ML20212N435
| ML20212N435 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/13/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20212N414 | List: |
| References | |
| NUDOCS 8608280224 | |
| Download: ML20212N435 (8) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.82 TO FACILITY OPERATING LICENSE NO. DPR-54 SACRAMENTO MUNICIPAL UTILITY DISTRICT RANCHO SEC0 NilCLEAR GENERATING STATION DOCKET NO. 50-312
- 1. INTRODUCTION A. DESCRIPTION OF PROPOSED ACTION The proposed action would amend Appendix A of the Technical Specifications for the Rancho Seco Nuclear Generating Station (the facility) by adding limiting conditions for operation and surveillance requirements for the Low Temperature Overpressure Protection (LTOP) System.
B. BACKGROUND INFORMATION Appendix G of 10 CFR 50 sets forth fracture toughness requirements
, applicable to ferritic materials of pressure-retaining components of the reactor coolant pressure boundary. These requirements are most restrictive at lower temperatures (i.e., at cold shutdown temperatures, as opposed tc those occurring during power operation). As a result of several significant pressure transients that had previously occurred during cold shutdown conditions at' operating reactors, the NRC, by letter dated August 11, 1976, requested the Sacramento Municipal Utility District (the licensee) to evaluate the susceptibility of the facility to overpressurization events and propose interim and permanent modifications to plant systems and procedures as necessary to reduce the likelihood and consequences of such events. The licensee initially responded to this request by letter dated October 14, 1976. Subsequently, additional correspondence between the NRC and the licensee culminated in issuance of the NRC's evaluation transmitted to the licensee by letter dated June 29, 1984 (the SE). One of the findings of this SE was that certain administrative controls inccrporated in plant operating procedures to prevent low temperature overpressurization events should be required by the Technical Specifications. Another finding was that test requirements for the LTOP System should be included in i.he Technical Specifications.
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One iten unresolved by the SE was the proper pressure limit for the LTOP Systen. The licensee had proposed a setpoint of 500 psig; but at the time the SE was is_ sued, the NRC staff had insufficient basis for concluding this value met regulatory requirements. Subsequent 8608280224 860813 2 DR ADOCK 0500
, 2 discussions and correspondence between the licensee and the NRC finally supported the conclusion that 500 psig was an acceptable setpoint. This was documented in the NRC letter to the licensee dated February 25, 1985. This letter also stated that inasmuch as NRC's concerns regarding the LTOP System were resolved, the licensee should propose Technical Specifications for the system.
The present action involves evaluation of the Technical Specifications proposed by the licensee in response to this request.
The administrative controls listed in the NRC's SE were as follows:
- 1. The Rancho Seco Overpressure Protection System is to be manually enabled prior to the reactor coolant systen (RCS) temperature dropping below 350 F during plant cooldown. An alarm will sound in the Control Room if the system is not enabled or if
. the PORV isolation valve is not open when the RCS pressure drops below 500 psig.
- 2. The plant is to be operated with a steam or nitrogen blanket in the pressurizer at all times except for system hydrostatic tests. The pressurizer water level is maintained at or below the high level alarm at system pressures above 100 psig and less than the high level alarm for pressures less than or equal to 100 psig.
- 3. The makeup tank water level is to be less than the high level alarm.
4 The core flood tank discharge valves are closed and the circuit breakers for the motor operators are " racked out" oefore the RCS pressure is decreased to 600 psig.
- 5. During a plant cooldown, the Engineered Safeguard Actuation of the High Pressure Injection (HPI) System is bypassed at 1650 psig. Prior to going below 350"F, the circuit breakers for the four HPI motor operated valves are tagged open with the valves in the closed position. This is accomplished by opening and tagging the selector switch in the Control Room
.and locking and tagging the breakers located at the Motor Control Center. The operator will receive an alarm in the Control Room if the overpressure protection alam is enabled and any of the four HPI valves is in the open position. '
- 6. The HPI test procedure ensures that only one (1) HPI pump is tested at a time and that no other HPI pump is operating during the test.
II. EVALUATION Introduction. We note at the outset, the licensee's submittal' generally conforms to the administrative controls described in the NRC's SE as set ,
forth above. Certain differences are noted, however, and these are '
addressed in the following evaluation. The licensee's submittal also
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involves certain changes to some of the existing text of the Technical Specifications. These changes, however, are editorial in nature and are needed to incorporate the new requirements into en existing section of the Technical Specifications. These changes, however, are addressed. As an aid to understanding the proposed specifications, it should be noted the nomenclature used by the licensee in this submittal differs somewhat from common usage. Specifically, the pressurizer relief valve commonly referred to elsewhere as the PORV, is referred to in the licensee's submittal as the EMOV (Electromatic Operated Valve). This understanding is necessary because the PORV/EMOV is the component utilized to limit the RCS pressure during low temperature operations.
Specification 3.2.
General. This specification presently is titled and addresses the High Pressure Injection and Chemical Addition Systems. The licensee has chosen this specification as the location for inclusion of the operational requirements applicable to the LTOP Systen. Accordingly, the licensee proposes to change the title te High Pressure Injection, Chemical Addition, and Lcw Pressure Overpressure Protection (LTOP) Systems. The licensee also proposes to renumber and reformat this section by assigning Section 3.2.1 to the High Pressure Injection and Chemical Addition Systems; and Section 3.2.2 to the LTOP System. Ve conclude these are editorial changes and are acceptable.
Applicability. The licensee proposes to revise this section of the specification to add the applicability requirements for the LTOP Systen.
The licensee states the specification will apply to the LTOP System when the RCS temperature falls below 350 F and is not open to the atmosphere.
The licensee also states the specification will not apply when the reactor vessel head is removed, one or more steam generator or pressurizer manways are open or a pressurizer heater bundle is removed. We note the temperature regime over which the licensee proposes to require this system corresponds to that previously accepted by the NRC staff; therefore, this portion of the proposed specification is acceptable. We also note the LTOP System is needed to protect against overpressurization events at reduced temperatures when the RCS is closed. If the system is open to the atmosphere (with a significant opening), however, the LTOP System is ,
not needed because system pressure cannot be significantly increased. We further note the above conditions, proposed by the licensee for when the LTOP System will not be required, are such that significant openings will exist in the RCS, Accordingly, we find the specific exceptions tc applicab111ty proposed by the licensee acceptable.
Objective. The licensee proposed to revise this section to add the objective applicable to the LTOP System and to reflect the organization of Specification 3.2. We conclude these are editorial changes and are acceptable. ,
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! 4 l J-Specification 3.2.2 The licensee proposes to add this specification to address the operational j requirements applicable to the LTOP System. The acceptability of each '
j provision of this proposed specification is addressed below:
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! 3.2.2.1. This paragraph is proposed by the licensee in response to the NRC staff position stated in I.B.1, above. The licensee's proposed specification would require the LTOP System to be manually enabled before
- the RCS temperature is decreased below 350'F. This conforms to the cited NRC staff position and is therefore acceptable. As indicated below, the licensee has also provided information indicating the alarms prescribed t j by the NRC staff position have been installed. Accordingly, we conclude j the licensee has acceptably implemented the Technical Specification and j hardware provisions of this NRC staff position.
i i 3.2.2.2. This paragraph is proposed by the licensee in response to the NPC 1 staff position stated in I.B.5, above. It has not been proposed by the licensee to require bypassing Engineered Safeguard Actuation of the HPI
. System below 1650 psig because such bypassing is an operational necessity
' (otherwise HPI actuation would occur during each shutdown). Accordingly, we find the licensee's omission of this provision acceptable. Regarding 4
the other provisions of the NRC staff position, the licensee proposes to i meet these by requiring that all HPI Systems be locked out whenever the RCS temperature is below 350'F and requiring .the opening.and tagging of the i
circuit breakers serving a specified motor-operated valve in each HPI injection line with the valve in the closed position. Although not stated
- in the specification, the licensee states this will be implemented by j providing alarms for the following conditions: (1)LTOPnotenabledwhen
- RCS temperature is below 450'F; and, when LTOP is enabled, additional alarms when (2) circuit breakers for the HPI pumps are not racked out; (3) seal injection flow is greater than 42 gpm or makeup flow 1:; greater j than 135 gpm; (4) valves in HPI lines are not closed and (5) the EMOV block
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j valve is not open.
Regarding the above provisions, it is noted the facility is equippeo with three identical high pressure pumps. Two of these are designated HPI pumps '
and one is designated the Makeup pump. Any one of the three, however, can 1
- . serve either function. It is also noted that although the Engineered
- Safeguards Actuation of HPI is disabled below 1650 psig (with the.two HPI pump breakers " racked-out" and alarmed below 350 F), the Makeup pump (or one J
oftheHPIpumpsiftheMakeuppumpisinoperable)iscontinuedinoperation !
1 during plant cooldown until the RCS temperature reaches about 200*F. This is done to permit addition of coolant to compensate for coolant shrinkage during i
reactor cooldown and to permit continued reactor coolant pump seal i injection. Based on discussions with the licensee, continued seal injection i is needed to prevent imposition of significant thennal ' transients on the :
reactor coolant pump seal region (in the absence of seal injection below 4
350*F regions previously cooled by seal injection would experlence rapid 4
heating by the adjacent hot reactor coolant). Based on this mode.of-operation, the licensee has provided an alarm on the seal injection line if 3 its flow exceeds 42 gpm, and on the makeup line if its flow exceeds 135 gpm.
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Since these are substantially the same values assumed for the Safety i i
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Evaluation submitted by the . licensee, and accepted by the NRC staff, we I
conclude these alarm levels are acceptable.
Regarding the makeup flow rate alann, it is noted the licensee has committed to provide a bypass line around the main valve used to control makeup flow following completion of Operating Cycle 7. This will permit closing the main valve and using the bypass line to limit makeup flow.
The licentee states the bypass line will be designed to limit the makeup flow to 138 gpm, which is the value found acceptable by the NRC staff.
Therefore, after Cycle 7, the limit on makeup flow rate will be provided by a hardware modification instead of the present (alarmed) administrative limit.
In this proposed specification,-the licensee states the circuit breakers will be opened and tagged for the following HP1 valves which will be placed in the closed position: SFV-23809, SFV-23811, HV-23801, SFV-23812. Our review of the facility piping and instrumentation drawings indicates these velves will isolate the HPI function for this plant condition. We therefore find the licensee's selection of these valves acceptable.
-Based on the foregoing, we conclude this proposed specification is in substantial conformance with the NRC staff position stated in paragraph I.B.5, above, and is therefore acceptable. '
3.2.2.3. This proposed specification would require the makeup tank water level to be less than 86 inches when the LTOP System is required._ Inasmuch ,
as 86 inches corresponds to the setpoint of the high level alarm, this proposed specification conforms to the NRC staff position stated in I.B.3, ,
above, and is acceptable.
3.2.2.4. This proposed specification is intended to implement the NRC staff position on pressurizer level limits (paragraph I.B.2, above). We find the specific levels (in inches) proposed by the licensee correspond directly to the setpoints for the level alarms specified in the NRC staff position. Accordingly, we find this element of the proposed specification acceptable.
The licensee does not explicitly address the requirement to maintain a steam or nitrogen blanket in the pressurizer at all times except during !
hydrostatic testing - as specified by the NRC staff position. Maintenance of a steam or nitrogen blanket in the pressurizer, howevct, has been and is a fundamental characteristic of B&W reactor operation. In addition, 1 the proposed limits on pressurizer level effectively require the -
maintenance of a steam or nitrogen blanket. Therefore, we conclude explicit ~rc:;tstci.cnt of this principle of operation in the Techtlical Specifications is not required. Accordingly, we find this element of the proposed specification acceptable.
The licensee proposes one exception to the pressurizer level l'imits l
- specified by the NRC staff. This exception relates to the allowable t pressurizer level while filling and draining the RCS. For these ;
conditions, the licensee proposes to allow a level of 320 inches (the maximum indicator level at which there is still in excess of 42 inches of
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! hemispherical gas space in the pressurizer). The justification for the f I higher allowable levels durincj filling and draining is described by the i
! licensee in the basis for the proposed specification. In particular, ;
because, during filling of the RCS, coolant is pushed (by nitrogen :
pressure) from the pressurizer to portions of the RCS which are at higher i
! elevations, a high pressurizer level is needed to provide the volume of !
! water necessary to fill the RCS hot leg " candy canes". Accordingly, the .
1 licensee fills the pressurizer to the maximum indication level (320 !
l inches) for this operation. Similarly, during draining, even though a :
) low pressurizer level is initially established, opening the high point . !
- vents in the RCS and pressurizer allows the water level to equalize at j about the 320-inch pressurizer level. Following this, the balance of the draining procedure may proceed. Therefore, because a high pressurizer ,
level.(about 320 inches) is needed for both draining and filling
- operations, because these are normal operational sequences used on t numerous instances in the past without incident, and because a steam or ;
i nitrogen blanket or atmosphere is maintained in the pressurizer during ,
j these operations, we conclude the exception to the NRC staff position i proposed by the licensee for draining and filling operations is acceptable, j l e l Based on the above, we conclude the specification proposed by the licensee f to meet this NRC staff position is acceptable.
i 3.2.2.5. This proposed specification has been submitted to conform to the !
l staff position stated in paragraph I.B.4, above. Inasmuch as the licensee's !
j proposal for this item is substantially. identical to the NRC staff position, we :
, conclude the proposed specification is acceptable.
! 3.2.2.6. This proposed specification is intended to respond to the NRC staff position in paragraph I.B.6. The staff position states the HPI test procedure should ensure that only one HPI pump is tested at a time and that !
no other HPI pump is operating during the test. The specification proposed j by the licensee would extend the requirement for single pump operation !
, beyond the single activity of testing to all situations when the LTOP !
! System is required. At the same time, the licensee anticipates the
! situation where it would be necessary to switch from one pump to another !
j and specifically provides for a transition period during which one pump i is shutting down and another is starting up. The licensee justifies the i j transition period on the basis of the need to maintain seal injection for !
j the reactor coolant pumps and to maintain makeup flow during cooldown (as ,
j discussed in connection with proposed specification 3.2.2.2, above). We l agree these goals provide a reasonable basis for providing for a transition i i period. We also note that because alams are provided to indicate l
! excessive seal injection or makeup flow, there is a reasonable basis for !
l concluding it is unlikely the transition period will be abused. Based on i the foregoing, we conclude the specification proposed by the licensee ,
satisfactorily meets the intent of the NRC staff position and is, '
j therefore, acceptable, ~
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1 l Basis.
The licensee proposes to amend the Basis for Specification 3.2 by adding the Basis for the specifications applicable to the LTOP System. Our review of the proposed Basis indicates it is in substantial conformance with the NRC staff's positions stated in the SE. Accordingly, we find the proposed revised Basis acceptable. We have corrected certain typographical errors identified in this section.
Table 4.1-2, Minimum Equipment Test Frequency.
The NRC's SE transmitted by letter dated June 29, 1984, stated that testing of the LTOP System should be performed to assure operability of the systen electronics prior to each shutdown and that a test for valve operability should be conducted as specified by Section XI of the ASME Boiler and i -
Pressure Vessel Code. The licensee's proposed revision to this Table would add a portion of these test requirements by requiring functional testing of the LTOP EMOV prior to the RCS temperature being reduced belcw 350'F, with the EMOV block valve closed. Inasmuch as ASME teiting requirements are being addressed by a separate licensing action, we conclude the licensee's proposed revision conforms to the staff position regarding non-ASME LTOP i System testing and is acceptable.
Table 4.1-1, Instrument Surveillance Requirements.
The licensee proposes to revise this table to add surveillance requirements for the LTOP System. These include the functional test described above, to be performed prior to each cooldown, and calibration to be performed during each refueling outage. As noted above, we find the test requirements acceptable, and we find the proposed calibration frequency to be the same as that required for other systems important to safety. Accordingly, we conclude the proposed revisions to this table are acceptable.
III. ENVIRONMENTAL CONSIDERATION This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. We 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 Comission 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 connect 1on with the issuance of this amendment. .
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1 IV. CONCLUSION We have concluded, based on the considerations discussed above, that i
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and j (2) such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to i the common defense and security or to the health and safety of the public.
Date: August 13, 1986
, Principal Contributor:
G. Zwetzig
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