Nuclear Ship Research Articles

原子力船「むつ」の放射線漏洩

原子力船「むつ」の放射線漏洩

Digital Control for a Competitive Nuclear Powered Merchant Ship

Closed loop digital control of nuclear reactors is being performed at some U.S. national laboratories and some foreign countries. Within the next ten years, application to U.S. central station reactors is expected to become a standard feature. At present Babcock and Wilcox is designing a digital control system for a nuclear powered merchant ship. The plant control system is being designed using concepts of modern control theory. The control algorithms are being developed and tested by using a minicomputer as a prototype controller and interfacing it with a hybrid simulation that serves as the plant. This paper will present the prototype controller ign and its implementation on a minicomputer system.

The Effect of Exposed Nonmetallic Inclusions on Corrosion Resistance of Type 304 Stainless Steel a Simulated Pressurized Water Reactor Environment

Abstract This paper describes tests conducted on samples of Type 304 tubing from which fuel cladding in the replacement core for the Nuclear Ship Savannah was manufactured. The major objective of the tests was to determine if exposed nonmetallic inclusions in the tubing would have a detrimental effect on the corrosion resistance of the material in the N.S. Savannah's pressurized water reactor environment. Inclusions were located by ultrasonic techniques and were exposed by metallographic methods. Two general types of inclusions were present: (1) stringers, consisting of complex Mn-Fe-Cr oxides ranging in length from 0.005 to 0.050 inch, and (2) blocks, consisting of complex Mn-Fe-Cr silicates with a maximum length of 0.010 inch. Inclusion thickness varied from less than 0.001 inch for stringers to about 0.002 inch for the block type; maximum width of both types was approximately 0.004 inch. Tests were conducted in a 5 gallon autoclave made of Type 316 stainless steel. Test solutions consisted of deoxygena...

Ethylene in nuclear ship

Ethylene in nuclear ship

No nuclear ship for Britain

No nuclear ship for Britain

Design for a nuclear container fleet

In a study to determine the economic viability of a nuclear powered container ship, a comparison is made between fleets of conventional and nuclear container ships operating on the same route. Both ships are of the maximum size to pass through the Panama Canal. The profitability criterion used in the economic assessment is the required shadow freight rate per ton of cargo necessary to give zero net present value (NPV) for a specified discount rate (RD)--where zero NPV is coincident with the point where the after tax rate of return on the proposed investment is equal to the specified discount rate. The results indicate that only when discount rates in excess of 9 percent are reached does the conventional vessel show any real advantage over the nuclear alternative. Details are given for the assumptions made as to ship characteristics and routes, and for the method of economic analysis.

Some aspects of the classification of nuclear ships

Three sets of conditions taken into account by the Classification Society for nuclear merchant ships are: (1) the ship must be protected, (2) the crew is not to be exposed to undue hazards, (3) when the ship is in port the general public is not to be exposed to undue hazards. Of greatest importance is the nature of the potential risk existing in the operation of a nuclear reactor. Any accident involving radiation hazards would certainly imply a wide emotional reaction by the public. Fuel element classification involves two principles: (1) nuclear factors which give the highest values of the neutron flux at characteristic spots, and (2) technological factors which take care of fabrication tolerances, deformations of the element in operation, coolant flow variations and accuracy and time lapse of the reactor control gear. Various conditions which need to be understood for proper classification of the pressure vessel and containment vessel are discussed, with great emphasis placed on the safety of operation outlined in the present classification systems. Present methods of examination of nuclear plants, including the use of ultrasonics, give results which aid in classification during the fabrication process. R&D programs are currently under way in some places to investigate in a more accurate manner the behavior of reactor systems under fault or accident conditions.

船舶推進用原子炉開発の現況と問題点

船舶推進用原子炉開発の現況と問題点

Shielding experiment for the First Nuclear Ship in Japan

The experimental investigations on the marine reactor shielding in Japan were initiated in 1957 as well as theoretical studies. Among others, a series of extensive shield mockup experiments were performed through 1965 to 1967 in connection with the final design of the First Nuclear Ship in Japan. These include mockups of the primary shielding both in the core radial direction and in obliquely upwards direction, secondary shield samples with cylindrical penetrations and samples having gaps between shield blocks. In this paper, after a brief historical survey of relevant works, the mockup experiments for the side primary shield, the instrumentation tubes arranged in the reactor shield tank, and gaps of thin rectangular slit formed between lead slabs, concrete blocks or both are described. The results thus obtained have established the applicability of design procedures to the shield configuration which is to be used in the actual shield under construction.

Reactor plant design of the First Nuclear Ship in Japan

This article gives a summary of the reactor part design for the First Nuclear Ship in Japan and presents basic information on general features of the reactor and its core, fuel assembly, control rods, pressure vessel, pressurizer and other heavy components. Additional information provides a general description about the main installation of reactor auxiliary plant.

Estimation of the extreme values of wave-induced ship motions and accelerations for the First Nuclear Ship in Japan

For the purpose of predicting extreme values of ship motions and accelerations induced by waves on the First Nuclear Ship in Japan, a model test in the Ship Research Institute's experimental basin as well as theoretical computations were carried out. Firstly, the response character of the ship in regular waves was obtained and the influences of wave directions as well as ship speed upon the responses were investigated. Secondly, the power spectrum and the cumulative energy density of the responses in certain given irregular waves were obtained by two kinds of methods, the one experimental and the other theoretical. The short-term probability distribution of the ship responses in various sea states were determined and the extreme values expected to be encountered in the most severe sea state were estimated. Finally, the long-term distribution of the responses was calculated by using the short-term probability distributions of the above mentioned responses and the statistical probability of occurrence of sea state in the northern North Atlantic Ocean, from which the extreme values expected to encounter for long periods of time as one year or all her life could be estimated. The estimated extreme values were compared with those obtained by various methods already derived. As a result, it is recognized that the probable extreme values of accelerations and ship motions are within the design standard of safety for the nuclear ship.

Safety evaluation of the First Nuclear Ship in Japan

This paper describes the main results of the examination carried out by the Advisory Committee on Reactor Safeguards (ACRS) to evaluate the safety of the First Nuclear Ship in Japan. After analyzing the hazards in various cases of ship and reactor accidents, the ACRS agreed that the safety of the ship could be secured. The results of a safety analysis on NS Savannah analyzed in accordance with the guide of Japan AEC is also presented.

General description of the first nuclear ship “Mutsu”

General description of the first nuclear ship “Mutsu”

The ship design of the First Nuclear Ship in Japan

The guarantee of safety in the Japan nuclear ship is a dominant design criterion; this means: not-to-sink, anti-collision, anti-grounding, good steering apparatus, fire protection, auxiliary propulsion and safe reactor control under all conceivable ship motions and in cases of malfunctioning of auxiliary equipments. This ship is provided with a reactor containment vessel safeguarding against release of fission products in the case of the maximum credible accident, and with biological shield structures of concrete, lead and polyethylene. The liquid and solid radioactive waste would not be discharged on the sea, but stored in tanks and stores. Their capacity should cover six-months voyage.

Environmental and on-board tests of the instruments

The performance tests of nuclear measuring instruments and the radiation monitoring system were carried out by simulating the ship's conditions and the environmental conditions which would be encountered in the ocean. The pendulum type clinometer was trially made and the same tests were performed. Furthermore, some tests were done on board. As a result, some problems on the manufacture of those facilities on the first nuclear ship in Japan and on the adaptability for use were clarified.

Thermo-hydraulic model test of the first nuclear ship reactor in Japan

A series of thermo-hydraulic model tests were carried out to confirm that the first nuclear ship reactor in Japan was properly designed. The major test models were a half-size core structural model, a full-size fuel assembly model and a half-size steam generator plenum model. The measured results were compared with the design calculation of the reactor. Most of the calculated results were found to be in good agreement with experiment. However, the pressure drop in the reactor vessel was found to be overestimated, and a necessary correction was made on the system design. Also flow velocity distribution was found to be much more distorted than expected in the fuel assembly, and an appropriate design modification was made in the lower end plate. Flow coastdown in the primary loop and coolant mixing in the fuel assembly are also discussed.

483. コンクリートの接合部におけるガンマ線の漏洩

An experimental study was performed on γ-ray leakage through a slit in a concrete shield. The work was undertaken at the JRR-4 dry shielding test facility, as part of a series of mockup tests for the first nuclear ship of Japan. The paths of the slits through the shield were either straight or cranked. In the immediate vicinity of the concrete surface, the leakage γ-rays through the slit was seen to contribute a significant portion of the distributed γ-dose rate, but it rapidly diminished with distance from the surface. This was due to the relatively thick shield, in reference to the slit width, adopted in the present experiments, and also because of the strong scattering characteristics of the γ-rays with in the slit channel.The penetration components calculated by the ray analysis method were compared with the experimental results, and it was indicated that this method of calculation should prove useful for making rough estimations of the dose rate distribution of leakage γ-rays.

German nuclear ship “Otto Hahn” delivered in February

German nuclear ship “Otto Hahn” delivered in February

Mockup experiments for the irregular shield of the first nuclear ship of Japan

Shielding mockup experiments were performed in order to obtain useful experimental data for complicated configurations of the primary shield of the first nuclear ship of Japan, a special cargo ship of 8350 gross tons, with a pressurized water reactor of 36 MWt. Spatial distributions of gamma-ray dose rate and thermal neutron flux were measured around the primary shield mockups placed in the pool of JRR-4, a swimming pool type research reactor of 2.5 MW, stalled at Japan Atomic Energy Research Institute for special shielding research purposes. The calculations were carried out to compare the experimental results using point kernel integration codes SPAN-3 and SPAN-SLAB. The computed results with SPAN-SLAB seem to give a rather good agreement with measured values for some points which were little influenced by air voids. But the calculated thermal neutron flux densities in the coolant nozzle, neglecting the streaming radiation through the nozzle, were less than the measured data by a factor of about 10. The experiments showed that the preliminary design is sufficient for the primary shield except around the coolant nozzle. The detail design will be proceeded taking the results of the mockup experiment into consideration.

On the Ship Motions and Accelerations of a Nuclear Ship in Waves

Researches to predict the ship motions and accelerations to be induced on a nuclear ship in waves were carried out by model tests and theoretical computations.Firstly, the responses of the ship, which advances with various speed in regular waves coming from various directions, were measured and compared with the computed results by so-called strip theory.Secondly, the model tests in irregular waves having a certain energy spectrum were carried out, and the short term distribution of the probability of the responses were estimated through the cumulative energy density of the spectrum of the responses which were derived both by the test results and the computations.Finally, the long term distribution of the responses were also estimated by using the derived short term distribution and the probability of occurrence of sea state at the northern North Atlantic Ocean.