ML20034A272

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Requests Interim Relief from Tech Spec 3.2.2 Re Low Temp Overpressure Protection,Based on Defueled Plant Condition. Relief Would Permit Util to Preserve RCS in Wet Condition to Ensure Overpressure Protection
ML20034A272
Person / Time
Site: Rancho Seco
Issue date: 04/12/1990
From: Keuter D
SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20034A273 List:
References
AGM-NUC-90-124, NUDOCS 9004200665
Download: ML20034A272 (14)
v • d • e


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[; gsuun SACRAMENTO MUNICIPAL UTRUTY DISTRICT D 6201 S Street, P.o. Box 15830, Sacramento CA 96862-1830,(916) 452-3211 l

AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA AGM/NUC 90-124 April 12, 1990 U. S. Nuclear Regulatory Commission Attn: Docunent Control Desk Washington.. DC 20555 Docket No. 50-312 Rancho Seco Nuclear Generating Station License No. DPR-54 INTERIM RELIEF REGARDING TECHNICAL SPECIFICATION 3.2.2:

LON TEMPERATURE OVERPRESSURE PROTECTION Attention: George Knighton Rr:ference:

SMUD Letter AGM/NUC 89-261 " Technical Specifications Applicable in the Defueled Condition" dated December 4, 1989 The District intends to formally lay up the Reactor Coolant System (RCS) by mid May 1990. Management has decided to use a wet layup method consisting of demineraliz w water with hydrazine and a nitrogen blanket (in the pressurizer).

The District previously 7.crformed an evaluation of its Technical Specifications to dete".; section by section applicability for the undefined defueled mode.

In the ;eterence, the District determined.that the Technical Specification for Low Temperature Overpressure Protection (LTOP) was not applicable when fuel was removed from the reactor vessel in conjunction with the future statut. of Rancho Seco.

I The NRC has acknowledged the future status of the facility'in recent correspondence:

1.

Rancho Seco is defueled with all fuel in the spent fuel pool building.

2.

The District does not intend to resume power operations at Rancho Seco.

3.

Design basis accidents for a nuclear facility in a defueled condition are all associated with loss of fuel pool ~ water inventory or with fuel handling.

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George Knighton AGM/NUC 90-124 Hith the Cecision to preserve the RCS in a wet condition, the District re-evaluated Technical Specification Section 3.2.2 LTOP.

Through its administrative procedure, RSAP-0908 Technicr? Specification Interpretations, the Rancho Seco Safety Review Committees reconfirmed the determination on LTOP applicability.

This interpretation and supporting material is enclosed.

However, discussions with the NRC staff indicate there may be a difference of opinion concerning LTOP applicability.

The District therefore requests a formal waiver from compliance with the specific actions stated in Technical Specification Section 3.2.2 LTOP.

The waiver will allow the District to preserve the RCS in a wet condition using methods describt: in the enclosed Engineering Report to ensure the overpressure protection of the RCS.

In that no fuel is in the Reactor Building and protection of the RCS is only an economic concern for the District, this waiver will not adversely affect the health and safety of the general public.

The District requests that this waiver be effective until NRC approval of Proposed Amendment 182 - Defueled Mode Technical Specifications.

Members of your staff with questions requiring additional information or clarification may contact Steve Crunk at (209) 333-2935, extension 4913.

Sincerely, f

Dan R. Keuter Assistant General Manager Nuclear Enclosure I

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J. B. Hartin, NRC, Halnut Creek l

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e TECHNICAL SPECIFICATIONS INTERPRETATION TSI # 90-0001-Technical Soecif1 cation Affected:

3.2.2 - Low Temperature Overpressure Protection (LTOP) Systems Interoretation:

The LTOP renuirements of Specification 3.2.2 are not applicable when the reactor is defueled.

Details:

Specification 3.2.2 does not address the applicability of LTOP requirements in a long term defueled mode. With no fuel in the reactor vessel, LTOP is not required to protect the public's health and safety.

Engineering Report ERPT M-0214 describes administrative overpressure protection methods which protect the reactor vessel and preserve the RCS for-possible future use.

BAlli:

With no fuel in the reactor vessel, the RCS is INOPERABLE and the basis for LTOP (to ensure the core remains covered with coolant in a cold, closed condition; i.e., the RCS < 350*F and not open to atmosphere) is not applicable.

This conclusion of RCS INOPERABILITY and LTOP inapplicability stems from the Tech Spec definition for OPERABLE. Tech Spec 1.3 defines OPERABLE, in part, as follows:

"A component or system is OPERABLE when it is capable of performing its intended function within the required range."

1 I

Clearly, with the reactor vessel defueled, the RCS cannot perform its intended function; i.e., provide the means to produce safe, controlled nuclear power.

With no core to protect -LTOP is irrelevant and therefore not applicable.

Furthermore, since LTOP is not required to protect the health and j

safety of the public, the requirements of Specification 3.2.2 (LTOP) are not applicable. With the' reactor defueled and RCS operation no longer needed or desired, "overpressu.e protection" of the RCS is needed only to protect the District's investment and preserve the RCS for possible future use.

Engineering Report ERPT H-0214 describes the methods for protecting the RCS from cold overpressure conditions in the dafueled mode, implements good. engineering practices, and reflects the District's reviewed and approved LTOP position documented in Memo NL 90-006.

ERPT M-0214 provides the technical basis that supports the District's LTOP position.

Approval:

AGM, Nuclear Ar e val Date: _ 4/zbo Expiration Date:

N/A Applicable PA _,,182. Rev. 1

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i SACRAMENTO MUMICIPAL UTILITY DISTRJCT uptcc usuonAmovu February 27, 1990 oare:

Jim Shetler NL 90 006 i

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Steve Crunk yN 3' FROM:

ITION ON LTOP PROTECTION FOR THE REACTOR LICENSING sum IN THE DEFUELED CDNDITION SMUD To NRC Letter AGM/NUC 89-261, dated December 4, 1989, TECHNICAL SPECIFICATIONS

Reference:

APPLICABLE IN THE DEFUELED CONDITION Licentina Position Technical Specification 3.2.2, Low Temperature Overpressure Protection (LTOP) System, is not applicable in the defueled With the reactor vessel defueled, overpressure protection of the RCS is not required to protect the health and condition.

safety of the public, i

Diseunion During power plant operations lechnical Specification 3.2.2 assures, in cold conditions, that the core will be covered with water by preserving the physical integrity of the reactor vessel, thereby r

This is protecting the health and safety of the public. accomplished b vessel from an inadvertent pressurization when the pl L

Without fuel in the the reactor and the RCS not open to atmosphere.

reactor vessel the RCS is not needed, nor is overpressure protection needed to ensure the protection of the health and-safety of the public.

A list of Technical Specifications applicable in the defueled condition was provided in the referenced letter, and Specification Administ utive controls, 3.2.2 was not considered applicable.nevernina RCS lavun that inn be inal-nted to nrovide overnressure orotection for the RC commensurate with a defueled condition.

defueled and RCS operation no longer necessary or desired, overpressure protection is needed only to protect safety of the public.

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9 ERPT M-0214/1 l

nahCER OXTM SYSTRM 1AYUP OVERPRESSURE PROTECTION I.

Introduction and History A. Why is Overpressure Protection necessary?

Overpressurization of the Reactor Coolant System (RCS) 1.

is always a significant concern.

The most Ilmiting component of the RCS is the reactor vessel and more specifically the beltline region.

This material became embrittled due to irradiation sustained during operation.

However, depending on the actual temperature, stress levels, etc., other components may be of as much concern.-

At lower temperatures the concern becomes more significant because the material loses some ductility.

Extra provisions therefore, have been taken at Rancho Seco to protect against brittle fracture when the plant is in low temperature conditions.

These provisions are callcd Low Temperature overpressure Protection (LTOP) and are governed by Technical Specification 3.2.2 and our operating procedures.

B. LTOP at Rancho seco

1. As defined by Technical Specification Bases, LTOP consists of passive and active subsystems.

The passive subsystem is based on plant design and operating philosophy to preclude the plant being in a water solid condition.

The active subsystem consists of providing a way of relieving pressure before limits are reached.

This-is provided for by having a second setpoint in the Electromatic operated Valve (EMOV) circuitry that can be selected when RCS temperature is at or below 350 degrees F.

The setpoint for the ENOV to lift is then 550 psi and it will resent at 500 pai.

Alarms that warn the operator of possible overpressure causing occurrences are also considered part of the active subsystem.

2. High energy system isolation takes place to prevent the RCS from being taken solid inadvertently.

These systems are High Pressure Injection '(HPI) and. core Flood System (CFS).

Special provisions are taken to allow filling and venting ~ of the RCS.

Since seal-injection is allowed and requires operation of one HPI or Makeup pump, the Makeup TankLlevel is limited to i

86 inches to limit the' amount of water - that could enter the RCS from that source.

Pressurizer level is also limited to allow enough-surge volume to slow a pressure increase down so operator action can be taken.

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ERPT M-0214/2 i

Review of Federal Codes

1. Review of 10 CFR 50, Appendix G and ASME Boiler and C.

Pressure Vessel Code Section III Appendix G has been completed.

The requirements for brittle fracture prevention remain in effect and must be followed unt The brittle fracture limits now imposed on j

l License.

l the RCS are to remain our limiting conditioner.

D. LTOP and RCS layupIt is the goal of the Rancho seco layup Ph.l.*an to place systems in a condition that will all's for 1.

reduced maintenance and preserve the Dbtrict's investment until license changes are authorized.

is an overpressure protection of the RCs in layup is to be addressed-in the engineering concern andSince only conclusions are documented in layup plan.

this ERPT :provides the discussion the layup plans, The which will document the basis for the layup plan.

purpose of this ERPT is to document an alternative approach to the present methods of LTOP and provide justification for an alternative approach.

The following discussion will explain the means for fill and maintenance of the RCS in a wet layup condition while also protecting the RCS (including the reactor vessel) from brittle fracture failure.

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i ERPT M-0214/3 l

II. Method of RCS Fill and lavun A. RCS layup plan is to place it in a wet

1. The Layup Plan of the RCS i

layup condition with a nitrogen ovsrpressure on the

)

keep the hot legs of the coolant loops completely wet.to l

will be revised to change the source of fill water and To get to require the Pressurizer filled solid prior to l

nitrogen addition.

B. RCS fill and vent

1. RCS fill water will' come from the Domineralized Storage Tank.

The pumps for this Reactor Coolant tank, which will provide the motive force for the fill l

The water, have approximately 150 psig shutof f head.

r low head performance pump does not present an In order to vent overpressure concern to the RCS.

j the air completely off the top of the Pressurizar and establish a

pure nitrogen environment, it is recommended that the Pressurizer be filled and vented completely during RCS fill and before adding nitrogen.

This should not increase the possibility of overpressurization since the water supply pressure is For additional well within brittle fracture limits.

protection the area'in the hot leg " candy canos" with an elevation above the Pressurizer vont will provide surge volume until nitrogen is added to adequate Overpressure create a gas space in the Pressurizar.

protection as established by operations procedures is therefore adequate for the filling of the RCS.

C. RCS layup maintenancePressurizer level and RCS pressure will be monitored 1.

The systea lineup and the wet in the control room.method will assure overpressure layup maintenanceAn operating Procedure A.1 or B.10 lineup protection.

for the RCS in wet layup will include isolations from These inputs are the HPI, possible energy inputs.

Seal Injection and Makeup (SIM), and CFS systems, as nitrogen and auxiliary pressure well as high Low Pressure Injection (LPI) will pressurizar spray.

also be isolated even though it does not pose an It will be necessary to have a overpressure threat.

section in A.1 or B.10 for maintaining the RCS in wet The procedure will require ~that pressurizer layup.

heaters be de-energized and HPI and Make UP pump power It is also-recommended that supplies be racked out.

the pressurizer leve), is maintained below 275 inches i

to create a surge volume as an extra margin of i

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I ERPT M-0214/4

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protection. Control room alarms for pressurizer level l

should also be kept functional.

2. The addition of makeup water and chemicals as well as recirculation for mixing will be provided by the DRCST It has already been pumps and RC Drain Tank Pumps.

discussed that the DRCST pumps cannot present an j

overpressur hazard.

The RC Drain Tank Pumps (p-601 A&B) cannot present a hasard either, since these pumps have a maximum discharge pressure of aprroximately 110 psi.

3. Nitrogen will be supplied by the low pressure nitrogen j

header which is normally at about 50 pai at :,ts This header is ' supplied by the Nitrogen 2

source.

sphere (converts liquid r.itrogen to gas by the use of evaporator coils) and is backed by a 50 psi reducer-from the nitrogen bottles.- The header has a 60 psi valve downstrema of the reducer.

Multiple i

relief failures including relief valve failure and reducer failure could cause high pressure nitrogen to be e

admitted to the RCS. It is therefore recommended that nitrogen be added as = needed and controlled by the layup procedure.

Nitrogen _ addition. should be accomplished by manual valve manipulation on top of the pressuriser.

The operator would then be-in easy reach of a

vent path should pressure increase l

l uncontrollably.

A local pressure gauge will indicate This pressure gauge will have a maximum RCS pressure.

(peak) indicating-needle driven by the variable pressure indicating needle.

4. Following these guidelines precludes the necessity of _

f having _ the ENOV available to the RCS as a pressure relief device and therefore the ENOV block valve can be part of the RCS layup boundary.

The SIM system When this inputs will also be isolation beundaries.

boundary is opened for recirculation of makeup water and chemical.additon, the HPI and Make Up Pumps will This be de-energized with their breakers racked out.

will eliminate the need. for Makeup Tank level All other requirements of the Technical monitoring.

Specifications as they are presently in section 3.2.2 will be satisfied by the layup procedure.

_.___ _ _..._._ _._ _._ _ ~. _, _. _ _. _..

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i ERPT M-0214/5 1

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III. cenelusion I

A. Engineering concerns

1. Since the Reactor has been
defueled, i

overpressurization of the RCS is no longer a concern to protect the health and safety of plant workers and the general public.

It is, however, a engineering concern to layup the system in the best possible l

manner to protect the system from possible occurrences It is that could damage the Districts investment.

also a engineering concern to layup associated systems for their protection.

Both of these goals can be-accomplished by laying up the RCS wet with nitrogen overpressure in the pressuriser.

By controlling the the energy input and providing a surge volume to mitigate any possure transients, the RCS will be i

provided with low temperature overpressure protection.

B. Maintaining a history of RCS pressure while in layup

1. By installing pressure indicating instrumentation that can monitor peak RCS pressure while in layup, a

history of RCS pressure will be gained that will be helpful in future analysis of the RCS condition.

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