ML20076E208
| ML20076E208 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 08/09/1991 |
| From: | William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20076E211 | List: |
| References | |
| TXX-91299, NUDOCS 9108190083 | |
| Download: ML20076E208 (11) | |
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5 amm Log # TXX-91299 File # 910 (3/4.1)
Ref. # 10CFR50.90
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Z 10CFR50.92 TUELEC1RIC August 9, 1991 Wimam J. Cablu. Jr.
EarrutM Vwe Prerant i
U. S. Nuclear Regulatory Commission f
Attn:
Document Control Desk Washington. DC 20555 l
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) - UNIT 1 DOCKET NO. 50 445 LICENSE AMENDHENT RE0 VEST 91-014 INCREASE IN H0DE 5 SHUTDOWN HARGIN Gentlemen:
I Pursuant to 10CFR50.90. TV Electric hereby requests an amendment to the CPSES Unit 1 Operating License (NFP-87) by incorporating the enclosed changes into tue CPSES Unit 1 Technical Specifications.
-The proposed changes increase the required minimum SHUTDOWN HARGIN for H0DE 5 l'
operation from 1%a k/k to 1.3%a k/k. and increase the minimum boration l
requirement from a SHUTDOWN HARGIN equivalent to 1% A k/k at 2000F to a SHUTDOWN MARGIN equivalent to 1.3%A k/k at 2000F for the ACTION of the LlHITING CONDITIONS FOR OPERATION for boration systems.
The proposed changes f
result from revisions to the analysis for the Boron Dilution event to account for cycling time delays associated with the Boron Dilution Mitigation System (Flux Doubling),
Westinghdase has revised the Doron Dilution event analysis as part of the Cycle 2 reload safety evaluation to support the implementation i
of the proposed change. This change is not required to support the remaining
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CPSES Unit 1. Cycle 1 operations.
' provides a detailed description of the proposed changes, the basis for the changes, and'TU Electric's determination that the proposed changes do not involve a significant hazards consideration.
, provides the affected Technical Specification pages which have been marked up to reflect the proposed changes.
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.TXA 91299 Page 2 of 2 i
TU Electric. requests approval.of the proposed amendment by October 1,1991, with an allowable implementation period of 30 days following the date of issuance.
This will allow for orderly implementation of the changes during the refueling outage.
Administrative controls to maintain the shutdown margin at the revised value in this proposed change are being incorporated into plant operating procedures and will be in effect prior to reloading fuel into the CPSES Unit I reactor vessel for Cycle 2.
This revised shutdown margin value is conservative with respect to the current Technical Specification value and therefore can be implemented prior to approval of this change, final Safety Analysis Report (fSAR) updates will be provided through the normal amendment process in a future FSAR amendment, t
Should you have any questions in this matter please contact Jimmy Seawright at
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(214) 812-4375.
Sincerely, William J. Cahill, Jr.
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JDS/grp Attachment Enclosures c - Mr. R. D. Hartin, Region IV Resident inspectors, CPSES (2)
Mr. T. A, Bergman, NRR i
Hr. D K. Lacker Bureau of Radiation Control Texas Department of Public Health 1100 West 49th Street i
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At'tachment-to TXX 91299.
'Page 1 of 1
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.i UNITED STATES OF AMERICA N
NUfLEAR REGULATORY COMMISSION 9
-In the matter of
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. Texas Utilities Electric Company)
Docket No. 50 445
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.(Comanche Peak Steam Electric
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Station, Unit 1)-
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i AFFIDAVIT i
William J, Cahill Jr. being duly sworn, hereby deposes and says that he is Executive Vice President, Nuclear of TV Electric, that he is duly authorized
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1 to sign and file with the Nuclear Regulatory Commission this transmittal ~of i
License Amendment Request 91-014;-that he is familiar with the content
- i thereof: and that the' matters set forth therein are true and correct to the best of:his knowledge, information and belief.
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Vfl.liamJ.=Cahil1[Jr.
-i Executive Vice President, Nuclear I
STATE OF TEXAS
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xCOUNT_Y OF SONERVELL
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Subscribed and sworn to:before me, a Notary Public, on this 9th day of f
August i 1991, j
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]A Q.
l PATRICIA WILSON j'.
Notary Public r
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March 16,1993 /
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SIGNIFICANT HAZARDS CONSIDERATION
[ -to TXX-91299 Page 1 of 8
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.. to TXX-91299 Page 2 of-8 SIGNIFICANT HAZARDS CONSIDERATION PROPOSED CPSES UNIT 1 TECHNICAL SPECIFICATICE CHANGE SHUTDOWN MARGIN REQUIREMENT FOR COLD SHUTDOWN (MODE 5)
I.
BACKGROUND The-Boron Dilution Mitigation System (BDMS) is designed to detect and mitigate a boron dilution event occurring in MODES 3, 4, or 5 prior to the complete loss of the shutdown margin.
The BDMS detects a boron dilution event by monitoring the output of the source range neutron flux detectors to determine if the neutron flux has increased by a factor of two or more over a specified time period.
Upon detection of a flux-doubling, the BDMS initiates the opening of isolation valves to the Refueling Water Storage Tank (RWST) and the closure of isolation valves to the Volume Control Tank (VCT).
This change in valve alignment blocks the source of the diluted water and lines up the borated water from the RWST for injection into-the Reactor Coolant System (RCS).
These functions must be completed in sufficient time to prevent the loss of shutdown margin, i.e.,
to prevent a return to critical.
Therefore, important items to consider for the analysis are the time to flux-doubling, the time to critical, and the time differential from flux-doubling to critical.
A potential discrepancy was noted by TU Electric that pertains to the modelling of the BDMS flux-doubling detection circuitry for the safety analyses.
Specifically, the circuitry _ delay associated with averaging of the source range flux signal over a specified time period for the generation of the flux-doubling signal may not have been
Enclosure i to TXX-91299 Page 3 of 8 properly modelled.
As a result, the response of the BDMS assumed in-the-licensing-basis boron dilution event analysis presented in Final Safety Analysis Report (FSAR) Section 15.4.6 may be quicker than the actual system response.
Westinghouse orally informed TU Electric, and subsequently documented in correspondence dated March 12, 1991, that'the boron dilution issue appeared to be a valid concern.
The CPSES operations staff was immediately notified of the issue.
TU Electric, in conjunction with Westinghouse, performed a technical evaluation of the issue.
This evaluation concluded, based on the information available at the time and the documented core exposure, trat a shutdown margin of 1% Ak/k was sufficient to preclude a eturn to critical during a boron dilution event for Cycle 1.
To resolve the boron dilution issue for CPSES, Westinghouse performed an analysis, which was documented in correspondence dated August 2, 1991, of the licensing-basis boron dilution event initiated from MODES 3, 4,
and 5.
The analysis demonstrated that for Cycle 2 an increase to the Technical Specification minimum SHUTDOWN MARGIN from 1.0% Ak/k to 1.3% Ak/k when T,y s 200*F is required.
The analysis further_ demonstrated that for the entire Cycle 1 operation, using the current shutdown margin requirement of 1.0% Ak/k in conjunction with cycle specific parameters, sufficient shutdown margin is maintained to preclude a return-to critical during a boron dilution event.
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Page 4 of 8 II.. DESCRIPTION OF. TECHNICAL SPECIFICATION CHANGE REQUEST The proposed Technical Specification ch nge increases the minimum SHUTDOWN MARGIN for MODE 5 from 1.0% Ak/k to 1.3% Ak/k.
The specific Technical Specifications to be revised are 3.1.1.2 SHUTDOWN MARGIN - T, LESS THAN OR EQUAL TO 200'F, 3.1.2.2 FLOW PATHS - OPERATING, 3.1.2.4 CHARGING PUMPS - OPERATING, and 3.1.2.6 BORATED WATER SOURCES - OPERATING.
The BASES for the affected Technical Specifications are revised to reflect these changes.
A detailed discussion of those changes is provided below:
A.
Specification 3/4.1.1.2 Specification 3/4.1.1.2 is changed to increase the minimum SHUTDOWN MARGIN for MODE 5 from 1.0% Ak/k to 1.3% Ak/k.
The associated BASES are changed to identify the new requirement and to clarify _that the required SHUTDOWN MARGIN when the RCS T,, is less than or equal to 200*F is based on the. boron dilution accident.
B.
Specification 3.1.2.2 The ACTION for Specification 3.1.2.2 and its associated BASES are changed to increase the minimum boration requirement from a SHUTDOWN MARGIN equivalent to 1.0% Ak/k I
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. to TXX-91299 Page 5 of 8 at 200'F to a SHUTDOWN MARGIN equivalent to 1.3% Ak/k at 200*F.
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Specification 3.1.?.4 The ACTION for Specification 3.1.2.4 and its associated BASES are changed to increase the minimum boration requirement from a SHUTDOWN MARGIN equivalent to 1.0% Ak/k at 200*F to a SHUTDOWN MARGIN equivalent to 1.3% Ak/k Tt 200'F.
D.
Specification 3.1.2.6 The ACTION for Specification 3.1.2.6 and its associated BASES are changed to increase the minimum boration requirement from a SHUTDOWN MARGIN equivalent to 1.0% Ak/k at 200*F to a SHUTDOWN MARGIN equivalent to 1.3% Ak/k at 200*F.
III. ANALYSIS
-The basic description of the boron dilution event as provided in the CPSES FSAR (see Section 15.4.6) and the i
CPSES Safety Evaluation Report (NUREG-0797, Section 15.2.3.1) are unchanged, although the boration parameters and event times in the time sequence are different based on
'the_ proposed SHUTDOWN MARGIN and the supporting analysis.
In MODE 5,' the new minimum SHUTDOWN MARGIN, 1.3% Ak/k, precludes a return to critical during a boron dilution event.
In MODES 3 and 4, the existing minimum SHUTDOWN MARGIN, 1.G4 Ak/k, continues to preclude a return to critical.
Increasing the minimum boration requirement m--_--_ -
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. to TXX-91299 Page 6 of 8 i
i during a condition of reduced boration capability (sco ACTIONS for Specifications 3.1.2.2, 3.1.2.4, and 3.1.2.6) ensures that adoquato SHUTDOWN MARGIN for MODE 5 is established in a timoly manner.
This ensures that the MODE 5 SHUTDOWN MARGIN requiremont can be established prior to entering MODE 5 in spite of the reduced boration capability.
IV. SIGNIFICANT HASARDS CONSIDERATION DETERMINATION L
TU Electric has ovaluated the no significant hazards consideration involved with the proposed changos in accordance with tho throo standards not forth in 10CFR50.92(c) as discussed below l
Does the proposed chango (1)
Involvo a significant ircreaso in the probability or consequencas of an accident previously evaluatod?
Operation with the propocod minim;m shutdown margin requiroc.ont en17 Affects F o transient responso i
followin; an initiating event from MODE 5.
Thorofore, the probability of an initiating event is unaffected by the proposed change.
The accident analyses havt boon ovaluated and the only accident of concern is the boron dilution event in MODE 5.
This event has boon analyzod and the :pplicablo event acceptanco critoria continuo to bo st with the conclusions of the FSAR remaining
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. Enclosure 1 to TXX-91299 Page 7 of 8 i
t Therefore, the proposed Technical Specification changes
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do not involve an increase in the probability or
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consequencos of an accident previously evaluated, f
(2)
Croato the possibility of a now or different kind of accident from any accident previously ovaluated?
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The use of the increased minimum shutdown margin
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requirement for MODE 5 does not involvo any dead,n changes to the fuel, Reactor Coolant System oi
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engineered safety features.
Thus, implementation of f
the increased minimum shutdown margin requirement for MODE 5 does not result in any new or different types of accidents.
i Thorofore, the proposed Technical Specification changes l
do not create the possibility of a new or difforont kind of accident from any accident previoucle f
evaluated.
(3)
Involve a significant reduction in ca.e margin of f
safety?
As described in the FSAR, the SER, and the Technical Specification BASES for those specifications, the margin of safety is established by precluding a return to critical for a postulated boron dilution event in MODE 5.
The boron dilution event has boon analyzed using methodology approved for CPSES and the proposed i
minimum SHUTDOWN MARGIN.
The result of this analysis is that the reactor romains suberitical.
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Therefore, the proposed Technical Specification changes do not involve a reduction in the margin of safety.
j Based on the above evaluations, TU Electric concludes that l
the above described changes natisfy tho.& significant l
hazards consideration standards of 10CFR50. Site) and, f
accordingly, a no significant hazards finding is justified.
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V. ENVIRONMENTAL EVALUATION l
i TU Electric has evaluated the proposed changes and han determined that the changen do not involve (i) a significant f
hazaros consideration, (11) a significant change in the i
types or significant increase in the amounts of any offluent i
that may be.rolossed offsite, or (iii) a significant i
increase in individual or cumulative occupational radiation exposure.
Accordingly, the proposed changes moot the eligibility critorion for categorical exclusion set forth in
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10CFR51. 2 2 (c) (9).
Thorofore, pursuant to 10CFR51.22(b), an j
onvironmental assessment of the proposed change is not required.
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