ML20030A462
| ML20030A462 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 02/27/1976 |
| From: | Bilby C, Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8101090568 | |
| Download: ML20030A462 (6) | |
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DOCKET 50-155, LICENSE DPR-6 6/
BIG ROCK POINT PLANT Transmitted herewith are three (3) executed and thirty-seven (37) conformed copies of a request for change to the Technical Specifications of License DPR-6, Docket 50-155, issued to Consumers Power Company on May 1,1964 for the Big Rock Pod.nt Plant.
This proposed change, when approved, will allow the time delays associated with opening of the Big Rock Point Plant enclosure sprays to be set at fifteen min-utes rather than five minutes as presently required. The fifteen-minute time delay was specified in the original Technical Specifications and evaluated as described in the FHSR.
This proposed change is a result of the extensive evaluation of Big Rock Point ECCS performance, a report of which is being submitted to Mr S. Chilk, Secretary of the Commission, by letter dated February 27, 1976.
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Ralph B. Sewell Nuclear Licensing Administration CC: Schilk, USNRC JGKeppler, USNRC i.
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CONSUMERS POWER COMPANY Docket No 50-155 Request for Change to the Technical Specil'ications License No DPR-6 For the reasons hereinafter set forth, it is requested that the Technical Specifications of License DPR-6 issued to Consumers Power Company on May 1,
.1964 for the Big Rock Point Plant be changed as follows:
I.
Changes A.
Remove the existing Caction 6.1.h(c) and replace it with the following:
"(c) Core Spray, Backup Core _ Spray, Containment Spray and Backup Contain nent Spray System Set Points The following tabulation gives the actuation set points fcr devices associated with the core spray, backup core spray, containment spray and backup containment spray systems:
b Actuation Setting and Sensor Contacts Tolerance Function Low Reactor Water 2 Switches / Valve Elevation 610'-
Actuates MO-7051 and Level (h~ Level 1 out of 2 6"
1 Inch MO-7061 in conjunction Switches)
Coincidence with reactor pressure.
Low Reactor Water 2 Switches / Valve Elevation 610'-
Actuates MO-7070 and Level (h Level 1 out of 2 6" i 1 Inch MO-7071 in conjunction
. Switches)
Coincidence with reactor pressure.
Low Reactor Pres-2 Switches / Valve 200 Psig i 20 Psi Actuates MO-7051 and sure Switches (h 1 out of 2 MO-7061 in conjunction Pressure Switches)
Coincidence with low reactor water level.
Low Reactor Pressure 2 Switches / Valve 200 Psig i 20 Psi Actuates M0-7070 and Switche 1 out of 2 M0-7071 in conjunction Coincidence with low reactor water level.
High Enclosul 2 - 1 of 2 1.5 0.2 Psig Actuates a time delay sure Switches (2 Required mechsnism that initi-Pressure Switches) ates M0-706h (contain-ment spray system) within 15 minutes un-less the control is
'I manually overridden.
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Sensor Contacts Tolerance Function
,High Enclosure Pres 1 of 2 2.0 1 0.2 Psig-Actuates a time-delay sure Switches Required mechanism that initi-ates M0-7068 (backup e
containment spray sys-tem) within 15 minutes unless MO-7064 is open or the control is man-ually overridden.
j Valve Position 1
75% - 100% of Blocks automatic actu-1 Switch MO-706h Fbil Open ation of MO-7068 when MO-706h is full open."
B.
Change Section 6.1.6 to read as follows:
"6.1.6 The automatic actuation of the containment spray system and the backup. containment spray system shall occur within 15 minutes of the receipt of a high containment pressure signal."
II.' Discussion This change is proposed to allow the operator more time to respond such that he may identify and take appropriate corrective action associated with abnormal flow
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conditions in the fire water system in a post LOCA accident situation prior to allowing additional demands to be placed on the fire system.
The contaimment performance analysis contained in Section 13 of the FHSR associ-ated with'the. maximum credible accident (MCA) for the Big Rock reactor assumes initiation of one containment spray system after 15 minutes of reaching a contain-ment internal pressure of 2 psig. It is clear from the review of Section 13 that containment sprays are not required to terminate the pressure transient associ-ated with the MCA. Section 13.4.2.2 of the FSAR states, "The calculated enclosure pressure and temperature transient curves are shown in Figure -13.1.
As indicated by these curves, operation of the Post-Incident spray system in the core spray l
. system results in containment vessel temperature and pressure subsident sooner than would be the case in the event neither operated. Both of these spray systems I
would be Lbrought into service automatically in accordance with the descriptions given.in earlier sections of this report."
The prime: advantage of utilization of the containment sprays is that they reduce
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the pressure and, therefore, reduce the leakage rate from the containment.
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On December 23, 1965 Consumers Power Company proposed a change to the Technical Specifications which would allow the use of a zirconium-clad reload fuel.
The evaluation that acccmpanied that application and subsequent rr.sponses to USAEC questions revealed that even if the core spray were assumed to not operate (Big Rock Point had only one core spray system at that time) that the heat evolved from 'he total recombination of the hydrogen evolved in the reaction associated with a core melt would not cause the containment design pressure to be exceeded prior to actuation of the containment spray 15 minutes following the accident.
Even so, at that time it was deemed desirable to provide more margin and the containment spray initiation time was changed to 5 minutes.
Since that time Consumers Power Company has modified the core spray system to provide a redundant system. In addition, the Final Acceptance Criteria limits the total metal to water reaction to extremely small values. Thus, the consider-ation of the heat evolved associated with the recombination of a large amount of hydrogen is no longer valid. Further, even if it were still valid, the 15-minute initiation time would be adequate to prevent containment pressure from being exceeded.
Flow in the fire system core spray systems and containment spray system was evalu-ated during your review and approval of our 1971 modifications to the Big Rock Point core spray system (refer to July 27, 1971 approval of Change No 26 to the Big Rock Point Technical Specifications). Flow in the fire system to the core spray and backup core spray systems has been reevaluated under a variety of similar and'different conditions during the consideration of the " Plant Life Exemption Request." Based on the reviews of this flow data we have concluded that no operator action is required to establish proper flow in the core spray systems during the early stages of a Loss of Coolant Accident. However, in light of the wide range of situations, some predictable and some unpredictable, that might occur, we believe that it would be prudent to maximize the time interval available for operator evaluation of system operation prior to the automatic initiation of a new system demand. Thus, we have proposed that the containment spray actuation time be delayed until 15 minutes following achieving 1.5 psig con-tainment pressure. This will provide more time for the operator to evaluate f
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whether the core _ spray systems have and are functioning properly prior to the initiation of _ containment spray flow. If he is concerned that flows are not proper,in the core spray systems, he can block the actuation of the containment spray. system for the period of time that is required to evaluate the flows more thoroughly and reach an appropriate conclusion and take appropriate action.
III. Conclusion Based on the foregoing, the Safety and Audit-Review Board has concluded that this change does not involve an unreviewed safety question.
CONSUMERS POWER COMPANY l
By
_M C. R. Bilby, Vice P dent Date: February 27, 1976
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Sworn and-subscribed to before me this 27th day of February 1976.
h Sylvla/B. Ball,'liotary Public Jackson County, Michigan My commission expires-May 18, 1976
u.s. NUCLE A:: r.ECULATORY COMM ON DOCKET NUMIE D ERC FrRM 195 f
50-155 12
- i NRC DISTRIBUTION FoM PART 50 DOG:(ET MATERIAL Tis:
FROM: CUhSUMGb PU'JER CUllFAliY DATE OF DOCUMENT JACKSON, MI 2 27-76 NRC DATE RECEIVED R B SEWELL 3-1-76 DLETTE R gNOTORIZ E D PROP INPUT FORM NUMBER OF COPIES RECEIVED 3 SIGt:ED/37 COPIES ORIGINAL pVNCLASSIFIED IOPY TOTAL 40 REC..
DESCRIPTION ENCLDSURE LTR NOTORIZED 2-27-76..... PROPOSED TECH REQUEST FOR C lANGE TO Tile TECil SPEC SPEC CHANGE WOULD ALLOW THE TIME DELAYS LICENSE NO DP(-6..........
TO BE SET AT 15-MIN VICE 5-MIN....
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e ILANI NAME: BIG ROCK POINT SAFETY FOR ACTION /INFORMATION ENVIRO, _, _ n,. a II ASSIGAED AD :
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