ML20128B205
| ML20128B205 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 08/03/1973 |
| From: | Stello V US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Skovholt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9212030593 | |
| Download: ML20128B205 (2) | |
Text
..~
teu
/
e
'm n.za
.. /
D. J. Skovbolt, Assistant Director for Operating Reacters, L N00fTICEL1h OPERATICII The enclosed report summarises the conditions and bases acceptable to Licensing for the recurs to power for Monticello with respect to the i
control rod problem.
Originai sined by
. Victor Str IM Victor Stallo, Jr., Assistaat Director for Reactor Safety Directorate of Licenslag Enclosure Revised Shutdown Margia for Monticello Operation ect S. Emmauer J. Hendria D. F. Ross A. Giambasse E. Bailey Distribution:
Docket file J. G. Ka$plar CPB Reading J. Shea L Reading (M. Groff) i l
l L
p i
l r
./
,((h,
.,, ADQy......
CPB l
CPB cma,
. ;.vs D,to....
E. Bailey; bin.
DF.
s_ _. _
summ >
(
m.c8//73 8/> /73 8/az73
.1m US GOVERNMENi mMYNtG 0FTK1.lter- & M4 400 Fortu AEC 818 (Rey, S-63) 9212030593 730003 i
PDR-ADOCK 05000253 PDR
[
].
l 4
~ ;- --
)
RE_ VISED SilUTDOWN MARCIN F(u MONTICELLO OPERATION There is ir.dicatiot that some Monticello control assemblics may have manufacturing defects that could have a significant effect on the reactor shutdown margin.
(A discussion of this problem with respect to the Millstone Unit 1 Plant is presented in a special report issued by the j
Millstone Power Company on July The manufacturing defects could result in settling of B C powder in th
" Reactor Control Blade Evaluation").
control blades during reactor operation.
4 a decrease in the shutdown margin.
Such settling would result in The current Technical Specification requirement is that be at least 0.25% throughout the cycle. The Regulatory staff has reviewed the shutdown margin the Monticello control rod problem and bas concluded that an additional margin of 0.55 be added to this shutdown margin requirement possible settling of B C.
to allow for 4
This means that with the most rod out of the reactor, a minimum shutdown margin of 0.75% must be present reactive control-at any time during the cycle.
These det erminations of shutdown margin should allow for transient Sm and Xe, if present.
requirement on shutdown margin is sufficientWe believe this additional 0.5%
in margin due to settling of E G in the control rods.to allow for short-term changes Because of the B C during operation, further measurements of the shu g
4required periodically.
shortly by the Licensing staff.The frequency of these measurements will be established e
Prior to startup of Monticello, shutdown margin demonstrations should be made with each control rod withdrawn, in turn.
that definitely limits the possibility of defective control assembliWe are not aware those manufactured at Wilmington, N. C.
es to In addition, we believe it is desirable to make several measurements of the shutdown margin up to a critical reactor state prior to power operation (these measurements should not violate Technical Specification limits).
These critical measurements will verify the actual shutdown margin.
This value can be compared with results of later measurements to determine changes in the shutdown margin during the cycle.
i The problem associated with insufficient t
return to criticality following a coolucan, with the mostshutdown margin is a possibl out.
If, for example, an extreme amount reactive rod. stuck ceivable that k cf settling occurred, it supercritical sbe could be negated in whole or in part bin the c is con-This the operator of boric acid from the Standby Liquid C y the addition by from equilibrium operation, due to the rapid buildup ontrol System.
!!owever, owing a cooldown phenomenon woulti l35 This to add more boron, if necessary.be dominant for over 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, providing s e
i time not operative, the reactor would seek a stable level based on thin ca temperature coefficient.
In that e negative removc the generated heat.
case, we believe, the RHR systems could
,