During the lunch break you can choose to bring your own food or to have lunch at CNR canteen.
Inside the CNR area there are also two cafès where you can buy salads or sandwiches.
If you want to have a walk you can also try the following:
Pizzeria-Ristorante "Il Pizzomane" ( Str. Provinciale 2 Vicarese, 36, 56010 Pisa PI)
Pizzeria "Trittica" (Via angelo Batteli, 1, 56127, Pisa)