ML20116E718
| ML20116E718 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 08/28/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20116D885 | List:
|
| References | |
| FOIA-96-237 NUDOCS 9608060099 | |
| Download: ML20116E718 (7) | |
Text
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done UNITED STATES i
NUCLEAR REGULATORY COMMISSION n
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i WASHINGTON, D. C. 20556 i
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ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO TECHNICAL SPECIFICATION CHANGES FOR LOW TDFERATURE OVERPRESSURE PROTECTION BALTIMDRE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT 1 DOCKET NO. 50-317 l
1.0 INTRODUCTION
By letter dated August 13, 1990, the Baltimore Gas and Electric Company (the l
licensee) proposed to amend the Technical Specifications (TS) of the Calvert Cliffs Nuclear Power Plant, Unit 1.
In its submittal, the licensee provided l
l TS changes to support Appendix G heatup and cocidown Pressure-Temperature (P/T) curves applicable to the Unit I reactor vessel for a period up to 12 l
effective full power years (EFPY). The changes include revised heatup and cooldown rates, a change in the Power Operated Relief Yalve (PORV) pressure i
setpoint for Low Temperature Overpressure Protection (LTOP), a modification to Reactor Coolant Pump (RCP) controls when in LTOP conditions, and changes to the bases for the affected Limiting Conditions for Operation (LCOs) to justify the changes. The staff evaluation included a review of the Calvert Cliffs Unit 1 (CC1) LTOP system description provided as Attachment 2 to the licensee's letter dated August 13., 1990.
2.0 BACKGROUND
The most recent staff review of the CC1 Appendix G heatup and cooldown curves j
was in connection with a review of the Low Temperature Overpressure Protection l
System Description provided in Attachment 4 to an Emergency License Amendment j
Request transmitted t licensee letter dated July 18, 1990. This prior review j
was performed to allos, a continuation of the CCI outage while analyses were completed for long tenn reactor coolant pump (RCP) start controls. In License 4
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2 Amendment No. 145 dated July 24, 1990, the staff granted temporary, approval effective for a short term outage prior ~to the plant entering operational Mode 2 (Startup).
As stated in Amendment No.145, in its evaluation of the P/T limits and supporting changes for the temporary TS request, the staff used the following NRC regulations and guidance: Appendices 6 and H to 10 CFR Part 50; the American Society of Testing Materials (ASTM) Standards and the American i
Society of Mechanical Engineers (ASME) Code, which are referenced in Appendix G and H; 10 CFR Part 50.36(c)(2); RG 1.99, Rev. 2; Standard Review Plan (SRP)
Sections 5.2.2 and 5.3.2; and Generic Letter 88-11. These regulations also apply to the current amendment request and conclusions drawn in Amendment No.
l 145 relative to approved analytical methods remain applicable.
The long term approval of LTOP TS changes for CC1 requires that all analyses be perforined for higher decay heat loads that exist shortly after a reactor shutdown. The RCP start controls implemented in Amendment No. 145 only apply l
to plant conditions prior to entering Mode 2 when decay heat loads are low.
The licensee has completed the required analyses and has proposed new RCP start controls, in conjunction with revised pressure-temperature limits and an increased PORY setpoint, to prvvent challenges to the PORY for energy addition transients that may occur if the RCPs are started in response to a loss of decay heat removal when decay heat loads are high and letdown is isolated.
Only the energy addition transient analysis is affected by the assumed higher decay heat load. The mass addition transient analyses are not affected by the new assumption; thus the mass addition controls are not changed from those approved in Amendment No.145. Thc:c controls were a modifkation to High Pressure Safety Injection (HPSI) pump controls when in LTOP conditions.
l The LTOP enable temperature (MPT enable) was originally developed using the 9uidance found in NRC SRP Section 5.2.2, Revision 2.
The value of 327'F for the enable temperature was approved in License Amendment No.145. The enable i
temperature is not affected by the change in decay heat level assumed in the i
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3 cnergy addition transient analysis. Therefore, no change in the previously i
approved enable temperature is required.
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3.0 EVALUATION 4
New 12 EFPY P/T heatup and cooldown curves have been developed to replace the existing 12 EFPY heatup and cooldown curves-in the CCI TS approved on a temporary basis in Amendment No.145. To acconnodate the more restrictive pressure-temperature _ limits resulting from consideration of Regulatory Guide 1.99, Revision 2, a new LTOP pressure setpoint, and new heatup and cooldown rates are proposed. The revised LTOP setpoint and the heatup and cooldown rates were chosen to: (1) ensure that given a limiting mass or energy input i
to the reactor coolant system (RCS) during normal operations, anticipated operational occurrences and system hydrostatic testing, the Appendix G pressure-temperature limits are not challenged, and (2) ensure that operational flexibility is maintained. In order to accomplish this, the LTOP enable pressure setpoint will be lowered, and in general heatup and cooldown will be l
slowed, i.e., the rates reduced, for specified RCS temperature ranges. Some changes to RCP start criteria are required to reflect plant conditions which must be satisfied to avoid challenging the PORV.
The PORV pressure setpoint is commonly set by two design criteria. These are 1
the limiting transients for mass addition and energy addition. Only the limiting energy addition transient is affected by this Amendment request. The limiting energy addition transient is the startup of a reactor coolant pump while steam generator secondary temperature is greater than the primary coolant temperature. This transient was reanalyzed for CC1 assuming a decay heat level applicable to operation to Mode 2 and above. A reactor coolant pump startup 'in one loop with a steam generator primary to secondary temperature difference equal to 30*F and a bubble in the pressurizer was modeled by the licensee using the RETRAN computer code and calculated results demonstrated that the peak pressure would be less than the PORY lift setpoint.
Current Calvert Cliffs TS specify conditions under which a reactor coolant pump may not be started, which include conditions corresponding to LTOP. To be
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within the limiting condition, the pressurizer indicated water levgl is administratively controlled to maintain'an adequate steam bubble for mitigating the energy addition transient and the startup of a RCP is restricted to when the secondary temperature of each steam generator is less than or equal to 30*F above the RCS temperature. Revisions to numerical values in the applicable
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Technical Specifications have been proposed to be consistent with the assumptions in the reanalysis of the coolant pump startup transient.
For a RCS temperature at or below 327'F, the anticipated low temperature l
overpressurization transients may be adequately mitigated by the automatic action of the pressurizer PORVs or by allowing sufficient time for operator response. Based on the results of the reanalysis of the energy addition
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transient, the licensee proposed TS PORY setpoint is less than or equal to 430 psia. The licensee proposed PORV setpoint in proposed TS 3.4.9.3 the heatup and cooldown rates identified by proposed TS 3.4.9.1 and the associated bases section reflect the above discussed LTOP considerations. The staff finds that they are based on approved Regulatory guidance, are reasonably conserva-l
- tive and are acceptable.
l The licensee provided its updated pressure-temperature curves in proposed j
Technical Specification Figure 3.4-2a (for heatup) and Figure 3.4-2b (for l
csoldown). The necessary adjustments of LTOP controls are as follows:
I Technical Specification 3.4.9.1, " Reactor Coolant System Pressure /
Temperature Limits," provide LCOs for acceptable heatup and cooldown rates based on an average RCS temperature limit (T,yg). The maximum heatup rate in LC0 3.4.9.1.a has been lowered from 60*F in any one hour period to a proposed rate of 40*F per hour with T,,, in the range 70*F to 313*F and 10*F per hour with T,yg in the range 314*F to 327*F. The cooldown rate in LC0 3.4.9.1.b is lowered from 20*F per hour to 10*F per hour when RCS temperature is below 170*F. These changes are necessary as a result of i
the new P/T limit curves for 12 EFPY and the supporting Appendix G f
analysis. They are acceptable based on the use of approved NRC guidance in the Regulatory Guide 1.99, Revision 2 methodology.
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l Technical Specification 3.4.9.3, " Overpressure Protection Systems "
identifies the overpressure protection requirements to be met.to ens 0re that Appendix G limits are maintained. The LCO is revised to identify the proposed PORY lift point setting of 430 psia. Editorial changes are j
proposed for references to the MPT enable temperature to change the j
wording from "below 327'F" to "327'F or less." These changes occur at i
various affected pages within the TS as identified in the August 13, 1990 submittal. The staff has confirmed that the changes serve to clarify the 1
reference and are acceptable.
Technical Specification 3.4.1.3, " Coolant Loops and Coolant Recirculation
- Shutdown," concerns reactor coolant pump contruls. To accomodate the LTOP conditions for Modes 4 and 5, a footnote "***" appended to the 5
Applicability of the LCO is revised to require that a reactor coolant pump not be started when a RCS cold leg temperature is less than or equal to 327'F unless (1) the pressurizer indicated water level is less than 170 inches, (2) the secondary water temperature of each steam generator is less than or equal to 30*F above the RCS temperature, and (3) pressurizer pressure is less than or equal to 290 psia. These changes reflect the analysis assumptions for the limiting energy addition transient discussed above and are acceptable. A reference to a plant computer or equivalent precision instrument to measure pressure is being deleted since it applied only to the temporary approval granted for the period prior to entering Mode 2.
In a related change, a footnote "**" is adoed to the Applicability of TS 3.4.1.2 to provide RCP start controls consistent with those in TS 3.4.1.3.
The proposed changes as identified in the licensee's amendment request are acceptable based on the supporting analysis and staff review discussed above.
3.0 CONCLUSION
Based on the staff evaluation in Section 2.0 above, the staff concludes that the licensee proposed changes to Technical Specification LCOs 3.4.9.1.a.
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,6 3.4.9.1.b 3.4.9.3.a.1, and 3.4.1.3 are, acceptable to support the Appendix G l
Pressure-Temperature limits applicable for a period up to 12 EFPY.,
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will l
not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations, and issuance l
of this amendment will not be iniciical to the common defense and security or to the health and safety of the public.
l Contributor:
M. A. McCoy i
ENCLOSURE 2 SYSTEMATIC ASSESSMENT OF LICENSEE PERFORMANCE l
FACILITY NAME Calvert Cliffs Unit 1
SUMMARY
OF REVIEW The licensee provided Technical Specification modifications to provide long term controls for low temperature overpressure protection at the Calvert Cliffs Unit 1.
Staff review required confirmation of the acceptability of an j
additional analysis for reactor coolant pump (RCP) start in operational Mode 2 and above.
NARRATIVE DISCUSSION OF LICENSEE PERFORMANCE - SAFETY ASSESSMENT /00ALITY YERIFICATION The licensee proposed an acceptable submittal to identify the necessary TS changes to allow long term LTOP controls for the facility. No additional information was required to complete the review.
I AUTHOR:
M. McCoy DATE:
8/23/90