ML17305B391
| ML17305B391 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/12/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17305B390 | List: |
| References | |
| NUDOCS 9103180478 | |
| Download: ML17305B391 (4) | |
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UNITEDSTATES CLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE 2
SAFETY EVALUATION BY RADIATION'ROTECTION BRANCH OFFICE OF NUCLEAR REACTOR REGULATION
- 1. 0 INTRODUCTION In a letter dated January 18, 1991, Arizona Public Service (APS) provided an analysis related to the potential failure of a tube in a high pressure seal cooler (HPSC).
Under certain conditions, such.a failure could result in a reactor coolant system (RCS) leak which bypasses the containment.
In the January 18 letter and its attachment, the licensee provided information re-lated to the postulated leak, the results of radiological analyses performed by the licensee,,
and compensatory measures the licensee plans to implement until appropriate plant modifications can be effected.
The Radiation. Protection Branch was requested to review this material and identify any safety concerns.
In reviewing the licensee's submittal, PRPB considered the situation'o be similar to the case of a failure of a small line carrying primary coolant outside containment.
- Appropriate criteria for use in analyzing the radiological effects of such a failure are described in Standard Review Plan (SRP) 15.6.2 "Radiological Consequences of the Failure of Small Lines Carrying Primary Coolant Outside Containment."
2.0 EVALUATION In the licensee's January 18, 1991 submiital, the (previously unidentified) scenario was described and the results of radiological analyses were presented.
The licensee, in performing its analysis, postulated a number of scenarios with differing assumptions, differing degrees of conservatism, and different results.
Of the analyses performed by the licensee, the applicable one involved the guillotine rupture of a high pressure seal cooler tube.
Using assumptions applicable to this scenario in accordance with conservative criteria described in regulatory documents (e.g.
Standard Review Plan and Regulatory Guides) the licensee calculated that thyroid doses at the exclusion area boundary could exceed 10 CFR 100 limits within the first 30 minutes.
The licensee performed other analyses, using less conservative assumptions, and estimated exclusion area boundary (EAB) thyroid doses at 10.2 rem for the two-hour period.
Because of uncertainties in failed fuel percentages, iodine spiking factors, and to eliminate any undue, risk to the public, the licensee has proposed monitoring failed fuel and reactor coolant system (RCS) iodine activity levels.
The licensee has proposed that if RCS dose equivalent I-131 levels exceed 0.2 9103180478 9i0312 PDR ADOCK 05000528 P
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't) iP microCi/cc "engineering will re-.evaluate the Justification for Continued Operation IBCOI and if deemed necessary, add compensatory actions."
heither the criteria to be used in making, this determination,
.nor the nature of the compensatory actions to be implemented are specified.
The Radiation Protection Franch has reviewed the l.icensee's January 18, 1991 submittal and finds that the postulated event is analogous to thai described in HUREG-0800 Standard Review Plan (SRP) Section 15.6.2 "Radiological Consequences o.
the Fai luve uf Sriall L'ir es Carrying Fvimary Coolant Outside Containment."
Consequent>y, the stafi believes that the assumptions, metho-
- doicgy, and acceptavice critcevia set forth in SRF'5.E'.2 are appropriate and should be applied to the case at herc'.
Thc staff has evaluated the potential vedic,logical consequericcs of a break in a reactor coolant pump (RCP) high pressure seal cooler (HPSC'; at the Palo Verde nuclear Genevating Station (PVflGS) and.firds that the analyzed consequerces ray si~nifica>>tly exceed the acceptance criteria of SPP 15.6.2 (i.e.
a small fraction (10K) of the exposure guideline of 10 CFR 100.)
Further, the acc&ptaf ice cl i'evia o.
10 CFf: IC(ould also be exceeded using the as umptions ana methodologies set forth in the SRP.
3.0 CONCLUSIOH The licensee has identified a possible condition which could result in an interfacing system LOCA (ISLOCA) with containment bypass at any of the three Palo Verde units.
It is noted that the postulated scenario involves a small 1'ine
(
1.2'") arid would riot likely lead to core melt.
The Radiation Protection Brarich has reviewed the information provided by the licensee and has performed calculatiors which indicate that the postulated scenario may result in consequences which exceed regulatory acceptance cvitevia.
The licensee should take actior t<<provide assurance that radiological consequences.
of a hig,'i pvessure seal coolev tube failure are within'regulatory acceptance criteria.
Such actiors may include reduce<<'ermissible levels of cuolc 1st raciuiodsr.c, ir.creasec sampling aries ana lysis of reactor coolarit to dc:terrrsine radioiodine levels, as v:eil as more restrictive operating practices which wouic reduce i.hc. pctential and actual levels of iodire activity in the reactor coolant.
With regard to more stringer t operating practices,
- the, licensee should consider, for example, implementing startup,
- shutdown, and vperating procedures and controls which would reduce vaoioicdine concentrations in the reactor coolant.
Further, the licensee should establish a level of t.quilibviur~ iodirie activity concentrations above whicl the hRC staff shrill be prompt ly not ified.
Finally, the licensee should prcvide details of its proposed actions to correct this issue as well as a more detailed schedule for.,impl'ementation, of corrective rieasures at each Palo Verde unit.
Principal Contributor:
Kenneth T. Eccleston
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