Occupational Exposure to Neutrons at the Beloyarsk NPP

Studies of the energy distribution of neutron radiation at the workplaces of the Beloyarsk NPP were carried out. At 1 and 2 power units, occupational exposure of neutron irradiation occurs during operations for loading spent nuclear fuel into special railway carriage. At power units 3 and 4, operations accompanied by neutron irradiation can be divided into 3 groups: (1) work in rooms adjacent to the reactor core; (2) manipulation of radioisotope neutron sources; (3) work with fresh and spent nuclear fuel. Based on the data obtained on the energy distribution of the neutron radiation flux density, the ‘true’ values of the ambient dose equivalent rate H*(10), the individual dose equivalent rate Hp(10) and the integral neutron radiation flux density at individual workplaces were determined. For each group of workplaces, Fluence-toambient dose equivalent conversion coefficients are determined, which lie in the range from 12 to 295 pSv⋅cm2. Correction factors for individual thermoluminescent dosimeters, taking into.

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Neutron dosimetry at workplaces of JC “Institute of Nuclear Materials”

Radiatsionnaya Gygiena = Radiation Hygiene ◽

10.21514/1998-426x-2021-14-2-89-99 ◽

2021 ◽

Vol 14 (2) ◽

pp. 89-99

Author(s):

M. D. Pyshkina ◽

A. V. Vasilyev ◽

A. A. Ekidin ◽

E. I. Nazarov ◽

M. A. Romanova ◽

...

Keyword(s):

Angular Distribution ◽

Flux Density ◽

Radiation Flux ◽

Neutron Radiation ◽

Correction Factors ◽

Individual Dose ◽

Dose Equivalent ◽

Ambient Dose Equivalent ◽

True Values ◽

Ambient Dose

If the neutron fields at personnel workplaces differ from the neutron fields in which individual dosimeters are verified, there is a possibility of additional errors in the assessment of such dosimetric quantities as ambient dose equivalent, individual dose equivalent or effective dose. To take into account the energy distribution of the neutron radiation flux density and the geometry of the irradiation of workers, it is necessary to study the characteristics of the fields of neutron radiation at the workplaces of the personnel. In order to obtain conditionally true levels of personnel exposure to neutron radiation at nuclear facilities, studies of the energy and angular distribution of the neutron radiation flux density were carried out at the workplaces of the Institute of Reactor Materials JSC, Zarechny. The energy distribution of the neutron radiation flux density was obtained using an MKS-AT1117M multi-sphere dosimeter-radiometer with a BDKN-06 detection unit and a set of polyethylene spheres-moderators. The angular distribution of the neutron radiation flux density was estimated from the results of measurements of the accumulated dose of neutron radiation by individual thermoluminescent dosimeters placed on four vertical planes of a heterogeneous human phantom. The results of measurements of the energy and angular distribution of the neutron radiation flux density made it possible to estimate the conditionally true values of the ambient and individual dose equivalents. The calculated conventionally true values differ from the measured values from 0.7 to 8.9 times for the ambient dose equivalent and from 6 to 50 times for the individual dose equivalent. In order to reduce the error in assessing the effective dose of personnel using personal dosimeters, correction factors were determined. For different workplaces and types of personal dosimeters, correction factors are in the range of values from 0.02 to 0.16.

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Occupational exposure to Am-Be neutron calibration source mounted in OB26 shielding container

Nukleonika ◽

10.2478/nuka-2014-0016 ◽

2014 ◽

Vol 59 (3) ◽

pp. 97-103 ◽

Cited By ~ 1

Author(s):

Kamil Szewczak ◽

Slawomir Jednorog

Keyword(s):

Occupational Exposure ◽

Reference Points ◽

Radiological Protection ◽

Individual Dose ◽

Control Room ◽

Dose Equivalent ◽

Calibration Source ◽

Equivalent Rate ◽

Ambient Dose Equivalent ◽

Ambient Dose

Abstract Laboratory for Dosimetric and Radon Instruments Calibration which is a part of Central Laboratory for Radiological Protection (CLRP) in Warsaw is equipped with 241Am-Be neutron calibration source with activity of 185 GBq since 1999. The capsule was mounted in the OB26 type shielding container. The control room is separated from the above source by a concrete wall of 0.5 m in thickness. The calibration hall is adjacent to one side of the offi ce room. To comply with the requirements of the radiological protection system, the occupational exposure of persons that are working both in the offi ce and control room needs to be assessed. Two methods were involved for ambient dose equivalent rate determination. The active instrument measurements (AIMs) performed with the Berthold LB6411 neutron probe and the Monte Carlo simulation method (MCS) based on MCNP5 code. These estimations were completed for fi ve reference points. Additionally the γ radiation component was measured by RSS131 ionisation chamber. An increased value of the ambient dose equivalent rate from neutrons was observed in two reference positions. The fi rst observation was done in the control room while the second one in the offi ce room. Expected individual dose equivalents were evaluated based on the results of the AIM and on the expected working time in particular reference points. The annual individual dose equivalent associated with calibration activities using mentioned neutron source was estimated at maximum 0.8 mSv.

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IDENTIFICATION OF THE FUEL ROD CLADDING DESTRUCTION FROM THE CHANGE OF THE SNF STORAGE CASKS RADIATION

10.46813/2020-129-111 ◽

2020 ◽

pp. 111-119

Author(s):

V.G. Rudychev ◽

N.A. Azarenkov ◽

I.O. Girka ◽

Y.V. Rudychev

Keyword(s):

Numerical Modeling ◽

Gamma Radiation ◽

Dose Rate ◽

Nuclear Fuel ◽

Spent Nuclear Fuel ◽

Side Surface ◽

Neutron Radiation ◽

External Radiation ◽

Fuel Rods ◽

Fuel Rod

Two options for changing the distribution of spent nuclear fuel due to the possible destruction of the cladding of fuel rods, which causes a change in radiation outside the cask, are considered for VSC-24 casks used for storage of spent nuclear fuel by the dry method. The eﬀect of height reduction due to the destruction of the fuel rods of all 24 SFAs and 10 central SFAs on external radiation is studied analytically and by numerical modeling in the MCNP package. The destruction of 24 SFA is shown to lead to a signiﬁcant decrease in the dose rate of neutrons and gamma-radiation from 60Co on the weather lid of the cask, and of gamma-radiation from SNF isotopes at the mid-height of the side surface of the cask. The destruction of the ten central SFAs can be determined only from a change in the neutron radiation in the air inlets of the cask.

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