Wide-range krypton gas monitor using a plastic scintillation detector operated in current mode with a gate circuit

Takasaki, Koji; Kobayashi, Hirohide; Suzuki, Hideki; Ushigome, Sadaharu*

Journal of Nuclear Science and Technology, 47(3), p.255 - 261, 2010/03

https://doi.org/10.3327/jnst.47.255

The wide-range krypton-85 detector was developed for monitoring of krypton-85 gas, which was discharged from the stack of a nuclear fuel reprocessing plant and varied largely in concentration. The detector combined a current-mode-operated plastic scintillation counter with a gated photomultiplier. The discrimination voltage of gated photomultiplier was determined, and the effects of temperature and humidity were examined on the background measurement. The detector was calibrated by krypton-85 gas and the decision threshold was estimated. These examinations showed that the wide-range krypton-85 detector worked in the measurement range as wide as 10-10 Bq/cm in linearity and the decision threshold of krypton-85 concentration was 1.310 Bq/cm for 10-minute measurement. The parallel measurement was made between this detector and a GM counter in the reprocessing laboratory. Both concentrations showed a good agreement with each other.

Carbon-14 source, distribution and behavior around Tokai reprocessing plant

Koarashi, Jun; Takeishi, Minoru; Kobayashi, Hirohide

Proceedings of International Symposium on Environmental Modeling and Radioecology, p.223 - 230, 2007/03

no abstracts in English

Airborne radioiodine monitoring at Tokai reprocessing plant

Mikami, Satoshi; Koarashi, Jun; Miyauchi, Toru; Akiyama, Kiyomitsu; Kobayashi, Hirohide

Proceedings of 2nd Asian and Oceanic Congress Radiological Protection (AOCRP-2) (CD-ROM), p.308 - 312, 2006/10

As airborne radioiodine effluent monitoring in Tokai reprocessing plant (TRP), not only a weekly evaluation of exact discharged amount of radioiodine (I) for assessing environmental impact, but also continuous monitoring of radioiodine being discharged are performed for quick recognition of unexpected effluent tendency. Furthermore, to enhance effluent monitoring activity corresponding to features reprocessing plant, sequential radioiodine monitoring system without interference by the mingled Kr has been developed and effectively functioned as an assist during plant operation. The systematic configurations having these functions for airborne radioiodine monitoring corresponding to nuclear fuel reprocessing plant have been established.

A Simple and reliable monitoring system for H and C in radioactive airborne effluent

Koarashi, Jun; Mikami, Satoshi; Akiyama, Kiyomitsu; Kobayashi, Hirohide; Takeishi, Minoru

Journal of Radioanalytical and Nuclear Chemistry, 268(3), p.475 - 479, 2006/06

https://doi.org/10.1007/s10967-006-0193-7

A simple and reliable sampling system for H and C in airborne release from nuclear facilities was designed. The sampling system can collect H and C simultaneously with a condensation technique using a commercially available cold trap equipment and a CO absorption technique using an organic alkali solution monoethanolamine, respectively. In situ performance tests for the effluent from a reprocessing plant showed that the system has the high and stable efficiencies for collecting H and C for a one-week batch sampling at a sampling flow rate of 0.4 l min. These collection techniques also provided a simple procedure of following sample preparations for activity measurement by liquid scintillation counting. The detectable concentrations of the proposed monitoring method were 3.0Bq/m for H and 1.6Bq/m for C, respectively. The sensitivity would be acceptable level for routine monitoring of airborne release at nuclear facilities.

A Practical method for monitoring I concentration in airborne release

Koarashi, Jun; Akiyama, Kiyomitsu; Asano, Tomohiro; Kobayashi, Hirohide

Journal of Radioanalytical and Nuclear Chemistry, 267(1), p.155 - 159, 2006/01

https://doi.org/10.1007/s10967-006-0022-z

To establish a practical method for monitoringI concentration in airborne release from the Tokai reprocessing plant,I collecting performance of sampling media used in the method was tested by in situ experiments. The results indicated that the combinational use of an activated charcoal-impregnated filter paper and an activated charcoal cartridge gives the collection efficiency of more than 90% for one-week sampling of real airborne effluent at sampling flow rates of 40.6-75.0 l min-1. The sampling and measurement conditions suitable for a routine-based monitoring were demonstrated taking into account the findings.

Re-Evaluation of a Method for Monitoring AirborneC Discharge and its Contribution to Development of an Advanced Method

Koarashi, Jun; Isaka, Keisuke*; Yokota, Tomokazu*; Kozawa, Tomoyasu*; Mikami, Satoshi; Akiyama, Kiyomitsu; Kobayashi, Hirohide

JNC TN8410 2005-005, 55 Pages, 2005/05

JNC-TN8410-2005-005.pdf:2.0MB

Some investigations were made for re-evaluating collection and measurement techniques in an airborne C discharge monitoring at the Tokai reprocessing plant (TRP), which include (1)collection efficiency of CO in a carbon sampler using monoethanolamine as CO absorbent;(2)affect of incorporating tritiated water into the carbon sampler on quantitative estimation of C activity in airborne effluent; (3)affect of leakage in air sampling on evaluating airborne C discharge; and (4)determination of chemical forms of C in airborne release from the TRP. The results presented not only the validity of the TRP's monitoring method, but also the technical aspects required for establishing a more reliable and effective monitoring method.

Study on evaluation method of radionuclides discharged in criticality accident using stack gas monitor

Sanada, Yukihisa; Mikami, Satoshi; Kobayashi, Hirohide; Kurimata, Tomoyuki*; Fukazawa, Satoshi*

Program and abstracts, p.77, P. 77, 2005/02

It researched concerning the method of evaluating the radionuclide discharged by using the gas monitor at a criticality accident. The measurement condition was set from the evaluation result of the -ray spectrum at a criticality accident of the use of the calculation code. The measurement system was developed in consideration of those conditions. The evaluation after three hours is possible at a criticality accident according to this system. The evaluation before three hours was examined about the method of doing the detector pulse by high-speed processing by digital oscilloscope.

Discharge Monitoring by the Wide Range Radioactive Krypton Detector

Morita, Suguru; Tanizawa, Teruaki*; Masayuki, Morifuji,; Takasaki, Koji; Suzuki, Hideki*; Suzuki, Kazunori; Kobayashi, Hirohide

JNC TN8410 2004-011, 83 Pages, 2004/07

JNC-TN8410-2004-011.pdf:5.88MB

In the Chemical Processing Facility (CPF), after reconstruction was completed, the examination for advanced hydrometallurgy reprocessing was carried out from December 2002 to March 2004. In this examination,Kr were discharged from the stack. Discharge ofKr was measured and estimated by the wide range radioactive Krypton detector.GM Gas monitor of the CPF stack monitor was exchanged for the wide range radioactive Krypton detector in fiscal 1994. In discharge monitoring of this examination for advanced hydrometallurgy reprocessing,Kr gas were detected for the first time by the wide range radioactive Krypton detector of CPF. In this examination, the temporary gas monitor of the conventional GM detector was installed, and the result of measurement and inventory were compared.In this report the discharge ofKr is indicated by the wide range radioactive Krypton detector. As a result of comparative evaluation, it was confirmed that the discharge monitoring by the wide range radioactive Krypton detector was appropriate.

Development of the Self Moving Survey System

Ishikawa, Hisashi; Nemoto, Norio; Izaki, Kenji; Kobayashi, Hirohide; Tanizawa, Teruaki*; Kanazawa, Yoshito*

JNC TN8400 2004-008, 124 Pages, 2004/05

JNC-TN8400-2004-008.pdf:58.81MB

In order to strengthen the functions of the self moving survey system, the design of the truck and the data transmission system, the investigation of the handling function and the durability test assumed under the disaster environment were executed.As the basic performance of the self moving survey system, it was demanded to have the functions in order to run on the bumpy road, go up and down the stairs and open and shut of the door. And the remote control by the PHS line or the SS wireless is adopted as an operational method. Moreover, as the function that can monitor the disaster situation in the facility, it was assumed the design that make modular the measurement equipments, which mainly measure alpha ray, gamma ray and neutron, and installed it.In consideration of the radiation monitoring under the environment that assumes the critical accident and a fire and the explosion etc. heat test, humidity test, radiation test, and aerosol (smoke) test for monitoring equipments were executed. As a result of the tests, it was confirmed that all equipment except the semiconductor detector operated normally.

Annual Report on Activities of Radiation Protection Division at JNC Tokai Works in Fiscal Year of 2002

Shinohara, Kunihiko; Asano, Tomohiro; Momose, Takumaro; Takeishi, Minoru; Kobayashi, Hirohide; Oka, Tsutomu; Takasaki, Koji

JNC TN8440 2003-020, 125 Pages, 2003/09

JNC-TN8440-2003-020.pdf:11.14MB

This annual report summarizes the activities of the Radiation Protection Division at JNC Tokai Works in fiscal 2002.The Tokai Works undertakes various research and development for the reprocessing of spent fuel, plutonium fuel fabrication, fast reactor fuel recycling technology, and radioactive waste treatment and disposal, all of which are done under strict safety management.The major radiation facilities in the Tokai Works are the Tokai Reprocessing Plant (TRP), which has been in operation since 1977, three MOX fuel fabrication facilities, the first of which has been in operation since 1965, the Chemical Processing Facility (CPF) where fast reactor (FR) reprocessing technologies are being developed, and various other radioisotope and uranium research laboratories.The Radiation Protection Division is responsible for radiation control in and around these facilities, including personnel monitoring, workplace monitoring, consultation on radiological work planning and evaluation, monitoring of gas and liquid waste effluents, environmental monitoring, instrumentation, calibration, quality assurance, and safety research. The Division also provides technical support and cooperation to other international and domestic institutes in the radiation protection field.In fiscal 2002, the results of radiological monitoring showed the situation to be normal, and no radiological incident or accident occurred. The maximum annual effective dose to radiation workers was 6.5 mSv and the mean annual effective dose was 0.1 mSv. Individual doses were kept within the annual dose limit specified in the safety regulations. The estimated effective dose caused by gas and liquid effluents from the TRP to members of the public around the Tokai Works was 4.2 * 10mSv. Environmental monitoring and effluent control were performed appropriately in compliance with safety regulation and standards.