Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment
This research focuses on application of the ALARA principle to minimize the collective doses (both for NPP personnel and the public), relating to admission of personnel to the containment for accident management activities and depending on operation of ventilation systems. Results from assessment of...
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Державне підприємство "Державний науково-технічний центр з ядерної та радіаційної безпеки" Держатомрегулювання України та НАН України
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| Cite this: | Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment / V. Bogorad, O. Slepchenko, Y. Kyrylenko // Ядерна та радіаційна безпека. — 2016. — № 4. — С. 21-24. — Бібліогр.: 15 назв. — англ. |
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irk-123456789-1298352018-01-31T03:02:44Z Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment Bogorad, V. Slepchenko, O. Kyrylenko, Y. This research focuses on application of the ALARA principle to minimize the collective doses (both for NPP personnel and the public), relating to admission of personnel to the containment for accident management activities and depending on operation of ventilation systems. Results from assessment of radiation consequences are applied to a small-break LOCA with failure of LPIS at VVER-1000 reactors. The public doses are evaluated using up-to-date RODOS, MACCS and HotSpot software for assessment of radiation consequences. The personnel doses are evaluated with MicroShield and InterRAS codes. The time function and optimal value of the collective dose are defined. The developed approach can be applied for minimization of the collective dose for optimization of accident management strategies at NPPs. Дослідження спрямовано на застосування принципу оптимізації для мінімізації дозових навантажень на персонал АЕС та населення, пов’язаних з часом початку проведення відновлювальних робіт персоналом у контайнменті та режимом роботи вентиляційної системи. Наведено результати оцінки радіаційних наслідків аварії з малою течею та відмовою САОЗ НТ на реакторі типу ВВЕР-1000. Колективні дози опромінення населення розраховувалися з використанням сучасних програмних кодів RODOS, MACCS і HotSpot. Дози опромінення персоналу визначалися за допомогою кодів MicroShield та InterRAS. У рамках застосування принципу ALARA отримано функцію змінення колективної дози з часом та її оптимальне значення. Даний підхід може бути застосований для мінімізації колективної дози опромінення в оптимізації стратегій управління аваріями на АЕС. Исследования направлены на применение принципа оптимизации с целью минимизации дозовых нагрузок на персонал АЭС и населения, связанных с временем начала проведения восстановительных работ персоналом в контайнменте и режимом работы вентиляционной системы. Представлены результаты оценки радиационных последствий аварии с малой течью и отказом САОЗ НД на реакторе типа ВВЭР-1000. Коллективные дозы облучения населения рассчитывались с использованием современных программных кодов RODOS, MACCS и HotSpot. Дозы облучения персонала рассчитывались с помощью кодов MicroShield и InterRAS. В рамках применения принципа ALARA получена функция изменения коллективной дозы во времени, найдено ее оптимальное значение. Данный подход может быть использован для минимизации коллективной дозы облучения персонала и населения при оптимизации стратегий управления авариями на АЭС. 2016 Article Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment / V. Bogorad, O. Slepchenko, Y. Kyrylenko // Ядерна та радіаційна безпека. — 2016. — № 4. — С. 21-24. — Бібліогр.: 15 назв. — англ. 2073-6231 http://dspace.nbuv.gov.ua/handle/123456789/129835 621.039.58 en Ядерна та радіаційна безпека Державне підприємство "Державний науково-технічний центр з ядерної та радіаційної безпеки" Держатомрегулювання України та НАН України |
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This research focuses on application of the ALARA principle to minimize the collective doses (both for NPP personnel and the public), relating to admission of personnel to the containment for accident management activities and depending on operation of ventilation systems. Results from assessment of radiation consequences are applied to a small-break LOCA with failure of LPIS at VVER-1000 reactors. The public doses are evaluated using up-to-date RODOS, MACCS and HotSpot software for assessment of radiation consequences. The personnel doses are evaluated with MicroShield and InterRAS codes. The time function and optimal value of the collective dose are defined. The developed approach can be applied for minimization of the collective dose for optimization of accident management strategies at NPPs. |
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| author |
Bogorad, V. Slepchenko, O. Kyrylenko, Y. |
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Bogorad, V. Slepchenko, O. Kyrylenko, Y. Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment Ядерна та радіаційна безпека |
| author_facet |
Bogorad, V. Slepchenko, O. Kyrylenko, Y. |
| author_sort |
Bogorad, V. |
| title |
Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment |
| title_short |
Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment |
| title_full |
Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment |
| title_fullStr |
Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment |
| title_full_unstemmed |
Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment |
| title_sort |
application of the alara principle to minimize collective dose in npp accident management within the containment |
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Державне підприємство "Державний науково-технічний центр з ядерної та радіаційної безпеки" Держатомрегулювання України та НАН України |
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2016 |
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http://dspace.nbuv.gov.ua/handle/123456789/129835 |
| citation_txt |
Application of the ALARA Principle to Minimize Collective Dose in NPP Accident Management within the Containment / V. Bogorad, O. Slepchenko, Y. Kyrylenko // Ядерна та радіаційна безпека. — 2016. — № 4. — С. 21-24. — Бібліогр.: 15 назв. — англ. |
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Ядерна та радіаційна безпека |
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2025-07-09T12:16:01Z |
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ISSN 2073-6231. Ядерна та радіаційна безпека 4(72).2016 21
UDC 621.039.58
V. Bogorad, O. Slepchenko, Y. Kyrylenko
State Scientific and Technical Center for Nuclear and Radiation
Safety, Kyiv, Ukraine
Application of the ALARA
Principle to Minimize
the Collective Dose in NPP
Accident Management
within the Containment
This research focuses on application of the ALARA principle to minimize
the collective doses (both for NPP personnel and the public), relating
to admission of personnel to the containment for accident management
activities and depending on operation of ventilation systems.
Results from assessment of radiation consequences are applied
to a small-break LOCA with failure of LPIS at VVER-1000 reactors. The public
doses are evaluated using up-to-date RODOS, MACCS and HotSpot
software for assessment of radiation consequences. The personnel doses
are evaluated with MicroShield and InterRAS codes. The time function and
optimal value of the collective dose are defined.
The developed approach can be applied for minimization
of the collective dose for optimization of accident management strategies
at NPPs.
K e y w o r d s: ALARA principle, radiation consequences, minimization
of collective dose, small-break LOCA.
В. І. Богорад, О. Ю. Слепченко, Ю. О. Кириленко
Застосування принципу ALARA з метою мінімізації
колективної дози в процесі управління аварією
в контайнменті на АЕС
Дослідження спрямовано на застосування принципу оптимізації
для мінімізації дозових навантажень на персонал АЕС та населення,
пов’язаних з часом початку проведення відновлювальних робіт персо-
налом у контайнменті та режимом роботи вентиляційної системи.
Наведено результати оцінки радіаційних наслідків аварії з малою
течею та відмовою САОЗ НТ на реакторі типу ВВЕР-1000. Колективні
дози опромінення населення розраховувалися з використанням су-
часних програмних кодів RODOS, MACCS і HotSpot. Дози опромінення
персоналу визначалися за допомогою кодів MicroShield та InterRAS.
У рамках застосування принципу ALARA отримано функцію змінення
колективної дози з часом та її оптимальне значення.
Даний підхід може бути застосований для мінімізації колективної
дози опромінення в оптимізації стратегій управління аваріями на АЕС.
К л ю ч о в і с л о в а: принцип ALARA, радіаційні наслідки, мінімізація
колективної дози, аварія з малою течею теплоносія першого контуру.
© V. Bogorad, O. Slepchenko, Y. Kyrylenko. 2016
I
n order to improve safety of NPPs, an important step
towards implementation of the optimization principle
is to achieve minimum radiation exposure to personnel,
the public and the environment both in normal operation
and in accident conditions. In recent years, scientific and
research capabilities in this area have been expanding [1—4].
In particular, research of the processes leading to the formation
of radioactive releases during accidents involving spills of liquid
radioactive materials in areas with forced ventilation was
performed by SSTC NRS in [4]. Radiation exposure caused
by such processes is estimated in this study using a variety
of atmospheric transport models. They are implemented
in the program codes MACCS [5], RODOS [6] and HotSpot [7].
However, these codes are more often used for the safety analysis
of nuclear power plants (e.g. predictive assessments [8, 9] or
real-time calculations [6]) than for optimization of the accident
management strategies or improvement of the emergency plans.
Unfortunately, today the main criterion for the optimization
of emergency response is the factor of economic justification [10].
The aim of this study is to optimize the radiation accident
management strategy according to the criterion of radiation
impact on the public and personnel at every stage of the accident.
Radioactive release management. The main parameters
that influence the formation of public exposure doses in case
of accidents in the containment are:
activity of radionuclides in the air space of the containment;
radioactive steam-gas mixture flow into the environment
through containment leakages or by the exhaust ventilation
system;
weather conditions accompanying the release.
In case of some accidents, it becomes possible to control
the release. For example, it can be isolation of a small leakage
from the primary circuit, control of forced ventilation system
circulation, or bleed of air fraction into the adjacent containment
rooms.
There are many methods of reducing the radioactive release
from the containment. For example, the Filtered Containment
Venting System (FCVS) can be used [11]. The delay time
of radioactive substances within the containment is critical for
appropriate countermeasures to protect the public from exposure
to a radioactive cloud passing in the early phase of an accident
(shelter, evacuation, iodine prophylaxis, relocation) [12].
Even short-term retention of the steam-gas mixture
in the containment can significantly reduce the proportion
of noble gases and radioactive iodine radioisotopes in the release
due to radioactive decay. Even for 3 days of retention, iodine
activity reduces by 10 times and noble gas activity reduces by
approximately 3 times.
All of the above methods allow reduction in radiation doses
to some extent.
Evaluation of collective doses. On example of a small-break
loss-of-coolant accident (SB LOCA) with failure of the low-
pressure injection system (LPIS) at VVER-1000 reactors,
consider the dynamics of dose values over time.
After an accident with leak of the primary coolant and failure
of the system to maintain primary coolant inventory at low
pressure, operational personnel need to take actions to restore
the failed equipment. These actions include the restoration
of equipment whose failure led to the LPIS failure (recovery of at
least one channel for primary makeup). Obviously, the timely
recovery of failed equipment restores the system. As a result,
severe damage to the reactor core is prevented.
If exact time for emergency personnel actions is known,
uncertainty remains regarding the entry of staff into the access-
control area. Early entry into the containment premises is
associated with significant doses for mitigation of the accident
22 ISSN 2073-6231. Ядерна та радіаційна безпека 4(72).2016
V. Bogorad, O. Slepchenko, Y. Kyrylenko
(Fig. 1a) and high levels of equivalent dose rate (EDR). Late
entry of personnel leads to a massive release of the steam-gas
mixture into the environment (Fig. 1b).
Assessment of the collective effective dose for personnel and
the public includes the use of various special tools of exposure
dose assessment. Examples of such tools are shown in Table 1.
The values of doses for personnel and the public were obtained
with these tools (Figs. 2 and 3).
Table 1. Effective dose components
Group Irradiation ways Calculation tools
Personnel
External exposure from cylinder
(radioactive steam-gas mixture
within the containment) MicroShield
[13]
External exposure from disk
(liquid radioactive material)
Due to inhalation InterRAS [12]
Public
External exposure from cloud
RODOS/
MACCS/
HotSpot
Due to inhalation
Due to external exposure from
ground surface
EDR dynamics was found within the containment (Fig. 1a)
towards defining collective doses. The collective doses
to the public are calculated with several codes. The obtained
data were compared against the parameter effective dose rate.
The calculation results showed sufficient convergence and did
not exceed the 20 % relative error.
The most conservative results were show by the US codes
MACCS and HotSpot (Fig. 2) including a simplified model
of atmospheric transport in comparison with the RODOS
code (Fig. 3). The calculations showed that MACCS code was
suitable for probabilistic assessments of radiation consequences,
while RODOS was intended for predictive calculations of doses
in emergencies.
Unlike the American codes, RODOS can specify
a continuous source of release, gives the possibility to calculate
the dose rate with a time step from 10 min, and allows using
the current weather and population density databases. Therefore,
the RODOS code is the most suitable option for the evaluation
of the collective dose to the public.
Table 2. Activity data for MicroShield code (maximal
values of activity within the containment)
Group Radionuclide
Activity, Bq
Steam-gas
mixture
Released
coolant
Long-lived
radionuclides
Sr-90 5,63E+05 9,25E+06
Ru-103 9,98E+05 1,64E+07
Ru-106 5,27E+04 8,65E+05
Cs-134 6,44E+09 1,06E+11
Cs-137 9,59E+09 1,57E+11
Ce-141 7,05E+06 1,16E+08
Ce-144 4,34E+05 7,12E+06
Iodine
I-131 8,92E+11 1,78E+11
I-132 2,23E+12 4,46E+11
I-133 2,46E+12 4,92E+11
I-134 1,52E+12 3,04E+11
I-135 2,07E+12 4,14E+11
Noble gases
Kr-85 1,18E+11 0,00E+00
Kr-85m 2,21E+12 0,00E+00
Kr-87 1,99E+12 0,00E+00
Kr-88 5,79E+12 0,00E+00
Xe-133 1,86E+13 0,00E+00
Xe-135 5,52E+12 0,00E+00
Xe-135m 8,40E+11 0,00E+00
Fig. 1. Equivalent dose rate within the containment (a) and I-131 release into the atmosphere (b) for different ventilation flow rates
a b
ISSN 2073-6231. Ядерна та радіаційна безпека 4(72).2016 23
Application of the ALARA Principle to Minimize the Collective Dose in NPP Accident Management within the Containment
Application of the ALARA principle. For SB LOCA,
ALARA optimization [14] of the collective dose is made
on the assumption that the individual doses do not exceed
the level of deterministic effects, i.e. conditions for the linear
no-threshold model “dose-effect” are met [15].
In the case of a radiation accident within the containment,
minimization of the collective dose is reduced to determine
the time of entry into the containment:
min( ) ( ) ( )
0
( ) , ,
t T t
w p
t S
f t n D t dt m x y D t dtdS
+
= + →
∫ ∫ ∫
Dw(t) — individual effective dose rate to body (personnel), Sv/sec;
Dp(t) — individual effective dose rate to body (public), Sv/sec;
n — number of personnel, man; m(x, y) — population density, man/m2;
S — square of contaminated territory, m2; T — time of mitigation
(period of operations the restoration of the failed equipment
and decrease of the leakage rate), sec; t — time of entry, sec.
Fig. 4 shows the curves of the collective doses to personnel
and the public for SB LOCA with LPIS failure at VVER-1000
that were obtained for the early phase of an accident (1st day).
These values depend on the time of emergency personnel entry
into the access-control area. Curve 1 shows the collective
dose to be received by personnel (3 persons) for 30 min
of operations on the restoration of the failed equipment and
decrease of the leakage rate. Curve 2 describes the collective
dose to the public due to release to the environment. Curve 3 is
the total collective dose to the public and personnel.
Emergency entry of 3 persons into the containment
to mitigate an emergency release on the 6th hour of an accident
will allow the lowest possible value of collective dose in the early
phase of the accident to be achieved — 6 man⋅mSv.
The results show that the optimum function of the collective
dose is not observed in all cases. In condition of stable
a
b
Fig. 2. Effective dose evaluation using HotSpot code (data for I-131): contour (a), centerline (b)
a
b
Fig. 3. Effective dose evaluation using RODOS code: field of effective dose rate (a),
effective dose dynamic at a distance (4 km) from release source (b)
24 ISSN 2073-6231. Ядерна та радіаційна безпека 4(72).2016
V. Bogorad, O. Slepchenko, Y. Kyrylenko
atmosphere and light wind, nearby settlements with a high
population density may be exposed to the collective dose
by orders of magnitude greater than the predicted collective
dose for personnel. In this situation, the failure function
of collective dose will be disproportionately low in comparison
with the absolute values of doses. Minimization of radiation
exposure does not bring an expected effect.
The optimization principle with the collective dose criterion
can be applied for the following conditions:
compliance with the permissible leakage for the containment
(0,3 % of the containment volume per day for VVER-1000 [11])
with disabled ventilation;
controlled release through ventilation systems using
treatment filters;
timely implementation of urgent countermeasures to protect
the public;
unstable atmosphere conditions (stability categories from
A to C according to Pasquill classification [1]) and strong winds
(more than 4 m/sec);
low population density in areas surrounding the nuclear
power plant.
Conclusions
In this research, the approach on application of the ALARA
principle to minimize the collective dose in NPP accident
management within the containment was developed. On example
of SB LOCA, it has been shown that such accidents can be
managed using the criteria of the total collective dose to personnel
and the public. A series of the calculations using different
computer tools for public dose evaluation (RODOS, MACCS,
HotSpot) were done, the obtained results are well correlated.
The limitation of the developed approach was identified.
The proposed ALARA principle of collective dose optimization
can be introduced into the emergency operating procedures,
accident management guidelines and emergency plans.
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Fig. 4. Collective doses to personnel and
public (hermetic containment)
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