000 hours using a scheme with real helium filter and of ~10 hours in the case without filter for specific alpha-activity of ~10⁵ Bq/kg. (a threshold level for the RAW disposition).
|
| issn |
1562-6016 |
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https://nasplib.isofts.kiev.ua/handle/123456789/80117 |
| citation_txt |
On possibility of alpha-radioactive thick-layer waste analysis using high-vacuum technique methods / N.P. Dikiy, A.N. Dovbnya, L.K. Myakushko, L.V. Reprintsev, A.Eh. Tenishev, V.L. Uvarov // Вопросы атомной науки и техники. — 2002. — № 2. — С. 64-65. — Бібліогр.: 6 назв. — англ. |
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2025-11-27T01:19:17Z |
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| fulltext |
ON POSSIBILITY OF ALPHA-RADIOACTIVE THICK-LAYER WASTE
ANALYSIS USING HIGH-VACUUM TECHNIQUE METHODS
N.P. Dikiy, A.N. Dovbnya, L.K. Myakushko, L.V. Reprintsev, A.Eh. Tenishev, V.L. Uvarov
National Scientific Centre “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
e-mail: uvarov@kipt.kharkov.ua
A practical possibility of specific alpha-activity measurement of the radioactive waste (RAW) as much as thou-
sands tons placed in the 4-th Chornobyl wrecking unit is demonstrated by means of determination of the helium
content (on the account of Pu, Am decay) in the hermetic containers filled with the RAW. The method using appli-
cation of helium filter is acceptable but filterless one seems to be more economical. The latter is based on a con-
straint of all gases into choused gaseous medium but helium. The appraisal of necessary time for passive helium ac-
cumulation up to partial pressure of ∼10-7 Pa (a value to be measured by mass-spectrometer) is of ∼1000 hours using
a scheme with real helium filter and of ∼10 hours in the case without filter for specific alpha-activity of ∼105 Bq/kg.
(a threshold level for the RAW disposition).
PACS: 06.60.Mr, 07.30.Hd, 07.77.-n, 81.70.-q
1. INTRODUCTION
Investigation of thousands tons of the 4-th Cher-
nobyl unit radioactive waste (RAW) for the purpose of
determination of their activity group can be carried out
by means of measurement of the helium making rate
from the α radiators (Pu, Am, U). The disposable facili-
ties for measurement of the low partial pressure of gases
and the use of helium accumulation in a closed volume
allows to determine sufficiently low specific activities
including conditionally secure ones, when the RAW
does not demand of especial deposition [1,2]. Two
methods and two schemes of measuring plant concern-
ing this problem are proposed and analyzed in the re-
port.
2. METHOD WITH USAGE OF HELIUM
FILTER
It is possible to represent a measuring plant supplied
with a helium filter as a hermetic container having gas
volume V1 (Fig.1). The latter is filled with studied ma-
terial and connected to measuring volume V2 through a
filter having conductivity for helium G [3].
V1
3 2
V2
1
Fig. 1. Simplified scheme of measuring plant (for
calculation): 1 – container with RAW; 2 – helium filter;
3 – filter valve
In case when the helium flux from the RAW is B,
and the filter is opened after a time of helium accumula-
tion (only in the free volume V1) t0 then an increase of
the helium pressure P in the measuring volume as a
function of the time t from filter opening can be de-
scribed by expression
,1)()( 0
21
−−+
+
=
−
ττ
t
ett
VV
BtP (1)
where ( ) .
21
21
VVG
VV
+
⋅=τ (2)
So, when the plant parameters as well as the times t0,
τ and a material mass are known it is possible to calcu-
late the helium flux and specific α activity of the RAW
by means of single measurement of helium pressure. It
is important to know precisely and to be sure of tempor-
al stability of two parameters: a sensitivity of the mass-
spectrometrical pressure measurer and a filter conduct-
ivity. A static mass-analysing magnet seems to be most
suitable for a real application [4]. A filter maid of fused
quartz has the most stable conductivity for helium.
These assemblies can be calibrated previously at a
routine plant with a sufficient guarantee of their para-
meters keeping. Taking into account a gas type it should
be assumed also for the larger accuracy, that the helium
pressure must to be more than 10-7 Pa.
To estimate a necessary time for helium accumula-
tion let us consider a case of the RAW with the specific
α activity 1⋅105 Bq/kg. – a mean value in the region of
particle interest [6]. The container of 200 l. volume has
been filled with a destructured concrete having the ap-
parent density 1.6 kg./l. and solid mass 320 kg. So, the
volume of solid matter is 140 l. and the pore volume –
60 l. Let us assume also that V1=70 l. including some
technological vessels. The measuring volume let be
V2=5 l. (together with the mass-spectrometer and heli-
um purification devices). The helium filter (coaxial
quartz tubes: ∅100x1 and ∅96x1 of 60 cm length) has
conductivity G=8⋅10-6 l./s. under quartz temperature 800
°C according to the known data [5], so τ is equal to
186 h. Total α activity of the material in the container is
3.2⋅107 Bq, that causes the helium flux B=1.33⋅10−10 l.⋅
Pa/s. Dependence of the helium pressure P in measuring
volume on the time from filter opening calculated from
the expression (1) is represented in Fig. 2.
It is seen that the total time (t0+t) to achieve a pres-
64 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2002, № 2.
Series: Nuclear Physics Investigations (40), p. 64-65.
sure to be measured is the least when a helium filter is
previously opened. However, taking into account the
energy for the filter heat, it seems to be profitable to
keep a number of prepared containers with closed fil-
ters. A choice of the measuring regime is obviously
compromise. In this example the time of accumulation
and measurement can not exceed of 500 h. A real plant
will be, of course, sufficiently complicated in comparis-
on with the scheme described above and a measuring
procedure will be rather labour-consuming. In particu-
lar, it is necessary to provide a material drying, a meas-
urement of gas volume in the filled container (for in-
stance, using the method of controllable compression), a
removal of the atmospheric background helium (obvi-
ously, by means of pumping out using a powerful oil-
diffusion pump), preliminary gassing of quartz from the
atmospheric helium.
0 20 40 60 80 100
t, hours
0
5
10
15
20
25
P,
To
rr
x
10
0
10
20
30
P,
P
a x
1
0
6
5
4 3
2
1
-1
0
-8
Fig. 2. Helium pressure in measuring volume vs
time from filter opening for several values of helium
preliminary accumulation time t0 in container of V1
volume only (in conditions of example). 1 - t0=0 ; 2 -
t0=0.1, τ=18.6 h.; 3 - t0=0.2, τ=37.2 h.;4 – t0=τ
=186 h.; 5 – t0=2τ=372 h.;6 – t0=5τ=930 h
The gas pressure in the measuring volume in pres-
ence of acceptable size filter is much less than in the
container. There is the expression for this pressure and
for the overfall of the pressure through the filter:
.1)( 0
1
−+=∆
−
τ
τ
ττ t
et
V
BtP (3)
In the particular case of t0=τ, the pressure overfall
does not depend on the time, ∆P=V⋅τ/V1. The pressure
overfall is approaching to this value in time under t0<τ
or t0>τ from the side of less or more values correspond-
ingly. In the adduced example ∆P is about 1.3⋅106 Pa. It
is possible to rise sufficiently an increase of the meas-
ured helium pressure by application of a thin filter with
a large surface manufactured of some organic materials
having under indoor temperature more conductivity rel-
ative to helium than a hot quartz [5]. However, this fact
causes a grave doubt, generally, because a possible in-
stability of the organic filters conductivity as well as
taking into account a large gassing of them in a vacuum
and their large penetrability for a number of light organ-
ic compounds.
3. FILTERLESS METHOD
An analysis of the RAW can be speed up (and, may
be, cheapen) by usage of a filterless method. In condi-
tions of the sample mentioned above, the partial pres-
sure in the volume V1+V2=75 l. is increasing at the rate
of about 6.6⋅10-9 Pa/h. (∼5⋅10-11 Torr/h.). The pressure ∼
1.3⋅10-6 Pa (∼1⋅10-8 Torr) will be achieved for the accu-
mulation time of 200 h., that allows to increase the ac-
curacy of the pressure measurement and to reduce the
demands to completeness of evacuation of the atmo-
spheric background helium. It is eliminated also the un-
certainty caused by filter conductivity. The measuring
volume is connected to the container for a short period
and then cut off for a measurement. However, “the pu-
rification facilities” of the measuring volume must have
by far more gas capacity for absorption of predominant
component of the gassing in the container and can be
more complicated in comparison with a plant having a
helium filter. It should be noted that the measuring vol-
ume must be small because a mass-spectrometer itself
has a sufficient rate of the pumping out. As the estima-
tion shows, on ionizer of the mass-spectrometer (elec-
tron current of 5 mA at the distance of ∼2 cm) isolated
before measurement from the volume and working un-
der ultrahigh vacuum (∼10-9 Pa) can provide the helium
ion pumping at the rate up to 5⋅10-3 l./s. For the measur-
ing volume of 5 l. the ion pumping time constant is
about 1000 s. So, a measurement have to be carried out
for a time of ∼10 s. A realization of the filterless method
is facilitated by preliminary evacuation of the studied
material. A specific α activity I of the material with the
mass of M kg, gas volume of (V1+V2) l. and partial pres-
sure of the helium P (for the accumulation time of t s.)
is given by expression
,./)(1049.2 2117 kgBq
Mt
VVPI +
⋅= (4)
where 2.49⋅1017 – the number of gas atoms in 1 l. under
pressure of 1 Pa and temperature of 25°C.
4.CONCLUSION
This report is represented as a some technical pro-
posal. Not all issues are finally resolved. A rate of the
helium production in the grains of materials of the 4-th
Chernobyl unit and going out into gas environment has
reached of equilibrium during 15 years after the wreck.
Therefore, one can consider a helium flux from the
grains of the RAW as directly proportional to their α ac-
tivity. However, it is not clear how to use helium inside
the grains containing a good deal of information and
which can be released by especial treatment of the mate-
rial. It should be excluded a possibility of helium loss
under its cleaning, properly, by maintenance of the total
gas pressure not above of 10-2 Pa, that is necessary for a
normal work of the mass-spectrometer. A number of is-
sues demands of experimental study.
REFERENCES
1. Nuclear geology. M.: “IL”, 1956, 556 p. (in Rus-
sian).
2. A.G. Zaluzhny, Yu.N. Sokurskiy, V.N. Te-
bus. Helium in reactor materials. M.: “Ener-
goatomizdat”, 1988, 224 p. (in Russian).
3. Argon, Helium and the Rare Gases. The ele-
ments of the helium group. Pergamon Press, NY,
1963, 394 p.
4. A.I. Pipko, V.Ya. Pliskovskiy, E.A. Penchko.
Design and calculation of vacuum systems. M.:
“Energiya”, 1970, 281 p. (in Russian).
65
5. S. Dushman. Scientific foundations of vacu-
um technique. M.: “Mir”, 1964, 433 p. (in
Russian).
6. V.N. Gerasko et al. Object “Shelter”. History, state
and perspective. Kiev, 1997, p.94-114 (in Russian).
66
N.P. Dikiy, A.N. Dovbnya, L.K. Myakushko, L.V. Reprintsev, A.Eh. Tenishev, V.L. Uvarov
National Scientific Centre “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
e-mail: uvarov@kipt.kharkov.ua
1. INTRODUCTION
4.CONCLUSION
REFERENCES
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