ML20148J634

Discusses Recent Incident at PWR Facility Re Limited Boron Dilution Incident Due to Inadvertent Injection of Sodium Hydroxide Into Rcs.Requests Analysis of Potential for & Consequences of Boron Dilution Accidents

ML20148J634
Person / Time
Site:	Yankee Rowe
Issue date:	09/26/1977
From:	Schwencer A Office of Nuclear Reactor Regulation
To:	Groce R YANKEE ATOMIC ELECTRIC CO.
References
NUDOCS 8011250140
Download: ML20148J634 (3)

Text

, L L

. f a

> Es.ii SEP 2 61977 g

. . .5 Docket W . 50-29 . g Yankee Atomic Electric Company ATTH: Mr. Robert H. Groce Licensing Engineer Bi 20 Turnpike Road '

Uestboro, Massachusetts 01581 -

Gentl emen:

RE: YANKEE-ROWE AT0t1IC POWER STATION Recently at an _ operating PWR facility, a liuited boron dilution incident occurred due to the inadvertent injection of a portion of the contents Q cf the Na0H tank into the reactor coolant systen while the reactor was in the cold shutdown condition. While perfoming surveillance testing .

(valve cycling) of the HaOH tank isolation valve, with the Decay Heat iiN Removal (DHR) system lined up for reactor coolant recirculation, a portion of the tank's contents drained into the DHR system. Upon resunption of coolant recirculation this haOH was injected into the reactor coolant systen.  ;

~

In the above-mentioned case, only a limited amount of Ha0il (approximately 600 gallons) was injected and the reactor renained subcritical by a large nargin. However, this event highlighted the fact that a postulated single '

failure at this facility (i.e., nisposition of the isolation valve for the HaOH tank when the DHR system is lined up for recirculation or operating ,

in the recirculation node) could result in a moderator dilution incident .

which had not been praiously considered. Subsequent analysis by the -

licensee and his vendor revealed that, for certain conservative asswptions (e.g., reactor in the cold shutdown condition, vessel enperature less than ~*, ..

100 F, beginning of core life characteristics, vessel drained to a level approxir'ately equal to the height of the outlet nozzle, lowest inital baron concentration allowed by Technical Specification::, the naxir.ua worth control rod stuck in the fully out position, and no credit assumed for operator action), the injection of the Ha0H tank contents into tne reactor coolant systen due to the misposition of a single isolation valve could result in reactor criticality with the control rods inserted. ,

y F R g-elS DOCUMENT CONTAINS s

~

POOR QUAUTY PAGES

/ *

'orrson >

suMNAME>

SAT E M L NRC TORM 318 (9 76) NRCM 0240 W u. s. oovs muu sut paiwriwo orrec ts s e7e - eas.es4  !

49g ,g.p,g g

1 L

L Yankee Atonic Electric Co. Based upon our review of this particular incident,'we concluded s that the assumption'that operator action would not be taken in suf- r ficient time to terminate the event prior to reactor criticality would be overly conservative. This determination was influenced by the E length of the dilution time necessary before return to criticality E

~

and by the number of indications and alarms available to the operator 5 at this facility. Due to plant-specific system design and instrumen- " . . ~

~

tation differences. we are not able at this time to reach a similar con-clusion for all PWR's. Furthermore most PWR boron dilution analyses have been limited to addressing a malfunction in the makeup and purification system (chemical and volume control system). The incident discussed above is an example of a boron dilution accident not covered by these analyses. Therefore we are requesting that each licensee of a PWR facility provide an analysis of the potential for and consequences of boron dilution accidents at his facility.

You are requested to perform and submit the results of such an analysis within 90 days of receipt of this letter. Your analysis should be based . . . .

upco conservative assumptions consistent with the design of your facility 3 and your Technical Specifications and should include the assumption of the most limiting single failure. The analysis should also include an assess-ment of the-factors which affect the capability of the operator to take corrective artion which would teminate the postulated events prior to j achieving rea; tor criticality.

If, based on tne results of this analysis, you determine that corrective x actions (design or procedural) are required to preclude the occurrence I or mitigate the consequences of postulated boron dilution accidents, your response should include proposels for such actions.

DISTRIBUTION.

Docket Sincerely,  !!

NRC PDR LOCAL PDR j.

ORB =1 Reading ASchwencer

[

[L SMSheppard A. Schwencer, Chief 1 ABurger Operating Reactors Branch #1 OELD Division of Operating ileactors 01&E(3)

ACRS(16) cc: See next page CNelson DEisenhut [

TBAbernathy JRBuchanan 6,,,,,, DDR:0RB#1 00R:0RB#f DOR: J1

.u.~,,*. ABurger:1b CNed5 ASci@hcer i

om * ...9R3/.ZZh 9___/j/77 , 9/h/77 wac ronu sts (976) nacu ord

• vi . ova.~7.~r .i~ri~. o,rie s. i .7. ... ..

W__

I (L:. e:. ::.,::.

.Yankce: Atomic Electric Company- SEP 2 61977 iT: ...,

D

]

.cc: Mr. 'Donal d .G. - Allen, President

' Yankee Atomic Electric Company

20. Turnpike. Road Nestboro,: Massachusetts- 01581 0

-s Greenfield Public Library E

. 402 Main' Street Greenfield, Massachusetts. 01581 N' ..

.:q s t Y.h

, q:,

t

.[.. .

i

..1....

i 1

J 9

t t

i l

4 4

.1 q

.j

.