ML19259C521
| ML19259C521 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 10/27/1977 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19259C517 | List: |
| References | |
| NUDOCS 7906230127 | |
| Download: ML19259C521 (3) | |
Text
.
n Teaco Docket No. 50-316 EDISON Serial No. 396 LOWELL E ACE October 27, 1977 7ll,,[,'l,',",'
fatti 259 *242 l
k!Ci;p[]'s Director of Nuclear Reactor Regulation
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Attention:
Mr. John F. Stol, Chief p;g / 577 b Light Water Reactors Branch No. 1 l
f Division of Project Management p *** %3gy.% [
s l'nited States Nuclear Regulatory Co==ission 4._
NQ Washington, D. C. 20555
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Dear Mr. Stol:
Our letter to you dated July 18, 1977, regarding grid stability at Davis-Besse Nuclear Power Station Unit No. I proposed some modifications to increase certain safety margins. One of the changes requires a change to the Davis-Besse Nuclear Power Station Unit No. 1 Technical Specifications. Enclosed is the requested change to Page 3/4 3-13 and associated safety evaluation.
This change is requested on an emergency basis to allow operation cf Davis-Besse Nuclear Power Station Unit No. 1 in a tanner which better assures plant operability during grid voltage degradation.
Yours very truly, M4 A
2283 332 Attach =ents:
Davis-Besse Unit No. 1 Technical Specification Page 3/4 3-13 Safety Evaluation bt c/4 EXHIBIT 7 page 1 of 3
,/
7730602.5 THE TOLECO ECISCN CCYPANY E01 SON PLAZA 300 MACISCN AVENUE TCLEDO, CHiO A3552 9
790623 0 l L7
s Safety Analysis A result of our review of " Millstone Grid Stability Syndrome" was addi-tional undervoltage relaying on the 4.16 KV essential switchgear.
Serials 179 and 226 to the NRC explained that the relays functioned on 90% vc1tage and a 10 second time delay to trip incoming 4.16 KV source breakers.
In addition a 1 second time delay was added to the diesel generator breaker closure, only if the diesel had been started and was ready to accept load.
In Serial 293 to the NRC we responded that the changes in 4.16 KV protec-tion did not adversely affect the safety analysis.
However, to increase our margin in the safety analysis we proposed slightly more conservative settings of less than 90% 4.16 KV for 9 seconds and diesel generator breaker closure delay of.5 seconds.
The reduction in trip time from 10 to 9 seconds on 4.16 KV voltage relays 27A-1 through 27A-4 and the reduction in close time from 1 to.5 seconds on the diesel generator breaker was to assure ECCS injection within 30 seconds. The table celow compares the old scheme with the new scheme.
Time After LOCA In Seconds occurrence Old New LOCA occurs 0
0 LOCA detected and diesel generator started 5
5 Systei voltage less than 90%, greater than 59%
5 5
Voltage monitoring operates to open off-site source breakers 15 14 Diesel generator at voltage and frequency 15 15 Bus voltage decay and spurious dip allowance 16.5 15 Diesel generator breaker closed 16.5 15 Hign pressure injection pump starts - second step of diesel generator sequence 21.5 20 Low pressure injection pumps starts - third step of diesel generator sequence 26.5 25 High pressure injection pump up to speed 26.5 25 Low pressure injection pump up to speed 31.5 30 bt c/6 2283 333 4
EXHIBIT 7 page 2 of 3
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N d1 SAFETY FEAIURES ACTUATI0fl SYSlEM 1riSTRUMLfilAT10tl TRIP S[TP0lflTS N
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FUtiCT10t4AL UtilT TRIP SETP0! fit ALLOWABLE VALUES C{
lilSTRUMEf4T STRitiGS a.
Containment Radiation
_ 2 x Hackground at RATED y 2 x Background at TilERMAL POWER RATED TilERMAL POWER, b.
Containment Pressure - liigh 1 18.4 psia
< 18.52 psia #
c.
Conta inment Pressure - liigh-liigh 1 38.4 psia
< 38.52 psia #
d.
RCS Pressure - Low
> 1620.75 psig
> 1615.75 psig#
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RCS Prossure - Low-Low
> 420.75 psig
> 415.75 psig#
f.
BWST Level
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> 48.3 and 2
< 56.7 in. II 0 2
SEQUEflCL LOGIC CilAfif4ELS Essential Bus Feeder Bre.1ker Trip (90%)
a.
-> 3744 volts for
> 3558 volts for 7 + 1.5 sec
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for 7 + 1.5 sec#
l b.
Diesel Generator Start, Load Shed on Essential Bus (59%)
> 2071 and < 2450 volts
> 2071 and < 2450 for 0.5 + 0.1 sec volts for 0.5 + 0.1 sec#
IriTERLOCK CilAliflELS a.
Decay lleat Isolation Valve
< 530 and > 413 psig
< 535 and > 408 psig#
l'Allwable Value for CilAtitdEL liit:CTI0tlAL TEST and CilAlillEL CAllHRAT10fi.
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