Learning The Lessons Of The Titanic

In a recent news article1 about the evacuation zone around Sizewell nuclear power plant Jeremy Western, director of special projects and nuclear new build for EDF, said that the zone was so small because the likelihood of an accident was “exceedingly unlikely”.

This is rather like saying that an ocean liner does not need a full compliment of lifeboats because the chances of it sinking are “exceedingly unlikely”.

The accident at Fukushima has shown that the aim of emergency planning should be to be prepared for events that are not ”reasonably foreseeable”. What should be learnt from Fukushima is that we have ‘consideration of an extreme accident’ which could be caused by events that are beyond the design of the power plant. It is clear from Chernobyl and Fukushima that such events, even if they are “exceedingly unlikely” would require an evacuation zone of at least 20Km.

The nuclear industry constantly tell us that we should trust them and that they know what they are doing. How are we meant to do this if they have not learnt the lessons, not just from Fukushima but from the Titanic.


1 Sizewell: Accident evacuation zone ‘ridiculously small’, say campaigners, EADT, September 13, 2014 (http://www.eadt.co.uk/news/sizewell_accident_evacuation_zone_ridiculously_small_say_campaigners_1_3767935)

Black Holes – Classical Theory

This is just a short discussion about black holes which does not use any of Einsteins complicated field equations and relies (mainly) on school level physics with a few digressions on the way.

Escape Velocity

First of all I am going to discuss the ‘escape velocity’ – the speed that we would need to throw an object so as it escapes the Earth’s gravitational pull. To do so the kinetic of the object must be greater than the energy needed to go from the Earth’s surface to outer space (infinity).

Kinetic energy is given by

gr1

where m1 is the mass of the object and v is its velocity.

Newtons tells us that the force of gravity is given by

gr10

where G is Newtons gravitational constant and m1 and m2 are two masses separated by a distance r. The energy needed (again from Newton) is the force times distance. However, since the force on out mass changes with distance we cannot just multiply by the distance.

Inverse Square Laws – digression

Just a quick diversion into the reasons for inverse square laws. It is not that the ‘force gets weaker’ – it is just spread over a larger area as you move away from the Earth. The area it is spread over is the area of the sphere distance r from the Earth i.e 4πr2. This is explicit in the usual formula for the electrostatic force between two charges q1 and q2:

gr15

In Newtons gravitational equation the 4π is incorporated into Newston’s constant G.

Back to Escape Velocities

If we do a bit of calculus we find that the actual energy need to move a mass m1 from a distance r0 from mass m2 is given by1:

gr11

To escape the Earth’s gravitational pull this must equal the kinetic energy therefore:

gr5

cancelling the mass of our object – m1rearranging we can find the escape velocity:

gr6

We now can bring in some real numbers

Mass of Earth 5.97×1024 Kg
Gravitational Constant 6.67×10-11 N·(m/kg)2
Speed of light 2.999×108  m/s
Radius of Earth 6.371×106 m

putting these figures into the formula above gives the escape velocity for the Earth as 11,185 m/s (11.2Km/s).

The Sun’s Gravity – digression

This figure is much, much smaller than would actually be needed since the object would have to escape the gravitational pull of the Sun which is much larger. If it is so large then why do we not feel it on Earth? The reason is that we do and we are actually in free fall towards the Sun. However, since the Earth is also moving it continually misses – i.e. the Earth is in orbit.

Black Holes

Now if we keep the mass of the Earth the same but decrease its radius do we get to a point where the escape velocity is greater than the speed of light? That would mean that not even light could escape the gravitational pull – i.e. we would have a black hole.

If we go back a few steps and replace our escape velocity v by the speed of light c then we have:

gr7

We can now rearrange to find the radius r where this will happen

gr16

If we plug in some numbers again then we find that if the mass of the Earth was concentrated in a sphere of radius 0.0088m (8.8mm) then it would be so dense that light could not escape – i.e. it would be a black hole.

If we consider a body the mass of the Sun, 1.989 x 1030 Kg, then the radius is 2.95Km.

Although this simple classical analysis does not capture all the intricacies of black holes the radius calculated agrees well with those calculated by Swarzschild using Einsteins field equations.

If you want to play about with the numbers then my spreadsheet is here.


 1 If you don’t mind a bit of calculus then energy is given by

gr2

putting in Newtons gravitational force expression we get

gr3

evaluating this integral gives

gr11

While we are here we can also work out the kinetic energy. If we consider motion in the x direction and using F = ma then the energy becomes

gr12

we can now change the integration variable since we know that

gr13

this gives

gr14

Notice that we have an integration constant. We now know from Einstein that this is mc2. What most people know about Einsteins special theory of relativity (E=mc2) is in fact not relativitistic – it has always been hidden there, however Einstein also gives more terms in the expression of kinetic energy alongside E = mc2 + 1/2mv2

MP Response to Gaza Question

Dear Mr Lux,

Thank you for your email of 5th August about the Israeli-Palestinian conflict. I am grateful to you for expressing your concerns on this matter, which highlight two very important issues.

It is tragic that so many innocent civilians, including women and children, have been killed and injured. The Government has made clear to all parties at every opportunity that the current situation is in no one’s interest, and is harmful to prospects for the Middle East Peace Process. We now have a 72 hour ceasefire. The Government’s objective is to make that permanent so the killing stops.

The UK maintains a rigorous and transparent arms export control system; all applications are assessed on a case by case basis, against the Consolidated EU and National Arms Export Licensing Criteria. The Criteria make clear our commitment to assess the risk of exports being used for internal repression or to provoke or prolong armed conflicts or aggravate existing tensions or conflict in the country of final destination. The Government applies these criteria rigorously, including with respect to Israel, and does not allow any arms exports which are assessed to be contrary to those criteria.

In view of the situation in Gaza, we are keeping all licence applications under review to ensure that all our decisions remain consistent with our human rights commitments and all applicable criteria. If a decision is taken to suspend or revoke licences we will announce this to Parliament, and where possible we will do this in concert with our EU partners.

Extensive restrictions have been made on imports and exports into Gaza, including transfers between the West Bank and Gaza, which have had a major detrimental effect on Gaza’s economy and make investment in Gaza particularly difficult.

Overall, it is again important to re-iterate that a negotiated two-state solution remains the only way to resolve the conflict once and for all and to achieve a sustainable peace so that Israeli and Palestinian families can live without fear of violence. No other option exists which guarantees peace and security for both peoples, and I can assure you the UK will work with all parties to make progress towards this goal.

I hope that this response is helpful in addressing your concerns and thank you for contacting me.

Yours sincerely,

Peter Aldous
Member of Parliament for Waveney

‘Burning’ Nuclear Waste in Nuclear Reactors

I was recently asked for my opinion on the DUPIC (Direct Use of spent PWR fuel In CANDU) reactor. Although I do not have any comments about this reactor compared to other reactors which ‘burn nuclear waste’ I thought I would say a few words about the concept in general. Before we go onto that I just want to make few general points.

Spent Fuel

First of all it is important to get past the nuclear industries misleading wording on what is actually happening. They often say that ‘nuclear is the only power source which can actually burn its own waste’. What is actually happening is that modern fission power plants are very inefficient utilising between 4% and 6% of the energy available1. So most of the energy that is available in the fuel is usually thrown away in the ‘spent fuel’. Originally it was envisenged that the current type of nuclear power stations would be replaced by better designs which would utilise much more of the energy. However, despite many attempts this has not happened. There are several reasons for this including the more difficult technology, the fact that nuclear power did not take off as expected and there was not the expected shortage of natural uranium and that other technologies are more expensive.

Transuranic Elements and Fission Products

There are two types of radioactive elements present in spent nuclear fuel – fission products and transuranic elements produced by neutron capture (see Composition of Spent Fuel). Fission products tend to be much shorter lived than the transuranic elements. For example two of the major fission products Cs-137 and Sr-90 have half-lives of 30 and 28 years respectively. However, there are several fission products which have much longer half-lives, in particular Tc-99 (211,000 years).

On the whole transuranic elements have longer half-lives than fission products. For example Plutonium-239 has a half life of 24,000 years and Neptunium-237 has a half life of 2 million years. Unlike fission products the transuranic elements are fissionable and/or fertile i.e. they can either undergo fission or can undergo neutron capture and be transformed into something that can undergo fission.

‘Burning’ Nuclear Waste

Since the transuranic elements can still be used to produce power and their long half-lives creates more problems for long term disposal it is theoretically possible to ‘burn’ them to dispose of them and possibly create more power from the spent fuel. Several technologies have been proposed for this including fast reactors, PRISM and DUPIC.

When the transuranics are ‘burnt’ in the reactor they end up as fission products which tend to be much more radioactive but have shorter half-lives than the transuranics. This is a good thing since we do not know what to do with long lifetime waste (tens of thousands of years). However, it is not so good because you end up with much more radioactivity and we do not know what to do with the highly radioactive medium lifetime waste (hundreds of years). Even if all the transuranics were to be removed there are also several long lived fission products which would make the waste dangerous for tens of thousands of years. Even ‘natural uranium’ is not safe (see Is Natural Background Radiation is Safe?).

‘Burning’ Money

Any technology that reuses spent fuel will take a lot of money and time to develop. It decreases but does not eliminate the problem of disposing of long lived waste but also drastically increases the amount of highly radioactive medium lived waste (hundreds of years).

Nuclear power is already finding it difficult to compete with renewables. It is time to admit that enormous resources put into the development of nuclear fission (see UK R&D Expenditure on Energy)has been a waste of money and we should stop throwing good money after bad.


1 This is reasonably easy to estimage. If you assume that the fissioned atom splits 40%/60% it is easy to work our a rough idea of the mass change from looking at the atomic masses of the fission products, then you can calculate the expected energy using E = mc2. This gives a figure of about 1000GWd/TU. This figure is slightly too high since it ignores radiation losses including neutrinos. Alternatively you could just use the figure of 193.7MeV per fission and use this to calculate the maximum burnup which gives you 907GWd/TU.

Current burnup is about 40GWd/TU but it is hoped to get this to 60GWd/TU for new reactors.

Arming All Sides

arming_both_sides

Why do metals have low specific heat capacities? – they don’t

I came across the following answer to the question “Why do metals have low specific heat capacities?”:

Metal atoms in pure metal are very close together and are able to transfer heat easily via conduction from one atom exciting the other atoms next to it. So the amount of energy it takes to heat a metal is relatively small to that of water for example.

Non-metals have crystal structures generally farther apart and thus don’t transfer energy as efficiently.1

Most of the other answers are in similar vein as are the answers to the same question in WikiAnswers2.

The only problem is that the answers are totally wrong. My experience of such websites is that there is no point posting the correct answer since people prefer the simpler wrong answer.

The fact is that the specific heat capacities of metals differ little from non-metals of similar atomic mass. The relationship between specific heat capacities and atomic mass is given by the Dulong Petit Law3.

What Is Specific Heat

It is the amount of energy needed to heat up a certain amount of a substance (usually a gram) by one degree. Its units are J/(g K).

For an atom in a simple crystal lattice the energy goes into making the atom vibrate more. The more atoms there are in a given mass of substance the more energy it can absorb before raising the temperature by one degree. If we look at the heat capacity for the same number of atoms – the molar heat capacity (J/(mol K) then it is roughly constant (the Dulong Petit law):

Aluminium 24.20 J/(mol K)
Phosphorous 21.19 J/(mol K)
Sulphur 23.23 J/(mol K)
Iron 25.10 J/(mol K)
Arsenic 24.64 J/(mol K)

The heavier elements contain fewer atoms to absorb the energy per gram of material and therefore tend to have lower specific heat capacities.

Another factor is that a thin metal tray coming out of the oven is going to cool quicker than a thicker, heavier glass dish. While you can pick a metal tray up a few minutes of it coming out of the oven I suggest you do not try to do the same thing with a heavy metal frying pan.

So do not believe everything you read on the internet – particularly where people who do not know the answer to a question vote on what the best answer is.  Wikipedia tends to be much better since the contributions are discussed and edited although can still contain glaring errors.


1  Why do metals have low specific heat capacities, Yahoo Answers (https://uk.answers.yahoo.com/question/index?qid=20080917234005AA2jj94)

2 Do metals have low specific heats, WikiAnswers, (http://wiki.answers.com/Q/Do_metals_have_a_low_specific_heat)

3 Dulong-Petit Law, Wikipedia (http://en.wikipedia.org/wiki/Dulong%E2%80%93Petit_law)

Nuclear Strike Price and the ‘Open and Transparent’ Energy Market

I previously posted the response from Michael Fallon (Minister of State for Business & Energy) to a number of questions I asked my MP (Peter Aldous). The question was about how the strike price for nuclear (£92.5/MWh) was justified given DECC’s own analysis of future electricity prices (shown graphically here).

The response said that the DECC analysis I quoted was only a small part of the analysis carried out by DECC but the other analysis was not being released since it ‘could prejudice the ongoing negotiations’.

I have now written back to my MP asking him

If DECC are carrying out analysis about the costs and conditions necessary for future energy production then surely such information should be in the public domain. If not the a single company (i.e. EDF) has an unfair competitive advantage. For a proper competitive energy market to work correctly such price and contract indicators, given in the DECC analysis which is being withheld, must be available to all companies. I understand that it is in the interest of EDF to withhold such information since other nuclear (or non-nuclear) energy companies may undercut them. However, this would be of great advantage to the British electricity consumer.

I would like you to tell me how such restrictive practices are
compatible with a ‘transparent and open’ electricity market that you
government propose.

I have just had a ‘response’ from my MP. it seems to be the standard pro-nuclear letter:

Dear Mr Lux,

Thank you for contacting me about nuclear power.

As you know, the Government has reached a commercial agreement with energy company EDF on the key terms that pave the way for the first new nuclear power plant to be built in the UK for a generation. I support the Government’s efforts to secure the necessary private sector investment. The UK needs a lot of new power stations to deal with years of neglect and a legacy of underinvestment. This is the first time a nuclear power station in the UK will have been built without money from the British taxpayer.

It will provide a clean source of home-grown energy, powering nearly 6 million homes and help the country keep the lights on. It will also cut carbon emissions and reduce energy bills for households by £75 a year by 2030. To build enough onshore generation to match what the Hinkley Point C power station would generate, it would take around 6,000 onshore wind turbines. I strongly welcome this £16 billion worth of investment which will create 25,000 jobs, bring in billions in corporation tax and could see £100 million injected into the local economy every year during peak construction. A strategy published last year in partnership with industry establishes a long term approach for the sector to stimulate economic growth and create jobs in this country. I understand that the Government will ensure that the operator of Hinkley Point C will be responsible for the full costs of decommissioning and its share of the costs of waste management.

With regard to strike prices, I can say little beyond the Minister’s response. The deal is competitive with other large scale clean energy and with gas at a strike price of £89.50 for this first nuclear project compared with a £150 strike price for offshore wind. It is cheaper than onshore wind and will pave the way for a substantial fall in the cost of future nuclear plants as it is a clear signal to investors of Britain’s commitment to nuclear energy.

Whilst I appreciate that this is not the response you were hoping for, I am grateful to you for expressing your concerns on such an important issue.

Yours sincerely,

Peter Aldous

Member of Parliament for Waveney

I have now written back saying that it is not a response to my question.

Graphite Weight Loss at AGR Reactors

There have been several reports in the news1 about EDF wanting to raise the limits of the amount of graphite which can be lost from the moderator of the AGR nuclear reactors. As usual the reports seem to me to not give some very important information. Here are just a few points I think it is important to know.

  • The graphite blocks act as a moderator to slows down the neutrons which makes it more likely that they will cause nuclear fission.
  • In the AGR reactor they not only act as a moderator but are also vital structural components. The graphite blocks have channels in them for the fuel rods, control rods, emergency shut down systems as well as allowing the CO2 cooling gas to pass effectively over the fuel.
  • The figure of 8% is just one of the limits which EDF wants lifted. This figure is for the core as a whole. Some areas can have over 40% weight loss.
  • That the graphite blocks are also cracking as well as loosing weight.
  • Short of decommissioning the reactors it is very difficult to accurately determine the weight loss and cracking in the bricks.
  • This level of weight loss was not expected when the reactor was originally designed and the weight loss and cracking is still not adequately understood.

None of these points should be new to EDF or the ONR. However, what has been expressed in the media has been incomplete and sometimes more than just ‘economic with the truth’.

For example EDF has claimed2:

“[W]e’re still miles away from the boundary between safe and not, we’re not operating on that boundary and have extremely conservative limits,”

However, this is very different from the reports of meeting between EDF and the ONR3 (emphasis added):

However the interventions earlier in 2013 gave ONR cause for concern about the methodology being used to calculate weight loss itself. This concern applied both to the processes being used and the apparently small margins that existed between weight loss and the limits.

The problem of loss of graphite and cracking has been studied for a very long time since it was also a problem with the older Magnox reactors. Recently there has been several research projects to provide data to convince ONR that the new limits are safe.

First of all let us have a look at some of the possible safety problems since it gives an idea of why this area is problematic.

Block Cracking and Expansion

The brick as noted above are structural components. If they are weakened by too much weight loss they may be unable to support the bricks above. When they crack they also change dimensions which may impeded control rods or emergency shutdown procedures.

An accident may cause a sudden shock which may suddenly change the block alignments. Such problems have been discussed in an excellent report by Large Associates4 in 2006.

Under Moderation

Since the graphite’s main purpose is to slow down (called moderate) the neutrons then if there is less graphite then the reactor is under-moderated as compared with the original design. This can be compensated for in several ways such as increasing the enrichment of the fuel or moving the control rods out further.

One of the possible accident scenarios considered in the original design was water ingress into the reactor. Since water is a good moderator then this could cause a very sudden increase the power output (explosion). This effect with be much larger if the reactor is under-moderated.

Change in Neutron Density and Energy Distribution

Since the reactor is not as good at moderating neutrons then there will be changes to the energy distribution of the neutrons as well as their density since the loss of graphite is not homogeneous. The changes in the neutron distribution can change the way in which various components of the reactor age – including the moderator.

This brings us to some of the problems of measuring and determining the affects of the graphite weight loss.

It is possible to stake samples of the graphite blocks and determine the extent of cracking and weight loss from this. However, to determine the amounts of weight loss complicated statistical analysis had to be used5:

“We had all of this data, we actually had to bring in some real experts in statistics to help us rationalize the data to make it useful”, Stephen Grant, Fraser-Nash power and energy director

I will not go into some of the problems of using statistical analysis when the underlying mechanisms are not fully understood. However, the fact that the amount of weight loss and cracking cannot be directly observed is worrying.

One of the problems is that these affects are not independent. For example if a crack or weight loss occurs this can affect the local temperature and coolant flow which may increase or decrease the amount of weight loss and cracking5.

“Graphite is non-linear. You can’t say, ‘this is what happened in the last six months, this is what will happen in the next six months.’ “, Stephen Grant, Fraser-Nash power and energy director


 

1 Dungeness B nuclear plant operator wants safety limit raised, BBC, 4 June 2014 (http://www.bbc.co.uk/news/uk-27691207)

2 No concern over possible change to Dungeness nuclear safety rules, says regulator, Utility Week, 4 June 2014 (http://www.utilityweek.co.uk/news/no-concern-over-possible-change-to-dungeness-nuclear-safety-rules-says-regulator/1015832#.U5ArVnLtB0w)

3 Level 4 Meeting on NP/SC 7623 43% Graphite Weight Loss Safety Case (Hinkley Point B, Hunsterston B, Heysham 1 and Hartlepool Power Stations)Office for Nuclear Regulation (ONR), September 2013 (http://www.onr.org.uk/intervention-reports/2013/non-site-specific-13-022.htm)

4 Brief Review Of The Documents Relating To The Graphite Moderator Cores At Hinkley Point B And Other Advanced Gas -Cooled Reactor (Report Ref No R3154 – Graphite), Large Associates, 28n June 2006 (http://www.largeassociates.com/LA%20reports%20&%20papers/3154%20Graphite/R3154-Graphite%20FINAL%2028%2006%2006.pdf)

5 For the longest time, Nuclear Engineering International, 14 June 2013 (http://www.neimagazine.com/features/featurefor-the-longest-time/)

The Equality Trust Wealth Tracker 2014

rich

http://www.equalitytrust.org.uk/sites/default/files/TET%20Wealth%20Report%202014.pdf

Future Energy Costs and the Nuclear Strike Price

As I have posted previously I have been trying to find out from DECC how they justified the £92.5/MWh strike price for Hinkley C. Here is the latest response from Michael Fallon.

According to Michael Fallon the negotiations for Hinkley C have not concluded. So we still have to wait to see an explanation for the strike price. If you are interested then I have also posted the many letters to and from my MP ( Peter Aldous) and Michael Fallon.

scan