[en] In the event of a radiation emergency, it is necessary to assess intake and radiation dose for internally contaminated casualties. Bioassay methods consist of direct (in vivo) and indirect (in vitro) measurements. Direct (in vivo bioassay) methods commonly used to measure radioactive materials in the human body include whole-body counting and organ monitoring. Indirect measurements of radiation exposure (in vitro bioassay) involve measurements of excreta, such as urine, faeces, and/or blood. In this study, whole-body counting and biosample pretreatment and measurement were performed to assess the response to internal contamination under nuclear/radiological emergency conditions. First, the whole-body counting approach was validated for rapid and accurate internal contamination assessment in nuclear or radiological emergencies; validation requirements of whole-body counting were based on international standards. Our results indicated that the measurement system and procedures met international guidelines for sensitivity, accuracy, and measurement uncertainty for radionuclide detection in the human body. Second, Monte Carlo simulations were performed to improve the efficiency calibration of whole-body counter (WBC). Whole-body counting results are influenced by the subjects’ body shape, WBC detector type, and/or distribution of radionuclides in the human body. Our results indicated that the measurement geometry and material composition of BOttle Manikin ABsorber (BOMAB) phantoms well-represented the human body for stand-up-type WBC calibration purposes. For bed-scanning-type WBC, the measurement geometry and radioactive material distribution were dominant factors in calibration efficiency, thus requiring the appropriate anthropomorphic physical phantom for reliable calibration. Third, by using the whole-body counting system in the Korea Institute of Radiological Medical Sciences (KIRAMS), the potassium concentration in Korean subjects was measured to estimate the annual effective dose due to ⁴⁰K radiation. The results showed that potassium level in the body was not influenced by ethnicity or country (e.g., by variation in dietary habits), whereas sex, age, and body condition were important factors. Based on the ⁴⁰K measurement results, the annual effective dose estimates were 0.15 mSv for males and 0.13 mSv for females. Fourth, we established rapid and simple procedures for bioassay radioactivity measurements, including pretreatment of biosamples, measurement of samples, and evaluation of results. The established procedures can be applied for assessment of radionuclide intake and resulting radiation dose. Such capabilities should be made available for radiation emergency response preparedness. Based on our results, the procedures described herein will enable rapid, accurate measurement of radionuclide concentration in biosamples in the event of a radiation emergency. Lastly, we considered variability in the spot urine normalization method with respect to assessing the internal radiation dose of radiation workers who work with radiopharmaceutical products. The creatinine concentration method has commonly been used for normalization of spot urine under radiation emergency conditions. In this study, we measured and compared creatinine levels and ⁴⁰K activity. Our results showed that the ⁴⁰K activity concentration method is applicable as a complementary method for creatinine normalization in spot urine analysis in the event of nuclear or radiological emergencies. The procedures established in this study combine in vivo and in vitro bioassay assessments to accurately and rapidly assess radionuclide levels in the human body. Therefore, it is expected that the radiation dose assessment system of the KIRAMS could work effectively in mass casualty radiation emergency situations