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Yumoto, Yasuhiro Department of Radiation Research, Shikata Laboratory Okayama University Advanced Science Research Center (RIC)
Okada, Shigeru Department of General Medicine, Okayama University Graduate School, Medicine, Dentistry and Pharmacological Research
Kinno, Ikuo Department of Radiation Research, Shikata Laboratory Okayama University Advanced Science Research Center (RIC)
Nagamatsu, Tomohiro Department of Radiation Research, Shikata Laboratory Okayama University Advanced Science Research Center (RIC)
Nouso, Kazuhiro Department of Gastroenterology and Hepatology, Okayama University, Graduate School Medicine, Dentistry and Pharmacological Science
Nakayama, Eiichi Department of Radiation Research, Shikata Laboratory Okayama University Advanced Science Research Center (RIC)
The clearance of solid low-level radioactive laboratory waste (LLRW) after decay-in-storage (DIS) obtained from a research institute and thoroughly separated using the separation and classification protocols presented in this study was evaluated.
The radioisotope (RI) content of incinerated LLRW from the specified RI research group (group A); the RI content of LLRW obtained in fiscal year 2000, which contained radionuclides with half-lives of less than 164 d (LLRW2); and the RI content of the LLRW reported in group A's disposal records were compared. The LLRW2 and LLRW of group A were incinerated after 2 y of decay-in-storage and immediately after storage, respectively.
The highest ratio of the RI of incinerated LLRW to the value in the disposal records was 2.52 for ⁵¹Cr. The radioactivities of radionuclides in both the LLRW2 and LLRW for ³⁵S, ⁴⁵Ca, ⁵¹Cr, ¹²⁵I, ³²P, ³³P, and ⁹⁹mTc and the incinerated ash after 1 y later of decay-in-storage were below the clearance level defined by the RS-G-1.7 of the International Basic Safety Standard without contamination by ³H and ¹⁴C. These remains contained very small amounts of some long-half-life radionuclides of natural origin after 7 y of decay-in-storage.
This LLRW separation protocol was effective for the separation of ³H and ¹⁴C. LLRW2 after 2 years of DIS and its incinerated ash after one year later of DIS were below the clearance level for radioactivity and radioactivity concentration.
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