Radionuclide transport behavior

Hidaka, Akihide

Enerugi Rebyu, 35(9), p.20 - 24, 2015/09

http://ci.nii.ac.jp/naid/40020565747

Operation of nuclear power plant causes accumulation of radionuclides in fuel rods as a result of nuclear fission of uranium and plutonium. During severe accidents, large amount of radionuclides are released from fuel and transport in the reactor coolant system and/or the containment. When the containment fails or its confinement function is lost, radionuclides could be released into the environment. Meanwhile, radionuclides can be removed by condensation onto wall, natural deposition such as gravitational settling, the engineered safety features (ESF) such as containment spray and so on. After various processes described above, the species, amounts and timing of radionuclide released into the environment is called source terms. The behavior of radionuclide can be described mechanistically by condensation or evaporation of gaseous radionuclide, deposition, growth and removal of aerosol by ESF. Present paper summarizes the radionuclide behavior during severe accidents.

Positron lifetime measurement on centrifuged BiPb intermetallic compound

Ono, Masao; Huang, X. S.*; Shibata, Yasuhiro*; Iguchi, Yusuke*; Sakai, Seiji; Maekawa, Masaki; Chen, Z. Q.*; Osakabe, Toyotaka; Kawasuso, Atsuo; Naramoto, Hiroshi*; et al.

Proceedings of 1st International Conference on Diffusion in Solids and Liquids (DSL 2005), p.531 - 533, 2005/07

Recently, we formed atomic-scale graded structures in some miscible alloys and observed the decomposition in BiPb intermetallic compound by sedimentation of atoms under strong gravitational field. In this study, we measured positron lifetime of centrifuged BiPb, to which the composition change was very small as it was treated at low temperature. It was found that the positron lifetime became longer than that of starting state. This indicated that the point defects (vacancy or divacancy) increased in the sample by centrifugal treatment. We are now investigating the relationship between increase in point defects and sedimentation of atoms.

Relationship between composition of settling particles and organic carbon flux in the western North Pacific and the Japan Sea

Otosaka, Shigeyoshi; Noriki, Shinichiro*

Journal of Oceanography, 61(1), p.25 - 40, 2005/01

https://doi.org/10.1007/s10872-005-0017-3

Settling particles play an important role in transport of organic carbon from the surface to the deep ocean. It is known that major components of settling particles are biogenic silicates (opal), biogenic carbonate, lithogenic clays and organic matters. In this study, we estimated organic carbon fluxes that are carried by each component in the western North Pacific Ocean (WNP) including the Japan Sea. Mean organic carbon flux at 1 km depth in the WNP (13.5 mg/m/day) was larger than that in the Eastern North Pacific (7.4), central North Pacific (1.1), Equatorial Pacific (4.2), Southern Ocean (5.8) and Eastern North Pacific (1.8). In the WNP, opal was a dominant component and 55 % of particulate organic carbon was carried by opal particles. Opal is known as a major component even in the Eastern North Pacific and Southern Ocean and opal fluxes in these areas are as much as in the WNP. However, organic carbon flux that was carried by opal particles in the WNP was significantly larger than that in the Eastern North Pacific and the Southern Ocean. It was cleared that opal particles in the WNP had great abilities not only to activate the biological pump in the surface ocean but also to transport organic carbon to the deep ocean.

Sedimentation of substitutional solute atoms in condensed matter; New type of diffusion

Mashimo, Tsutomu

Defect and Diffusion Forum, 237-240(1), p.30 - 37, 2005/00

Mega-gravity field realizes the sedimentation of even atoms, and is expected to create a nonequilibrium crystal-chemical state in condensed matter. We presented a self-consistent diffusion equation for sedimentation of atoms in condensed matter. Next, we developed an ultracentrifuge to generate strong acceleration field of over 1 million g, and, recently, succeeded in realization of the sedimentation of substitutional solute atoms in some alloys. The diffusion coefficients of sedimentation on Bi-Sb alloy were estimated to be much greater than those of conventional one. It is suggested that the sedimentation of substitutional atoms in solids or liquids can be included in a new type of diffusion, where the diffusion mechanism was yet unknown. In this article, the recent progress in the investigation of sedimentation of atoms under mega-gravity field is reviewed, and the diffusion mechanism is discussed. The application of the mega-gravity field is also discussed.

Fluxes and balance of Pb in the northwestern Japan Sea

Otosaka, Shigeyoshi; Baba, Masami*; Togawa, Orihiko; Karasev, E. V.*

Pacific Oceanography, 1(2), p.149 - 157, 2003/12

A sediment trap experiment and sediment coring were carried out in the northwestern Japan Sea (Sta MS), and lead-210 (Pb) and major components in settling particles were measured. By drawing up a balance of Pb in the water column, it was estimated that the cycle of Pb in the Sta MS was controlled by 3 processes, (1) removal and vertical transport of Pb from the surface layer by settling particles, (2) decomposition of particles in the deep layer, and (3) export by the deep current. Flux of Pb at 3 km depth was large in winter and spring. The large Pb flux in this season would be caused by the horizontal import of Pb -rich seawater from the coastal region to the bottom layer of Sta MS. It was suggested that seasonal variation of particulate Pb flux at the deep layer in the northwestern Japan Basin indicated the renewal of the deep water in this area.

The Primary evaluation of the impacts of naturaI phenomena on the safety functions of the geological disposal system; An Example study on site generic phase

Makino, Hitoshi; ; Miyahara, Kaname

JNC TN8400 2000-033, 74 Pages, 2000/11

JNC-TN8400-2000-033.pdf:9.19MB

Natural phenomena is one of the potential factors perturbing the long-term stability of the geological environment, and for natural phenomena, it is necessary to consider uncertainties relevant to time, frequency and effect. Therefore it will be important to have information about the potential impacts of natural phenomena on the safety functions of geological disposal system in the future by assuming that natural phenomena perturbs the safety functions of the geological disposal system. In this report, we have considered 4 natural phenomena, 'uplift, subsidence and denudation', 'climatic and sea-level changes', 'earthquakes and fault movement' and 'volcanism', which had been extracted by investigation in foreign countries and by considering the characteristics of Japan as natural phenomena which may perturb the long-term stability of the geological environment. And we have considered mainly typical effects of naturaI phenomena on geological environment and investigated the typical impacts of those natural phenomena on the safety functions of the geological disposal system. On perturbation scenarios, the maximum of total doses have been less than regulatory guidelines in foreign countries in all situations except the cases assuming that a new fault, which causes significant pathway of groundwater flow and nuclide migration, intersects the waste packages. In the case, the maximum of total doses may reach the same level as regulatory guidelines in foreign countries or natural radiation exposure in Japan depending on fault generation time or grandwater flow rate through the fault. And, on isolation failure scenarios, it has been implied that nuclide mass/flux originated from geological disposal is comparable level with nuclide mass/flux in natural environment. These results could give useful information about the potential impacts of natural phenomena on the safety functions of geological disposal system, and also could show the potential importance of ...

None

PNC TJ7454 97-002, 79 Pages, 1997/03

PNC-TJ7454-97-002.pdf:1.86MB

no abstracts in English

A Study of uplifts and subidences (5)

Takano, Toyoji*; Sasaki, Yutaka*; Fuse, Keisuke*; Saito, Akira*; Sato, Yoshikazu*

PNC TJ1454 96-001, 295 Pages, 1996/03

PNC-TJ1454-96-001.pdf:15.79MB

None

Performance test using modified (6000rpm type) centrifugal clarifier (II); Vibration characteristic test(I)

; Yasu, Takami; Kawata, Tomio

PNC TN8410 91-325, 68 Pages, 1991/11

PNC-TN8410-91-325.pdf:2.12MB

[Purpose] We confirmed modified (6000rpm type) centrifugal clarifier happened unstable vibration in the downward rotation on the condition of including undissolved residue after the clarification operation. This report describes the cause of unstable vibration and the measurement results of vibration characteristic after taking countermeasure for vibration decrease. [Method] It was considered that the cause of unstable vibration was four items in the following. (1)Unbalance between damping force of lower bearing damper and vibration force arisen by rotational bowl (2)Effect of feed condition (3)Effect of self-excited vibration on the free surface (4)Effect of frame strength that be set modified. This test is for take countermeasure to each item (13 item) in the upper items, and for quantitative measure of vibration characteristic (amplitude of rotational bowl and shaft) in the downward rotation on the condition of including undissolved residue after the clarification operation and for select best countermeasure, that is most effective to vibration damping, and does not arise the fall of clarification performance (capture efficiency), the increase of leak rate of feed solution and the fall of sludge washing performance. [Results] (1)We could not confirme vibration damping, compared with spring constant k=9 kgf/cm, damping constant c=20㎏fs/cm and the former condition (k=600 kgf/cm, c=0.3 kgfs/cm). (2)In case of countermeasure that operate as balance ring by sludge cohering height on the inside wall of rotational bowl, we could confirm that the amplitude in the downward rotation is about 1/3, the leak rate of feed solution is about 1/6, compared with the case of feed solution 55㎜ in height from the lower plate of rotational bowl and the former condition (25mm in height from the lower plate of rotational bowl). (3)Compared with the case of setting the side baffle plate 150㎜ in height from the lower plate of rotational bowl for decreasing ...

The Validation of the ART code through comparison with NSPP experiments in the steam-air atmosphere

*; Muramatsu, Ken

CSNI-R-176, 13 Pages, 1991/00

no abstracts in English