CORIUM “CONE” EX-BUILDING FUEL LOCATION INVESTIGATION PROPOSAL INFORMATION
SimplyInfo.Org Research Team – Submission To IRID
OVERVIEW
https://e-reports-ext.llnl.gov/pdf/503271.pdf
The link above is a study performed by Lawrence Livermore Laboratory titled;
“Possible Methods to Estimate Core Location in a Beyond-Design-Basis Accident at a GE BWR with a Mark I
Containment Structure“
Many of the methods similar to our recommendations are identified in the LNL article concerning temperatures,
radiation levels and neutron generation population.
FUKUSHIMA UNIT 1-3 MELTED FUEL (CORIUM) STATUS AND LOCATION
There have been minimal efforts by TEPCO to quantify and qualify the melted fuel at Fukushima Reactor Units 1-3.
Multiple investigations into these buildings have revealed massive damage, extreme radiation levels and evidence of
potential corium and corium paths. TEPCO cannot tell us what the status is of the melted fuel from a subcritical
condition, no nuclear instrumentation has been employed to determine the neutron population and there are no
definitive reports or studies that show more than general overlay images.
We have studied this issue and have the following recommendations which will assist those involved to identify the
status of the corium including neutron generation, radiation, temperature and off gas generation. Our
recommendations will also create the supporting data to understand and map potential and direct locations of corium
that may have left containment (PCV) or the reactor building. In addition, once the ex-building corium identification
phase is completed, a similar approach can be utilized for in vessel/building fuel debris removal.
EX-BUILDING CORIUM LOCATION
The first phase of this process includes the investigation outside of the reactor buildings and focuses on an area
bounded by a cone shaped region. This emanates from the center of each core to an approximate 30-60 degree cone
area down from the core height and extending out of the building through the ground. The boundaries of this cone will
be used to envelope the potential area where fuel corium could be located.
(green = ground grade, black = drilling angles)
In order to compensate for any groundwater that may be encountered within the drilled holes, all instrumentation will
be enclosed in a sealed instrument container which will allow insertion into a wet environment. Tubing for sampling of
air activity will be inserted separate from the sealed instrument container and lowered to a level just above the water
level. As the drilling is progressing each drilling location data set will be used to compare other locations and added
to development of the 3D images.
The process involves:
1.
Locating the precise core drilling positions on 3 sides of each reactor building to allow drilling 3 holes at
different angles underneath the building into the intercept of the corium cone line.
2. Extending the drill hole and inserting the probe measurement equipment beyond the corium cone intercept
boundary as needed to obtain data from the instrument probe package.
3. Install a video camera with the instrumentation probe package, with backup, to videotape the monitoring process.
4. Complete a 3D map of each cone area utilizing the instrument probe insertion to the various holes. Upon
completion and generation of the 3D corium location mapping, keep the data packages in the drilled holes to create a
real time monitoring system for corium activity.
5. Measure the following in 1 meter increments with a sealed probe package inserted in the drilled holes:
• Neutron population using a fission chamber, signal conditioning and a LogN recorder
• Temperature profile
• Radiation profile
• Humidity profile
• Pressure profile
• Air activity profile
SUPPLIES AND EQUIPMENT SUGGESTIONS
Fission Chambers
Fission chambers similar to these sold by Centronic are suggested.
http://www.centronic.co.uk/sitemap.htm
From Centtronic’s website
e:
“Fission cha
ambers provide a very large pulse
e from a neutron induced reaction
n and can be use
ed in either pulse
e or direct
current mod
de. When used in
n pulse mode non
n-neutron pulsess can be discrimin
nated against faiirly easily, even at
a low
neutron fluxe
es. This makes them
t
ideal for usse in high mixed fields,
f
such as en
ncountered nearr a nuclear reacto
or as part of
In-core or Exx-core nuclear in
nstrumentation. Small
S
fission chambers, such as the
t Centronic FC
C4A, are designe
ed for flux
scanning in narrow tubes in the region of fue
el elements. DC fission
f
chamberss have a longer liifetime than boro
on ion
chambers; due
d to the fission
n coating not burn
ning up as quicklly as the boron coating.
c
Howeverr, fission productt activity
limits the dyynamic range of DC
D fission chamb
bers, typically to the top 2 decade
es of reactor pow
wer”
Geiger Mü
üller Tubes
GM tubes similar
s
to those
e sold by Centrronic could be used
u
for this pu
urpose.
http://www.centronic.co.u
uk/downloads/G
Geiger_Tube_th
heory.pdf
From Centtronic’s website
e:
“With increa
asing awareness of the environme
ent and of protecction levels, the detection
d
and me
easurement of nu
uclear radiation
becomes inccreasingly imporrtant. The Geigerr Müller tube, with
h its high detectiion sensitivity, robust construction
n and simple circcuitry,
continues to
o be one of the most
m
widely used radiation detecto
ors in all areas of
o application.”
Radiation Tolerant Prod
ducts
http://www.centronic.us/ra
adiation_detecctors.htm
From Centtronic’s website
e:
Features:
•
Non contact product.
•
Option of flush and non flush mounting models.
•
Radiation tolerant to 100 kGy or 1 MGy depending on model.
•
Can be supplied with screened and unscreened cables up to a length of 300m.
•
Intrinsically safe model available.
Temperature, pressure, radiation & humidity equipment:
These parameter instruments can be standard off the shelf instruments with probes packaged to fit in the core drill
hole size and can be equipped with recording and analyzing instrumentation.
Air Activity:
We recommend that air activity be measured with a sniffer tube that will be directly attached to an air activity monitor
with detector, recorder and alarm capability. A recommended range of detectors for application at each drill site are
manufactured by Canberra with the following units suggested:
http://www.canberra.com/products/env_rad_monitoring/integrated-systems.asp?Accordion1=1
CA
AM110FF Serie
es Continuous Air Monitors
From Canb
berra’s website
e:
The CAM110FF Series offerrs two options forr beta/gamma pa
articulate and iod
dine in air monito
oring:
•
•
th
he CAM110IFF fo
or 131I monitoring, or
th
he CAM110PIFF for beta/gamma particulate and iodine
i
monitoring
g.
The system monitors radioac
ctive airborne levvels in either worrking spaces, or via a process tub
bing connection to a remote stacck, duct
or other air space.
s
Visual ind
dication and conttact outputs for re
emote alarms arre provided for hiigh radiation and
d failure condition
ns.
Analog outp
puts are provided
d to the plant mon
nitoring system. The CAM110 Se
eries CAMs can be
b set for isokine
etic monitoring if
desired.
Another sugg
gested model is
i the Portable Gas Monitor PGM102
P
From Canb
berra’s website
e:
The PGM10
02 is a self-contaiined mobile mon
nitoring/sample collection station for radioactive noble gases, partiiculates, iodines
and tritium in
n a gaseous sam
mple media. The inlet gas sample
e passes first thro
ough a dual charrcoal cartridge an
nd a 0.3 micron
filter paper which
w
removes io
odines and particculates from the sample.
s
It then passes
p
through an
a unshielded 8.3
3 L counting
chamber witth a dual phosph
hor scintillation de
etector (plastic scintillator and BG
GO crystal). The BGO crystal pro
ovides a gamma
activity signa
al with a slower rise
r
time pulse, thus
t
allowing it to
o be identified byy the preamplifierr and used as a compensating
c
signal for the
e gamma backgrround.
Workers in protective
p
clothin
ng can readily mo
ove the handcartt station to a sele
ected site, conne
ect the electrical and
a pneumatic
systems, an
nd activate the mo
onitoring station functions in a fra
action of the time
e required to set up separate mon
nitoring and sam
mpling
systems.
The PGM10
02 is designed forr use at locationss where ac electrrical power and a source of presssure or vacuum is
i present for tran
nsport
of the samplle through the monitoring system
m. An external vacuum pumping system
s
may be connected to the air outlet connecction if
the inlet sam
mple flow is not pressurized.
p
CORE DRIILLING
Core drillin
ng capability will be needed to
o bore angled holes
h
from the locations
l
aroun
nd the reactor buildings
b
on 3 sides.
s
The equipm
ment will need to be able to drill holes at discrete angles frrom the surface
e and under the
e building to the
e
intersect off the cone anglles. Drilling is anticipated
a
to pass
p
through ge
eneral construcction backfill ass well as clay and
a
mudstone at the bottom of
o the core drille
ed holes.
One cavea
at is that the equipment used for
f the drilling process
p
will pro
obably not be able
a
to be remo
oved from the site
s to
be used elssewhere after being
b
used at Fukushima
F
Daiiichi due to con
ntamination issues. This cost should be refle
ected
in any costt analysis.
Two such drilling rigs are presented for consideration:
The first exxample is the directional
d
drillin
ng rig made byy the Sino core drill company
http://www.sinocoredrill.com/photo/sinoccoredrill/editor//201306251119
910_32111.jpg
g
This drilling
g rig adds a be
enefit with distance from the operating
o
cab to
o the actual drill head.
Thesse drilling rigs are capable of changing
c
direcction during the drilling processs as shown in the next image
e
The
e second example is a smaller drilling rig ma
ade by the Stre
ega Company:
o.th/images/rigss_tools/D50.jpg
g
http:///www.strega.co
DIAGRAMS AND REFER
RENCES
Dark blue = 30 degree cone
Light blue = 60 degree cone
Background information on "low flat angle drilling" called HDD - Horizontal Directional Drilling, or Directional Boring
http://construction.about.com/od/Special-Construction/a/Horizontal-Directional-Drilling.htm
Standard well drilling costs for comparison
http://wiki.answers.com/Q/What_is_the_average_cost_to_drill_a_well?#slide=2