ML20151S766
| ML20151S766 | |
| Person / Time | |
|---|---|
| Issue date: | 07/28/1988 |
| From: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Govaerts P VINCOTTE |
| Shared Package | |
| ML20151S769 | List: |
| References | |
| NUDOCS 8808160104 | |
| Download: ML20151S766 (6) | |
Text
m Ontted) Gicu)
[
t ![
D
+f 'o,,
c y
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555
%.....* JUL 2 81988 Mr. P. Govaerts, Chief Engineer Vincotte
~
Avenue du Roi 157 B-1060 Brussels Belgium
Dear Mr. Govaerts:
In your letter of June 28, 1988 you ex ressed a pumber of concerns regarding the moderator temperature coefficient MTC) th.at is or may be positive at the beginning-of-life (BOL), all rods out ARO), hot zero power (HZP), no xenon condition for PWRs with extended fuel cycles of 18 manths. You also provided a list of U.S. and foreign PWRs with their technical specification MTC limits.
L V Ari example of a typical positive MTC technical specification limit from this list is: the MTC would be no nore positive than +5 pcm/deg F below a reactor power of 70 percent and above 70 percent power the MTC would vary linearly from +5 pcm/deg F at 70 percent power tg 0 pcm/deg F at 100 percent power.
(Note that a em is a reactivity of 10- delta k/k.) Your letter requests information ( ) on the basis for approval of positive MTC technical specification limits for U.S. PWRs, (2) whether the accidents analyzed in the Final Safety Analysis Report (FSAR) are still bounded, (3) whether other accidents in the 0-100 percent power range need to be considered, and (4) whether other domains of operation like cold shutdown or the warm-up period to hot standby need to be considered.
The NRC bases its approval"of positive MTC technical specification limits on a licensee's reevaluation of all the FSAP transients and accidents for his plant.
In this reevaluation, the licensee provides reanalyses of, usually, the transients and accidents sensitive to a positive MTC. In general, these reanalyzed events are those which result in cora heatup or moderator density !
reductions. For each event that is reanalyzed, approved methods are used with the same or in some cases more conservative assumptions than for the FSAR analyses. These reanalyzed events must meet the NRC's acceptance criteria as l state 1, for example, in our Standard Review Plan. This reanalysis may be performed by a licensee as part of a reload core analysis. This reanalysis by l the licensee confirms that the FSAR transients and accidents remain bounded with respect to consequences.
No transients or accidents other than those in the FSAR need be considered in a licensee's reanalysis for a positive MTC over the 0 to 100 percent power range. However, the staff has this past year reviewed MTC trends with respect to the Anticipated Transients Without Scram (ATWS) analysis basis with the three PWR Owners' Groups. The conclusion of this review is that the MTCs used by the PWR vendors in ATWS analyses are still valid for the various classes of U.S. PWRs.
f p3 4'7 h' g d i\
8808160104 880728 i g PDR MISC [,
8808160104 PDC
Mr. P. Govaerts In the licensee #s reevaluation of FSAR transients and accidents discussed abou, limiting events (e.g., rod withdrawal from subcritical, rod ejection accident, and boron dilution event) are reanalyzed, as required, for the cold shutdown mode, the hot shutdown mode, the hot standby mode, startup mode, and low power operation. For low power levels, the positive MTC that may exist at BOL can lead to operational problems when transferring plant control from manual to automatic. Operator training may be useful in those instances where p the plant operators may not have encountered a positive MTC in previous cycle startups.
We do not believe that an arbitrary limit needs to be placed on the isothermal temperature coefficient (ITC) in order to restrict the MTC. We note that our General Design Criterion (GDC) 11 nust be met in the power operating range.
GDC 11 requires that the net effect of the prompt inherent nuclear feedback characteristics tend to compensate for a rapid reactivity insertion in the power operating range. In spite of the fact that plant technical specifications may allow a zero or slightly positive MTC at BOL, it was stated in our meetings with the PUR Owners' Groups that a plant would have a negative MTC at hot full power, AR0, equilibrium xenon conditions. The enclosed Figures 1, 2, and 3 present ITC and f1TC data for Westinghouse plants. These data were presented to the staff by the Westinghouse Owners Group at a meeting held on February 11, 1988.
In summary, all positive MTC technical specification change requests are reviewed by the NRC to ensure that the plant meets all applicable criteria with regard to plant response to FSAR transients and accidents. In addition, we have verified that flTC assumptions in the analyses supporting the ATWS rule are still valid. We will continue to monitor the MTC for operating plants to verify its acceptability.
We trust that our response answers your concerns and questions on positive MTCs.
"Wih #^
IomesM.
James it. Taylor Acting Deputy Executive Director for Operations
Enclosures:
Figures 1, 2, and 3 DISTRIBUTION Central Files Ditossburg, FD0 #3824 (12G-18) DFieno R/F (8E-23)
SRXB R/F FGillespie (12G-18) PDR JMTaylor(17G-13) FMiraglia (12G-18) EDO Reading THurley (12G-18) LShao, EDO #3824 JSniezek (12G-18) AThadani(7E-4)
TTMartin(12G-18) MWHodges (8E-23)
RJones(8E-23) DFieno (8E-23) thAYLOR 7j jgp D. florris (EDO-3824)
- SEE PREVIOUS CONCURREfiCE PAGE SRXB: DEST
- SRXD: DEST
- SRXB: DEST
- SAD: DEST
- 0: DEST
- ADT (RR D:{1RR '
J DFIENO:an RJONE5 MWHODGES ATHADANI LSHA0 TT Al'TIll t EZEK ff E 7/14/88' 7/14/08 7/14/88 7/15/88 7/18/88 7/LL/88 s 7 f(/88 / 48
,,.~
1
%i#
7 I
8 b-I-
9 1
s -
t . _
n c a =
e
_ 6 g
l D 3 P 7,_ E I
9 1
R
.. , P S. ..
C T
U e X ;
~.
- M e q E
=
I--
I- 5 8 p s ,
h::
D I
9 u u O R - E 1 t r
a o A .
R P t S
1 E
h P P C
R g U F - T e G Z ._- - -
H H I I i
n ,
L O-4 c 8 y l
F L .
,A t
4 I
O O 9C s B B . S 1 e C C
~
~
A E
W ~
T T ~
,~ M I
M ..
, C
, T e
g
~
I 3
8 k I X- 1 9
ar k
1 e
v A
0 5 0 %-
5 0 5 1 1 2 7-
^L T O N a
u o v e C e._ $ D o O e L 3 o ' e 0 rc * -
1
- ! l l
4 Average Westinghouse U.S. Plants .
1 C 0
- MTC: BOL, HFP, ARO, EqXe e
O N >
E __5_
o v
n.
- g3
/,/- Us'%,% ~~ ~""* ,.
C e
_ ____g "
,+- ,-
o ' ..,-
o , I e '
'T 5
- e O '
u I,,
e .
M 4 LOOP + AVERAGE c.
-I- 2 LOOP G 3 LOOF i E ~-
i i
i ,
56 87
$ 83 84 55 .
82 Cycle Startup FIGURE 2
e ............................g..g........................................................._
OO -
O
.O O M
e ,
I'~
. y
^
D
~
CD C e o a - +
a M
i.- -
c, , @ -
s,- - m - o an ._
c3
&) c; o -
o m
- D a w
$ ;; , ......................................s..O ..................s.........................
o-a
=
o -
e O D . <:
o '
m u. O O g 2 o -
_o o ,_r o
- m
.c: cn o, ty) rs w c N en
- g; a
o ===
e w O Ts m 3 o G
oo -
5 o l
1 0
- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . en .............
I-on co>o e co y,
-a 1 I I A o l
9 l
9 1
0 R fi I I i I
uuod) tuetotJJeoo eJnto;edu;eL (3 6e0 i i
1 l
l
((e s .. :,
p 5,
.e. citey 4
?ib jn UNITED STATES 8" 't NUCLEAR REGULATORY COMMISSIO h
I WASHINGTON, D. C. 20555 EDO Principal Correspondence Control FROM' DUE: 07/25/88 EDO CONTROL: 0003824
-DOC DT: 06/28/88 FINAL REoLY:
P. GOVAERTS TO '
JAMES M. TAYLOR FOR SIGNATURE OF: ** GRN ** CRC NO:
JAMES M. TAYLOF4 DESC: ROUTING:
'M TAYLOR REQUEST INFORMATIONADESIGN AND CONSTRUCTION OF US NUCLEAR POWER PLANTS DATE: 07/11/88 k
ASSIGNED TO: CONTACT:
'NRR MURLEY ,/ !
e SPECIAL INSTRUCTIONS OR REMARKS: f gd NRR RECEIVED: JULY 11, 1988
, ACTION: DEST SHAO?r NRR ROUTING: MURLEY/SNIEZEK MIRAGLIA MARTIN-GILLESPIE MOSSBURG ACTION DUE TO NRR DIRECTOR'S OFFICE B Y - % ,t q ,Lg p