ML19289C176
| ML19289C176 | |
| Person / Time | |
|---|---|
| Issue date: | 12/07/1978 |
| From: | Meyer R Office of Nuclear Reactor Regulation |
| To: | Beyer C, Buescher B, Klotz R BABCOCK & WILCOX CO., EECCOM, HANFORD ENGINEERING DEVELOPMENT LABORATORY |
| References | |
| NUDOCS 7812140322 | |
| Download: ML19289C176 (8) | |
Text
d COMMITTEE CORRESPONDENCE SOCIETY / COMMITTEE:
ADDRESS CORRESPONDENCE TO:
ANS-5.4 R. O. Meyer
SUBJECT:
U.S. NUCLEAR REGULATORY COMMISSION Fuel Plenum Gas Activity AGENDAITEM:
FILE NO.-
N/A DATE:
DEC 7 60 TO:
C. E. Beyer L. D. Noble Westinghouse Hanford A/59 General Electric Company, M/C 138 Hanford Engineering Development Lab.
175 Curtner Avenue P. O. Box 1250 San Jose, California 95125 Richland, Washington 99352 M. J. F. Notley B. J. Buescher Atom.
Energy of Canada, Ltd.
The Babcock & Wilcox Company Chalk River, Ontario P. O. Box 1260 Canada, K0J1JO Lynchburg, Virginia 24505 Chang S. Rim R. J. Klotz Korea Atomic Energy Research Institute Department 9492 P. O. Box 7, Cheong Ryang Combustion Engineering, Inc.
Seoul, Korea Windsor, Connecticut 07085 R. L. Ritzman R. A. Lorenz Science Applications, Inc.
Oak Ridge National Laboratory 2680 Hanover Street P. O. Box Y Palo Alto, California 94304 Oak Ridge, Tennessec S. E. Turner W. Leech Southern Science Applications, Inc.
Nuclear Fuel Division, W Corp.
P. O. Bc x 10 P. O. Box 355 Dunedin, Florida 33528 Pittsburgh, Pennsylvania 15230 Enclosed is the first complete draf t of our standard gas release model.
Not everything that is needed for a complete standard has been specified by the Working Group, so I have taken the liberty of making up specifications as needed to fill in the blanks (e.g., last sentence on p5). We will thus have to carefully review the model step by step at our next meeting.
78121403 4
Committee Correspondence DEC 719h3 Please note the clean typing job in the equations.
This draft is recorded on magnetic cards for an IBM word processing machine with a spray printer.
We can thus modify the text and equations without fear of causing a typing nightmare--the hard work has already been done.
Sincerely, l l.
- .=
g, x -
,~.
Ralph 0. Meyer, Leader Reactor Fuels Section Core Performance Branch Division of Systema Safety
Enclosure:
As stated cc: w/ encl.
K. Kniel G. Marino W. Johnston J. Voglevede P. Check NRC PDR C. Hann, PNL F. Panisko, PNL J.
Dearien,
INEL R. Mason, INEL G. Owsley, EXXON M. Remley, AI M. Weber, ANS
DRUT
~
ANS-E Oraft Fission Gas Release Standard
-1 I.
INTRODUCTION The ANS-5 fission gas release standard applies to noble gases (krypton and xenon) and, with lesser accuracy, to iodine, cesium, and tellurium.
The standard considers high-temperature and low-temperature releases and distinguishes between short half-life (radioactive) and long half-life (krypton-85 and stable isotopes) isotopes.
Releases for the species and half-life of interest are calculated with both high-temperature and low-temperature models, and the larger of the two releases is taken as the result.
II.
HIGH-TEMPERATURE MODEL For calculating high-temperature releases of noble gases, the fuel is divided into radial and axial nodes, and the model is applied to each node for the appropriate local values of temperature, time, and burnup.
Radial nodes are chosen so that the temperature difference between nodes does not exceed 100 C, and axial nodes are chosen similarly, but with two exceptions:
(1) a coarser mesh nodal scheme may be used for temper-atures below 1,000 C, and (2) any axial segment of fuel rod not exceed-ing 5% of the total fueled length may be exempted from fine-mesh subdivision.
A The irradiation period should be divided into a series of burnup incre-ments that do not exceed 2,000 mwd /t in magnitude provided that the burnup values used in the analysis correspond to the midpoint of the burnup increments.
Otherwise, the burnup increments should not exceed 1,000 mwd /t in magnitude.
The time variable should be related to the burnup variable for the fuel design being analyzed.
In the following equatione, approximations have been made so that only a finite number of terms remain.
The error introduced by making these 5
approximations is about one part in 10.
This error is not significant in gas release calculations.
A.
Stable Isotopes (including krypton-85)
The cumulative fractional release at the end of a single constant temper-ature increment is F = 1 g(t).
The cumulative fractional release at the end of k constant temperature increments (k 5 2) is k-1 k
F
- 1-N i(I 9i1 ~ I +1 1+1) O ] + B at 9 }/I B at g.
i 9 i
k kk j
jg k
1=1 i=1
- gr=
w31 L
3 The following definitions apply:
th B is the fission gas production rate (birth rate) during the i step j
th At is the length of the i time step j
k k
it=I Djat, Djat,...
k = O atk 12 r-I I
j j
k 1=1 1=2 gj = g(tj) = 1 - 44tj/n + 3t /2 for I 2 0.1 j
1 6 3
- PC'" " Ti) for I > 0.1 9j = g(T ) = 15t.
I j
t nini 1
i n=1 2
I Dj=[(D/a)exp(-Q/RT)]x100 g
j
~1 D /a2 = 0.61 sec g
Q = 72,300 cal /mol R = 1.987 cal /mol K th T is the temperature ( K) during the i time increment j
od is the accumulated burnup (megawatt-days per metric ton of j
th heavy metal) at the midpoint of the i time increment.
B.
Radioactive Isotopes (except krypton-85)
Half-lives of the most abundant radioactive isotopes of krypton (except krypton-85) and xenon are short (less than six days) compared with fuel
lifetimes.
Therefore a e n was derived that assumes that power and temperature have been constant for the last several half-lives.
While constant temperature is assumed, the diffusion parameter is still burnup-dependent and the fractional release is still time-dependent.
For the short half-life isotopes, the fractional release is defined as the fraction of the non-decayed inventory that resides in the gap (i.e.,
outside of the fuel pellet yet inside of the fuel rod cladding).
The release fraction is
[erf(8t) - 2Vpt/n exp( pt)]
F=1_,
g
_ 1 - (1 + pt)exD( pt) for I 2 0.1, P
and F=3 coth(6)-
)-1 exp x$
1~
3"f")
for I > 0.1.
2 2 The following definitions apply:
p = A/D' I = D't A is the decay constant (sec-1) t is the total accumulated irradiation time D' has the same definition as it does for stable isotopes except that the total accumulated burnup Bu is assumed to have accrued at a constant tempera'.ure T.
III. LOW-TEMPERATURE MODEL Radial nodes must not be used in applying the low-temperature model.
Axial nodes may be used if desired, but a single calculation per fuel rod is more appropriate.
A.
Stable Isotopes (including krypton-85)
The cumulative fractional release is
-8 F = 8.5 x 10 x Bu, where Bu is the total accumulated burnup in megawatt-days per metric ton of heavy metal.
The irradiation period is not divided up into increments.
B.
Radioactive Isotopes (except krypton-85)
For the short half-life isotopes, the fractioaal release is defined as the fraction of non-decayed inventory that resides in the gap.
The release fraction is
-12 F = 2.0 x 10 x P/A, where P is the specific power in megawatts per metric ton of heavy metal,
~1 and A is the decay constant in sec The specific power P should corres-pond to the highest sustained power level during the last two half-lives of operation.
J 4
IV.
IODINE, CESIUM, AND TELLURIUM RELEASES
~
A.
High-Temperature Releases The noble gas model is used except that the diffusion parameters are altered as follows.
-1 Diodine/Dnobie
= 5.72 x 10 exp(8,900/RT)
-2 Obesium/Djoble
= 7.58 x 10 exp(12,100/RT)
-3 Dtellurium/Dnoble = 1.10 x 10 exp(-12,500/RT),
where R is 1.987 cal /mol K and T is temperature in K.
Iodine-129, cesium-135 and cesium-137 should be treated as stable isotopes.
8.
Low-Temperature Releases Release fractions are assumed to be the same as for the noble gases.
Iodine-129, cesium-135 and cesium-137 should be treated as stable isotopes.