ML20155B050

Topical Rept Evaluation of Suppl 1 to NEDC-30851P, Tech Spec Improvement Analysis for BWR Control Rod Block Instrumentation. Analyses Acceptable to Support Proposed Extensions to 3 Months

ML20155B050
Person / Time
Issue date:	09/22/1988
From:	Office of Nuclear Reactor Regulation
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ML20154C334	List: ML20155B039 ML20155B050
References
NUDOCS 8810060168
Download: ML20155B050 (4)

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ENCLOSURE 1 SAFETY FVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l REVIEW OF BWR OWNER 5 M OUP REPORT NEDC-30851P. SUPPLEMENT 1 ON JUSTIFICATION FOR EXTENSION OF ON-LINE TEST INTERVAL 5 FOR BhR CONTROL R00 BLOCK INSTRUMENTATION 1.0

SUMMARY

The staf f has reviewed the General Electric Company (GE) Topical Report NEDC 30851P, Supplement 1. "Technical Specification Improvement Analysis for BWR Control Red Block Instrurentation." This report was issued by the BWR Owners' Group as a supplement to Topical Report NEOC 30851P. "Technical  !

Specification leprovement Analyses for BWR Reactor Protection System."

Supplement 1 to NEDC-30851P provides a basis for extending the control roo block function (CRBF) instrumentation surveillance test intervals (ST!s) from one to three months. The CRBF shares common instrumentation with the reactor protection system (RPS). The staf f has concludec that the analyses presented in the Owners' Group report (Supplement 1) provide an acequate basis for TS changes to extcnc the STI for CRBF instrumentation, subject to any limitations anc conditions presented herein.

2.0 BACKGROUND

item 4.5.3 of Generic Letter 83-28 (Ref. 1) requested that all licensees and applicants review the existing RPS on-line functional test intervals required by technical specifications (TS). This review was intended to ensure that current and proposed intervals (Ref. 2) for such testir.g are censistent witt a goal of achieving high RPS availability. Subject to plant specific conditions which must be met, extensions to RPS STls have been grented for BWR plants. The control red block function shares cormon instrumentation with the RPS. Extending ST!s i for the CRBF has the potential for reducing unnecessary plant scram occurrences ano wear due to excessive equipment test cycling. The combined effect of similar RPS and CRBF STI extensions should improve plant safety, i

3.0 APPROACH The BWR Owners' Group decided to attempt to resolve this issue genericall).

it corrnissioned GE to perform generic corparative analyses for further j application to the individual boiling water reactor (BWR) plants. The generic ,

' cerparative analyses are applicable to a vast majority of plants that have  :

relay-type RPSs as well as to the rest of the plants that have ,

sclid-state-type RPSs. l A GE topical report was issued: NEDC-30851P, Supplement 1 (Ref.3), which used comparative reliability and data anelyses--in response to questions (Ref.

3) to establish an upper bound of the contribution of the failure of the ,

control rod block f unction (CRFB) to scram initiating event frequency. If the -

change in this upper bound value due to the proposed extended CRBF ST!s is i l found to be negligibly small, these Sil changes wnuld be acceptable, i

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4.0 NRC ACTION The staf f engaged the services of Brookhaven National Laboratory (Bhl) to review the comparative methodolog) used in the GE report- This review was to determine the adequacy of the reliability approach used to establish a l technical basis for the modification of the CRBF instrumentation ST!s. The  !

proposed basis for acceptance of the Sil extensions is that a very slight I increase in risk oue to these extensions is of f set by the benefits associated  !

with the similar approved extended ST!s for the Re0ctor Protection System (RPS) (Ref. 2). Using this reasoning, the staff agtees with BNL on the basis for acceptance. Bhl issued a technical evaluation report (TER - Enclosure 2) presenting the details and results of its reviews.

5.0 C_0NCLUSIONS

. On tne basis cf its review of the TER, the staf f endorses the conclusion that the methedology used and results obtained in NEDC-30851P, Supplerent 1 were verified. The staf f therefore finds the analyses presented in this topical report acceptable to support the proposed extensions to control rod block function instrumentation test intervals from one to three months, since there will be no significant changes in the CRBF availability if the proposed TS changes are implerented. Table 1 lists plant-specific conditions that M4 licensee or applicant must reet to make any proposed TS changes fuily acceptable.

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6.0 REFERENCES

1. Eisenhut, 0.G., NRC Letter to All Licensees of Operating Reactors.

Applicants for Operating License, and Holders of Construction Permits.

! "Requested Actions Based on Generic Implications of Salem ATWS Events" July 8,1983. >

2. Safety Evaluation by the Of fice of huclear Reactor Regulation - "Review of BWR Owners' Group keports NEDC 30844 and 30851P on Justification for and Extension of On Line Test Intervals and Allowable Out-of-Service Times l for BWR Reactor Protection Systems". May 27, 1987.

S. itsweswaran and k.P. Sullivan, "Technical Specification Improvement 3.

Analysis for BWR Control Rod Block Instruerentation." General Electric j Corrpany NEDC-3C851P, Supplement 1. June 1986.

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. CONDITIONS TO CLOSE 0'Ji PLANTS TABLE 1 For plant-specific applicction of the TS changes for control rod block instrumentation that are proposed, the individual plant licensee must:

(1) Confirm the applicability of the generic analyses to the plant.

(2) Confirm that any increase in instrument drif t out to the extended i STis is properly accounted for in the setpoint calculation methodology, i (For additional information on this issue, see letter f rom C.E. Rossi l to R. F. Janecek, dated April 27,1988).

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