ML19319C454

Review Completed of Licensee Proposed Procedure for Stuck Rod Measurement & High Reactivity for Ejected Rod Accident. Proposed Test Considered to Exceed Bounds of Safety Analysis & Is Unacceptable

ML19319C454
Person / Time
Site:	Davis Besse
Issue date:	07/20/1977
From:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:	Knop R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
770770, NUDOCS 8002140831
Download: ML19319C454 (5)

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9 JUL 2 01977 9

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a91 diERMDUM FOR:

R. C. raiop, Reactor Projects Section 1. RIII FR01:

K. V. Seyfrit, Assistant Director for Technical Programs, ROI, IE SoEJECT:

STUCK dUa ciEA5UR0!E?iT FGR CA7I5 cC5SE LNIT tiO.1 (AITS F300ClH2) ine licensee's propcsed ;rccxarc fur e.ca;uring tae stucz roo north and :ae resulting hign reactivity for an ajected rod accidcat was reviewed as requested. At one coin: in tne procecure (Step E) tac racctor is critical with all of the regulating reds, having a total scrta cf accut tL a k/L (F5.'d Table 4-13), insertx in tha core. An estiaate of :nc ejected roc r.orcn for t.il: conditica caa bc J;rivec fra2 Figure 4.7-2 (Encicsure 1) of the Startup Rcpert fer Rancho Seco Cni: 1.

This figure gives an ejected rod ucrch of 1.9% a L/k for an insertec roc 'or:n of 31,.t P./k. As Tacoling's r.e:c.orancun indicates tne FSAR rod ejection analysis concluces (Paragrapa 15.4.3.2.5) that, a reactivi:/ grea:cr taan 1.52 a k/t cculd cause a rupture of the i

pressure vessel.

A conference was r. eld wita neabers of tne NRR Core Ferfomance Crance to ciscu.;s cne acceptabili ty of t..a proposed test.

There was unanitcas agrcccent that, if the prcposco test resulted in coeratica witn an Cjectdc rod WGrth grSater Onan the Value consiterO3 iu ne accident analysis, i: was aa: acceptaale.

Two possible solutions to the proclen were discussed. The fir:,t was a reanalysis of tne accidar.t by tne licansec to. lacluue ta.e conseciaencas of the nigaer ejected red acrtn. Tae new analysis woclu require submittal to, and approval.,y J.R prior :o the concuct of tae tast..

The secanu possibility wcald be tne eodification of tne prccedure to reduce tne taxi m ejected rod ucrth to a safe value.

Suca 2 prcceuvre was used for the Pancno Seco stuck red.:casursent, Rar.cno Seco Startup Test Procedurc 4.'d and Table 4.d.1 (Enclosure 2 1 3).

It involved naasuring tae reactivity cifference ce ween two roc drops frca critical. vita canX 6 partially,41tadrawn. Gne crop was cone wita :ne asseceu stack rad ru..ai.ing at 100% wittorawn, and the otr.er was done aitr. tae stuck rod inserted. This ceasurcuent has a larger uncertainty.

sir.ce corre.:tica facters ;aust Le applied to account for tne rod ucrth g9

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reduction at the lower initial inserted worth.

!!owever, this uncertainty is not considered to be significant encuga to justify the less conservative test.

The following ite:as aaaress the four questicas raised in Tanbling's-ac:crandura.

1.

The analysis of the consequences of the rou ejection test presented in the FSAR may be conservative, newever, it is tne only analysis availaole and o;;eratica cu: side of its limits snculd not de semitted.

2.

The accuracy to be gained by tne proposed test is net con-sidered to justify operatica outside of the counds of Ine analysis.

3.

A stuck rod measuren: ant sit::ilar to the one ccriducted at Rancho Seco is considered to te an acceptable alternate metnod.

4 The question of wno is responsiale for infoming tae licensee taat une test is unacceptcala was discussed witn tne fiRR h cjcct Hariager.

It is his position, anu we ccncur, that this is an IE responsibility, since tne determination of Ice udewacy of the test details is an IE functica.

As was discusseu, by pr.cne 'Wtueen i. a.

samoling and D. C. rsirkpatrick, we recccr.cnd that ne licensee be inforced tna; taa crecently proposec

cst is censidereo to exceeu tne councs of tne safety analysis and is unacceptable.

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K. V. Seyfrit, Assistant Jirac;cr for Tecnnical Progran:s, RGI, IE

Enclosures:

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sanc..o Seco Startup Rapcrt 9

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FAN'cHo SEC0 uni'rl .1TTAOUP h.!Mr 4.8 STUCK CONTROL R00 WORTH Technical Specifications require that the shutdown margin be at least 1% ak/k with the highest worth rod fully withdrawn. The rod calculated to have the highest worth, with all other rods fully inserted, or those symmetric to it. (See Figure 4.8-1). The reactivity worth of CRA H-2 and the shutdown cargin with CRA H-2 fully withdrawn were measured and compared with calculated values. The' stuck rod worth was measured at 532*F with APSR's 36% WD by performing two rod drops. In the first drop, all rods (except APSR's) were dropped from a critical state with CRG-5 at 48% WD. For the existing boron concen-tration, this drop measures the subcri tical reactivity with all rods in. The second drop was made at the same boron concentration but from a critical state with CRA H-2 at 100% WD and CRG-5 at 17% WD. All rods were dropped except the APSR's and CRA H-2 thus measuring the subcritical reactivity with CRA H-2 at 100% WD and all other rods in. The di f ference between the two drops i s, the re fore, the worth of CRA H-2 wi th all other rods in. An uncorrected j value for the reactivity i ntroduced by each drop was obtained. These values were multiolied by correction factors which had been determined frca measurements on a similar reactor by comparing results from rod drop and boron swap measure-The measured results are compared wi th predicted values in Table 4.8-l. men ts. j The value thus obtained f,r the stuck rod is well within test acceptance criteria of 3.91% Ak/k + 30%. ~ Since mis value is greater than the measured, it is the value used for shutdown margin cricula tions to insure conservatism is always applied. D %\\ 4.8-i x \\,>" \\ \\/ m \\ l .__y _.m

fYC$O $D' UW/f / 57Mr*UP frAer TABLE 4.8-1 COMPARISON OF MEASURED AliD PREDICTED STUCK. ROD WORTH Uncorrected Corrected Predicted Deviation CRG's Measured Worth Correction Measured Worth Worth from Dropped % 6 k/k Factor % 6 k/k " Ak/k Predicted 1,2 4.

1. 5 6.19 6.25

-1% 5(48 + 0% WD) 1,2 3,4 2,90 0.93 2.70 2.34 +15% 5(17 + 0% WD) CRA H-2100*: 1D and remains out Stuck Rod Uorth 3.49 3.91 -11% O hh 4 e 4.8-2 '}}