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

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.

1. Bolognese-Milsztajn T, Bartlett D, Boschung M, Coeck M, Curzio G, d’Errico F, et al. Individual neutron monitoring in workplaces with mixed neutron/photon radiation. Radiation Protection Dosimetry. 2004;110(1-4): 753–758. DOI:10.1093/rpd/nch220.

2. d’Errico F, Bartlett D, Bolognese-Milsztajn T, Boschung M, Coeck M, Curzio G, et al. Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part I: scope and methods of the project. Radiation Protection Dosimetry. 2007;125(1-4): 275–280. DOI:10.1093/rpd/ncm169.

3. Schuhmacher H, Bartlett D, Bolognese-Milsztajn T, Boschung M, Coeck M, Curzio G, et al. Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part II: conclusions and recommendations. Radiation Protection Dosimetry. 2007;125(1-4): 281–284. DOI:10.1093/rpd/ncm167.

4. Luszik-Bhadra M, Bolognese-Milsztajn T, Boschung M, Coeck M, Curzio G, d’Errico F, et al. Direction distributions of neutrons and reference values of the personal dose equivalent in workplace fields. Radiation Protection Dosimetry. 2007;125(1-4): 364–368. DOI:10.1093/rpd/ncm189.

5. Luszik-Bhadra M, Lacoste V, Reginatto M, Zimbal A. Energy and direction distribution of neutrons in workplace fields: implication of the results from the EVIDOS project for the set-up of simulated workplace fields. Radiation Protection Dosimetry. 2007;126(1-4): 151–154. DOI:10.1093/rpd/ncm032.

6. Park H, Kim J, Choi K. Neutron Spectrum Measurement at the Workplace of Nuclear Power Plant with Bonner Sphere Spectrometer. Journal of Nuclear Science and Technology. 2008;45: 298-301. DOI: 10.1080/00223131.2008.10875847.

7. Luszik-Bhadra M, Bartlett D, Bolognese-Milsztajn, Boschung M, Coeck M, Curzio G, et al. Characterization of mixed neutron–photon workplace fields at nuclear facilities by spectrometry (energy and direction) within the EVIDOS project. Radiation Protection Dosimetry. 2007;124(3): 219–229. DOI:10.1093/rpd/ncm419.

8. Fernandez F, Bakali M, Tomas M, Muller H, Pochat JL. Neutron measurements in the Vandellos II nuclear power plant with a Bonner sphere system. Radiation Protection Dosimetry. 2004;110(1-4): 517–521. DOI:10.1093/rpd/nch383.

9. Rimpler A. Bonner sphere neutron spectrometry at spent fuel casks. Nuclear Instruments and Methods in Physics Research A. 2002;476: 468–473. DOI:10.1016/S0168-9002(01)01492-9.

10. Lacoste V, Reginatto M, Asselineau B, Muller H. Bonner sphere neutron spectrometry at nuclear workplaces in the framework of the EVIDOS project. Radiation Protection Dosimetry. 2007;125(1-4): P. 304–308. DOI:10.1093/rpd/ncm161.

11. Luszik-Bhadra M, Derbau D, Hallfarth G, Matzke M, Wiegel B, Wittstock J. Measurement of energy and directional distribution of neutron fluence inside a nuclear power plant. Nuclear Instruments and Methods in Physics Research A. 2002;476: 457–462. DOI: 10.1016/S0168-9002(01)01490-5.

12. Alekseev AG, Pikalov VA, Sumaneev OV, Kosyanenko EV, Britvich GI, Spirov EG, et al. Measurement of neutron radiation spectra at workplaces of separation production of a uranium enrichment plant. ANRI. 2005;43(4): 49-60. (In Russian).

13. Alekseev AG, Kosyanenko EV, Sumaneev OV, Kryuchkov VP. Measurement of neutron radiation spectra during start-up of Unit 3 of the Kalinin NPP. ANRI. 2006;45(2): 55-61. (In Russian).

14. Alekseev AG, Alekseev PA. Neutron spectra at the workplaces of the Balakovo NPP personnel. Eurasian Union of Scientists. Technical science. 2020;70(2): 20-26. (In Russian). DOI:10.31618/ESU.2413-9335.2020.2.70.534.

15. Alekseev AG, Baranenkov NN, Britvich GI, Kosyanenko EV, Pikalov VA. Investigation of the characteristics of neutron radiation at nuclear physics facilities for methodological support of the IDK. Protvino: Preprint IPhHE; 2003. 12 p. (In Russian).

16. Pyshkina M, Vasilyev A, Ekidin A, Nazarov E, Nikitenko V, Pudovkin A. Study of neutron energy and directional distribution at the Beloyarsk NPP selected workplaces. Nuclear Engineering and Technology. 2020;53(5): 1723-1729. DOI:10.1016/j.net.2020.10.015.

17. Pyshkina M, Vasilyev A, Ekidin A, Zhukovsky MV. Development and testing of a neutron radiation spectrometer in fields of radionuclide sources. AIP Conference Proceedings. 2019;2163(1): 1-4. DOI:10.1063/1.5130115.

18. Compendium of Neutron Spectra and Detector Responses for Radiation Protection Purposes, Technical report series No. 403, IAEA, Vienna, Austria; 2001. 337 p.

19. d’Errico F, Giustu V, Siebert BRL. A new neutron monitor and extended conversion coefficients for Hp(10). Radiation Protection Dosimetry. 2007;125(1-4): 345-348. DOI: 10.1093/rpd/ncm316.

20. Chest phantom (FLT-05, 06). Available from: https://www. radek.ru/fantoms/flt0506/ (Accessed: April 27, 2021) (In Russian).

21. Sannikov АV, Lebedev VN, Kustarev VN, Savitskaya EN, Spirov EG. Personal dosimeter of mixed radiation DVGN01: development and investigation of its characteristics. Protvino: Preprint IPhHE; 2005. 13 p. (In Russian).

22. Thermo Scientific Harshaw TLD Materials and Dosimeters. Available from: https://assets.thermofisher.com/TFSAssets/LSG/Catalogs/Dosimetry-Materials-Brochure.pdf (Accessed: April 27, 2021).

23. Pyshkina M, Zhukovsky M, Ekidin A. The uncertainties of personal neutron dosimeters at various operational neutron fields. RAD Conference Proceedigs. 2018;3: 36-41. DOI: 10.21175/RadProc.2018.08.