ML19337A854
| ML19337A854 | |
| Person / Time | |
|---|---|
| Site: | 05000124 |
| Issue date: | 09/17/1980 |
| From: | Parkinson T VIRGINIA POLYTECHNIC INSTITUTE & STATE UNIV., BLACKSB |
| To: | John Miller Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8009300459 | |
| Download: ML19337A854 (4) | |
Text
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COLLEGE OF ENGINEERING r%)
VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY (W.
'Blacksburg,!!'ir inia 2406 NucL Aa Encawanalwc Gaove O
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September 17,1980 2
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/.) J I' y Mr. James R. Miller, Chief
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'I.S. Nuclear Regulatory Commission
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Washington DC 20555 Re: license No. R-62 Docket No. 50-124
Dear Sir:
In our preliminary analysis for operation at 500 Kw(t), we have determined that the present fuel element configuration will need to be modified to add more reactivity. Our current technical specifications limit us to operations with no more than 12 fuel plates per element and with a maximum k (excess) of 0.6%.
We request a temporary waiver of the technical specifications to permit tests of one 13-plate element without exceeding the limit on k (excess). Testing would be carried out at low power (< 1 kw(t) ) and should not require more than 30 days.
If possible we would like to perform the low-power physics tests during the period from Dec. 1-31, 1980. The specific tests to be done would involve measuring the change in k when the 13-plate element is exchanged for Subefkticalmultiplicationmeasurementswillbe a 12-place element.
cr made during the approach to critical to insure that we do not exceed the limit on k (excess). One or more dummy fuel plates will be substituted in the 12-plate elements as required.
Since we will not exceed the k (excess) limit of 0.6%,
a believe that no unreviewed safety hazard will exist. This measurement is classified as a "New Experiment"; therefore, it will be submitted to the Reactor Safety Committee for their prior review and approval.
The attached Safety Analysis indicates that if all twelve 12-plate elements were replaced with 13 plate elements, the thermal utilization change, af /f, would be 0.0039. Assuming that the non-leakage probability does not change, f
th e m d-k, k,
f stituting one 13-plate element for a 12-plate element would result in e = 0.0039= 0.0325%
k, 12 For the exchange of a particular fuel element, the above average change would be modified by the statistical weight, k
h scossoop gq 7
6 Mr. James R. Miller, Chief Septembe r 17,1980 Page 2
)'f,wherei,,, is the average thermal flux in the core and W=
core is the average flux for a fuel element located at the (1,j)th codrdinate. The objective of the proposed tests is to validate the with a 12-plate element located at the (i.j)pgate element is exchanged calculation of the change in k when a 13-fg coordinate position.
If you have any questions about this request, please call me at (703) 961-6510.
Sincerely yours, h{-t0 w ~
T. F. Parkinson, Director Nuclear Reactor Laboratory Attachment TFP/nf1 cc: Reactor Safety Committee A. P. Curtner (Reactor Supervisor)
Mark Embrechts
Safety Analysis Reactivity Change with 13-Plate Fuel Element Mark Embrechts The method of calculation is that used in reference 1; we wish to calculate the change in thermal utilization, f, if all the 12-plate fuel elements are replaced with 13-plate elements.
Let f and f' be,respectively; the value of f with 12-plate and 13-plate fuel elements.
~f
- (#} #
1 1
(1) i Then f=
4 y[
$ (r)dv + Ia 4 (r)dv Ia 1
y 2
4 where the subscripts 1 and 2 refer to the fuel and moderator, respectively.
For a unit cell in the plate-type fuel assembly, a
-1 2
2 f
=1+
F + (E-1)
(2) 1 7,1 y
where F = 4 /4,= <g R coth ec R (3) 2 y
y and E = K2 (R2 - R ) coth (R
-R)
(4) y 2
g In equations 3 and 4, R and R are the half-thicknesses of the fuel plate 7
3 and cell, respectively; i
K
= Ia /D and K
- I"2/D '
2 2
(
Reactor Physics of UTR-10, Report ASEA-19, Advanced Technology Laboratories, June 1957.
The values of the constants are collected in Table I.
Table I Thermal Utilization Constants Constant 12-Plate Element 13-Plate Element R
0.040 in. (0.1016 cm) 0.040 in. (0.1016 cm) g R
0.240 in. (0.6096 cm) 0.220 in. (0.5500 cm) 2 l
l Ia 2.6532 ci 2.6532 ci 1
1
-1 D
0.03857 cm 0.03857 cm 7
l
~
Ia 0.022 cm 0.022 ci 2
1
~1 D
0.7767 ci 0.7767 cm 2
1 l
g 0.1024 ci 0.1024 ci l
0.0171 c i 0.0171 c i g
2 F
0.9997 0.9997 E
1.000025 1.000020 f
0.9601 0.9640 i
Thus the reactivity change if all 12-plate elements are replaced with 13-plate elements would be I' ~f
= 0.0039
=
e
=
e