ML18065A819
| ML18065A819 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 07/12/1996 |
| From: | Smedley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9607190098 | |
| Download: ML18065A819 (6) | |
Text
consumers Power l'OWERINli MICHIGAN'S PROGRESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 July 12, 1996 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT SHUTDOWN COOLING TECHNICAL SPECIFICATION CHANGE -ADDITIONAL INFORMATION On January 5, 1996, Consumers Power Company submitted a Technical Specification Change Request which would revise the Shutdown Cooling requirements of Specification 3.1. 9. During discussions between Consumers Power Company and the NRC, the NRC reviewer requested that we supply some additional discussion of the effects of the proposed changes.
That discussion is included as Attachment 1 to this letter.
SUMMARY
OF COMMITMENTS This letter contains no new commitments and no revisions to existing commitments.
~
Si 1t::s: s =-=~
Richard W. Smedley
~
Manager, Licensing CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Attachment
--,,.....,_ f"\\. t:'l r*~' -
9607190098 960712 PDR ADOCK 05000255 p
PDR A CMS ENERGY COMPANY (loo(
! I
ATTACHMENT CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 SHUTDOWN COOLING TECHNICAL SPECIFICATION CHANGE-ADDITIONAL INFORMATION 4 Pages
SHUTDOWN COOLING TS CHANGE REQUEST -ADDITIONAL INFORMATION A change has been proposed to Specification 3.1.9, Shutdown Cooling, of the Palisades Technical Specifications (TS). The intent of the proposed change is to allow taking credit for a filled reactor cavity as the back up means of decay heat removal in the Palisades TS, allowing maintenance to be performed on the second Shutdown Cooling (SOC) train or its support systems.
Specification 3.9.1 is comprised of three parts:
Part 3.1.9.1 provides SOC requirements when the Primary Coolant System (PCS) temperature is between 200°F and 300°F, Part 3.1.9.2 provides SOC requirements when the PCS temperature is below 200°F with the PCS loops filled, and Part 3.1.9.3 provides SOC requirements when the PCS is below 200°F but with the PCS loops not filled.
The objectives of Specification 3.1.9 are to ensure that the PCS is mixed by forced flow to avoid the potential for *development of pockets of unborated or diluted coolant, and to ensure that sufficient decay heat removal capability is available during shutdown conditions. These objectives are fulfilled by requiring, in each part of the specification:
Forced flow through the reactor core, One OPERABLE system capable of decay heat removal to be in operation, and Another OPERABLE system capable of decay heat removal to provide a back up capability.
The availability of the necessary support systems for those systems required to be OPERABLE is assured by the TS definition of "OPERABLE", which is similar to that in NUREG 1432, Standard Technical Specifications, Combustion Engineering Plants (STS). Specification 3.7.3, Shutdown Cooling Electrical Requirements, provides requirements which ensure availability of redundant electrical power~
Parts 3.9.1.1 and 3.9.1.2 allow use of the PCS loops or of a SOC train to be used as the backup means of decay heat removal. These requirements are equivalent to the requirements of STS LCOs 3.4.6, RCS Loops - MODE 4, and 3.4.7, RCS Loops -
MODE 5, Loops Filled.
Currently, Part 3.1.9.3 only allows use of a SOC train as the decay heat removal 1
SHUTDOWN COOLING TS CHANGE REQUEST -ADDITIONAL INFORMATION backup capability. That limitation prohibits removing a SOC train or its electrical power supply from service during the period when the PCS !oops are not filled. STS LCO 3.9.4, Shutdown Cooling and Coolant Circulation - High Water Level, (which is applicable in mode 6 with the reactor cavity filled) only requires one SOC train to be in operation; thereby taking credit for the filled reactor cavity as the decay heat removal backup capability.
Both the Palisades TS and the STS provide exceptions to the requirements of these LCOs, for limited periods of time, to allow performance of refueling, surveillance, or maintenance activities. The proposed changes do not affect the allowances of the existing TS exceptions.
The existing wording of Part 3.1.9.3 is:
One SDC train shall be in operation providing~ 1000 gpm flow through the reactor core, and at least two of the means of decay heat removal listed below shall be OPERABLE:
- 1.
SDC train A consisting of an OPERABLE SDC pump and an OPERABLE heat flow path to Lake Michigan.
- 2.
SDC train B consisting of an OPERABLE SDC pump and an OPERABLE heat flow path to Lake Michigan.
One change adds a third item to the acceptable means of backup decay heat removal:
- 3.
The refueling cavity with water level ~ 647'.
An additional change adds the word "required" to the allowed "Exception 2" to assure that the time limit of that exception was not interpreted as applying to the allowance for use of the filled reactor cavity as the backup decay heat removal capability, when one SOC train might be rendered inoperable. The proposed change has no effect on the allowed exceptions to the specification.
The proposed changes would not alter the requirement to have one SOC train in operation providing ~ 1000 gpm flow through the reactor core, nor the requirement to maintain a decay heat removal backup capability. They would simply allow a filled reactor cavity to be credited as the backup capability for decay heat removal, allowing the second train of SOC to be made inoperable for maintenance.
A filled reactor cavity would provide a substantial heet sink for decay heat if the operating SOC system should become unavailable. This heat sink would ensure, for a reasonable period of time, that fuel design limits would not be exceeded, and thereby 2
~.....
SHUTDOWN COOLING TS CHANGE REQUEST -ADDITIONAL INFORMATION provide time to restore a SDC system to operation, or to provide other means of decay heat removal. Heat would be transferred from the reactor core to the water in the reactor cavity by natural convection with or without the Upper Guide Structure (i.e.
upper reactor internals) installed. The Palisades Upper Guide Structure (UGS) is an open structure and does not provide any significant restriction to natural circulation flow between the reactor core and the water in the reactor cavity. The only part of the UGS which tends to block flow is the Fuel Bundle Alignment Plate. This plate is located immediately above the fuel and carries pins which position the top of each fuel assembly. The plate is 148.75 inches in diameter and is penetrated by 97 holes 9.625 inches in diameter, six holes 6 inches in diameter, and some other smaller holes. Forty five of these larger holes provide clearance for the control rods and their shrouds; the remainder provide the path for normal pumped flow leaving the core.
With the proposed change, Part 3.1.9.3 would require one Operable SDC train to be in operation providing 1000 gpm flow through the reactor core, as it does now. In addition, it would allow the SDC backup capability to be provided by either a second Operable SDC train or the reactor cavity filled to at least the 647' elevation. Currently, only the second Operable SDC train may be used as the backup capability.
The proposed change would have an effect on application of electrical power LCO 3.7.3. The objective of LCO 3.7.3 is to assure that the capability for decay heat removal is not lost due to the loss of one offsite power source or loss of one 2400 volt safety bus.
Currently, 3.7.3 requires:
With the primary coolant system at ~ 300° F, and with fuel in the reactor, the shutdown cooling train(s) shall be electrically powered as follows:
- a.
One engineered safeguards bus (1C or 10) shall be operable and capable of being supplied by offsite power and an operable diesel generator.
- b.
If two trains of shutdown cooling are required to meet specification 3.1.9, one engineered safeguards bus (1C or 10) shall be operable and supplied by offsite power while the other engineered safeguards bus (1 O or 1 C) is operable and capable of being supplied by offsite power and an operable diesel generator.
If, when only one SDC train is required, the required offsite source was lost, power 3
SHUTDOWN COOLING TS CHANGE REQUEST -ADDITIONAL INFORMATION would be available to the SOC train through the OPERABLE diesel generator. If the 2400 volt safety bus was lost, the backup means of decay heat would be available (The PCS, with loops filled, can provide decay heat removal through natural circulation). If, when two SOC trains are required, the offsite source was lost, the SOC train powered by the OPERABLE diesel generator would be available for decay heat removal.
The proposed change would.allow substitution of a filled reactor cavity for the backup train of SOC with the PCS below 200°F and the loops not filled. That allowance would change the effective electrical power source requirement from paragraph 3.7.3.b to 3.7.3.a, thereby removing the requirement for the second bus to be supplied from offsite power. The requirement for one bus to be capable of being powered from offsite power and from an operable diesel generator is unchanged.
As discussed above, the purpose of the requirement for the second bus to be operable, and to be powered from offsite power, is to assure power is available to the second SOC train. That requirement is not necessary when the filled reactor cavity is providing the backup means of decay heat removal, since the filled cavity acts as a passive heat sink and requires no electrical power to perform its decay heat removal function.
The STS electrical power requirements are similar. STS LCO 3.8.2, AC Sources -
Shutdown, requires one offsite source and one diesel generator to be operable in modes 5 and 6 (i.e. below 200°F). The requirement for electrical power to be available for the second train of SOC, under conditions where two SOC trains are required, is provided in the OPERABLE - OPERABILITY definition. (The Palisades TS definition of OPERABLE also requires necessary electrical power to be available; making the 3.7.3.b requirement for a second bus somewhat redundant.)
The Palisades TS, as modified by the proposed changes, will therefore still meet the objectives of Specifications 3.1.9 and 3.7.3 and will have requirements for SOC and for electrical power sources which are equivalent to those in STS. The proposed requirements of Specification 3.1.9 assure the ability to control PCS temperature during the period when the plant is in Cold Shutdown or Refueling Shutdown, and assures the availability of a backup capability of sufficient capacity and capability so that fuel design limits are not exceeded.
4