ML20236D896
| ML20236D896 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 03/17/1989 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TXX-89147, NUDOCS 8903230336 | |
| Download: ML20236D896 (4) | |
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Log # TXX-89147 File # 10010 C
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908.2-Ref. #
F 102(a)
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k U.~S. Nuclear Regulatory Commission 4
Attn: Document Control Desk Washington, D. C.
20555.
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SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
. DOCKET NOS. 50-445 AND 50-446 REQUEST FOR ADDITIONAL INFORMATION PERTAINING TO FSAR CHAPTER 8 REVIEW i-REF:
'NRC LETTER FROM CHRISTOPHER I. GRIMES T0 f.
WILLIAM J. CAHILL, JR. DATED FEBRUARY 16, 1989 Gentlemen:
{
The referenced letter requested additional information for the NRC staff's
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review of Chapter 8 of the CPSES FSAR.
Attached are TV Electric's responses l
to the questions enclosed in that letter.
Sincerely,
- l William J. Chil, Jr.
WJH/vid Attachmert 4
c - Mr. R. D. Martin, Region IV Resident Inspectors, CPSES (3)'
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. Attacliment to TXX-89147
. March 17, 1989 Page 1-of 3 TV ELECTRIC RESPONSE-TO REQUEST FOR ADDITIONAL INFORMATION 1
4 NRC Questions on'FSAR d mter 8 1
1.
During preoperational testing, voltage levels-of the ESF buses willlbe verified as the buses are loaded.- Transformer taps are set in accordance-with the plant voltage analyses to obtain optimum voltage levels from no -
J load to fully loaded conditions.
Voltage levels will be compared.with.
.l design analysis. -The: staff' requests the applicant to provide, when
]
available, a comparison of the analytically derived voltages to the test results to confirm that the. analytical techniques-and assumptions usedlcan adequately predict electrical system voltages for expected supply voltage j
and system loading conditions.
Please provide a schedule for submitting this comparison.
1 2.
The second level of undervoltage protection at the 6.9kV-(set at 87.7% of.
l nominal) and.480Vac (set at-91.6% of nominal) safeguard buses start timers I
that will open the 6.9kV bus preferred source-breaker af ter 8 seconds if a -
safety. injection actuation is present.
The applicant must verify that the timing of ESF loads sequenced onto the safeguard buses is consistent with i
the Comanche Peak DBA.FSAR Chapter 15 analyses and is'not affected by the 8-second time delay.
If this can be acceptably shown, the staff will require that 8 seconds be used as the upper allowable limit for the periodic testing and calibration of the timers.
j TV Electric Response 1.
Based on the current preoperational testing schedule, a comparison of the analytically ' derived. voltages to the preoperational test results will be submitted by August 31, 1989.
2.
In accordance with the guidance of Branch Technical Position PSB-1, Position B.1.b)1), the TV Electric design provides a time delay for the second level of undervoltage protection "of a duration that established
[ sic] the existence of a sustained. degraded voltage condition (i.e.,
l something longer than a motor starting. transient)." For CPSES, this duration has been established as a design-time delay setting of 8 l
seconds with a maximum required response time of 10 seconds.
The 8 second value appears in the CPSES FSAR under start timers 27-3Y (for TEAT tripping preferred source breaker) and 27-3Y1 (for providing control room 1EA1 alarm) in Table 040.109-1 and.in Figure 040.109-1.
The maximum res time value appears in the CPSES Technical Requirements Manual (TRM)ponse in Table 1.2.1, functional unit 13, under "6.9kV and 480V Degraded Voltage with Safety Injection" (Refer to TV Electric letter logged TXX-89038 of January 24, 1989, attachment page 13 of 76).-
Start timer 27-3Y1, complies with the guidance of BTP PSB-1, Position TEAL 1
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Attachment to TXX-89147 March 17, 1989 Page 2 of 3 1
B.1.b)1), second sentence, that "following this delay, an alarm in the l
control room should alert the operator to the degraded condition".
Start timer 27-3Y, complies with the guidance of BTP PSB-1, Position IEAT B.1.b)1), third sentence, that "the subsequent [ editors emphasis]
occurrence of a safety injection actuation signal (SIAS) should l
immediately separate the Class 1E distribution system from the offsite power system".
Following the establishment of a sustained degraded l
voltage condition, which is established at CPSES by timer 27-3Y, an SIAS leal I
will immediately trip the preferred power source breaker (1EAl-1).
If a second level undervoltage condition also exists on the alternate offsite l
power source, the supply breaker for the alternate offsite power source 1
(1EAl-2) is tripped following a nominal 2 second delay (start timer 27-3Z).
This time delay allows the alternate offsite power source to 1EA1 energize the bus and prevents breaker cycling.
The device numbers referred to are for train A.
Train B is similar.
The CPSES Chapter 15 analyses are consistent with the time delays l
discussed above because the CPSES design basis does not consider a sustained degraded grid voltage condition coincident with a design basis
- accident, if a sustained degraded grid voltage is prasent (i.e., 27-3Y1 has timed j
1EA1 out) when an SIAS occurs, as suggested by the Branch Technical Position, the preferred power source will be separated from the Class 1E distribution system immediately.
If a second level undervoltage condition exists on the alternate offsite power source, the alternate offsite power l
source will be separated in a nominal two seconds.
Since the CPSES Chapter 15 analyses assume 12 seconds after an SIAS for the diesel generator to start and be ready to load, the existence of a sustained degraded grid voltage when SIAS occurs will not affect the CPSES Chapter 15 analyses.
j A coincident occurrence of a second level undervoltage condition, which
-l has not been present long enough to establish a sustained degraded voltage condition, and an SIAS is not considered a credible event, was not i
considered in the analysis of CPSES, and was clearly not suggested as a design criteria in the guidance provided by BIP PSB-1.
Although such an incredible scenario would probably not impact the CPSES Chapter 15 l
analyses, this event has not been analyzed.
l The time delay for the " sustained undervoltage condition" should not be j
limited to 8 seconc'.
The BTP PSB-1 guidance allows "something longer than a motor starting transient".
The CPSES design allows this time delay to be nominally 8 seconds, not to exceed 10 seconds.
These time delays are appropriate and should not be reduced.
Reduction of the time delay can potentially result in spuriously tripping the preferred power source breaker.
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1 i
b
ttachment to TXX-89147 March 17, 1989
' Page 3 of 3 i
Please note the fact that TU Electric has not in the past and does not now j
commit to compliance with Branch Technical Position PSB-1.
It has only i
been referenced for purposes of the discussion that the existing CPSES j
design complies with the guidance of BTP PSB-1.
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