Appendix K to Part 50—ECCS Evaluation Models
I. Required and Acceptable Features
of the Evaluation Models
5. Metal—Water Reaction Rate.
The rate of energy release, hydrogen generation, and cladding oxidation from
the metal/water reaction shall be calculated using the Baker-Just equation
(Baker, L., Just, L.C., "Studies of Metal Water Reactions at High
Temperatures, III. Experimental and Theoretical Studies of the Zirconium-Water
Reaction," ANL-6548, page 7, May 1962). This publication has been approved
for incorporation by reference by the Director of the Federal Register. A copy
of the publication is available for inspection at the NRC Library, 11545
Rockville Pike, Two White Flint North, Rockville, Maryland 20852-2738. The
reaction shall be assumed not to be steam limited. For rods whose cladding is
calculated to rupture during the LOCA, the inside of the cladding shall be
assumed to react after the rupture. The calculation of the reaction rate on the
inside of the cladding shall also follow the Baker-Just equation, starting at
the time when the cladding is calculated to rupture, and extending around the
cladding inner circumference and axially no less that 1.5 inches each way from
the location of the rupture, with the reaction assumed not to be steam limited.
"Studies of Metal Water Reactions at High Temperatures,
III. Experimental and Theoretical Studies of the Zirconium-Water
Reaction," ANL-6548
7
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The Shift Manager for TMI-1 has determined that based upon the existing |
|
procedural guidance and the past simulator training experience, there is |
|
reasonable expectation that procedurally directed operator actions will |
|
successfully shut down the reactor coolant pumps within 1 minute of loss
of |
|
sub-cooling margin and therefore, the peak cladding temperature will
remain |
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below the 2200 degrees Fahrenheit limit of 10 CFR 50.46. Thus, the TMI-1 |
|
emergency core cooling systems continue to be operable because, based upon |
|
engineering judgement, the systems are capable of performing their
intended |
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safety function.
RULEMAKING ISSUE
NOTATION VOTE
March 1, 2012
SECY
-
12
-
0034
FOR
:
The Commissioners
FROM
:
R. W. Borchardt
Executive Director for Operations
SUBJECT
:
PROPOSED RULEMAKING
–
10
CFR
50.46c: EMERGENCY CORE
COOLING
SYSTEM PERFORMANCE
DURING LOSS
-
OF
-
COOLANT
ACCIDENTS (RIN 3150
-
AH42)
The staff has prepared a proposed
rule (
Enclosure 1
)
that would replace the current
regulations
for
E
CCS, found in §
50.46, by establishing p
erformance
-
based requirements. The proposed
rulemaking would incorporate recent
research findings which identified previously unknown
cladding embrittlement mechanisms
and expanded the
U.S.
Nuclear Regulatory Commission’s
(
NRC
or the
Commission
)
knowledge of previously identified
mechanisms. The proposed rule
would also expand applicability of
ECCS acceptance criteria to all light water reactors,
regardless of fuel design or
cladding materials (as per Commission direction, and the request of
petition for rulemaking (PRM)
PRM
-
50
-
71)
.
Finally, the proposed rule would
require licensees
to evaluate the thermal effects of
crud and oxide layers which may have developed on the fuel
cladd
ing during normal operation. This
requirement would address a request of
PRM 50-84
.
REGULATORY GUIDE 1.157
paragraph 50.46(b). Paragraph
50.46(b)(1) requires that the calculated maximum temperature of fuel element
cladding not be greater than 2200'F.
Reference
11 --- Cathcart NUREG-17, August 1977
§ 50.46 Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors
(b)(1) Peak cladding temperature. The
calculated maximum fuel element cladding temperature shall not exceed 2200° F.
RNL/NUREG-1
7
Zirconium
Metal-Water Oxidation Kinetics IV. Reaction Rate Studies
J. V. Cuthcart R. E. Pawel
MAXI
The specimen consists of a 46 cm (18 in.) length of Zircaloy tubing. A
small segment of the tube in close proximity to the thermocouple stations
actually serves as the basic specimen; the remainder functions simply as
support for the specimen and the thermocouple leads. The specimen is cut from a
standard PWR tube section.
MINI
The reaction chamber consists of a 60 mm (2.36 in.)
OD quartz tube 60 cm (23.6 in.) long with a Zircaloy-4 PWR tube sp'ecimen [30
mm-long by 10.92 mm OD by 9.65 mm ID (1.18 x 0.430 x 0.380 in.)] supported at
its center between two smaller quartz tubes. During an experiment, steam flows
past the outside surface of the specimen, and a slight /5 Vposit~ive-pressure
of helium is maintained-inside the support tubes in I Ft 16 order to prevent
ingress of steam to the interior of the specimen. A helium flow rate of X' 0.2
cc/s is used for this purpose. Steam is generated in an all-glass boiler (not
shown in the figure). For most experiments the steam flow rate was adjusted to
30 g/min (0.066 lb/min) which corresponds to a linear velocity of about 1 m/s
(3 ft/s) past the specimen in the reaction tu
WAPD-104
THE HIGH TEMPERATURE OXIDATION OF ZIRCALOY IN WATER
by W. A. Bostrom
March 19, 1954
EXPERIMENTAL PROCEDURE The materials used were Zircmloy-2
with a nominal composition of 1.5% S§n 0.12% Fe, 0.10% Cr, 0.05% Ni, balance Zr
and Zircaloy-B which is Zircaloy-2 with 5.5% U aid 0.037% B added. The samples
were ring shaped as shown in Fig. 1, and the effective original surface area
was 13 square cm,
OECD
LOFT-T--3804
OECD LOFT Project
Quick-Look Report on OECD LOFT
Experiment LP-FP-2
September 1985
Care must be taken in determining
the temperature at which the metal water reaction initiates, since the
precursory heating can occur at a much lower temperature. It can be concluded
from examination of the recorded temperatures that the oxidation of zircaloy by
steam becomes rapid at temperatures in excess of 1400 K (2060°F).
From ANL-7609 we learn: "A true simulation of loss-0f-coolant accident conditions requires a large number of fuel rods to achieve a realistic thermal environment for each rod." (page 24 of 38)
Cladding-steam and bundles: ANL 7609
Argonne
performed single rod and also small bundle tests (four rods) with zircaloy clad
fuel rod simulators.
http://www.osti.gov/bridge/servlets/purl/4132278-dAViPP/
http://www.osti.gov/bridge/servlets/purl/4132278-dAViPP/
From ANL-7609 we learn: "A true simulation of loss-0f-coolant accident conditions requires a large number of fuel rods to achieve a realistic thermal environment for each rod." (page 24 of 38)
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