ML19317G081

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AO-75-08:error Found in Positive Imbalance Portion of Trip Envelope in Reactor Protection Sys Flux/Imbalance/Flow Limiting Safety Sys Settings.Caused by Misreading.B&W Provided Util W/Corrected Info.Proposed Figure 2.3-2 Encl
ML19317G081
Person / Time
Site: Rancho Seco
Issue date: 05/30/1975
From: Davis E
SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:
Shared Package
ML19317G075 List:
References
NUDOCS 8002210773
Download: ML19317G081 (5)
v • d • e


Text

__ -

pj'iSMUD D

\\j SACRAMENTO MUNICIPAL UTILITY DISTRICT C 1708 59th Street Box 15830. Sacramento California 95813;(916) 452 3211 O

May 30, 1975 Mr. Angelo Giambusso Director for Reactor Licensing Division of Reactor Licensing Nuclear Regulatory Commission Washington, D. C. 20545 Re: Abnormal Occurrence Report No. 75-8 Submitted May 7,1975 to Mr. Angelo Giambusso

Dear Mr. Giambusso:

In accordance with 10 CFR 50.59, the Sacramento Municipal Utility

['

District hereby proposes to amend its Operating License DPR-54 for Rancho Seco Nuclear Generating Station, Unit No. 1, by submitting forty (40) copics of Proposed Amendment No. 34.

The Proposed Amendment No. 34 contains a change to the Rancho Seco Unit No. 1 Technical pecifications concerning Figure 2.3-2 " Protective 3

Q System Maximum Allowable Setpoints".

As discussed in the referenced document, during a review of the Rancho Seco RPS flux / imbalance / flow limiting safety system settings, defined in Technical Specification 2.3, an error was found in the pos-Itive imbalance portion of the trip envelope (see Figure 1). The ca l--

culations were being reviewed to determine consistent setpoints for a RPS-Il module to be placed in service at the Rancho Seco site.

The error was a misreading of one point of the offset versus power limits during the conversion of the core axial offset to core axial im-

,i balance. As can be seen in Figure 1, the corrected imbalance limits (with the appropriate instrumentation and calibration errors included) fall inside the positive imbalance limiting safety system setting currently defined in the Rancho Seco Technical Specifications.

The horizontal portion of the flux / Imbalance / flow envelope represents the flux to flow ratio which protects the unit against violating the DNB criteria for loss of flow accidents.

The sloped portions of the envelope

~

j represent reductions in the allowable flux to flow ratio for core axial i

imbalance. This portion of the envelope protects the unit against steady state imbalance conditions which could result in central fuel melting.

J / ~2r RAT' }

Figure I shows the flux / imbalance / flow envelope c,urrently in the p

Rancho Seco Technical Specifications, with the corrected positive imbalance (j

T versus power limits.

Figure 2 shows the interim flux / imbalance / flow trip settings used as reported in A0-75-8 until the revised envelope could be s

defined. Also shown in Figure 2 is the Operational Power Imbalance Enve-cm sur mm 80()2 210 /73 am Ah ELECTRIC SYSTEM SERvlNG MORE THAN 600.000

'N THE HEART GF CAllFORNIA"

[m i

Angelo Giambusso May 30, 1975.

1 lope from Figure 3.5.2-2 of the Rancho Seco Technical foecifications.

Figure 2.3-2 shows the recommended revision to the Rancho Seco flux /

imbalance / flow limiting safety system settings.

The specific parameters associated with this Figure are: B g = -40.0, B2 3

= -17.1, B = +7.74, B4 = +25.0, My = +0.906 and M2 = -2.03 As can be seen by comparison of the three figures described above, the interim flux / imbalance / flow envelope represents the most restrictive RPS settings and is presently in effect for Rancho Seco. The Operational Power imbalance Envelope shown on Figure 2 lies entirely within the inter-im RPS settings. The Operational Power imbalance Envelope has not been exceeded by positive imbalance during normal operation at Rancho Seco as was stated in detail in A0-75-8.

B&W Informed SMUD of the error in the Rancho Seco Technical Spect-fication limiting safety system settings immediately upon the determi-nation that an error did exist. A very conservative interim positive d

imbalance limit (Figure 2) was reviewed by the safety committies on April 29, 1975 and remained in effect until the corrected positive imbalance portion of the envelope was developed.

SMUD implemented the interim positive imbalance trip settings and informed the NRC Regional Office of the problem and the actions taken

()

on the same day, April 29, 1975 B&W has provided SMUD with the corrected flux / imbalance / flow 4

envelope and this information is being submitted as Figure 2.3-2 as Proposed Change No. 34 to the Rancho Seco Unit i Technical Specifications.,

Respectfully submitted,

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SACRAMENT IC UTILITY DlSTRICT

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General Manager

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Dhy 10 S. KAPL N General Coun 1 of

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Sacramento M nicipal Utility District

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Subscribed and sworn to before me this

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30th day-of May, 1975.

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the County gf Sacramento, State of f/i California

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FIGURE 2.3-2 PROTECTIVE SYSTEM MAXIMUM RANCHO SECO UNIT 1 ALLOWABLE SET POINTS TECHNICAL SPECIFICATIONS u:

CHANGE '~ M 1

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. SACRAMENTO MUNICIPAL UTILITY DISTRICT O

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