ML032260478

CNS- Init Exam - 06/2003 - Licensee Post Examination Comments

ML032260478
Person / Time
Site:	Cooper
Issue date:	06/27/2003
From:	Thomas J. Palmisano Nebraska Public Power District (NPPD)
To:	NRC Region 4
References
50-298/03-301 50-289/03-301
Download: ML032260478 (5)

Text

N Nebraska Public Power District Always there when you need us NLS2003075 June 27, 2003 Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011

Subject:

Post Examination Comments The purpose of this letter is to transmit post-examination comments resulting from the Senior Reactor Operator and Reactor Operator initial licensing examinations which were administered at Cooper Nuclear Station (CNS) June 13, 2003.

Per NUREG- 1021 Revision 8, Supplement 1, a post examination analysis was performed by CNS and two comments on the examination are enclosed for your consideration. Feedback from the applicants is included in these comments.

Should you have any questions or require additional information, please contact Lisa Edwards, Nuclear Training Manager, at (402) 825-5402.

Respectfully, T. J. Palmisano Site Vice-President

/jr Enclosures cc: G. E. Werner Chief Examiner USNRC - Region IV COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.nppd.com

Original Exam Question: 13 (RO and SRO Exams)

The plant was operating at power with the "A" Core Spray subsystem in full flow test at 5000 gprn.

An accident occurs that results in increasing drywell pressure and lowering reactor water level and lowering reactor pressure. The following plant conditions exist:

- Drywell pressure I I psig (rising)

> Reactor water level -21 " (wide range, lowering)

> Reactor pressure 375 psig (lowering)

What is the pressure response of the A Core Spray system at this time?

Core Spray system pressure ...

a. remains the same.

b. increases to pump shut-off head.

c. decreases to just above reactor pressure.

d. increases to iust below pump shutoff head.

Original Exam Answer: Answer: d.

a. Core Spray pressure would not remain the same because system flow rate would become significantly reduced when the initiation signal occurred and the test line isolated.

b. Core Spray system pressure would be below shut-off head because of the flow that exists through the minimum flow valve.

c. Core Spray pressure increases.

Question/Answer Problem Statement:

Given the facts that the test valve (CS-MO-26A) has a fast stroke time (approx. 5 seconds) and the minimum flow valve (CS-MO-5A) has a relatively long stroke time (29.1 to 39.3 seconds),

Core Spray pump discharge pressure will increase to pump shut-off head for a brief time during this transient. Because the question does not stipulate any time factor (other than "at this time") to be considered in determining the correct response, the examinee may evaluate the entire transient and decide that the best answer is the one that describes that period of time, albeit brief, when Core Spray pump discharge pressure is greatest. That period of time would exist when the full flow test valve, CS-MO-26A, has closed, but before the system minimum flow valve, CS-MO-5A, has started to open.

The conditions of the test item were replicated in the CNS simulator. Core Spray Pump A discharge pressure increased to shutoff head before stabilizing at a slightly lower value.

References:

CNS Procedure 2.2.9, Core Spray System CNS Procedure 6.1CS.201, CS Motor Operated Valve Operability Test (IST) (Div I)

Engineering Calculation Number NEDC 03-025 I Recommend Resolution: Also accept choice b.

Original Exam Question: 21 (RO and SRO Exams)

Given the following:

- The plant is operating at 100% power at Beginning of Life (BOL)

> A loss of off-site power occurs

> All control rods fully inserted

> Pressure rises to 1090 psig, THEN lowers to 875 psig

> 20 minutes later, pressure is cycling between 1015 and 875 psig What is the status of Low Low Set (LLS) and why?

(NOTE: NO operator action is taken.)

a. LLS is controlling pressure. LLS logic has no AC powered inputs or components.

b. LLS is controlling pressure. With RPS power unavailable, the LLS logic can arm irrespective of reactor pressure.

c. LLS is NOT controlling pressure. With RPS power unavailable, the SRVs must operate on mechanical relief setpoint to control pressure.

d. LLS is NOT controlling pressure. A fault must exist in the LLS logic as all conditions are present for LLS to automatically control pressure.

Original Exam Answer: Answer: b.

a. LLS logic is armed by RPS high pressure signal.

c. LLS logic will arm on high pressure with no RPS power available.

d. LLS is controlling pressure.

Question/Answer Problem Statement:

In choice "a", the LLS logic has no AC powered inputs because the associated RPS AC power supplies are deenergized following a loss of off-site power. When off-site power is lost, the emergency buses (41 60vac I F and I G) will be deenergized for a period of at least 10 seconds.

This is due to the fact the the Startup Transformer (preferred backup to the Normal Transformer) and the Emergency Transformer (which connects to both emergency buses within I second if the Startup Transformer breakers fail to "fast transfer" following a loss of the Normal Transformer) will both be deenergized under conditions of a loss of off-site power.

Undervoltage on the emergency buses will cause the diesel generators to start, but their output breakers will not close until the associated emergency buses have been deenergized for a minimum of 10 seconds, as a result of a time delay relay function. During this 10 second (or more) time frame, the RPS motor generator sets will trip on undervoltage. There is no automatic power supply transfer feature associated with the RPS buses. As a result of this event sequence, there is no AC power supply currently providing power to the Reactor Protection System, including the 5A-K27A/B relays, which provide the high Reactor pressure input signal to the Low Low Set logic. Therefore, at this point in time and due to the unavailability of R-PS power, "LLS has no AC powered inputs or components".

Choice "a" is correct as stated

References:

CNS Procedure 2.2. 1, Nuclear Pressure Relief System CNS drawing 944E689, Low Low Set CNS drawing 791E256, sheets 9 and 10, Reactor Protection System Recommnend Resolution: Also accept choice a.

Recommend Resolution: Also accept choice a.

ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS Correspondence Number: NLS2003075 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only and are not regulatory commitments. Please notify the NL&S Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.

COMMITTED DATE COMMITMENT OR OUTAGE NONE i

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