ML20117J216

Forwards Proposed TS Amend,Consisting of Revised (or Deleted) Definitions for Terms Reactor Secured,Reactor Shutdown,Reactor Operating,Reference Core Condition & Reactivity Limits

ML20117J216
Person / Time
Site:	University of Virginia
Issue date:	05/28/1996
From:	Mulder R VIRGINIA, UNIV. OF, CHARLOTTESVILLE, VA
To:	Alexander Adams NRC (Affiliation Not Assigned)
Shared Package
ML20117J218	List: ML20117J216 ML20117J220
References
NUDOCS 9605310021
Download: ML20117J216 (5)

Text

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. SCHOOL OF ENGINEERING G .

May,28,1996 & APPLIED SCIENCE  !

l NUCLEAR REACTOR FACILITY  !

Mr. Alexander Adams, Jr. Department of Mechanical, j Senior Project Manager Aerospace & Nuclear Engineering i Non-power Reactors and Decommissioning University of virginia l Charlottesville, VA 22903 2442 l Project Directorate U.S. Nuclear Regulatory Commission 804 982 5440 fax: 804 982 5473 l M.S. 0-11-B-20 l Rockville, MD 20852-2738

Subject:

Proposed Amendment to a few definitions contained in the Technical Specifications (TS) for the University of Virginia Reactor (UVAR), Docket No. 50-62, License R-66.

Dear Mr. Adams:

On Ju!y 21,1995, numerous editorial and cosmetic changes to the UVAR Technical

Specifications were approved and issued by the NRC at our request. These changes were not l

connected with the reactor's fuel conversion to LEU, rather, they were made to update the TS and bring them into line with present-day standards. Among these changes were some which j were made to cenain definitions contained in TS 1.0 DEFINITIONS. Upon further discussion o among the U Va. reactor staff and management, additional improvements in a few of the defmitions appears possible. These proposed wording changes were submitted for review to our Reactor Safety Committee, and approved on May 22,1996. f In the attachments included, please find the proposed TS amendment, consisting of revised (or i deleted) defidions for the terms Reactor Secured, Reactor Shutdown. Re_e actor Operatina.  !

Reference Core Condition. and Reactivity Limits. A discussion of the advantages associated I with the proposed amendment is presented. Also included in attachaent are replacement sheets for the UVAR TS should the amendment be approved by the NRC without modification. We are requesting the NRC to review and approve these changes. As always, please contact me at (804) 982-5440 if there are any questions.

^;ty/coen'.y cf b%1d!w Sincere 1y).b Commonwealth of Virginia f-

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, i I hereby certify that the attached document is a true and m fb d:L cxact copy of a bb . presented before R'o bert U. Muldh, Director "**"""

U.Va. Reactor Facility & 3yL

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Assoc. Prof. of Nuclear Eng. ..,,, j

• I by ,' $ 'I 5' u br' sam or om n ,'*.as x6ne.wesano cc: Mr. Craig Basset, NRC Region II, Atlanta, Ga.

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Document Control Desk, NRC, Washington, DC /  % w.c l

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9 CURRENT AND PROPOSED WORDING CHANGES TO UVAR TS 1.0 DEFINITIONS Current Wording: Reactor Secured: The reactor is secured when:

(1) Either there is insufficient moderator available in the reactor to attain criticality or there is insufficient fissile material present in the reactor to attain criticality under optimum available conditions of moderation and reflection, or

, (2) The following conditions exist: I

a. All shim rods are fully inserted,

b. The console key is in the OFF position and is removed from I the lock, and

c. No work is in progress involving core fuel, core structure, i installed control rods, or control rod drives unless they are physically decoupled from the control rods, and

, d. No experiments are being moved or serviced that have, on movement, a reactivity worth exceeding the maximum l reactivity value allowed for a single experiment, or one dollar, whichever is smaller.

, Proposed Wording: Reactor Secured: The reactor is secured when the following conditions j

! exist: I

a. The reactor is shutdown.

b. The console key is in the OFF position and is removed from the lock, and

c. No work is in progress invoMng core fuel, core structure, installed control rods, installed experiments or experimental facilities with a reactivity worth greater than 0,60$, or control rod drives unless they are physically decoupled from the control rods.

Discussion

Operators have difficulty correlating item (1) in the present wording with particular reactor I configurations. Moreover, item (1) is unnecessary to the definition, particularly when the term shutdown is defined clearly (see below). The removal ofitem (1) and the slight rewording of item (2), as proposed, makes for a shorter, cleaner and more precise definition. It also corresponds exactly with the staff's understanding of what a secured reactor should be in practice.

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i Current Wording: Reactor Shutdown: The reactor is shutdown ifit is suberitical by at least one dollar in the reference core condition with the reactivity worth of all j installed experiments included.

Proposed Wording: Reactor Shutdown: The reactor is shutdown when all installed shim rods  !

are seated or there are only six or fewer fuel elements on the grid plate.

1 Discussion l The idea expressed in item (1) of the current defmition for reactor secured has been incorporated l in this proposed definition, albeit in a more practical form. It is not possible for a reactor operator  !

to know exactly when or how the reactor is suberitical by one dollar. However, the operator can  ;

always determine accurately the number of fuel elements on the gridplate, or the seated state of  !

shim rods. It is also known for certain that the UVAR reactor is subcritical by at least one dollar when there are only six or fewer fuel elements on the gridplate. Here as well, the proposed definition is leaner, cleaner and more precise than the present definition. I l

l Current Wording: Reactor Operating: The reactor is operating whenever it is not secured or 1 shutdown. j ProposedWording: Reactor Ooeratina (onerations. operated. ..h The reactor is operating j when it is not shutdown.  ;

Current Wording: Reactor Operation: The reactor is in operation when not all of the shim rods are fully inserted and six or more fuel elements are loaded in the grid plate.

Proposed Deletion: Reactor Ooeration: --- redundant, since it can be readily understood from the definition for " reactor operating."

Discussion The minimum " set of states" necessary to describe the UVAR are shutdown, secured, or operating. Unfortunately, the current definitions of" Reactor Operating" and " Reactor Operation" are inconsistent. When these terms are considered together with the definitions of

" Reactor Shutdown" and " Reactor Secured," apparently it is possible for the reactor to be

" operating" yet not be "in operation". This is highly confusing to the staff, since all grammatical variations of the word " operation" should logically refer to the root word " operation." Once the proposed definition for reactor operating is accepted, a definition for " reactor operation" is not l needed. The sum of all proposed changes serves to make the definitions self-consistent and do not require an operator to perform reactivity calculations to determine the state of the reactor.

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. l Current Wording: Reference Core Condition: The condition of the core when it is at ambient -

temperature (cold) and the reactivity worth of xenon is negligible (<0.305).

Proposed Deletion: Beference Core Condition: -- not needed, since it is defined in the ,

definition ofReactivity Limits (see below). j Current Wording: Reactivity Limits: Reactivity limits for experiments are quantities referenced to an average pool temperature of <90 F with the effect of xenon poisoning on core reactivity accounted for if greater than or equal to 0.07$. The reactivity worth of samarium in the core will not be included in reactivity limits. The reference core condition will be known as the cold, xenon-free critical condition.

Proposed Wording: Reactivity Limits: Reactivity limits are referenced to an average pool temperature of <90* F with the effect of xenon poisoning on core reactivity accounted for if greater than or equal to 0.075. The reactivity wonh of samarium in the core will not be included in reactivity limits. The reference core condition will be known as the cold, xenon-free critical ciondition.

Discussion The current definitions for reference core condition and reactivity limits are not consistent, and the former is redundant. The proposed amendment assures that all required reactivity-measurements, not just those associated with experiments, will be made (as they have always been made) in the reference core condition with the maximum permitted xenon wonh to be equal to or )

less than 0.07$ (equivalent to 0.05% delta k/k, a value which originated during the reactor's l infancy).

For your reference, the definitions in the "old HEU" UVAR Technical Specifications were:

Reactor Operation: Reactor operation is when not all of the shim rods are fully insened and six or more fuel elements are loaded in the grid plate.

Reactor Shutdom: The reactor is in a shutdown condition when all shim rods are fully insened.

Reactor Secured: The reactor is secured when (1) all shim rods are fbily inserted, (2) the console key is in the OFF position and is removed from the lock, and (3) no work is in progress in-core involving fuel or experiments or maintenance of the core structure, control rods, or control rod mechanisms.

Reactivity Limits: Quantities are referenced to an average pool temperature of(<90' F) with the effect of xenon poisc ning on core activity accounted for if greater than or equal to 0.05% delta k/k. The reactivity wonh of samarium in the core will not be included in reactivity limits. The reference core condition will be known as the cold, xenon-free critical condition.

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