ML19206A558
| ML19206A558 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/07/1978 |
| From: | Taylor J BABCOCK & WILCOX CO. |
| To: | Varga S Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19206A540 | List: |
| References | |
| NUDOCS 7904200137 | |
| Download: ML19206A558 (3) | |
Text
/
JUy J Q '
BaccocimWilcox m 12im
%cemm e, c, P.O. E c x 12 E0. Lynchburg. Va. t45C 5 Te'e;hene: (M4) 334-5111 June 7, 1973 Mr. C teven A. Varga, Chief Light Water Reactors Branch 4 Division of Project Management Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. V:
.roa:
O Earlier today, Messrs. Tokar and Meyer of the NRC asked several questions of 35ii relating to 3A?i-14 96, "3PRA Re tainer Design Report", whic." cas forwarded to you by my letter of June 2, 1973.
The cuestions were directed pri arily towards use of the retainer f:r holddo in of modified orifice rod assemblies (MORA).
' his letter is beina.orovided to formalize o
BEil'r responses to these questions so that they may be used in support of licensing activities associated with retainer use.
The MORA used with primary neutrcn scurces can be visuali:cd by re ferring to Figure 3-la of 3AW-1490.
the orifice rod assembly (ORA) spider is the same shape at that sho m in Figure 3-la.
The MORA is produced fren a stindard ORA by rencving the four Y-shaped arms of the spider ind the eight orifice rods attached to these arns.
In additica, the tour orifice rods on the inner rod circle created by the n
remaining straigat spicer arms (on t,e rue,. assemb., y diagonals in Figure 3-la) are removed slightly belcw the spide.
A short rod portion remains below the spider arm and the nut above the spide r remains.
In essence, the MORA is now a spider arrangement with fuur straight arms and four unmodified orifice rods at the outermost locatien on these arms.
The nuts at the inner location on the straight arms are retained because they act as loca ting fixtures for the retainer as described on Page 3-2 of BAN-1496.
The weight of the MORA is approximately eight pounds af ter modification as compared to fif teen pounds Prior to modification.
The minimum holddown criteria for retainer use is that the ma gin to conponent lift must be greater than thirty pounds witn the re tt.ine r in use.
Analyse s pe rformed by 30l (:cking into acccent the hydraulic forces acting on the MORA, the MOR.\\
weight, and the retainer helddown force) shou tha t the net hol d d ot:n
':0R/. wi th a retaine-irs talicd is annroxinate2' en an th' rt' - f12e p o wids J.
th0 Davis-325se 1 r e a u 's o r.
I!!e re fo re,
f tais design criteria is met, 79042001M rs
.v 9' The 8:tccek & W fcot C:m:cm / Est;bw ed IE57
cock &WUcox Mr. Steven A. Varga Page 2 June 7, 1978
/
The fuel assembly growth criteria stated on Page E-2 of BAU-1496 is based on a fuel assembly design burnup used as a basis for the retainer design.
Since the maximum burnup seen in one cycle of operation will be less than the burnup used as a design basis, the fuel assembly growth criteria is met.
It should be noted that the retainer will be used for only one cycle of operation.
It is postulated that a retainer failure could cause reler.se of a retainer and, possibly, an MORA into the reactor vessel.
The neutronic and thermal-hydrculic consequences of this event are insignificant.
Although interference with control roc motion is very unlikely, this concern has also been considered.
Analyses of s tuck-out control rod transients for B5W 177-FA plants have shown that these plants can be safely shut down in his event.
The re fo re, should interference with control red mo:i:n occur, the plant could still be safely shut down.
The major concern associated with retainer failure is plant damage and potential cutages for repair.
This damage would be p revented ~c. the Loose Parts Monitoring System (LPMS) which is provided ca all B6W operating plants.
The LPMS has the capability to detect a failed retainer in either the reactor vessel or steam generator.
The importance of LPMS indications has been emphasized to plant operating s taffs to preclude possible eculpment damage in the unlikely event of retainer failure.
Even though the retainer is designed for'only one cycle of operation, B5N uill recommend to utilities using the retainer
.that surveillance inspections be made folicwing re tainer use to provide additional confirmation of acceptable operati on.
The results of these ciscussions will be provided to the NRC and definice plans vill be nrovide 2 as they are formulated.
We hope that this adequately answers the questions raised
,in the discussion today.
Should any further information be required, please contact Mr.
L.
R. Gray (Ext. 2553) of cv staff.
Verv. t y" 1 v.
y,o u r s,, 7) n,, ' -
J "n
swm n/
Taylor /
V 9
James H.
Manager, Licensing JHT:dsf o,
UI bA
=
MWm==-v-c.:v-a
-.m-
,/
a
_,c z w :..
d!k c_ockL?R!Cox Mr. Steven A. Varga Page 3 June 7, 1973 7
cr:.
R. B.
Borsum (BGW)
L..B. Engle (NRC)
H. Silver (NRC)
- M. Tokar (NRC)
L. E. Roc (Toledo Edison)
R. W. Heward (General Public Utilities)
'~'bec:
J.
S. Tulenko J. C. Deddens
~"
W.
R. Gray G. O.' Geissler I
r!. O. Stein E. R. Kane B. J. Short I'--
G. A. Meyer M. W.
Croft R. Berchin 1L. R. Pletke E.
G. Ward W.
R.
Gibson R. E. Kosiba J.
P. Jones
~
G. M. Olds J. T. Janis o
=
?"
k#
s2 $4 g
$5f
. -. r(. G
BA'J-1497 g
June 1978 JUSTIFICATION FOR REMOVAL OF CRIFICE RCD ASSEM3 LIES IN TERIE MILE ISLuiD UNIT 2, CYCLE 1 t
~ C,a,.O M
u a u n' s. C O. :n/
U4~
o. ag
~.h.as