ML082200051

Comment (2) of David P. Helker, on Behalf of Exelon and Amergen, Concerning Draft Regulatory Guide DG-1195, Availability of Electric Power Sources.

ML082200051
Person / Time
Site:	Dresden, Peach Bottom, Oyster Creek, Byron, Three Mile Island, Braidwood, Limerick, Clinton, Quad Cities, Zion, LaSalle
Issue date:	07/09/2008
From:	David Helker AmerGen Energy Co, Exelon Nuclear
To:	Rulemaking, Directives, and Editing Branch
References
73FR28791 00002, DG-1195
Download: ML082200051 (4)

Text

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July 9, 2008 cp Rulemaking, Directives, and Editing Branch Office of Administration U)

U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Comments Concerning Draft Regulatory Guide DG-1 195, "Availabilityof Electric Power Sources" (Federal Register Notice 73FR29791, dated May 22, 2008)

Exelon Generation Company, LLC (Exelon) and AmerGen Energy Company, LLC (AmerGen) are submitting this letter in response to a request from the Nuclear Regulatory Commission (NRC) for comments concerning Draft Regulatory Guide DG-1195, "Availabilityof Electric Power Sources," published in the Federal Register (i.e.,

73FR29791, dated May 22, 2008).

DG-1 195 describes the operating procedures and restrictions that the NRC considers acceptable for implementation if the available electric power sources are less than the Limiting Conditions for Operation (LCO).

Exelon/AmerGen appreciate the opportunity to comment on DG-1 195, and offer the following comments for consideration by the NRC.

General Comments B. Discussion Section 1. Loss of Offsite Power

1. Exelon/AmerGen suggest that the phrase "...inadequatevoltage following a trip of the plant..., "in condition (2)be deleted. The offsite sources should only be declared inoperable under real time conditions, and for conditions expected to be caused by a unit accident (i.e., a trip of the plant). Exelon/AmerGen do not believe that there is a licensing basis or probabilistic basis to require the source to be declared inoperable due to a contingent loss of a transmission element, unless the loss of that transmission element can be linked to the effects of the accident.

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U. S. Nuclear Regulatory Commission Comments on Draft RG DG-1195 July 9, 2008 Page 2

2. Exelon/AmerGen request further clarification regarding the first sentence in the third paragraph: "Forthe passive plant designs that are exempted from providing the two offsite ac sources requiredby GDC 17 or for passive plant designs that fully meet the requirementsof GDC 17 are not required to have any technical specification requirements for their offsite ac source(s) because passive plant designs rely on passive safety-related systems for core cooling and containment integrity." Exelon/AmerGen believe there may be a grammatical error, and therefore, further clarification would be helpful.

Section 2.1 - Meeting the Limiting Condition for Operation

3. Exelon/AmerGen suggest deleting the words "single" and "double" from the discussion. The words do not seem to lend value to this discussion, and may even add confusion since they have very specific meanings in the safety systems. The NRC responded to an earlier comment related to DG-1 153 referencing SECY-77-439, which discusses the relationship between the single failure criteria and GDC-1 7, which does not apply. SECY-77-439 is not readily identifiable in ADAMS for retrieval purposes. Exelon/AmerGen suggest rewording the first sentence to read: "...capableof withstandinga system contingency such as: (a) a loss of generationby the nuclear unit, any other criticalgeneration source, or loss of power from a transmission system element; or (b) failures involving a loss of power...." References to single and double failures were deleted from the discussion.

Section 2.2 - Period of Continued Operation

4. Exelon/AmerGen suggest deleting the sentence: "...Forexample, the risks associatedwith immediate shutdown upon loss of the onsite ac power source during a period of light transmission system load with high operating reserve would tend to be less than those resulting from shutdown during a peak load period with less operating reserve because the electricalgrid may be able to accommodate a loss of power generation...,"or replace the word "would" with "may." This statement may not necessarily be true. Under periods of light load, the relative value of a single generator will be more significant such that its loss may result in greater grid issues.

Section 3.1 - The Available Offsite AC Power Sources Are One Less Than the LCO

5. With regard to the last two sentences in the first paragraph concerning risk, Exelon/AmerGen believe that the statements should be substantiated by data.

Any risk needs to include an evaluation for duration or restoration. If there is not adequate data to justify these statements, Exelon/AmerGen suggest deleting these sentences.

U. S. Nuclear Regulatory Commission Comments on Draft RG DG-1 195 July 9, 2008 Page 3

6. Exelon/AmerGen recommend revising or clarifying the sentence: "Thus, the loss of an offsite source resulting from such a cause should be treatedas equivalent to the loss of both requiredoffsite sources." The second sentence in Section 3.1 states: "However,the remaining offsite power system retains full capability."

These two sentences appear to be contradictory. If the first source is lost due to a fire or ice storm, then the susceptibility of the second source needs to be evaluated for potential common cause, and if appropriate treated as equivalent to the loss of both offsite sources. The second source may come from a different direction, or be underground, or possess some other design feature that would not make it susceptible to common cause failure.

Section 3.2 - The Available Onsite AC Power Sources Are One Less Than the LCO

7. With regard to the discussion in this paragraph, if a generator trip results in the loss of an offsite source, or the total loss of AC power, then that source should not be considered operable. If the offsite source, and onsite AC power are both less than the LCO, then Exelon/AmerGen would not consider this paragraph applicable, but rather the guidance in Section 3.4, "The Available Offsite and AC Power Sources Are Each One Less Than the LCO," of DG-1 195.

Section 3.5 - The Available Onsite AC Power Sources Are Two Less Than the LCO

8. Exelon/AmerGen believe that shared onsite power supplies are prohibited by Regulatory Guide (RG) 1.81, "SharedEmergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants,"for plants with construction permit applications after June 1, 1973. Since there is no backfit proposed on DG-1 195, then Exelon/AmerGen do not believe that it is appropriate for sharing of onsite supplies.

9. Nuclear plant operators do not take system-wide actions; this is the responsibility of the grid operator. Even in an integrated utility, the best the station control room operator can do is to inform the grid operator of the imminent shutdown.

Section 3.6 - The Available Onsite DC Power Sources Are Less Than the LCO

10. Exelon/AmerGen suggest deleting the parenthetical statement "(e.g., a subsequent single failure could render the entire power system ineffective on a generatortrip)." Although this phrase is true, Exelon/AmerGen do not believe there is a regulatory basis to assume a single failure during a plant transient (only during accidents).

U. S. Nuclear Regulatory Commission Comments on Draft RG DG-1 195 July 9, 2008 Page 4 C. Requlatory Position

11. The allowable out-of-service times were eliminated from Regulatory Positions 1 and 3, and the phrase, "time period allowed for continuedoperation as specified in the plant technicalspecifications,"is used in the discussion. This is a change to the wording in Regulatory Guide 1.93, and was probably prompted by previous comments on DG-1 153 indicating that the time frames are plant specific, and contained in other NRC documents. Regulatory Positions 2 and 4 still have time frames specified for certain actions. Exelon/Amergen suggest that the specific time frames be removed from Regulatory Positions 2 and 4.

If you have any questions or require additional information, please do not hesitate to contact Mr. Richard Gropp at 610-765-5557.

Respectfully, David P. Helker Manager - Licensing