DEVELOPMENT OF THE DUAL COUNTING AND INTERNAL DOSE ASSESSMENT METHOD FOR CARBON-14 AT NUCLEAR POWER PLANTS

  • Published : 2009.06.30

Abstract

In a pressurized heavy water reactor (PHWR), radiation workers who have access to radiation controlled areas submit their urine samples to health physicists periodically; internal radiation exposure is evaluated by the monitoring of these urine samples. Internal radiation exposure at PHWRs accounts for approximately 20 $\sim$ 40% of total radiation exposure; most internal radiation exposure is attributed to tritium. Carbon-14 is not a dominant nuclide in the radiation exposure of workers, but it is one potential nuclide to be necessarily monitored. Carbon-14 is a low energy beta emitter and passes relatively easily into the body of workers by inhalation because its dominant chemical form is radioactive carbon dioxide ($^{14}CO_2$). Most inhaled carbon-14 is rapidly exhaled from the worker's body, but a small amount of carbon-14 remains inside the body and is excreted by urine. In this study, a method for dual analysis of tritium and carbon-14 in urine samples of workers at nuclear power plants is developed and a method for internal dose assessment using its excretion rate result is established. As a result of the developed dual analysis of tritium and carbon-14 in urine samples of radiation workers who entered the high radiation field area at a PHWR, it was found that internal exposure to carbon-14 is unlikely to occur. In addition, through the urine counting results of radiation workers who participated in the open process of steam generators, it was found that the likelihood of internal exposure to either tritium or carbon-14 is extremely low at pressurized water reactors (PWRs).

References

  1. Whillans DW, Thind KS. Internal Dosimetry for Short- Range Emitters. In: Health Physics Society 1995 Summer School (Radiation Protection at Nuclear Reactors). Medical Physics Publishing Madison, Wisconsin. 1995
  2. Korea Electric Power Corporation. Final Safety Analysis Report for Wolsong Unit 2,3,4 Nuclear Power Plants, Rev. 31. 2000
  3. Korea Electric Power Corporation. Final Safety Analysis Report for Yonggwang Unit 3,4 Nuclear Power Plants. 2000
  4. Korea Electric Power Corporation. Final Safety Analysis Report for Ulchin Unit 3,4 Nuclear Power Plants. 2000
  5. Korea Hydro & Nuclear Power Corporation. Development on the C-14 Internal Dosimetry for Nuclear Power Plant Workers. 2008
  6. Kim HG, Lee HS, Ha GH. An Analysis of Carbon-14 Metabolism for Internal Dosimetry at CANDU Nuclear Power Plants. Journal of Radiation Protection 2003 Sep.;28(3):207-213
  7. Kong TY, Kim HG. Preliminary Study on the Internal Dosimetry Program for Carbon-14 at Korean CANDU Reactors. Proceeding of the Korean Nuclear Society Fall Meeting, Gyeongju, October 26-28, 2005
  8. Kim HG, Kong TY, Yang YH, Kang DW, Lee SG, Park SC. Internal Dose Assessment of Carbon-14 at Korean CANDU Reactors. Proceeding of the Korean Association of Radiation Protection Spring Meeting, Gyeongju, November 23-24, 2006
  9. Han SJ, Lee GJ, Kim HG, Kong TY, Lee SG, Ahn YM. Dual Counting Method for Tritium and 14C Using Urine Samples of Radiation Workers. Proceeding of the Korean Association of Radiation Protection Fall Meeting, Tongyeong, Novermber 20-21, 2008
  10. Korea Electric Power Research Institute. Technical Report of the Analysis Method of Tritium and C-14 in Urine Samples of Radiation Workers. Technical Memo. 2007
  11. Atomic Energy Control Board. Bioassay Technical Reference Criteria Radioactive Carbon - Report of the AECB Working Group on Internal Dosimetry. 1994
  12. Whillans DW. Structure of a Physiologically Based Biokinetic Model for Use in $_{14}$C and Organically Bound Tritium Dosimetry. Radiation Protection Dosimetry 2003:105(1-4) https://doi.org/10.1093/oxfordjournals.rpd.a006221
  13. Kim HG, Kong TY. Internal Dose Assessment and Metabolism Attributed to the Inhalation of Carbon-14 of NPP Workers, Proceeding of the Korean Association of Radiation Protection Fall Meeting, Tongyeong, Novermber 20-21, 2008