ML20148J416

Hazards Analysis Supporting Proposed Change 40 to Tech Specs

ML20148J416
Person / Time
Site:	Yankee Rowe
Issue date:	09/20/1963
From:	Bryan R US ATOMIC ENERGY COMMISSION (AEC)
To:
Shared Package
ML20148J415	List: ML20148J409 ML20148J416
References
NUDOCS 8011240062
Download: ML20148J416 (2)

Text

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a a IINITED STATES ATOMIC ENERCY CO'NISSION HA~ARDS ANALYSIS BY TiiE RESEARCll AND POWER REACTOR S AFETY BRANCII O -

a DIVISION OF LICENSINC N;D RECT!LATION a]

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IN Tile MATTER OF YNEEE AT0"1C ELECTRIC CC"PANY PROPOSED CilANCE NO. 40 J

DOCrET NO. 50-29 Introduction Pursuant to the provisions of Section 50.59 of the Commission's regulations, j Yankee Atomic Electric Corpany in Proposed Change No. 40, dated July 17, 1953,  ?

requested authorization to use control rods of a different design than those ))

presently installed in their reactor. The present nickel-plated silver- ..a indium-cadmium control rods would be replaced with twenty-two hafnium rods and fj two inconel clad silver-indium-cadmium rods. Two spare rods will be avail- ,

.Q X

abic to form a completo set of hafnium rods for use in the core, should this E.

prove to be desirable. 73 Discussion H At the end of Core 1 life, inspection of the diffusion bonded nickel plate on the silver-indium-cad.aiun rods revented extensive deterioration of the plating caterial. This deterioration allowed radioactive silver to be releastd fron the control rods and contaninate the reactor water during the refueling cncration. Because control rods of an niternato design could not be obt:.ined in sufficient tir.e, Core II can locded usinr nc.s control rod:

of essentially the same desita as those used during Core I life. ,

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in order to clieinate the cladding probler durinr Core III life , Yanhec proposes to use hafnium as the poison catorial in the absorber sections of i the Core III control rods. Along with this basic type of control rod, tuo control rods having inconel clad silver-indiuc-cadmium absorber sections ,

would be installed to determine the serviceability of the rods during Core III operation. The thickness of the inconel is such as to cininize the possibility of cladding failure.

!!c believe that both new tvnes of control rod absorber sections should clininate the probica of excessive contanination of the primary systen due to netivated raterial fron the control rods entering the reactor coolant water. In addition, we expect there will 5e littic change in the reactivity worth of these control rods from those used in Corcs I and II. Yankee intends to experinentally verify the actual worths o' the roJs during the start-u, testing progran, omcE > ... .. - - - . .... . . . - - - .... -. - - - . . . . . _

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- 2-There are two other safety considerations of innortance regarding the Proposed Change. One consideration is that drou to: ting of the inconel cind silver-indium-cadniun control rods has not been perforced, and the detailed design of those rods is different - froa that utilized in any control rods thus far used in re acto r:: . Iloucvor, these two rods will be the lest withdrawn from the core during Core III operation; and, at the tino of withdrawal, the reactor control rod systen iiill have a very large shutdown nargin capability. Accord-ingly, control of the reactor would not be impaired even though these control rods should fail to function prope'rly. h*c belicyc that the Technical Specifica-tions should provide that:

"The plant shall he operated in a canner so that contml rod insertion ,

will provide not less than 2% 1: k/k shutdown nargin if the maxirum worth rod is stuck in its fully withdrawn position and the silver-

'indlun-cadniun rods are stuck at their operating positions."

liith the above condition in effect, we believe that there is adequate assur-ance that the use of the two silver-indlun-cadmiun rods will not result in unsafe operation of the reactor. .

A second safety consideration relates to the testing program for the new control rods after installation in the reactor. Yankee has been requested to furnish infornation regarding the operational testing of the control rods prior to .nd * -

during Core III operation. ric believe that the use of the control rods during y Core III operation should be conditional upon Yankee submittint in formation -

prior to reactor operation demonstrating that an adequate control rod testing procron vill be in e'fect. Accordingly, the following condition should be incorporated into tl 'i cchnical Specifications:

"The renctor shall not be coerated at power with the new tvpos of control rods installed until additional inforr ;tica regardinr the prorrm- for functional testin?. of the control raJs nrior to and durina Core III life is subritted to the Cor .inien and authori-zatien to use the control rods during power oneration is franted."

Con clusion Subject to the above conditions rcrarding use and testing of the control rods, it is our opinion .that Proposed Change No. 40 does not present significant hazards considerations not described or inplicit in the hazards sunnary ,

report, and that there is reasonabic assurance that the henith and safety j of the public will not be endangered.  ;

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f/d. & ,w P.ohert !!. Drvan , Chi ef j Re s e a rc's. r Power Peactor Safety Branch j Division of Licensing f Pegulatien i j 1

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( ' Form A1;C.3M Oter.9-53) u. s. sonenero nmme emcr 14-ene t-a i

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