Post # 32: Understanding and Comparing Boiling Water Reactors (BWRs)

The situation at Fukushima Dai-Ichi continues to evolve and world attention is focused on the unfolding events.  There web is rampant with misinformation and often confusing information.

In the midst of this unfolding tragedy, I think it's important to pause and clarify the most basic facts about the plants themselves and their potential relevance to our plants in the United States.

First, it's important to understand how rare it is for any two nuclear plants at different sites to be identical – particularly for the vintage of plants we're concerned with here.  So even when reactors have the same "make and model number" (to use automobile language for a moment), they are usually not identical units.

Boiling Water Reactor (BWR) Nuclear Plant Nomenclature

First, some nomenclature that is very important.  BWR nuclear plants have a "make and model".  In terms of organizational roles or "makes", every nuclear plant has a designer, a manufacturer, a constructor, and a licensee, and an operator.  Sometimes the same organization plays multiple roles.  Due to the complexity of modern power plants, there are actually hundreds, if not thousands, of equipment suppliers involved in making these plants a reality.

With regard to the physical configuration of the plants, BWRs are characterized by the reactor "type", and the primary containment "type".  Based on historical General Electric nomenclature, there have been six "vintages" of commercial BWRs (not including the ABWR and ESBWR).  These are referred to as BWR-1, BWR-2, BWR-3, BWR-4, BWR-5, and BWR-6 reactors.  Then, there's the primary containment.  These are referred to as Mk-I ("Mark-One"), Mk-II ("Mark-Two"), and Mk-III ("Mark-Three") designs.

Now let's look at how all of this is relevant to today's events.

Fukushima Dai-Ichi Plant

As indicated on Wikipedia ( http://en.wikipedia.org/wiki/Fukushima_I_Nuclear_Power_Plant ) Fukushima Dai-Ichi consists of six boiling water reactor or "BWRs".  Unit 1 is a BWR-3 / Mk-I system.   Units 2, 3, 4, and 5 are BWR-4 / Mk-I systems, and Unit 6 is a BWR-5 / MK-II system.  Thus there are actually three different operational plant configurations at the Fukushima Dai-ichi site.  In addition, two Advanced Boiling Water Reactors are under construction at the site.

US BWRs

There are 35 operating BWRs in the U.S.  As seen below (based on a sort of plant information taken from the U.S. NRC web site Appendix A @ http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1350/ ).  These thirty five plants can be divided into 6 generic categories based upon their reactor / primary containment combinations.

As can be seen from the table, there are six US plants (yellow) with the same generic configuration as Fukushima Dai-Ichi 1, fifteen plants with the same generic configuration as Fukushima Dai-Ichi Units 2-5 (light blue), and 4 US plants with the same generic configuration as Fukushima Dai-Ichi Unit 6 (green).

Generic Plant Type Is Important But Plant Specific Differences Matter


I've noted there are a plethora of significant design details that differ even between plants of the same generic type.  To illustrate, this, I've noted in the table below some significant design differences between four US BWRs of the same generic type (BWR-4 / MK-I) as Fukushima Units 2-5 (excerpted from Table 1.7-4 of the Browns Ferry FSAR):

A quick look at the last three rows of the table will aptly illustrate my point about plant specific differences.

The Bottom Line

As we discuss the events on-going in Japan, we should not jump to conclusions about applicability of events there to plants here in the US.  Similarities with regard to generic plant types are important and very relevant, but these similarities can be overwhelmed by differences in accident initiators, siting, plant design details, plant operating procedures, and a host of other factors.  The DETAILS MATTER.

Post # 31: BWR Station Blackout Severe Accidents - Primer Documents

My heart goes out to the Japanese people who are dealing with an overwhelming natural disaster that has resulted in the death of thousands and the destruction of untold billions of dollars in property and infrastructure.   Like almost everyone else, I've been watching the unfolding events at Japan's Fukushima Dai-ichi plant with a mixture of horror and admiration for the heroic efforts of the plant staff to contain and terminate the accident progression in Units 1-4.

Many of you know I've spent my career at Oak Ridge National Laboratory.  I've been at ORNL since 1978.  From 1980 through the late 1990s, ORNL had a pioneering program in the investigation of severe accidents in boiling water reactors or "BWRs". This work was primarily funded by the U.S. Nuclear Regulatory Commission.   During the almost twenty years of research at ORNL, the Lab produced a large number of reports, journal articles, and professional society presentations on the accident progression and phenomenology of beyond-design-basis severe or "core melt" accidents in BWRs.  During that period, we utilized several U.S. BWR plants as our reference plants for analysis.  These include the Browns Ferry and Peach Bottom (BWR-4/Mk-I) plants, Limerick (BWR-4/Mk-II), and Grand Gulf (BWR-6/Mk-III) plants.

In light of the on-going events at Fukushima, and with an eye toward the inevitable re-examination of such accidents this event will catalyze, I thought I would post here an extremely abbreviated bibliography of ORNL publications relevant to Fukushima's station blackout severe accident and related reactor building hydrogen deflagration/detonation phenomena.

Some critical words of caution regarding applicability of the analyses referenced below to Fukushima:

1. The Fukushima Dai-ichi units were NOT analyzed.  My understanding is that Fukushima Dai-ichi #1 is a BWR-3 / Mark I containment system.  (The alternative nomenclature "MK-I" is often used).  Units 2,3, and 4 are BWR-4 / Mark I plants.  As previously mentioned, the reference plants used in the analyses below were U.S. BWR-4/MK-I plants.

2. The "station blackout" accidents analyzed in these reports began with the assumption that: (1) all off-site AC power was lost, (2) the diesel generators were unavailable to provide backup AC power, and (3) the station batteries were available to provide DC power until the batteries were exhausted.  According to all available accounts, these three head-end events appear to have occurred at Fukushima. HOWEVER, the HUGH difference in the scenarios analyzed below and last week's event is that the historical analyses did not include an earth quake and tsunami as the "top events".  Thus any damage from these two natural events that may have occurred at Fukushima is not accounted for in the analyses reference below.

3. Some of the sequences referenced below assume specific plant operator responses that may or may not be applicable to the Fukushima events.

So, similar reactors and containments, and similar top events BUT caveat, caveat, caveat...

NRC NUREG REPORTS:

• NUREG/CR-2182, Vol 1, Station Blackout at Browns Ferry Unit One – Accident Sequence Analysis, D. H. Cook, S. R. Greene, R. M. Harrington, S. A. Hodge, D. D. Yue,  November 1981

• NUREG/CR-2182, Vol 2, Station Blackout at Browns Ferry Unit One – Iodine and Noble Gas Distribution and Release, R. P. Wichner et al.,  August 1982

• NUREG/CR-2973, Loss of DHR Sequences at Browns Ferry Unit One – Accident Sequence Analysis, D. H Cook, S. R. Greene, R. M. Harrington, and S. A. Hodge, May 1983

• NUREG/CR-2940,  Realistic Simulation of Severe Accidents in BWRs – Computer Modeling Requirements, S. R. Greene, April 1984

• NUREG/CR-3617, Noble Gas, Iodine, and Cesium Transport in a Postulated Loss of Decay Heat Removal Accident at Browns Ferry, R. P. Wichner, et al., August 1984

• NUREG/CR-5317, Primary Containment Rsponse Calculations for Unmitigated Short-term Station Backout at Peach Bottom, S. A. Hodge, C. R. Hyman, L. J. Ott, 

• NUREG/CR-5565, The Response of BWR Mark II Containment to Station Blackout Severe Accident Sequences,  S. R. Greene, S. A. Hodge, C. R. Hyman, M. L. Tobias,  May 1991

CONFERENCE PAPERS

• CONF-8310143-11, BWR Severe Accident Sequence Analyses at ORNL – Some Lessons Learned, S. A. Hodge, 11th Water Reactor Safety Information Meeting,  Oct. 25, 1983

• CONF-8410142--85, Fission Product Transport Analysis In A Loss Of Decay Heat Removal Accident At Browns Ferry, R. P. Wichner et al., 12th Water Reactor Safety Information Meeting, Oct 23, 1984

• CONF-871011--6, The Impact of BWR MK-I Primary Containment Failure Dynamics on Secondary Containment Integrity,  S. R. Greene, 15th Water Reactor Safety Information Meeting,  Oct 29, 1987

• CONF-890546--1, Thermalhydraulic Processes In The Reactor Coolant System of A BWR Under Severe Accident Conditions, S. A. Hodge, Jan 1 1989 

• CONF-9104223--1, Identification and Initial Assessment of Candidate Late-Phase In-Vessel Accident Mitigation Strategies, S. A. Hodge, April 1991

JOURNAL ARTICLES

• Nuclear Engineering and Design, Vol 120, Issue 1, 1 June 1990, Pages 75-86, The Role of BWR Secondary Containments In Severe Accident Mitigation: Issues and Insights From Recent Analyses, S. R. Greene

•  Nuclear Engineering and Design, Vol 148, Issue 2-3, Pages 185-203, July 1994, Assessment of Two BWR Accident Management Strategies, S. A. Hodge

Some nice accident analysis work was also done at other National Labs during the period.  One particularly-relevant analysis out of Brookhaven National Laboratory:

• NUREG/CR-5850,  Analysis of Long-Term Station Blackout Without Automatic Depressurization at Peach Bottom Using MELCOR (Version 1.8), I. K. Madni, May 1994

The major  universities also produced some relevant analysis work.  Here's one from the University of Tennessee,

• Matthew Wesley Francis, Long-Term Station Blackout Sequence and Mitigation MELCOR Model, A Thesis Presented for the Master of Science Degree, May 2006

Finally, I would also recommend as a general primer on light water reactor severe accident phenomena

• NEA/CSNI/R(91)12, "Invessel Core Degradation In LWR Severe Accidents: A State Of The Art Report To CSNI," OECD/NEA, November 1991, which can be found at  http://www.oecd-nea.org/nsd/docs/1991/csni-r91-12.pdf

Over the next several days, I will expand this list and attempt to add URL pointers to the document.  In the mean time, I believe all or almost all of these documents are available through the DOE OSTI Information Bridge @ http://www.osti.gov/bridge , or at online journal archive sites such as ScienceDirect @ http://www.sciencedirect.com/.  A diligent google search should turn them up.

Sherrell

Post # 30: Oil, the Strategic Petroleum Reserve, and Heads In The Sand

I was listening to radio as I drove home from work this evening.  First was a dialog from Washington regarding the urgent need to open the Strategic Petroleum Reserve (SPR).  The SPR holds 727 million barrels of oil.  (This is only ~ 75 days worth of our average daily petroleum import of 9.7 million barrels.)  The hope among those who are advocates for opening the SPR is that doing so would relieve the upward price pressure on gasoline at the pump.  It's a sad situation when a 30-cent spike in the price of gasoline at the pump sends us into such a panic.

The next discussion I heard had to do with enforcing a "no fly" zone over Libya.  While there a plethora of humanitarian and political reasons for taking such steps, the bottom line is that one of the major factors behind the thinking of many who advocate this step is their hope that stabilization of the Libyan crisis will also stabilize oil prices.  We have and we will again fight wars over oil.

What a price we pay and our children will pay for our "addiction to oil" (to use President Bush's language).

We need a sustainable energy policy... NOW.

Just thinking...

Post # 29: What is "Sustainable Energy" ?

One of the most significant insights of my life I gained from studying a second language in high school.  The process of learning a second langauge made me aware that one's native tongue frames one's entire thought process and to some extent, one's world view.  The constraints of one's native tongue also constrain one's thoughts.  Words have meaning.  Words can communicate, inform, inspire, enlighten.  Words can hurt, distort, harm.  Words can bring us closer together, or words can separate us.

We hear the word "sustainable" and "sustainability" a lot these days.  Got me to thinking...What, really, is the definition of "sustainable energy"?

One definition I've encountered frequently is quoted in the Wikipedia article on sustainable energy @ http://en.wikipedia.org/wiki/sustainable_energy .  It reads,

"Sustainable energy is the provision of energy that meets the needs of the present without compromising the ability of future generations to meet their needs."

This definition, which is as useful as any I've encountered, is fascinating if one pauses to really think about it.  It's all about balance.  The key words are   "provision", "energy", "needs", "present", "without compromising", and "future".

• energy... In all its forms.

• needs of the present...  Not wants. 

• without compromising...  That is, without constraining.

• future generations...  As in forever?

• their needs ... What will they be?

This definition is deceptively complex.  It witnesses to a plethora of inter-relationships and trade-offs that determine our quality of life and that of the small blue planet we inhabit.  It raises a number of tough questions such as:

• What am I to assume in my decision making regarding the forward march of science and technology though time?
• How do we distinguish between "needs" and "wants", and who makes the decision?
• What is the role of government verses the individual in this grand play?
• How are present perceived "inequities" in access to energy between nations and peoples addressed?
• And for the social Darwinists out there, what about "survival of the fittest" ?  

In an event, there's much to ponder in this simple word, "sustainable".  There is an interesting discussion of the various definitions of "sustainability" on the website of the Citizens Network For Sustainable Development at:  http://qwww.citnet.org/What+Sustainability.  I recommend you take a few minutes to read and reflect on the many definitions of sustainability archived there.

Just thinking...

Post # 28: Environmental Stewardship and Sustainable Energy

The spring flowers are just beginning to peep through the brown over-burden of Winter-killed vegetation here in East Tennessee.  Spring is a wonderful time of year to be out and about in the mountains and river valleys of this beautiful region of the country.  Seeing the awakenings of Spring always starts me to thinking about our responsibilities as stewards of God's Creation.  And being a good steward of the environment, while addressing the every-growing energy needs of a world seeking the quality of life enjoyed by those of us in the West is an ever-growing challenge.  That's one reason I'm such a strong supporter of nuclear power.

Nuclear power generates ~ 17% of the world's electrical energy while generating lower carbon dioxide emissions per MW-hr of energy than any other energy form except hydro power (and there are some estimates that indicate it's actually lower than everything except run-or-the-river or "kinetic" hydro power.)  If one is concerned about the amount of carbon emitted by energy production, one has to look positively on nuclear power.

Nuclear power is a frugal user of land - generating the highest energy production per acre of land used (or conversely using the least land per unit of energy produced) of any energy production resource - even when uranium mining is considered.  I recently ran across a fascinating paper from on this subject entitled   "Energy Sprawl or Energy Efficiency: Climate Policy Impacts on Natural Habitat for the United States of America," by Robert I. McDonald, Joseph Fargione, Joe Kiesecker,William M. Miller, Jimmie Powell.  It can be found at 


http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006802

Here's a quote from the paper relating to land-use intensity of energy production:

The land-use intensity of different energy production techniques (i.e., the inverse of power density [16],[17]), as measured in km² of impacted land in 2030 per terawatt-hour per year, varies over three orders of magnitude (Fig. 3). Nuclear power (1.9–2.8 km²/TW hr/yr), coal (2.5–17.0 km²/TW hr/yr) and geothermal (1.0–13.9 km²/TW hr/yr) are the most compact by this metric. Conversely, biofuels (e.g., for corn ethanol 320–375 km²/TW hr/yr) and biomass burning of energy crops for electricity (433–654 km²/TW hr/yr) take the most space per unit power. Most renewable energy production techniques, like wind and solar power, have intermediate values of this metric.


So there you have it.  If one is concerned about land "consumed" in the production of electrical energy (along with associated issues such as human and biological population displacement and habitat destruction), one has to look positively on nuclear power.


An then there is water usage.  Water usage is a challenge for all large central generation power plants.  Presently, there are two dominant approaches to cooling both fossil and nuclear power plants.  The "once-through" cooling approach "borrows" water from the river or reservoir that serves as the cooling water source.  This water is heated as it cools the plant.  About 99% of the water is returned back to the river.  Federal and state regulations set limits on the allowable warming of the river or lake from which the water is drawn.  The second major approach to cooling power plants utilizes "wet cooling tower".  This approach consumes twice as much water as the once through cooling approach, and a larger volume of this water is actually "consumed" in the process (i.e. the net water lost from the river or reservoir is greater.)


According to the Nuclear Energy Institute, "Nuclear energy consumes 400 gallons/MWh with once-through cooling and 720 gallons/MWh with wet cooling towers.  Coal consumes less, ranging from about 300 gallons/MWh for plants with minimal pollution controls and once-thorough cooling to 714 gallons/MWh for plants with advanced pollution control systems and wet cooling towers.  Natural gas-fueld plants consume even less, at 100 gallons/MWh for once-through, 370 gallons/MWh for combined cycle plants with cooling towers, and non for dry cooling."  To put this in perspective, "a typical nulcear power plant supplies 740,000 homes with all of the electricity they use while consuming 13 gallons of water per day per household in a once-through cooling system, and 23 gallons per day per household in a wet cooling tower system.  By comparison, the average U.S. household of three people consumes about 94 gallons of water per day."   (Nuclear Energy Institute @ 

http://www.nei.org/resourcesandstats/documentlibrary/protectingtheenvironment/factsheet/water-use-and-nuclear-power-plants/?page=1 )

So,  water usage issue is actually one of the most complicated and challenging issues in energy production - especially for large nuclear and fossil-powered plants.  The reason for this complication is the numerous ways in which water is used at different points in the energy production supply chain for different energy production technologies (fossil, nuclear, solar, geothermal, etc.)  We can and we should do better.  New technology and new approaches to water management show promise for improving this picture.  This "energy – water nexus" will be subject of a future post.


Just thinking ...


Sherrell

Post # 27: Rare Earths, E-Waste, China, and Sustainability

China announced this past December it will curtail its 2011 export quota for rare earths by 35%.

See for example, http://www.reuters.com/article/2010/12/29/us-china-rareearth-idUSTRE6BR0KX20101229

What are "rare earths", and why should the Sustainability Community care?

Rare earths are a group of seventeen elements that are essential in the production of a wide variety of electrical components and clean energy technologies.  They are found in Group 3 of the periodic table, and have names like gallium, europium, samarium, and thorium.  These rare earths are used in the manufacture of iPods, flat-screen TV's and computer monitors, high performance magnets, wind turbines, and a wide range of other consumer and industrial electronics.

China currently supplies 97% of the worlds annual rare earth demand.  The U.S. doesn't have a single active rare earth mine in production though we do have significant deposits that could be mined.  China's actions have some of the U.S.'s top strategic planners so worried, the U.S. has threatened action with the World Trade Organization to force China to loosen it's grip on this strategic material.

What's all this have to do with electronic waste or "e-waste"?

According to the U.S. Environmental Protection Agency, ( http://www.epa.gov/osw/conserve/materials/ecycling/docs/fact7-08.pdf ), the U.S. discarded 1.5 – 1.8 million TONS of electronic waste in our landfills in 2005.  During that same year, we recycled less than 380,000 tons of surplus electronics.  The problem: as these discarded materials breakdown in the landfill, they release their stores of lead, mercury and other hazardous ingredients into the environment,

A typical personal computer contains economically recoverable quantities of gold, silver, copper, and palladium, and there are a number of firms that specialize in recovering these materials.  But what about the rare earths?  These electronics also contain significant quantities of rare earths – although at considerably lower concentrations that the aforementioned precious metals.  Well, it appears economically-competitive methods for recovering rare earths from e-waste are just becoming available.  According to press reports, Dowa, a Japanese mining company, recently began recovering rare earths from e-waste.  Research continues on many fronts, and major improvements are needed if these rare earth recovery technologies are to be widely deployed.  See for example:

 http://www.greentechmedia.com/articles/read/guest-post-achieving-rare-earth-indepdence/ .

So here we see another strategic sustainability issue buried in today's headlines.  Rare earths are essential strategic materials for our national and energy security.  China has the world market cornered.  The U.S. (and the rest of the world) is annually discarding a mother-load of these materials and creating a significant environmental hazard in the process.  What's wrong with this picture?

Though I can't go into the details here, there are a variety of interesting options for improving this picture and a number of provocative questions one can ask.  Why isn't the U.S. mining our own resources?  What are the most promising avenues of research into improved rare earth recovery technologies?  How can we reduce our dependence on rare earths?  What can we do to move away from our "throw-away" consumer electronics culture?  How would massive "cloud computing" paradigms influence the production and generation of e-waste?

President Obama announced a new E-Waste Task Force in November to tackle some of the problems I mention here:

http://urbanmining.org/2010/11/17/obamas-new-e-waste-task-force-spurs-recovery-of-metals-minerals/ ).

http://www.ens-newswire.com/ens/nov2010/2010-11-16-092.html

Let's wish them luck.  We all have a stake in their success.

Cheers,
Sherrell

Post # 26: Building Energy Use - A Major Sustainable Energy Challenge

We recently replaced thirteen windows in our thirty year old home with high-efficiency Energy Star-rated windows.  Wow - what a difference over those thirty-year-old wood-sashed windows!  We actually saw a non-trival drop in our residential heating bill the first month despite it being the coldest month of the year.  This inspired me to revisit the data on building energy uses in the U.S.

Building energy usage is the single largest consumer of primary energy in the U.S.  According to the DOE 2009 Buildings Energy Book (found at http://buildingsdatabook.eren.doe.gov/ ), residential and commercial buildings are responsible for ~ 40% (100 quads) of total U.S. primary energy consumption.  (The Industrial and Transportation Sectors consumed ~ 32% and 28% respectively.)  The DOE data also break down the 2006 building energy usage data to reveal the specific sources of this energy usage:

• 19.8% Space Heating
• 17.7% Lighting
• 12.7% Space Cooling
• 9.6% Water Heating
• 7.8% Electronics
• 5.8% Refrigeration

These six uses account for just over 73% of the total energy consumed by our residential and commercial buildings.

These statistics prompted me to wonder how difficult it will be to significantly reduce total building energy consumption.

The most convenient opportunity to positively impact residential and commercial energy consumption is in the construction of new buildings.  A new build offers the opportunity to integrate modern energy-efficient technologies in a way that simply isn't possible with an existing building.  I found an enlightening presentation by S. Shyam Sunder of the National Institute of Standards and Technology entitled, "Building Energy Efficiency – Net-Zero Energy, High-Performance Green Buildings" ( http://www.fedcenter.gov/_kd/Items/actions.cfm?action=Show&item_id=16615&destination=ShowItem ) that addresses this issue.  Sunder points out that the replacement rate of building stock in the U.S. is only ~1% per year, and that the majority of current building energy efficiency retrofits target only the 5% of our buildings (commercial and residential) that are categorized as "large" buildings.  With only a 1% replacement rate in buildings,  I have to conclude we simply cannot look to new buildings as the solution to our building energy consumption challenge.

By the way, I also ran across a dandy little residential buildings fact sheet from the University of Michigan's Center for Sustainable Systems ( http://css.snre.umich.edu/css_doc/CSS01-08.pdf ) that indicates the average residential area per person grew from 292 sq. ft. in 1950, to 850 sq. ft. in 2000 – almost a factor of three!  Wow... that's something to think about.

Anyway, where do these facts leave us?  The answer: WE NEED A BREAKTHROUGH IN AFFORDABLE,  RETRO-FITTABLE ENERGY CONSERVATION TECHNOLOGIES FOR EXISTING BUILDINGS.  Otherwise it will be almost impossible to dramatically impact the total building energy usage in the U.S. in the lifetime of anyone reading these words.

The bad news is (going back to the building energy usage splits cited above),  there's no one "silver bullet" that will accomplish a transformational reduction in building energy usage given the diversity of building energy loads.  The good news is that even small improvements are magnified by the "law of large numbers" – the fact we have so many buildings to which any given improvement can be applied.

So..., as I've said in the past, I believe the recipe for a sustainable energy future has four key ingredients:

1. Energy Conservation - everywhere and in everything, but especially in buildings
2. Nuclear Power for central station electricity generation - supplemented as we can with all other clean energy sources
3. A Fortified Electric Grid
4. Electric Vehicles (private and mass transit).

Go to run for now...
Sherrell