Saturn's Rings

Saturn’s rings.

Saturn is the sixth planet from the sun. Image Credit: NASA

 
Saturn is not the only planet with rings. Jupiter, Uranus and Neptune have rings, too. But Saturn's rings are the biggest and brightest.

Galileo was the first person to see Saturn's rings. He spotted them while looking into space through a telescope in 1610 and scientists have been trying to learn more about Saturn's rings ever since.

Saturn's rings are made of ice and rock. These pieces vary in size. Some are as small as a grain of sand. Others are as large as a house. Scientists aren't sure though when or how Saturn's rings formed but think they have something to do with Saturn's many moons.

Earth has only one moon. But Saturn has at least 60 moons orbiting it that we know about. Asteroids and meteoroids sometimes crash into these moons and break them into pieces. The rings could be made from these broken pieces of moons. The rings may also be made from material left over from when Saturn first formed.

This close-up view of Saturn's rings shows that many tiny rings make up the larger rings around the planet. Image Credit: NASA

 
From far away, Saturn looks like it has seven large rings. Each large ring is named for a letter of the alphabet. The rings were named in the order they were discovered. The first ring discovered was named the A ring, but it is not the ring closest to or farthest from Saturn.

Some of the rings are close together. Others have large gaps between them. The rings do not sit still. They circle around Saturn at very high speeds. A closer look shows that each large ring is made up of many small rings. The small rings are sometimes called ringlets. More rings and ringlets could still be discovered.

Saturn is much larger than Earth. More than 700 Earths could fit inside Saturn. Saturn's rings are thousands of miles wide. If there were cars in space, it would take more than a week to drive across some of Saturn’s rings. On the other hand, the rings are quite thin. They are only about 30 to 300 feet thick.

Cassini is the latest NASA spacecraft to explore Saturn. Cassini left Earth in 1997 and arrived at Saturn seven years later, in 2004. The spacecraft has been orbiting the planet since then. Cassini sends new pictures and information back to Earth all the time. Cassini has taken amazing pictures of Saturn's rings.

For more information on Saturn or to view additional images visit:-
http://ciclops.org/

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What are Nuclear Weapons?

Given this is in the news of late, we ask what are Nuclear Weapons?

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission ("atomic") bomb test released the same amount of energy as approximately 20,000 tons of TNT. The first thermonuclear ("hydrogen") bomb test released the same amount of energy as approximately 10,000,000 tons of TNT.

A modern thermonuclear weapon weighing little more than 2,400 pounds (1,100 kg) can produce an explosive force comparable to the detonation of more than 1.2 million tons (1.1 million tonnes) of TNT. Thus, even a small nuclear device no larger than traditional bombs can devastate an entire city by blast, fire and radiation. Nuclear weapons are considered weapons of mass destruction, and their use and control have been a major focus of international relations policy since their debut.

The basics of the Teller–Ulam design for a hydrogen bomb: a fission bomb uses radiation to compress and heat a separate section of fusion fuel.

Fusion Weapons

This type of nuclear weapon produces a large proportion of its energy in nuclear fusion reactions. Such fusion weapons are generally referred to as thermonuclear weapons or more colloquially as hydrogen bombs (abbreviated as H-bombs), as they rely on fusion reactions between isotopes of hydrogen (deuterium and tritium). All such weapons derive a significant portion, and sometimes a majority, of their energy from fission. This is because a fission weapon is required as a "trigger" for the fusion reactions, and the fusion reactions can themselves trigger additional fission reactions.

Fusion reactions do not create fission products, and thus contribute far less to the creation of nuclear fallout than fission reactions, but because all thermonuclear weapons contain at least one fission stage, and many high-yield thermonuclear devices have a final fission stage, thermonuclear weapons can generate at least as much nuclear fallout as fission-only weapons

The International Atomic Energy Agency was created in 1957 to encourage peaceful development of nuclear technology while providing international safeguards against nuclear proliferation.

Apart from their use as weapons, nuclear explosives have been tested and used for various non-military uses, and proposed, but not used for large-scale earth moving. When long term health and clean-up costs were included, there was no economic advantage over conventional explosives.

Synthetic elements, such as einsteinium and fermium, created by neutron bombardment of uranium and plutonium during thermonuclear explosions, were discovered in the aftermath of the first thermonuclear bomb test. In 2008 the worldwide presence of new isotopes from atmospheric testing beginning in the 1950s was developed into a reliable way of detecting art forgeries, as all paintings created after that period may contain traces of cesium-137 and strontium-90, isotopes that did not exist in nature before 1945.

25 Aug 2010 - "Storax Sedan" underground nuclear test - July 1962

Storax Sedan (yield 104 kt) - shallow underground nuclear test conducted by the United States on 6 July 1962 at Nevada Test Site. The main purpose of the detonation was to asses the non military dimension of a nuclear explosion.

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions in all environments, for military or civilian purposes. It was adopted by the United Nations General Assembly on 10 September 1996 but it has not entered into force as of December 2012

See http://www.ctbto.org/ for more details on the Comprehensive Nuclear Test Ban Treaty Organisation

Also visit http://en.wikipedia.org/wiki/Nuclear_bomb

The Safe use of Gas Cylinders

Following on from last week's article on Liquid Nitrogen, this week we take a quick look at the safe use of gas cylinders.
 
INTRODUCTION

Accidents involving gas cylinders can cause serious injury or even death. HSE guidance provides simple practical advice on eliminating or reducing the risks associated with using gas cylinders.

 

The legal term that covers gas cylinders is “pressure receptacle”. This is a generic term covering a number of types of pressure receptacle: tube, pressure drum, cryogenic receptacle, bundle of cylinders as well as cylinders themselves, plus the valve(s) fitted directly to the receptacle. But for the purpose of this guidance, the term “gas cylinder” shall be taken to mean all these various types of pressure receptacle.

 

Gas cylinders used in adverse or extreme conditions, such as for breathing apparatus, may require special precautions. Although the advice in this guidance is valid for all uses of gas cylinders these special precautions, such as different frequencies for periodic inspections, are not covered.

 

As an employer or self-employed person, you have a duty to provide a safe workplace and safe work equipment. Designers, inspectors, manufacturers, suppliers, users and owners also have duties.

 

Employers have a further duty to consult any safety or employee representatives on health and safety matters. Where none are appointed, employers should consult the workforce directly.

 

The main hazards are:

• Impact from the blast of a gas cylinder explosion or rapid release of compressed gas;
• Impact from parts of gas cylinders or valves that fail, or any flying debris
• Contact with the released gas or fluid (such as chlorine);
• Fire resulting from the escape of flammable gases or fluids (such as liquefied petroleum gas);
• Impact from falling cylinders;
• Manual handling injuries;

The main causes of accidents are

• Inadequate training and supervision
• Poor installation;
• Poor examination and maintenance;
• Faulty equipment and / or design (eg badly fitted valves and regulators);
• Poor handling;
• Poor storage;
• Inadequately ventilated working conditions;
• Incorrect filling procedures;
• Hidden damage

HOW TO REDUCE THE RISKS

Anyone who examines, refurbishes, fills or uses a gas cylinder should be suitably trained and have the necessary skills to carry out their job safely. They should understand the risks associated with the gas cylinder and its contents. In particular:
 

• New employees should receive training and be supervised closely;
• Users should be able to carry out an external visual inspection of the gas cylinder, and any attachments (eg valves, flashback arresters, and regulators), to determine whether they are damaged. Visible indicators may include dents, bulges, evidence of fire damage (scorch marks) and severe grinding marks etc.
• Valves should only be removed by trained personnel using procedures that ensure that either the cylinder does not contain any pressure or that the valve is captured during the removal process.

 Handling and Use

• Use gas cylinders in a vertical position, unless specifically designed to be used otherwise.
• Securely restrain cylinders to prevent them falling over.
• Always double check that the cylinder/gas is the right one for the intended use.
• Before connecting a gas cylinder to equipment or pipework make sure that the regulator and pipework are suitable for the type of gas and pressure being used.
• When required, wear suitable safety shoes and other personal protective equipment when handling gas cylinders.
• Do not use gas cylinders for any other purpose than the transport and storage of gas.
• Do not drop, roll or drag gas cylinders.
• Close the cylinder valve and replace dust caps, where provided, when a gas cylinder is not in use.
• Where appropriate, fit cylinders with residual pressure valves (non-return valves) to reduce the risk of back flow of water or other materials into the cylinder during use that might corrode it (eg beer forced into an empty gas cylinder during cylinder change-over).
• Ensure that the valve is protected by a valve cap or collar or that the valve has been designed to withstand impact if the cylinder is dropped.

Lifting

• Use suitable cradles, slings, clamps or other effective means when lifting cylinders with a hoist or crane.
• Do not use valves, shrouds and caps for lifting cylinders unless they have been designed and manufactured for this purpose.
• Gas cylinders should not be raised or lowered on the forks of lift trucks unless adequate precautions are taken to prevent them from falling.

Transport

• Fit suitable protective valve caps and covers to cylinders, when necessary, before transporting. Caps and covers help prevent moisture and dirt from gathering in the valve of the cylinder, in addition to providing protection during transport.
• Securely stow gas cylinders to prevent them from moving or falling. This is normally in the vertical position, unless instructions for transport state otherwise.
• Disconnect regulators and hoses from cylinders whenever practicable.
• Do not let gas cylinders project beyond the sides or end of a vehicle (eg fork-lift trucks)
• Ensure gas cylinders are clearly marked to show their contents (including their UN Number) and the danger signs associated with their contents.
• It may be necessary to take special measures with certain types and quantities of compressed gases and fluids in order to ensure their safe carriage. If you have any doubts seek further guidance (see Further Advice on page 11).
• The transport of gas cylinders is subject to carriage requirements. For example, that:

i)        The vehicle is suitable for the purpose;
ii)       The vehicle is suitably marked to show that it is carrying dangerous goods;
iii)     The driver is suitably trained; and
iv)      The driver carries the appropriate documentation about the nature of the gases being carried.

Storage

• Gas cylinders should not be stored for excessive periods of time. Only purchase sufficient quantities of gas to cover short-term needs.
• Rotate stocks of gas cylinders to ensure first in is first used.
• Store gas cylinders in a dry, safe place on a flat surface in the open air. If this is not reasonably practicable, store in an adequately ventilated building or part of a building specifically reserved for this purpose.
• Gas cylinders containing flammable gas should not be stored in part of a building used for other purposes.
• Protect gas cylinders from external heat sources that may adversely affect their mechanical integrity.
• Gas cylinders should be stored away from sources of ignition and other flammable materials.
• Avoid storing gas cylinders so that they stand or lie in water.
• Ensure the valve is kept shut on empty cylinders to prevent contaminants getting in.
• Store gas cylinders securely when they are not in use. They should be properly restrained, unless designed to be freestanding.
• Gas cylinders must be clearly marked to show what they contain and the hazards associated with their contents.
• Store cylinders where they are not vulnerable to hazards caused by impact, eg from vehicles such as fork-lift trucks.

While the cylinder label is the primary means of identifying the properties of the gas in a cylinder, the colour coding of the cylinder body provides a further guide.

Cylinder shoulder - European standard colour coding

The colour applied to the shoulder, or curved part at the top of the cylinder, signifies the European standard colour coding.

The aim of the new standard (EN 1089-3), which has replaced the old cylinder colour scheme (BS349), is to help improve safety standards within the gases industry.

A number of gases have been assigned a specific colour and some of these are shown below:

 

 

For more detail you should refer to:

·     The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2004 (SI 568/2004 The Stationery Office 2004 ISBN 0 11 0490630).

·     The Pressure Equipment Regulations 1999 SI 1999/2001 The Stationery Office 1999 ISBN 0 11 082790 2

·     European Agreement concerning the international carriage of dangerous goods by road (ADR) and protocol of signature done at Geneva on 30 September 1957 (www.unece.org/trans/danger/publi/adr/)

·     Regulations concerning the International Carriage of Dangerous Goods by Rail (RID)

·     Guidelines on the appointment of conformity assessment bodies for transportable pressure vessels in Great Britain: The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2004 (copies available from HSE at 020 7717 6303 or from HSE’s web site at http://www.hse.gov.uk/cdg/pressure.htm.

 

Approved construction standards are posted on HSE’s web site http://www.hse.gov.uk/cdg/pressure.htm

Safe Handling of Liquid Nitrogen

Handling Liquid Nitrogen

 

Hazards

Liquid nitrogen has two main properties that are potentially hazardous:-

• It’s extremely cold. At atmospheric pressure, liquid nitrogen boils at -196°C.

• Small amounts of liquid vaporise into large amounts of gas. Roughly 700 times expansion.

Cold Burns

Extremely low temperatures can freeze flesh very rapidly. When spilled on a surface the liquid tends to cover it completely and intimately, cooling a large area. The gas issuing from the liquid is also extremely cold. Delicate tissue like eyes can be damaged by exposure to cold gas alone which would be too brief to affect skin.

Unprotected body parts contacting objects cooled by liquid nitrogen may stick fast. This may result in flesh injuries whilst attempting to withdraw from the object.

It is often stated that small splashes of Liquid Nitrogen will run off bare skin due to a vapour layer forming between the skin and the liquid. This must never be relied upon.

Asphyxiation

Liquid Nitrogen rapidly vaporises to gas.  The gas may has the potential to kill by asphyxiation. When the Oxygen concentration in air is sufficiently low, a person can become unconscious without any warning symptoms.

Over Pressure

Because Liquid Nitrogen boils rapidly users must ensure that it is never used in a closed system.  Tape exposed glass parts to minimise the hazard of flying glass shards. Therefore do not use thermos flasks, and it may be necessary to punch holes in cryovials.

Cryotube Explosions

Cryotubes used to contain samples stored under liquid nitrogen may explode without warning. Tube explosions are thought to be caused by liquid nitrogen entering the tube through minute cracks and then expanding rapidly as the tube thaws

When thawing Cryotubes take the following precautions :

• Wear a face shield, or at least safety goggles.

• Wear heavy gloves.
• Wear a lab coat and trousers or long skirt.
• Place the Cryotube in a heavy-walled container (e.g., a desiccator) or behind a safety shield while it is thawing.

Embrittlement.

Many ordinary materials cannot withstand cryogenic temperatures. Never dispose of cryogenic liquids down the drain. Materials exposed to cryogenic temperatures for long periods or which have undergone periodic warming and freezing should be examined for cracks and crazing.

Lifts

It is unlikely that a Dewar will spill its contents whilst in a lift thus putting the handler at risk of injury or death. It’s also unlikely a lift will breakdown whilst one is being transported. There is a small risk that should a person remain in a closed lift for a prolonged time the venting gases may reduce the Oxygen level sufficiently to cause harm. However to eliminate these risks the following practice should be followed when transporting Dewars.

• No one should accompany the Dewar.

• One person should send and another should receive the Dewar from the lift.

Precautions

Storage of Dewars
Dewars should not be stored in sealed rooms (e.g. walk in refrigerated rooms) because the reduced ventilation may be inadequate to mitigate against spillage and general evaporation.

Containers

Use only containers designed for low-temperature liquids.

Cryogenic containers (eg Dewars) are designed to withstand the rapid changes and extreme temperature differences encountered in working with Liquid Nitrogen. However, these special containers should be filled SLOWLY to minimise the internal stresses that occur when any material is cooled. Excessive internal stresses can damage the container.

• Do not cover or plug the entrance opening of any Liquid Nitrogen refrigerator or Dewar.

• Do not use any stopper or other device that would interfere with venting of gas.

Cryogenic liquid containers are generally designed to operate with little or no internal pressure. Inadequate venting can result in excessive gas pressure which could damage or burst the container. Check the unit periodically to be sure that venting is not restricted by accumulated ice or frost.

Protective Clothing

When using or decanting Liquid Nitrogen a face shield or safety goggles must be used.

Always wear appropriate cryogenic gloves when handling anything that is, or may have been, in immediate contact with Liquid Nitrogen. Use tongs to withdraw objects immersed in the liquid, and handle the object carefully. Do not put hands (even in the best gloves) into Liquid Nitrogen.

Inadequate protective clothing can absorb the Liquid Nitrogen and result in even more severe burns than would otherwise have resulted.

Training

Safety precautions must be followed to avoid potential injury or damage. Do not attempt to handle liquid nitrogen until you fully understand the potential hazards, their consequences, and the related safety precautions.

Decanting of Liquid Nitrogen

Never overfill Dewars. Spillage damages flooring and may cause injury. Insert pipes and funnels slowly to avoid splashing. Great care should be exercised to ensure that space is left to replace lids/tops on Dewars especially those that insert a considerable distance into the vessel. Spills and splashes can set off oxygen monitors

Maintenance of Dewars

Condensed moisture or frost on the outer shell of a refrigerator or Dewar and abnormally rapid evaporation of the liquid nitrogen are indications of vacuum loss. If vacuum loss is evident or suspected, transfer the materials stored in the unit to another refrigerator as soon as possible and remove the unit from service.

Use correct equipment

Use a phase separator or special filling funnel to prevent splashing and spilling when transferring Liquid Nitrogen into or from a Dewar or refrigerator. The top of the funnel should be partly covered to reduce splashing. Use only small, easily handled Dewars for pouring liquid. When liquid cylinders or other large storage containers are used for filling, follow the instructions supplied with those units and their accessories.

Never use hollow rods or tubes as dipsticks. When a warm tube is inserted into liquid nitrogen, liquid will spout from the bottom of the tube due to vaporisation and rapid expansion of liquid inside the tube. Wooden or solid metal dipsticks are recommended.

Transport

Keep Dewars upright at all times.

Rough handling can cause serious damage to Dewars and refrigerators. To protect the vacuum insulation system, handle containers carefully.

Do not place Liquid Nitrogen containers in closed vehicles where the nitrogen gas that is continuously vented can accumulate.

Disposal

Never dispose of cryogenic liquids down the drain. Allow waste Liquid Nitrogen to evaporate naturally in a fume hood or, preferably, pour the liquid slowly on gravel or bare earth, from which other people are excluded, where it can evaporate without causing damage.