Hi there,
There are a variety of different dry cask designs, with the main
difference being whether they have an external layer of concrete or
not. But considering they all have to adhere to government standards,
most of the answers will be similar regardless of design.
1: What the temperature of the inner shell is?
USA Storage Requirements:
Ambient temperature: 38°C (max)
Temperature of cladding <357°C
[Source A]
The peak cladding temperature for commercial spent nuclear fuel was
calculated to be 282°C (542°F), with the peak occurring 35 years after
emplacement.
[Source B]
"The inner metal canister can reach temperatures of 400 degrees
Fahrenheit"
http://www.h-o-m-e.org/Forum/NIRS_DryCask.PDF
2: What are the materials used in the construction of the casks?
A simple interlocking plate structure was chosen using boronated
aluminium, a material specially developed by TransnucleŽaire for spent
fuel cask applications. The
aluminium basket structure provides both mechanical strength and an
effective means of transferring the residual fuel decay heat to the
cask inner walls. The uniformly dispersed boron in the aluminium
provides an effective neutron poison for criticality safety.
All TN 24 type casks are made from a forged steel body and welded base
surrounded by a layer of neutron shielding resin which is encased in
an outer steel shell. The forged steel body provides most of the gamma
shielding and, for the TN 97 L, the proportions of steel/resin were
finely tuned to maximise the shielding characteristics within the
overall maximum weight limit.
During transport, TN 24 type casks typically use shock absorbing
covers made from steel casings filled with energy absorbing materials
such as wood. Such shock absorbing cover was chosen for the lid end
but the large diameter of the cask meant that the traditional
type shock absorber was best suited to absorb energy from axial and
oblique impacts. This led to the development of lightweight aluminium
rings for protection against lateral impacts. A new design lightweight
aluminium base shock absorbing cover was chosen because
it gave significant weight savings and thus helped to optimise the
overall shielding performance of the cask.
[Source A]
Interlocking Plates - The interlocking plates are made of either
Neutronit A 978 (a stainless steel and boron alloy) or SA 516 Grade 70
carbon steel and range between 5 and 10 mm (0.2 and 0.4 in.) in
thickness.
Thermal Shunts - All the waste package designs for commercial spent
nuclear fuel except the 24-BWR require thermal shunts. These shunts,
which are made of 5-mm (0.2-in.) thick SB 209 6061 T4 (an aluminum
alloy), are placed alongside the interlocking plates (CRWMS M&O
2000au, Section 2.4.1.3). The shunts are added to help transfer heat
from the waste form to the walls of the waste package.
Structural Guides - The structural guides for each waste package are
made of 10-mm (0.4-in.) thick SA 516 Grade 70 carbon steel and are
placed inside the inner layer of the waste package to hold the basket
structure in place.
--
After assessing potential materials available for waste package
corrosion barriers, analysts selected nickel- and titanium-based
alloys as the most promising candidate materials for corrosion
resistance in an oxidizing environment such as Yucca Mountain. Using a
corrosion-resistant material as the outer barrier of the waste package
will significantly lower the risk of waste package failure from
corrosion. Alloy 22 was selected as the preferred material for the
outer barrier because it has excellent resistance to corrosion in the
environment expected at Yucca Mountain; it is easier to weld than
titanium; and it has a better thermal expansion coefficient match to
Stainless Steel Type 316NG than titanium. A structurally strong
material (stainless steel) was chosen for the inner layer of the waste
package.
Alloy 22 also offers benefits in the areas of program and operating
flexibility. It is extremely corrosion-resistant under conditions of
high temperature and low humidity, such as those that would prevail
for hundreds to thousands of years in a repository designed to allow a
relatively high thermal output from the waste packages. At low
temperatures, Alloy 22 is extremely corrosion-resistant in either low
or high humidity.
[Source B]
3: How thick are the materials used in the construction of the casks?
The thickness of some of the internal components is mentioned above.
The outer metal shell has a thickness of between 0.6 inch and 15
inches, depending on whether there will be a layer of concrete or not.
The inner package is placed in the outer package that is welded shut.
The outer package is constructed of 2- to 2.5-cm thick C-22 (a
corrosion-resistant nickel alloy) that, under expected repository
conditions, will last more than 10,000 years.
[Source C]
Shell Thickness: 0.60 inches
[Source D]
The containers are either full-metal casks which have metal walls up
to 38 cm thick, or canisters, which have much thinner metal walls and
are designed to be placed in thicker concrete or metal "overpacks" for
storage.
[Source F]
4: How much radiation is given off by the cask?
USA Storage Requirements:
Dose at site boundary less than 25 mrem.y-1 to the nearest resident.
(External dose rate (on the storage pad) is usually less 400 mrem.h-1
at surface).
[Source A]
According to an official of one of the European cask manufacturers,
the dose rates at the outside surface of a fully loaded cask are about
500 microsieverts per hour. An unprotected adult could stand 2 meters
from a cask, where the dose rate is 100 ”Sv per hour, and it would
take 10 hours to accumulate the annual dosage permitted by the
International Commission on Radiological Protection, in Stockholm,
Sweden. People who are not nuclear workers would not receive those
kinds of doses, however, because fences, berms, or walls around the
compound would cut their exposure to almost nothing.
[Source F]
"Technical Specification 1.2.4, "Maximum External Surface Dose Rate,"
established external dose rate limits of 20 mrem/hr on the sides of
the concrete cask and 50 mrem/hr on the top. Air inlet and outlet dose
rates were limited to 50 mrem/hr."
http://www.nrc.gov/NRR/OVERSIGHT/ASSESS/REPORTS/ano_2001010.pdf
5: What is the actual weight of the radioactive materials stored in
the casks?
6: How much does the cask weigh?
The materials weigh approximately 10-15 tons, and an empty cask weighs
approximately 120-125 tons.
Loaded weight in tonnes:
In Storage - 133
In Transport - 137
[Source A]
They weigh approximately 125 tons empty and up to 140 tons loaded with
spent fuel.
[Source E]
Each cask can hold 10 to 15 metric tons of spent nuclear material.
[Source F]
7: How much High Level nuclear waste is produced in a year?
2,000 metric tons annually, in the USA. 9,000 metric tons worldwide.
"Thirty thousand metric tons of spent fuel rods from power reactors
and another 380,000 cubic meters of high level radioactive waste, have
been produced in the United States since the beginning of the nuclear
age. Presently, these fuel rods are stored at the nuclear reactors in
water filled basins and accumulate at the rate of six tons per day."
[6x365=2190 tons per year]
http://www.goshen.edu/bio/Biol410/Biol410SrSemPapers97/Hoover.html
"But the Yucca Mountain site is not expected to open until 2010 and
still faces legal and regulatory hurdles, while the amount of reactor
waste -- now about 45,000 tons nationwide -- is growing by 2,000 tons
annually."
San Francisco Examiner, Aug 20, 2002
http://www.examiner.com/headlines/default.jsp?story=n.nuke.0820w
"A typical large commercial nuclear reactor discharges an average of
20-30 metric tons of spent fuel per year - about 2,000 metric tons
annually for the entire U.S. nuclear power industry."
http://216.239.51.100/search?q=cache:ZH0oYgRRgIkC:www.earthscape.org/p1/hom01/+%22dry+cask%22++tons+annually&hl=en&ie=UTF-8
"A typical nuclear power plant produces about 20-30 metric tons of
high-level nuclear waste per year. The United States produces a total
of about 2,000 metric tons annually. Russia produces about 600 metric
tons per year. Worldwide about 9,000 metric tons of spent nuclear fuel
are produced."
http://www.russiaproject.org/part2/nuclear/faq.html
Sources
-------
A) Taken from a paper that compares the requirements for cask
licensing in Europe and the USA and showing how two particular BWR
cask designs were developed by TransnucleŽaire. Contains a good cask
diagram.
http://www.ntp.org.uk/samples/rmtp2000114301.pdf
B) Yucca Mountain Science and Engineering Report, Technical
Information Supporting Site Recommendation Consideration, February
2002
http://www.ymp.gov/documents/ser_b/
C) Rethinking Multipurpose Spent Nuclear Fuel Casks and Canisters
http://www.ornl.gov/~webworks/cppr/y2001/pres/112708.pdf
D) McConaghy Casks
http://fessp.llnl.gov/nuclear_coop/session1/ McConaghy_William.pdf
E) US Nuclear Regulatory Commission: Typical Dry Cask Storage System
http://www.nrc.gov/waste/spent-fuel-storage/diagram-typical-dry-cask-system.html
F) "Canned Heat", Spectrum Online
http://www.spectrum.ieee.org/WEBONLY/publicfeature/nov01/nwaste.html
Google Search Strategy
----------------------
"dry cask" temperature "inner shell"
"dry cask" thickness
"thousand metric tons of spent fuel"
"dry cask" tons annually
"high level nuclear waste" "metric tons" annually worldwide
I trust this answers your question. If any portion of my answer is
unclear, please ask for clarification.
Best wishes,
robertskelton-ga |
,
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