Measurement of ambient gamma dose rate in Metro Manila, Philippines, using a portable NaI(TI) scintillation survey meter.

Radiological data such as ambient dose equivalent rate obtained from radiation monitoring in Metro Manila are useful for the detection of any anomalous increase of radiation dose rate levels due to nuclear or radiological emergencies. In this study, ambient dose equivalent rates were measured in different locations in Metro Manila using a portable NaI(Tl) scintillation survey meter to determine the background radiation levels within the capital. Ambient dose equivalent rates measured range from 32.7 ± 2.2 to 59.3 ± 8.7 nanosieverts per hour (nSv/h) with computed mean and median values of 41.7 and 39.6 nSv/h, respectively. These values were lower than the Philippines' average dose rate which is 52 nanograys per hour (nGy/h). No significant trend was also observed in the monthly variation of ambient dose equivalent rate for most locations, with the dose rates being relatively consistent throughout a year. No significant trend was further observed in the monthly variation of ambient dose equivalent rate for the whole Metro Manila. Data obtained in this study were used to develop a dose rate distribution map of Metro Manila which could be used as a baseline reference of emergency responders for environmental radioactivity monitoring during nuclear or radiological emergencies that may affect Metro Manila.

MEASUREMENT OF AMBIENT GAMMA DOSE RATES ALONG TWO INDUSTRIAL FACILITIES IN LEYTE ISLAND, PHILIPPINES.

Natural background radiation to which humans are continuously exposed to come from the primordial radionuclides on the surface of the Earth. Industrial activities which concentrate natural radionuclides usually in residues and waste materials may enhance natural radioactivity on the ground via airborne contamination. In this study, ambient gamma dose rates were measured inside and outside two industrial facilities in Leyte, Philippines, to assess possible contribution of NORM materials in enhancement of natural radiation background in these areas. Ambient gamma dose rates measured at selected sites from Tacloban City to Isabel, Leyte and in nearby areas of Kananga and Ormoc City, Leyte were within the range of the background ambient gamma dose rates measured in the Philippines, ranging from 21 to 124 nSv/h. The workers in the phosphate rock storage and phosphogypsum pond areas in the phosphate fertiliser production plant received the highest annual effective external dose of 0.76 mSv.

Assessment of temporal variations of natural radionuclides Beryllium-7 and Lead-212 in surface air in Tanay, Philippines.

Detection of radionuclides in surface air allows researchers to gain further insight on the behavior of radionuclides that may affect human radiation exposure especially in the event of a nuclear emergency. In this study, activity concentrations of naturally-occurring radionuclides Beryllium-7 (7Be) and Lead-212 (212Pb) in surface air and meteorological data collected in Tanay, Philippines from January 2012 to December 2017 were evaluated to determine the impact of atmospheric conditions and processes to airborne radioactivity. Surface air concentrations of 7Be and 212Pb were found to range from 0.00779 ±â€¯0.00188 to 11.2 ±â€¯0.116 mBq/m3 and from 1.371 ±â€¯0.036 to 106.6 ±â€¯1.075 mBq/m3, respectively. 7Be and 212Pb show distinct annual trends, suggesting that atmospheric conditions affect both radionuclides differently and independently. 7Be shows two peak concentrations annually, with the first peak occurring between January to April and the second lower peak occurring between October and November. 212Pb, on the other hand, shows annual peak concentrations occurring between April and June. Ambient temperature showed strong positive correlation with 212Pb concentration in surface air and a weak negative correlation with 7Be; relative humidity and precipitation showed varying degrees of negative correlation with radionuclide concentrations in surface air. Source locations for the unusually high 212Pb activity concentrations detected on 11-13 May 2013 and 19-31 May 2015 determined using WEB-GRAPE and HYSPLIT atmospheric transport models are presented as a case study. The data and findings of this study shall serve as basis for further studies on local and regional atmospheric transport and radiological impact assessment for the implementation of an effective nuclear and radiological emergency preparedness and response system in the country.