ML17328A410
| ML17328A410 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 08/22/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17328A409 | List: |
| References | |
| NUDOCS 9008310107 | |
| Download: ML17328A410 (7) | |
Text
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n +**~4 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
TO FACILITY OPERATING LICENSE NO.
DPR"58 INDIANA MICHIGAN POWER COMPANY DONALD C ~
COOK NUCLEAR PLANT UNIT NO.
1 DOCKET NO. 50-315
1.0 INTRODUCTION
By letters dated January 31, and May 14, 1990 (Refs.
1 and 2), respectively, Indiana Michigan Power
- Company, the licensee for operation of Donald C.
Cook Nuclear Plant, proposed changes to Technical Specifications (TS) of D.
C.
Cook Units 1 and 2 regarding the main steam isolation response times.
Specifically, the licensee proposed to (1) change Surveillance Requirement 4.7. 1.5. 1 by increasing the full closure time, upon any closure actuation signal, of each steam generator stop valve from 5 to 8 seconds; and (2) change TS Table 3.3-5, "Engineered Safety Features'esponse Times," by increasing by 3 seconds the response times of the steam line isolation upon reaching the set points of High Steam Flow Coincident With Low-Low T (average reactor coolant temperature),
High Steam Flow Coincident NPh Low Steam line Pressure, and High-High Containment Pressure, respectively.
In addition, the licensee in its May 14, 1990, submittal also proposed several editorial changes to Unit 2 TS Table 3.3-5.
These editorial changes use the words "less than or equal to" to replace the symbol "~," and have no consequences.
The staff evaluation of the proposed TS changes regarding the steam generator stop valve closure time and steam line isolation response times follows.
2.0 EVALUATION In support of the proposed TS changes,'the licensee has performed an evaluation of the limiting accident scenarios which rely upon closure of the steam generator stop valves, or main steam isolation valve (MSIV), in the safety analyses to ensure that the licensing basis accident analyses remain acceptable with the 3 seconds increase in the MSIV closure time and the steam line isolation response times.
These accidents are evaluated in the following sections.
2.1 Main Steam Line Break Core Res onse Limitin Case The analyses of main steam line break (MSLB) core response for D.
C.
Cook Units 1 and 2 were performed with an assumption of a steam line isolation delay time
'f 11 seconds.
The Unit 2 MSLB analysis was documented in Appendix B to a February 6, 1990, submittal (Ref. 3) in support of Cycle 8 reload with a transition from the ANF fuel to Westinghouse 17xl7 Vantage-5 fuel.
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NSLB was previously analyzed and documented in Section 3.3.4.13 of MCAP-11902 (Ref. 4) in support of reduced temperature and pressure operation.
The limiting NSLB case was found to be the double-ended rupture located upstream of the flow restrictor with off-site power available.
The results of the analysis showed that the minimum departure from nucleate boi ling ratio (DNBR) remained above the minimum DHBR limit of 1.45 for the W-3 critical heat flux correlation at pressure below 1000 psia and, therefore, no fuel failure was calculated.
WCAP-11902 states that the NSLB analysis for Unit 1 assumed the NSIVs to close in less than 7 seconds from receipt of actuation signal, which is 2 seconds longer than the current TS value of 5 seconds but is shorter than the proposed TS value of 8 seconds.
However, Supplement I to MCAP-11902 (Ref. 5), which was submitted in support of a rerating program with reduced temperature and pres-sure operation, amended the statement and indicated that the NSLB analysis did not specifically model the NSIV closure time.
- Rather, the analysis modelled only the total delay time for steam isolation by assuming ll seconds delay from the time the High Steam Flow Coincident With Low Steam Pressure set point is reached until the time the NSIVs are fully closed.
Of the 11 second total
- delay, 8 seconds is allocated for the closure time of the NSIVs and 3 seconds will account for signal processing and electronic delay.
This is consistent with current TS where the total delay time for the set point of High Steam Flow Coincident With Low Steam Pressure is 8 seconds, vrith a stop valve closure time of 5 seconds and a
3 second signal processing and electronic delay. Therefore, this total delay time of 11 seconds used in the analysis supports the relax-ation of the NSIV closure time from 5 to 8 seconds.
2.2 S
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R Section S-3.3.4.1 of Supplement 1 of WCAP-11902 provided a
new analysis of the mass and energy release for a steam line break inside containment for both Units l and 2.
The resulting mass and energy releases were used as input to perform containment integrity aralysis documented in Section S-3.4.2.1.
The analysis assured a steam line isolation within ll seconds after the set point is reached for either High-High Steam Flow with Low Steam Pressure or High-High Containment Pressure.
THe limiting scenarios were a break size of 4.6 ft'ccurring at 102$
power with a main steam isolation failure for the double ended rupture and a
break size of 0.86 ft'ccurring at 102K power with an auxiliary feedwater run out protection failure for split rupture.
The resulting mass and energy release and the corresponding peak containment temperature and pressure are bounded by those in the FSAR which was analyzed with conservatively higher reactor coolant temperature ard secondary pressure.
Therefore, the containment integrity remains acceptable with an increase of steam line isolation to 11 seconds.
h'ith regard to the effects of the increased steam isolation response times on equipment qualification, the licensee indicated that hestinghouse had reanalyzed the mass and energy release for the limiting cases of NSLB outside containment with the increased 3 seconds delay in the steam line isolation, and that the
licensee had evaluated the effects of these mass and energy release rate changes on the main steam enclosure temperature.
They found that the effects were minimal and remained bounded by existing thermal limits, and concluded that the instruments remained qualified.
In the Chapter 15 USAR steam generator tube rupture (SGTR) analysis for D. C.
Cook Units 1 and 2, the primary to secondary break flow was assumed to be terminated at 30 minutes after accident initiation.
The operator actions to terminate the break flow and isolate the ruptured steam generator were not explicitly modelled in the analysis.
Therefore, there is no impact of an increase of the HSIV closure time to the analysis of the SGTR accident.
2.4 Loss-of-Coolant Accidents )LOCA)
In the licensing basis LOCA analysis, the main steam isolation was assumed to occur iwoediately after the reactor trip on low pressurizer pressure.
This instantaneous steam isolation assumption results in a stored energy in the secondary side which would be conservatively greater than what would exist if the main steam isolation time delay was considered.
For a small break
- LOCA, the higher energy in the secondary coolant will reduce the heat transfer from the primary to the secondary
- side, maximize the steam produced in the reactor coolant system (RCS),
arid minimize the transient water level in the core.
This will result in a more conservative calculation with respect to the core un-covery following a small break LOCA.
For a large break LOCA analysis, the higher stored energy iri the secondary coolant will increase the amount of thermal energy to be transferred into the RCS and incr ease the potential for steam binding to occur in the steam generator tubes during blowdown phase of the transient.
This will prolong the time of blowdown and result in higher peak cladding temperature.
Therefore, an increase in the HiSIV closure time and steam isolation time by 3 seconds does not have an adverse effect on LOCA aria lyses.
2.5 Hain Feedline Break The licensee has performed a main feedline break (MFLB) analysis for Unit 2 to support the proposed transition to the Westinghouse 17x17 Vantage-5 fuel assembly assuming an steam isolation time which included an additional 3
seconds delay of main steam isolation.
The results of the analysis demonstrate that the acceptance criteria for the event are met.
Though no reevaluation of the HiFLB was performed for Unit I, this is acceptable because an increase in the steam isolation time delay will not have an adverse impact on the HFLB result.
Following a HFLB, the reactor coolant system wi 11 initially undergo a
cooldcwn due to expulsion of secondary water through the broken feedline.
The RCS temperature transient will quickly turn around following the isolation of the main steam lines.
An increase in the HSIV closure time will result in additional heat removal from RCS.
- Hence, the RCS will stabilize at a slightly lower temperature than in the licensing basis HFLB analysis.
Thus, the results of a HFLB analysis with increased HSIV closure time are less severe than the results of the licensing basis HFLB analysis.
The staff has reviewed the limiting accident scenarios which rely upon the HSIV closure for mitigation of consequence.
An increase of NSIV closure time has no adverse effect on the consequences of accident scenarios such as LOCA and HFLB.
An increase of MSIV closure time has no effect on a
SGTR accident because the isolation of ruptured steam generator tubes was not modelled in the analysis.
The NSLB core response, and mass and energy release were analyzed with assumption of a steam line isolation response time of 11 seconds upon reaching the set point of high steam flow coincident with low steam pressure.
The results of HSLB analysis remain acceptable and justify the proposed TS change to increase the response time.
In the total response time of 11 seconds, 8 seconds is being allocated for HSIV stroke time for closing, and 3 seconds is for signal processing and electronic delay.
Therefore, the analyses with an 11 second steam isolation delay support the proposed changes to increase the hSIV closure time from 5 to 8 seconds, arid changes of TS Table 3.3-5 to increase the response times from 8 and 7 seconds to ll and IO seconds, respectively, for the High Steam Flow Coincident With Low Steam Pressure and High Containment Pressure set points.
The licensee also proposed to increase the steam line isolation response time upon High Steam Flow Coincident With Low-Low T from 10 to 13 seconds.
This is acceptable since it was considered as a b38up signal and was not modelled in the licersing basis safety analysis.
We have reviewed the licensee's
- analysis, methodology and underlying calculations and find them acceptable.
Therefore, the staff concludes that the licensee's proposed changes to the Units 1 and 2 TS Surveillance Requirement 4.7.1.5.1 and Table 3.3-5 regarding the NSIV closure time and steam isolation delay times are acceptable.
3.0 ENVIRONttENTAL CONSIDERATION This amendment involves a change in a requirement with respect to the installation or use of a facility component located within the restricted area as defi~ed in 10 CFR Part 20 and a change in a surveillance requirement.
Me have determined that the amendment involves no significant increase in the
- amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding.
Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
- 4. 0 CONCLUSION We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of,the public wi 11 not be endangered by operation in the proposed
- manner, (2) such activities will be conducted in compliance with the Commiission's regulations, and (3) the issuance of the amendments wi 11 not be inimical to the common defense and security or to the health and safety of the public.
5.0 REFERENCES
1.
Letter from Vi. P. Alexich ( Indiana Michigan Power) to USHRC, "Donald C.
Cook Nuclear Plant Unit 1, Docket No. 50-315, License Ho. DPR-58, Expedited Technical Specification Change
- Request, Steam Generator Stop Valves," AEP:NRC:1120, January 31, 1990.
2.
Letter from M. P. Alexich (Indiana Michigan Power) to USNRC, "Donald C.
Cook Nuclear Plant Unit 2, Docket No. 50-316, License No. DPR-74, Technical Specification Change
- Request, Steam Generator Stop Valves,"
AEP:NRC:1123, May 14, 1990.
3.
4.
Letter from M. P. Alexich (Indiana Michigan Power) to USNRC, "Donald C.
Cook Nuclear Plant Units 1 and 2, Docket Nos. 50-315 and 50-316, License Hos.
2 Cycle 8 Reload Licensing, Proposed Technical Specifications for Unit 2 Cycle 8, and Related Unit 1 Proposals,"
AEP:NRC:1071E, February 6, 1990.
VCAP-11902, "Reduced Temperature and Pressure Operation for Donald C.
Cook Unit 1 Licensing Report," October 1988.
5.
HCAP-11902, Supplement 1, "Rerated Power and Revised Temperature and Pressure Operation for Donald C.
Cook Nuclear Plant Units 1
5 2 Licensing Report," September 1989.
August 22, 1990 Principal Contributor:
Y. Hsii, HRR/SRNB
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