Hoạt động trong Becquerel Khi một nguyên tử tan rã, bức xạ được phát ra. Nếu tỷ lệ của disintegrations lớn, một nguồn phóng xạ được coi là có một hoạt động cao. Các đơn vị cho hoạt động của một nguồn phóng xạ được đặt tên sau khi Becquerel (viết tắt là Bq) và được định nghĩa là: 1 Bq = 1 tan rã mỗi giây. Trong một số quốc gia, đơn vị cũ, curie (viết tắt là Ci và được đặt tên sau khi Marie Curie) vẫn được sử dụng. Curie-Các đơn vị được định nghĩa là các hoạt. | Chapter 4 Activity and Dose gray becquerel sievert Activity in Becquerel When an atom disintegrates radiation is emitted. If the rate of disintegrations is large a radioactive source is considered to have a high activity. The unit for the activity of a radioactive source was named after Becquerel abbreviated Bq and is defined as 1 Bq 1 disintegration per sec. In a number of countries the old unit the curie abbreviated Ci and named after Marie Curie is still used. The curie-unit was defined as the activity in one gram of radium. The number of disintegrations per second in one gram of radium is 37 billion. The relation between the curie and the becquerel is given by 1 Ci . 1010Bq The accepted practice is to give the activity of a radioactive source in becquerel. This is because Bq is the unit chosen for the system of international units SI units . But one problem is that the numbers in becquerel are always very large. The opposite holds true when a source is given in curies. For example when talking about radioactivity in food products 3 700 Bq per kilogram of meat is a large number. The same activity given in Ci is a really small number curie per kilogram. 2003 Taylor Francis 28 Radiation and Health Most people are used to measuring the amount of a substance in kilograms or liters not in becquerels or curies. Using the best balances in the world one can accurately measure down to about one microgram of substance 10- 6 gram . By using our knowledge of radioactive detection amounts more than a million times smaller than this can be measured. Radioactive sources as small as 10 Bq to 100 Bq can be readily measured this corresponds to only about 10-14 gram. Some examples will help develop some familiarity with the Ci and Bq units. Around 1930 radium sources were introduced in many hospitals and used for cancer therapy. Radium was rather expensive and the sources used for teletherapy see page 29 were 2 to 10 Ci. With these samples placed only about 10 cm .
